UNIT VII: SKELETONS SKELETAL SYSTEM ❑ The skeletal system forms the framework of the body. It provides support, protection, and movement, and serves as an anchor for muscles, tendons, and ligaments. ❑ It is made up of bones, cartilage, ligaments, and joints, all working together to give shape, stability, and mobility to the body. ❖ Total number of bones in an adult human: 206 ❖ Total number in infants: around 270 ❑ OSTEOLOGY- branch of biology that study the structure and function of the skeleton and bones. TYPES OF SKELETON 1. HYDROSTATIC SKELETON ❑ Found in soft-bodied invertebrates such as earthworms, jellyfish, and sea anemones. ❑ Formed by a fluid-filled compartment within the body, called the coelom. ❑ Movement is achieved when muscles contract and push the fluid, changing the body’s shape. ❑ Functions: ❖ Allow flexibility and movement. ❖ Provide structure and shape without bones ❖ Acts as a cushion against external pressure ❑ Example: Earthworm uses its hydrostatic skeleton to move by contracting and relaxing muscles against the fluid pressure inside its body segments. 2. EXOSKELETON ❑ An external skeleton consists of a hard encasement on the surface of an organism. ❑ It is a hard outer covering that protects internal organs and supports the body. ❑ Found in arthropods (insects, crabs, spiders) and mollusks (snails, clams). ❑ Made of chitin (in arthropods) or calcium carbonate (in mollusks).

❑ Functions: ❖ Protects soft tissues from injury. ❖ Prevents water loss (important for terrestrial arthropods). ❖ Provides points of attachment for muscles. ❖Limitation: Does not grow with the animal, must be molted (shed) and replaced regularly. ❑ Example: Crab shell (carapace) is a strong exoskeleton that shields the crab from predators. 3. ENDOSKELETON ❑ A skeleton that consists of hard, mineralized structures located within the soft tissue of organisms. ❑ It is an internal skeleton composed of bones and cartilage. ❑ Grows with the organism and provides structural support without restricting growth. ❑ Functions: ❖ Supports the body and maintains posture ❖ Protects internal organs(ex:skull protects brain,ribs protect heart and lungs) ❖ Provides attachment sites for muscles. ❖ Aids in movement through the jointed system. ❑ Example: The human skeleton, made up of 206 bones. ❑ An example of a primitive endoskeleton structure is the spicules of sponges. ❑ The bones of vertebrates are composed of tissues, whereas sponges have no true tissues. DIVISION OF THE SKELETAL SYSTEM ❑ The human skeletal system is divided into two major parts: A. Axial Skeleton (Red) B. Appendicular Skeleton (Blue)

A. AXIAL SKELETON ❑ Forms the central axis of the body. It is composed of 80 bones. ❑ Main components: 1. Skull 2. Vertebral Column 3. Rib cage 4. Hyoid bone 5. Auditory Ossicles 6. Sternum 1. HUMAN SKULL (22 BONES) ❑ Consists of the cranium (for brain protection) and facial bones ❑ Cranium is made of 8 plate-shaped bones connected at sutures. ❑ Remaining 14 bones form the facial structure ❑ Mandible is the only movable bone.

❑ Remaining 14 bones form the facial structure • Coronal Suture: Runs from ear to ear, joining the front bone to the top-side bones. • Sagittal Suture: Runs down the top center of the head, joining the two parietal bones. • Lambdoid Suture: Located at the back of the head, joining the top-side bones to the rear skull bone. • Squamous Suture: Located above the ear, connecting the temporal and parietal bones. • Metopic Suture: Runs down the middle of the forehead; it usually closes up in early childhood ❑ Functions of the Skull ❖ Providdes protection and support for the brain, meninges, eyes, cerebellum, cerebrum, and brainstem. ❖ Supports facial muscles and scalp attachments. ❖ Safeguards vessels and nerves for facial muscles, brain, and related parts. ❖ Hardens and fuses during development for internal content protection.

2. HYOID BONE ❑ U-shaped bone situated in the front of the neck. ❑Serves as a link between the skull and postcranial skeleton. ❑ Assists in tongue movement and swallowing. ❑ Not connected or articulated with other bones. 3. AUDITORY OSSICLES (6 SMALL BONES) ❑ Auditory ossicles namely malleus, incus, stapes are three bones in the middle ear ❑ Are the smallest bones in the human body. ❑ Function: to transmit sound from the air to the cochlea. 4. RIBS (24 RIBS) ❑ Long curved bones forming the rib cage,totaling 24 bones in 12 pairs. ❑ Constructs the protective enclose around the thorax. ❑Posteriorly connects with the vertebral column and ends anteriorly as cartilage. ❑ Functions: ❖ Safeguards the internal organs within the thoracic cavity. ❖ Protects the heart and lungs

5. STERNUM ❑ Long bone situated in the center of the chest. ❑ Forms the rib cage along with the ribs ❑ Connected to the first seven ribs and the clavicle (collarbone) 6. VERTEBRAL COLUMN (26 BONES) ❑ The vertebral column protects the spinal cord. ❑ Provides stiffening to the body ❑ Provides structural support by balancing the body weight ❑ Provides attachment to pectoral and pelvic girdles and other muscles ❑ In humans and many vertebrates, the vertebral column is divided into five main regions: 1. Cervical 2. Thoracic 3. Lumbar 4. Sacral 5. Coccygeal

1. CERVICAL VERTEBRAE ❑ Delicate and thin bones in the vertebral column. ❑ Consists of 7 vertebrae aligned along the neck ❑ Named from superior C1 (Atlas) to C7 holding up the skull and enabling head rotation ❑ While C2 (Axis) facilitates head and atlas rotation. 2. THORACIC VERTEBRAE ❑ Located in the mid-back region ❑ Primarily supports the rib cage, safeguarding the heart and lungs ❑ Comprised of 12 vertebrae, named T1 to T12 ❑ Uniquely associated with supporting and articulating with the ribs 3. LUMBAR VERTEBRAE ❑ Largest vertebrae in the vertebral column ❑ Consists of 5 bones located between the rib cage and pelvis, named L1 and L5. ❑ L1 is closest to the thoracic vertebrae ❑ L5 is adjacent to the pelvis. ❑Functions as primary load-bearing structure in the spine. 4. SACRAL VERTEBRAE ❑ Comprise 5 vertebrae bones (S1-S5) that fuse to create a sacrum. ❑ Sacrum is a long, wedge-shaped vertebrae at the base of the spine. ❑ Strong bone supporting upper body weight and transferring it across the pelvis to the legs.

5. COCCYX VERTEBRAE ❑ Composed of 3 to 5 fused rudimentary bone, forming a small triangular bone. ❑ Also known as the tailbone. ❑ Functions as an attachment point for ligaments, tendons, and muscles. ❑ Susceptible to fracture in cases of sudden falls or impact. B. APPENDICULAR SKELETON ❑ Includes the limbs and girdles that attach to the axial skeleton. Composed of 126 bones. ❑ Main components: 1. Shoulder/Pectoralis girdle 2. Arms and forearms 3. Hands 4. Pelvis 5. Thighs and legs 6. Feet and ankles 1. SHOULDER (PECTORAL) GIRDLE ❑ Composes 4 bones connecting each arm. ❑ Forms part of the appendicular skeleton, associated with the upper limbs. ❑ Includes the scapula (shoulder blade) and clavicle (collarbone) in humans. 2. ARMS AND FOREARMS ❑ The arm and Forearm are constituted of 6 bones. ❑ The large bones of the arm include: ❖ Humerus – runs from the shoulder socket and joins the radius and ulna at the elbow

❖ Radius – is a forearm that runs from elbow to the thumb side of the wrist. ❖ Ulna – a forearm that runs from the elbow to the “pinky” side of the elbow. 3. HANDS ❑ The hands consist of 54 bones which provide support and flexibility to the soft tissues. ❑ The bones of hands are categorized into three: ❖ Carpals – are a set of 8 irregularly shaped bones located in the wrist area. ❖ Metacarpals – are bones that are related to each digit, there are 5 metacarpal bones. ❖ Phalanges – the bones of the fingers. There 3 phalanges in each finger, except for the thumb which has two phalanges only. 4. PELVIS (PELVIC GIRDLE) ❑ Situated in the lower trunk as a ring-like bony structure. ❑ Comprised of the sacrum, coccyx, and paired hip bones.

❑ Hip bones consist of the ilium, ischium and pubis, forming each side of the pelvic girdle. ❖ Ilium – the longest bone in the girdle that provide a strong connection to the backbone. ❖ Pubis – front part of the hip bone that protects bladder, uterus, and intestines. ❖ Ischium – bottom and back part of the hip bone that supports the body’s the body’s weight when sitting. ❑ Functions: ❖ It transfers the weight of the body from the axial skeleton to the appendicular components, especially during the movement. ❖ Provides attachment from several muscles and ligaments enabling movement ❖ The majority of women have a gynecoid pelvis and males have an android pelvis. ❖ The differences in the structure create a great pelvic outlet enabling the process of childbirth. 5. THIGHS AND LEGS ❑ Integral part of the appendicular skeletal system, supporting lower limb muscles. ❑ Facilitate walking, running, standing, and jumping.

❑ Require strength to effectively bear and support the body’s weight. ❑ The Femur or thigh bone is the largest and heaviest bone in the human body. At the proximal end of the Femur, there is a rounded prominence which is called as the Head of the Femur. ❑ The Tibia and Fibula are two long bones in the lower leg. They are two separate bones but are closely linked at the knee and the ankle. ❑ The top of Tibia connects to the knee joint and bottom connects to the ankle joint. Although Tibia carries all the body weight, it needs the support of Fibula 6. FEET AND ANKLES ❑ The foot is a firm platform which supports the weight of the body. ❑ It is formed of many bones such as the: ❖Tarsals–A set of 8 irregular bones situated proximally in the foot in the ankle area. ❖Metatarsals–A set of 5 bones each one for a digit. These bones connect tarsals with the phalanges. ❖Phalanges–Each toe has 3 phalanges namely the proximal, intermediate and distal. ADDITIONAL PARTS OF THE SKELETAL SYSTEM 1. TENDONS ❑ Tendons joint bones to skeletal muscles. They are made up of connective tissues. 2. LIGAMENTS ❑ Ligaments join two bones together. They are also a type of connective tissue.

3. CARTILAGE ❑ Protects bones at the joints from wear and tear. ❑ Are firm yet softer and more flexible than bones ❑ Forms a structural framework of many parts of the bod, e.g. ear, nose, ribs, bronchial tubes, etc. UNIT VIII: MUSCLES MUSCLES ❑ Muscles are soft tissues composed of specialized cells called muscle fibers that have the unique ability to contract (shorten) and relax (lengthen) to produce movement, maintain posture, and generate heat. ❑ They work in coordination with the skeletal system and nervous system to perform voluntary and involuntary body movements.

❑ Muscles convert chemical energy (ATP) into mechanical energy, which enables motion. ❑ Main Characteristics of Muscles: 1. Irritability: Ability to respond to stimuli (usually from nerves). 2. Contractility: Ability to shorten forcefully when stimulated. 3. Extendibility: Ability to stretched without being damaged. 4. Elasticity: Ability to return to original shape after being stretched or contracted. TYPES OF MUSCLES 1. SKELETAL MUSCLES ❑ Attached to bones of the skeleton through tendons. ❑ Found in muscles such as biceps, triceps, quadriceps, diaphragm, and facial muscles. ❑ Control: Voluntary (controlled consciously by the somatic nervous system) ❑ Appearance: ❖ Striated (striped) under a microscope due to the regular arrangement of actin and myosin filament. ❖ Multinucleated – each muscle fiber contains many nuclei located at the periphery of the cell. ❖Long and cylindrical fibers ❑ Skeletal muscles are made up of bundles of fibers (fascicles) surrounded by connective tissues: ❖ Endomysium (around each fiber) ❖ Perimysium (around fascicles) ❖ Epimysium (around entire muscle) ❑ Function: ❖ Responsible for body movements. ❖ Maintains posture and body position. Myofibril

❖ Generates heat during contraction (important for temperature regulation). ❖ Supports and stabilizes joints. 2. SMOOTH MUSCLES ❑ Found in the walls of hollow internal organs, such as: ❖Digestive tract (stomach, intestines) ❖ Blood vessels and lymphatic vessels ❖ Urinary bladder ❖ Uterus ❖ Respiratory tract ❖Iris of the eye ❑ Control:Involuntary – controlled by the autonomic nervous system and hormones. ❑ Appearance : ❖Non-striated (smooth appearance) because actin and myosin filaments are irregularly arranged. ❖Spindle-shaped cells (tapered at both ends) ❖Single, centrally located nucleus. ❖Usually organized in layers, circular and longitudinal layers that contract alternately. ❑ Contraction is slow and sustained, but can last for long periods without fatigue. ❑ Uses less energy (ATP) compared to skeletal muscle, making it efficient for continuous work. ❑ Plays a vital role in maintaining homeostasis, such as regulating blood pressure and digestion. ❑ Function: ❖ Peristalsis in the digestive system (wave-like contractions pushing food). ❖ Vasoconstriction and vasodilation in blood vessels. ❖ Control of pupil size and airway diameter. ❖ Uterine contractions during childbirth.

3. CARDIAC MUSCLES ❑ Found in the walls of the heart. ❑Control:Involuntary – regulated by the autonomic nervous system (ANS) and specialized pacemaker cells (sinoatrial node). ❑ Has auto-rhythmicity, meaning it can contract without external nerve stimulation (due to pacemaker cells). ❑ Appearance : ❖ Striated like skeletal muscle but branched in structure. ❖Single nucleus per cell, centrally located. ❖ Contains intercalated discs — specialized junctions that connect cardiac cells and allow electrical impulses to pass quickly. ❖Highly vascularized (rich blood supply). ❑ Functions : ❖ Responsible for pumping blood throughout the body. ❖Ensures rhythmic, coordinated contractions of the heart chambers. ❖ Provides continuous and fatigue-resistant activity. PHYSIOLOGY OF MUSCLE CONTRACTION ❑ Muscle contraction is the physiological process by which muscle fibers generate tension and shorten, producing movement in the body. ❑ This process involves the interaction between the nervous system, muscle fibers, and contractile proteins within the muscle cell.

❑ The entire mechanism operates under a principle known as the Sliding Filament Theory, which explains how muscle filaments slide past each other to shorten the sarcomere, the functional unit of contraction. ❑ Fascicles - bundles of muscle fibers that are grouped together to form a skeletal muscle ❑ Muscle Fiber – skeletal muscle cell. ❑ Myofibrils – long cylindrical structures that lie parallel to the muscle fiber which give the cell its striated appearance. ❖ Sarcolemma – plasma membrane, site of action potential conduction which triggers muscle contraction. ❖ Sarcoplasm – cytoplasm of the muscle cells. ❖ Sarcoplasmic Reticulum – specialized smooth endoplasmic reticulum, which stores, releases, and retrieves calcium ions. STRUCTURE OF MYOFIBRILS ❑ Thick filaments – made primarily of myosin. Myofibrils

❑Thin filaments – made primarily of actin, along with regulatory proteins troponin and tropomyosin. ❑ A band (dark band) – contains thick filaments and overlapping thin filaments. ❑ I band – contains only thin filaments. ❑ Z line (Z discs) – defines the boundaries of each sarcomere. ❑ H zone – Central region within the A band where only thick filaments exist (no overlap). ❑ M line – Center of the sarcomere, holds thick filaments together. STRUCTURE OF SARCOMERE ❑ Sarcomere ✔ functional unit of a skeletal muscle fiber ✔ Bundled within the myofibril ✔Highly organized arrangement of the contractile myofilaments actin (thin filament) and myosin (thick filament), along with other support proteins. ❖ striated appearance of skeletal muscle fibers is due to the arrangement of the myofilaments actin and myosin. ❑ Z line (Z disc) – anchors thin filament. ❑ M line – Center line ❑ A band – region of myosin, remains constant in length during contraction. ❑ I band – region of actin filaments, shortens during contraction.

❑ Actin (thin filament) – Protein filament that interacts with myosin for contraction; has active sites for myosin binding. ❑ Myosin (thick filament) – Protein with heads that bind to actin to form cross-bridges; uses ATP to generate movement. ❑ Tropomyosin – Protein that blocks myosin- binding sites on actin when the muscle is relaxed. ❑ Troponin – Protein complex that binds calcium ions, causing tropomyosin to move and expose binding sites on actin. SLIDING FILAMENT THEORY ❑ The sliding filament theory explains how muscles contract by the sliding movement of actin and myosin filaments. ❑ The filaments do not change in length, rather they slide past one another shortening the sarcomere and thus the muscle fiber. 1. NERVE IMPULSE INITIATION ❖ A motor neuron sends an action potential (electrical signal) to the muscle fiber at the neuromuscular junction (NMJ). ❖ The nerve ending (axon terminal) releases the neurotransmitter acetylcholine (ACh) into the synaptic cleft. 2. ACETYLCHOLINE RELEASE AND BINDING ❖ ACh binds to receptors on the sarcolemma (muscle cell membrane). ❖ This opens sodium (Na⁺) channels, causing depolarization of the muscle cell membrane.

3. ACTIVATION OF MUSCLE FIBER (EXCITATION) ❖ The action potential spreads across the sarcolemma and travels deep into the fiber through T-tubules (transverse tubules). 4. RELEASE OF CALCIUM IONS FROM THE SARCOPLASMIC RETICULUM ❖ The electrical signal traveling through the T- tubules triggers the sarcoplasmic reticulum (SR) to release calcium ions (Ca²⁺) into the sarcoplasm (cytoplasm of the muscle cell). ❖ These calcium ions play a key regulatory role in starting the contraction process. 5. BINDING OF CALCIUM TO TROPONIN ❖ The released Ca²⁺ binds to troponin, changing its shape. ❖ This causes tropomyosin to shift away from the binding sites on actin, exposing them to myosin heads. 6. CROSS – BRIDGE FORMATION ❖ The myosin heads, energized by the breakdown of ATP → ADP + Pi, attach to the exposed binding sites on actin, forming cross-bridges. 7. POWER STROKE ❖ The myosin head pivots, pulling the actin filament toward the center of the sarcomere (the M-line). ADP and Pi are released, and the sarcomere shortens (this is the power stroke).

8. CROSS – BRIDGE DETACHMENT ❖ A new ATP molecule binds to the myosin head, causing it to detach from the actin filament. 9. REACTIVATION OF MYOSIN HEAD ❖ The myosin head hydrolyzes the ATP to ADP + Pi, returning it to its “cocked” position, ready for another power stroke. 10. TERMINATION OF CONTRACTION ❖ When the nerve impulse ends, ACh is broken down by acetylcholinesterase (AChE) in the synaptic cleft. ❖Calcium ions are actively pumped back into the sarcoplasmic reticulum. ❖ Troponin and tropomyosin return to their original positions, covering actin binding sites. ❖The muscle fiber relaxes, and the sarcomere returns to its resting length. Nervous System → Acetylcholine Release → Muscle Depolarization → Calcium Release → Troponin Activation → Cross-Bridge Formation → Power Stroke → ATP Use → Relaxation PHASES OF MUSCLE ACTIVITY 1. LATENT PHASE (LAG PHASE) ❑ Brief delay after stimulus. ❖ This is the short period between the application of a stimulus and the beginning of contraction. ❖ During this time, the action potential travels along the sarcolemma and down the T-tubules. ❖ Calcium ions (Ca²⁺) are released from the sarcoplasmic reticulum, and the troponin–tropomyosin complex shifts to expose binding sites on actin. ❖ No visible shortening of the muscle occurs yet.

2. CONTRACTION PHASE ❑ tension rises as the muscle shortens. ❖ Begins when cross-bridges form between actin and myosin. ❖ The myosin heads pivot, pulling the actin filaments inward, resulting in sarcomere shortening and tension generation. ❖ ATP is used during this phase for the power stroke. ❖ The muscle becomes visibly shorter and harder. 3. RELAXATION PHASE ❑ tension decreases as the muscle returns to resting state. ❖ Occurs when stimulation ends. ❖ Acetylcholine (ACh) is broken down by acetylcholinesterase, and Ca²⁺ ions are pumped back into the sarcoplasmic reticulum using ATP. ❖ Troponin and tropomyosin return to their resting positions, covering the actin binding sites. ❖ The cross-bridges detach, and the muscle returns to its original length. RELEVANCE TO BODY MOVEMENT 1. Controlled movement - The precise timing of contraction and relaxation phases allows smooth transitions between muscle actions. 2. Force Generation - Important for activities that require strength, such as jumping or lifting. 3. Posture and Stability - Muscle tone (partial contraction) from repeated contraction–relaxation cycles keeps the body upright and stable. 4. Energy Efficiency - The relaxation phase conserves energy and prevents muscle damage by allowing recovery. 5. Coordination with other system - The timing of these phases is synchronized with signals from the nervous system and antagonistic muscles, ensuring balanced movement.

UNIT IX: NUTRITION ❑ Nutrition is the process by which organisms obtain and utilize food materials. ❑ The food consumed must be broken down into simpler substances that can be absorbed and used by cells in the process known as digestion. ❑ Digestive System – It is a complex series of organs and glands that process food, extract nutrients, and expel waste. PHYLOGENETIC TREE ❑ A branching diagram that shows the evolutionary relationships and history among different species or organisms TYPES OF DIGESTIVE SYSTEMS ACROSS ANIMALS ❑ Animals have evolved different digestive systems and processes depending on their body structure, complexity, and diet. 1. Intracellular Digestion ❑ Digestion that takes place inside the cell, within specialized compartments such as food vacuoles or lysosomes. ❑ Food particles are engulfed by endocytosis into vacuoles; undigested material is expelled by exocytosis. ❑ E.g., Protozoans (Amoeba, Paramecium), Sponges ❑ Suitable for simple organisms with no specialized tissues or organs. ❑ Their small size allows nutrients to diffuse quickly throughout the cell. Energy-efficient since digestion occurs directly where nutrients are needed.

2. Incomplete Digestion (One Opening) ❑ A digestive system with only one opening that functions as both mouth and anus. ❑ E.g., Cnidarians (Hydra, Jellyfish), and Flatworms (Planaria) ❑ Food enters the gastrovascular cavity. ❑ Enzymes break down food, cells absorb nutrients. ❑ Undigested materials are expelled through the same opening. ❑ Adequate for simple body structures that don’t need continuous food processing. ❑ Function: Food enters and waste exits through the same opening. Limited digestion efficiency. 3. Complete Digestion (Two Opening) ❑ Two separate openings: mouth and anus, with specialized regions for digestion and absorption. ❑ Food enters through the mouth, travels through organs (pharynx, esophagus, stomach, intestines), and exits via the anus. ❑ E.g., Humans and Earthworms ❑ Function: Efficient, continuous digestion with specialized organs. ❑ Ideal for active animals that require constant energy supply. 4. Ruminant Digestion ❑ Multi-chambered stomach for digesting cellulose in plants. ❑ Specialized form of complete digestion in herbivorous mammals that need to digest cellulose from plant cell walls. ❑ Stomach divided into four chambers — rumen, reticulum, omasum, abomasum.

❑ E.g., Cows, Goats, Sheep, Deer ❑ Structure ❖Rumen – the rumen is the largest compartment and acts as a storage area for ingested plant matter. It contain microorganisms. ❖ Reticulum – Work closely with the rumen. It acts as a filter, trapping larger, undigested food particles that require breakdown. ❖ Omasum – contains numerous tissue folds which increase the surface area available to absorb excess water and nutrients from the digested material. ❖Abomasum – “true stomach”, functions like the stomach of a non-ruminant animal. ❑ Food first enters rumen and reticulum, where microbes ferment cellulose. ❑ The animal regurgitates cud (partially digested food) to chew again. ❑ Rechewed food goes to omasum (water absorption) and abomasum (true stomach with acids and enzymes). ❑ Maximizes nutrient extraction from plant material. ❑ Adapted for herbivorous diet where food is fibrous and low in nutrients. ❑ Symbiotic bacteria enable the breakdown of tough plant fibers. (Mutually beneficial relationship) 5. Monogastric Digestion ❑ Digestive system with a single- chambered stomach. Food passes sequentially through the mouth, stomach, and intestines. ❑ Enzymes act on carbohydrates, proteins, and fats in different sections. ❑ E.g., Humans, Pigs, Dogs ❑ Adapted for omnivorous or mixed diets that include both plant and animal matter. ❑ Efficient for rapid digestion and nutrient absorption.

❑ Less complex than ruminant digestion, suitable for animals with high-energy, easily digestible diets. 6. Avian Digestion ❑ Specialized digestive system designed for flight efficiency and rapid food processing. ❑ E.g., Chicken, Pigeon, Eagle ❑ Structure: ❖ Beak – for picking food (no teeth) ❖ Crop – stores food temporarily ❖ Proventriculus – secretes digestive enzyme ❖Gizzard – muscular organ that grinds food. ❑ Function: Birds lack teeth, so gizzard compensates for grinding. ❑Lightweight and efficient system supports energy- demanding flight. 7. Aquatic Digestion ❑ A relatively short and straight digestive tract adapted for quick food processing in aquatic environments. ❑ Shorter intestines reduce body weight and increase buoyancy. ❑ Quick digestion suits cold-blooded metabolism and frequent feeding. ❑ E.g., Tilapia (Fish), Frogs (Amphibians)

MAJOR ORGANS OF THE HUMAN DIGESTIVE SYSTEM A. Alimentary Canal (Gastrointestinal Tract or Digestive Tract) ❑ The alimentary canal is the main passageway through which food travels in the body from the mouth to the anus. ❑ It is a continuous, hollow, muscular tube responsible for the mechanical and chemical breakdown of food, absorption of nutrients, and elimination of waste. ❑ Think of the alimentary canal as the "food highway" — the main route food follows as it gets processed by the body. 1. Mouth (Oral Cavity) ❑ Begins digestion through mastication (chewing) and saliva secretion. ❑ Saliva contains amylase, which starts breaking down starch. ❑ The tongue helps in mixing food and forming the bolus (soft ball of food) for swallowing. 2. Pharynx ❑ Serves as a passageway for food and air. ❑ During swallowing, the epiglottis closes over the trachea to prevent food from entering the lungs. 3. Esophagus ❑ A muscular tube connecting the pharynx to the stomach. ❑ Moves food via peristalsis (wave-like muscle contractions). ❑ Ends with the lower esophageal sphincter, which prevents backflow (acid reflux).

4. Stomach ❑ A J-shaped muscular organ that stores food temporarily. ❑ Secretes gastric juice containing: ❖Hydrochloric acid (HCl)–kills bacteria and activates enzymes. ❖ Pepsin – begins protein digestion. ❖ Gastric Lipase – begins the break down of fats ❑ Churns food into a semi-liquid form called chyme. ❑ Controlled by the pyloric sphincter, which regulates the passage of chyme to the small intestine. 5. Small Intestines ❑ Major site of chemical digestion and nutrient absorption. ❑ Inner lining has villi and microvilli to increase surface area for absorption. ❑ Receives bile from the liver and digestive enzymes from the pancreas. Divided into 3 sections: ❖Duodenum-first section; receives bile and pancreatic juices to neutralize acid and continue digestion. ❖ Jejunum – middle section; main site for nutrient absorption. ❖ Ileum–final section; absorbs remaining nutrients such as bile salts and vitamin B₁₂. 6. Large Intestines ❑ Absorbs water, electrolytes (salts), and vitamins produced by intestinal bacteria. ❑ Houses beneficial bacteria that produce vitamins K and B-complex. ❑ Compacts undigested food into feces for elimination.

7. Rectum ❑ Final part of the large intestines ❑ Stores feces until elimination. Stretch receptors signal the need to defecate when full. 8. Anus ❑ Opening at the end of the digestive tract where feces exit the body. ❑ Controlled by internal and external anal sphincters to regulate defecation. B. Accessory Organs ❑ These organs do not form part of the food passage but play essential roles by secreting digestive enzymes and other substances that aid digestion. 1. Salivary Glands ❑ Secrete saliva containing amylase, which starts carbohydrate digestion and lubricates food. 2. Liver ❑ Produces bile to emulsify fats, stores vitamins and glycogen, and detoxifies harmful substances. 3. Gallbladder ❑ Stores and concentrates bile; releases it into the small intestine when fats are present. 4. Pancreas ❑ Produces digestive enzymes (lipase, amylase, trypsin) and bicarbonate to neutralize stomach acid before it enters the small intestine. 5. Teeth and Tongue ❑ Assist in mechanical digestion by chewing and mixing food, forming a bolus for swallowing.

UNIT X: GAS EXCHANGE GENERAL FUNCTION OF THE RESPIRATORY SYSTEM ❑ Facilitates exchange of oxygen (O₂) and carbon dioxide (CO₂) between the organism and its environment. ❑ O₂ is essential for cellular respiration and ATP production (energy). ❑ CO₂ is a metabolic waste that must be removed to maintain acid–base balance and homeostasis. MAJOR ORGANS OF THE HUMAN RESPIRATORY SYSTEM ❑Nostrils (nares)– openings for air intake; filter dust via hairs and mucus. ❑Pharynx–common passageway for air and food. ❑Larynx–contains vocal cords and helps prevent food from entering the trachea. ❑Trachea(Windpipe) – Tube with C- shaped cartilage rings that help prevent collapse. ❑Bronchi– two main tubes leading to each lungs. ❑ Bronchioles – smaller airways controlling the air flow via smooth muscles ❑ Capillaries - facilitate the diffusion of essential substances between the bloodstream and surrounding body tissues. ❑Diaphragm – large dome-shaped muscle located below the lungs that separates the chest cavity from the abdominal cavity. ALVEOLI: THE SITE OF GAS EXCHANGE ❑ Alveoli - tiny, thin-walled air sacs where gas exchange occurs by diffusion. ❖ Their large surface area supports efficient exchange.

❖ The moist lining and rich capillary network keep gases close to the diffusion surface. ❖ The epithelium is only about one cell thick. ❑ WHEN YOU BREATHE IN – the diaphragm contracts and moves downward, which increases the volume of the chest cavity. Creates a vacuum, pulling air into the lungs. ❑ WHEN YOU BREATHE OUT - the diaphragm relaxes and moves upward, which decreases the volume of the chest cavity and, combined with the natural elasticity of the lungs, forces air out. MAJOR ORGANS OF THE HUMAN RESPIRATORY SYSTEM Respiratory Structures Across Animals ❑ Protozoans – plasma membrane; simple diffusion. ❑ Cnidarians – thin body wall; diffusion across body surface. ❑ Annelids – moist, vascularized skin. ❑ Aquatic mollusks - gills ❑ Arthropods – tracheal ❑ Fish – gill arches, filaments, and lamellae.

❑ Amphibians – lungs + moist skin. ❑ Reptiles – septate lungs. ❑ Birds – parabronchial lungs + air sacs. ❑ Mammals – alveolar lungs + diaphragm. SIMPLE DIFFUSION: PROTOZOANS AND CNIDARIANS PROTOZOANS ❑ Gas exchange occurs directly across the plasma membrane. ❑ The entire cell surface is exposed to water. ❑ A large surface-area-to-volume ratio supports diffusion. ❑ O₂ diffuses in; CO₂ diffuses out. CNIDARIANS ❑Thin body wall consists of epidermal and gastrodermal cell layers. ❑ Every cell is close to the surrounding water. ❑ No circulatory system is needed for gas exchange. ❑ Diffusion occurs between the body surface and water. CUTANEOUS AND GILL RESPIRATION EARTHWORMS ❑ Cutaneous Respiration ❑ Moist, vascularized skin. ❑ Mucus and coelomic fluid help keep the skin moist. ❑ Capillaries beneath the epidermis receive O₂ and release CO₂. MOLLUSKS ❑ Ctenidia (gill filaments) are leaf-like or comb-shaped. ❑ Located inside the mantle cavity. ❑ Countercurrent flow supports efficient O₂ uptake. AQUATIC ARTHROPODS ❑Branchial gills have feathery filaments. ❑ Gills are enclosed in a branchial chamber. ❑ Appendage movements ventilate the chamber. ❑ Countercurrent exchange increases O₂ absorption.

HIGHLY EFFICIENT GILL RESPIRATION FISH ❑ Gills are supported by branchial arches. ❑ Filaments are covered with thin lamellae, increasing surface area. ❑ Water and blood flow in opposite directions— countercurrent exchange. ❑The operculum protects the gills and helps water flow. ❑ oxygen extraction of up to 80–90%. DUAL RESPIRATION AMPHIBIANS ❑ Simple, sac-like lungs with few internal septa and relatively small surface area. ❑ Buccopharyngeal respiration: gas exchange through the mouth lining.

❑ Cutaneous respiration: gas exchange through highly vascularized, moist skin. ❑Positive-pressure breathing (buccal pumping) forces air into the lungs. ❑ Using both lungs and skin allows amphibians to function in aquatic and terrestrial settings. SEPTATE LUNGS REPTILES ❑ Lungs contain internal folds or septa that increase surface area. ❑ Alveoli-like chambers support more efficient gas exchange than the simple amphibian lung. ❑ Thoracic muscles create negative pressure for ventilation. ❑ Dry skin reduces the importance of cutaneous gas exchange. ❑ These features support higher activity than in amphibians. PARABRONCHIAL LUNGS AND AIR SACS BIRDS ❑Lungs are small and rigid;air sacs extend into the body and bones. ❑ Air moves unidirectionally through the parabronchi. ❑ Air and blood exchange gases by a crosscurrent arrangement. ❑ A given air molecule participates in two breathing cycles, so fresh air reaches the gas-exchange surface during both inhalation and exhalation. ❑ The system supports the high metabolic demands of flight. TRACHEAL RESPIRATION INSECTS ❑ Air enters through spiracles. ❑ Air travels through tracheae and tracheoles directly to cells. ❑ Blood does not need to transport O₂ to tissues. ❑ Ventilation can be aided by body movements or abdominal pumping.

ALVEOLAR LUNGS WITH A DIAPHRAGM MAMMALS ❑ Millions of alveoli provide a very large surface area. ❑ Elastic tissue helps the lungs recoil. ❑ The diaphragm and intercostal muscles create negative pressure for ventilation. ❑ Surfactant helps prevent alveolar collapse. ❑ The combination supports efficient gas exchange and the demands of active, warm-blooded metabolism. MECHANISMS OF RESPIRATION AND GAS EXCHANGE VENTILATION: INHALATION VS. EXHALATION EXTERNAL RESPIRATION: LUNGS ↔ BLOOD ❑ Occurs in the alveoli and pulmonary capillaries. ❑ O₂ diffuses from the alveoli into the blood. ❑ CO₂ diffuses from the blood into the alveoli and is exhaled. ❑ O₂ binds to hemoglobin in red blood cells, forming oxyhemoglobin.

INTERNAL RESPIRATION: BLOOD ↔ BODY CELLS ❑ Occurs in systemic capillaries and body tissues. ❑ O₂ diffuses from the blood into body cells. ❑ CO₂ diffuses from cells into the blood. ❑ CO₂ is transported as bicarbonate ions (HCO₃⁻), dissolved gas, or bound to hemoglobin. MECHANISMS OF RESPIRATION BY ANIMAL TYPE SIMPLE DIFFUSION- Protozoans, sponges, cnidarians CUTANEOUS - Earthworms, amphibians, and reptiles GILL RESPIRATION - Fish, Aquatic Arthropods, mollusks TRACHEAL - Insects PULMONARY - Amphibians, reptiles, birds, mammals VENTILATION PATTERNS ❑ Positive pressure – Force air in by buccal cavity (amphibians) ❑ Negative pressure – expand thoracic cavity (reptiles & mammals) ❑ Unidirectional flow – continuous fresh air (birds) GAS-EXCHANGE ADAPTATIONS HABITAT ❑ Aquatic – large gill surface area & countercurrent exchange help extract O₂ from water. ❑ Amphibious – lungs and skin provide dual respiration. ❑ Terrestrial – internalized lungs and mucus-lined passages reduce dependence on a wet external surface. ❑ Aerial/high activity – air sacs and unidirectional airflow support high oxygen demand. ❑ Burrowing or low - O₂ environments – highly vascularized skin and lower metabolic demand can aid survival.

ACTIVITY LEVEL UNIT XI: INTERNAL TRANSPORT CIRCULATORY SYSTEM ❑ The circulatory (cardiovascular) system is the body network that transports blood which contains nutrients, gases (O₂, CO₂), hormones, and waste products. It consists of: Heart – muscular pump Blood vessels – arteries, arterioles, capillaries, venules, veins Blood – plasma + formed elements (red cells, white cells, platelets). ❑ Function: Deliver oxygen, nutrients, remove CO₂ and wastes, distribute hormones, maintain temperature and pH, and defend against infection. HEART A. CHAMBERS OF THE HEART 1. Right Atrium- Receives deoxygenated blood from the body. 2. Right Ventricle- pumps deoxygenated blood to the lungs. 3. Left Atrium- receives oxygenated blood from the lungs. 4. Left ventricle – pumps oxygenated blood to the entire body.

B. VALVES 1. Tricuspid Valve – between right atrium and right ventricle. 2. Pulmonary Valve – between right ventricle and pulmonary artery. 3. Bicuspid or Mitral Valve – between left atrium and left ventricle. 4. Aortic Valve – between left ventricle and aorta. C. MAJOR BLOOD VESSELS 1. Superior Vena Cava – brings deoxygenated blood form the upper body. 2. Inferior Vena Cava – brings deoxygenated blood from the lower body. 3. Pulmonary Arteries – carry deoxygenated blood to the lungs. 4. Pulmonary Veins – carry oxygenated blood from the lungs to the heart. 5. Aorta – the main artery that carries oxygenated blood from heart to the body. BLOOD FLOW IN THE HEART 1. Deoxygenated blood enters the right atrium. • Superior vena cava • Inferior vena cava 2. Blood moves to the right ventricle • Right atrium contracts pushing the blood through the tricuspid valve. • Enters the right ventricle 3. Right ventricle pumps blood to the lungs. • RV contracts, the pulmonary valve open to pushed blood into pulmonary trunk • Right pulmonary artery > right lung • Left pulmonary artery > left lung 4. Gas Exchange in the Lungs • Travels through capillaries • CO2 is released > O2 is absorbed

5. Oxygenated Blood Returns to the Left Atrium. • Pulmonary veins > left atrium 6. Blood moves to the Left Ventricle • LA contracts, forcing blood through the mitral valve into LV. 7. Left ventricle pumps blood to the whole body. • LV contracts, aortic valve opens. • Blood is pumped into the aorta • Oxygenated blood is distributed 8. Blood returns back to the heart. ORGANS AND FUNCTIONS OF CIRCULATORY SYSTEM `HEART ❑ Four-chambered muscular organ (2 atria, 2 ventricles). ❑ Pumps blood in two circuits. ❑ Valves ensure one-way flow: tricuspid, pulmonary, mitral, aortic ❑ Generate pressure to move blood, separate oxygenated and deoxygenated blood ❑ Mitral (Bicuspid) valve have two leaflets whiletricuspid valve have three leaflets. ❑ The left ventricle of the heart has thicker muscular tissue than the right ventricle.

ARTERIES AND ARTERIOLES ❑ Thick-walled, elastic (arteries) and muscular (arterioles). ❑ Arteries - Carry blood away from heart to different parts of the body. ❑ Arterioles - Control the flow of blood from arteries into capillaries and regulate blood pressure. CAPILLARIES ❑ Thin, extensive network in tissues. ❑ Exchange of gases, nutrients, and wastes between blood and tissues fluid. VEINS AND VENULES ❑ Thin-walled, large lumen ❑ Collect blood from capillaries, return to heart. ❑ Act as blood reservoir BLOOD ❑ Plasma- watery fluid with dissolved proteins, electrolytes, nutrients, wastes. ❑ Red blood cells (erythrocytes)- O2 transport via hemoglobin. ❑ White blood cells (leukocytes)- immunity ❑ Platelets (thrombocytes) - clotting ❑ Hemoglobin is the protein in red blood cells that carries oxygen from the lungs to the body's tissues and then returns carbon dioxide to the lungs ❖ INNATE - The body's fast, built-in, and nonspecific first line of defense against general classes of pathogens ❖ ADAPTIVE – A slower, highly specialized response that targets specific pathogens and builds immunological memory for long-term protection.

GRANULOCYTES (WBC) ❑ These cells contain tiny sacs filled with microscopic chemical enzymes that help destroy foreign invaders. ❖ Neutrophils - The body's "first responders" to an injury or infection. They are highly effective at engulfing and destroying invading bacteria and fungi. ❖ Eosinophils - Mainly responsible for fighting off parasitic infections. They also play a significant role in triggering allergic reactions and asthma symptoms. ❖ Basophils - The rarest type of white blood cell. They release histamine and heparin, which aid in inflammation and prevent rapid blood clotting during an allergic response AGRANULOCYTES (WBC) ❑ These cells have a smoother cytoplasm and focus heavily on targeted, long-term immune protection. ❖ Lymphocytes - Essential components of your adaptive immune system. ❖ Monocytes: the largest of the white blood cells. Once they migrate into surrounding tissues, they mature into macrophages or dendritic cells, which act like cleanup crews to clear out dead tissue, cellular debris, and other pathogens SYSTEMIC CIRCULATION VS. PULMONARY CIRCULATIONC PULMONARY CIRCULATION ❑ Exchange CO2 for O2 in the lungs. ❑ Low pressure, low resistance circuit (shorter distance, less muscular vessels) ❑ Pulmonary arteries carry deoxygenated bloodCOLLEG ❑ Route 1. Right atrium 2. Right Ventricle 3. Pulmonary trunk 4. Pulmonary arteries 5. Lung (capillaries) 6. Pulmonary veins 7. Left atriumCOLLEGE OF

SYSTEMIC CIRCULATION ❑ Deliver oxygen and nutrients to tissues and collect CO2/wastes. ❑ High pressure, high resistance circuit (longer distance, thicker left ventricle) ❑ Veins carry oxygenated blood.COLLEGE O ❑ Route 1. Left ventricle 2. Aorta 3. Arteries 4. Arterioles 5. Capillaries 6. Venules 7. Veins 8. Superior/Inferior vena cava 9. Right atrium

UNIT XII: EXCRETORY SYSTEM ❑ Main Function: Remove metabolic wastes, maintain water–salt balance, regulate pH, and control blood volume and pressure. Key excretory organs: 1. Kidney – primary organ for filtering blood and producing urine. 2. Ureters – tubes that transport urine from kidneys to urinary bladder. 3. Urinary bladder – stores urine temporarily. 4. Urethra – carries urine from bladder to the outside of the body.COLLEGE OF ARTS & SCIENCES KIDNEY: PARTS AND FUNCTIONS EXTERNAL STRUCTURE 1. Renal Cortex : The outer layer of the kidney where blood filtration begins. It contains the renal corpuscles (glomerulus). 2. Renal Medulla : The inner part of the kidney which contains structures like the renal pyramids. It houses the loops of Henle and other tubules 3. Renal Pelvis : A funnel-shaped structure located in the innermost part of the kidney. It collects urine from calyces and directs it into ureter. 4. Calyses : Small, cup-like structures that collect urine from the renal pyramids before it moves into the renal pelvis.COLLEGE OF ARTS & S 5. Renal Capsule : A fibrous membrane that covers and protects the outside of the kidney.COLLEGE OF ARTS & SCIENCES INTERNAL FUNCTIONAL UNIT: Nephron ❑ Each kidney contains about 1 million nephrons Two types of nephrons • Cortical nephrons: Their renal corpuscles lie in the cortex, and their loops of Henle are generally shorter. • Juxtamedullary nephrons: Their renal corpuscles lie near the boundary between the cortex and medulla, and they have longer

loops of Henle that extend deeper into the medulla.COLLEGE OF PARTS OF THE NEPHRON 1. Glomerulus- Network of capillaries involved in filtration. 2. Bowman’s capsule- cup-shaped structure surrounding the glomerulus. 3. Proximal Convoluted Tubule (PCT)- is the region of renal tubule where reabsorption of essential substances (water, electrolytes, glucose, etc.) takes place. 4. Loop of Henle: has an ascending and descending limb. 5. Distal Convoluted Tubule (DCT)- the last part of the nephron, connects and empties its contents into collecting ducts that line the medullary pyramids. 6. Collecting Duct- is a long, straight tube where H+ and K+ ions are secreted to maintain the electrolyte balance of the blood.COLLEGE OF ARTS & SCIENCES URINE FORMATION The Kidney forms urine through three Major steps: 1. Glomerular Filtration 2. Tubular Reabsorption 3. Tubular SecretionCOLLEGE OF ARTS & SCIENCES

1. Glomerular Filtration Occurs in the glomerulus and Bowman’s capsule. High blood pressure forces water and small solutes out of the blood into Bowman’s capsule.COLLEGE Filtrate contains water, glucose, salts, amino acids, urea, uric acid. Not filtered: Blood cells, platelets, and large proteins (hard to pass). Produces about 180 liters of filtrate/day, but most will be reabsorbed.COL\ LEGE OF ARTS 2. Tubular Reabsorption Occurs mainly in PCT, some in Loop of Henle, DCT, and collecting duct. Return useful substances from the filtrate back to the blood.COLLEGE OF ARTS & Reabsorbed substances include: 1. Water 2. Glucose (100% in healthy individuals) 3. Amino acids 4. Sodium, potassium, and chloride ions 5. Bicarbonate ions (for pH balance)COLLE  Loop of Henle creates a concentration gradient: a. Descending limb: permeable to water > water leaves. b. Ascending limb: permeable to salts > salts leaves, water stays.  About 99% of filtrate is reabsorbed.COLLEGE OF ARTS & SCIENCES 3. Tubular Secretion  Occurs mainly in DCT and collecting duct.  Active transport of additional substances from blood into nephron.COLLEGE OF ARTS & S  Secreted substances: 1. Hydrogen ions – controls blood pH 2. Potassium ions 3. Ammonium ions 4. Drugs, creatinine, and toxins  Final product: urine, containing urea, uric acid, creatinine, water ions.COLLEGE OF

EXCRETORY ADAPTATIONS ❑ Freshwater animals- experience excess water intake, so they produce large amounts of dilute urine and actively retain salts ❑ Marine animals- living in salty environments, risk dehydration and therefore produce small amounts of very concentrated urine, drink seawater, and excrete excess salts through kidneys or specialized organsCOLLEGE OF ARTS & SCI ❑ Terrestrial animals must conserve water; many have efficient kidneys, and desert mammals have long loops of Henle to produce extremely concentrated urine. ❑ Birds and reptiles, excrete uric acid, which requires minimal water, and some birds use salt glands for removing excess salt. UNIT XIII: NERVOUS SYSTEM ❑The nervous system is the body’s rapid-response control, communication, and information- processing system. Its fundamental unit is the neuron, a specialized cell that transmits electrical and chemical signals.COLLEGE OF ARTS & SCIENCES ❑ The Central Nervous System (CNS) is the command center, consisting of the brain and the spinal cord. It is protected by bone (skull and vertebrae), membranes (meninges), and cushioning fluid (cerebrospinal fluid). ❑ The nervous system is often divided into components called gray matter and white matter. a. Gray matter: gray in preserved tissue but pink or light brown in living tissue, contains a relatively high proportion of neuron cell bodies. b. White matter: is composed mainly of axons and is named because of the color of the fatty insulation called myelin that coats many axons.C OLLEGE OF ARTS & SCIENCES

PARTS AND FUNCTION OF THE BRAIN AND SPINAL CORD A. Brain ❑ The brain is the major processing center, controlling everything from basic vital functions to complex thought and emotion. Its main parts include: 1. Cerebrum (Forebrain) 2. Cerebellum (Hindbrain) 3. Brainstem 4. DiencephalonCOLLEGE 1. Cerebrum (Forebrain) ❑ The largest part, responsible for higher-level functions like conscious thought, memory, language, and voluntary movement. ❑ It is divided into two hemispheres (left and right), connected by the corpus callosum.COLLE ❑ The outer layer, the cerebral cortex (gray matter), is folded into four main lobes: a. Frontal lobe: Controls voluntary motor function, personality, planning, problem-solving, and speech production (Broca's area). b. Parietal lobe: Processes sensory information from the skin (touch, temperature, pain) and is involved in spatial orientation. c. Temporal lobe: Processes auditory stimuli, language comprehension (Wernicke's area), and memory. d. Occipital Lobe: Responsible for visual processing.C 2. Cerebellum (Hindbrain) ❑ Located under the cerebrum, it is known as the "little brain." ❑ Primary function is coordination of muscle movement, maintenance of posture, and balance.COL 3. Brainstem ❑ Connects the cerebrum and cerebellum to the spinal cord and is composed of the midbrain, pons, and medulla oblongata.

❑ Controls essential involuntary functions necessary for survival, such as breathing, heart rate, blood pressure, and digestion.COLL 4. Diencephalon (within the forebrain) ❑ Includes two key structures: a. Thalamus: Acts as a relay station for almost all incoming sensory information, directing it to the appropriate area of the cerebral cortex. b. Hypothalamus: A crucial center for homeostasis, regulating body temperature, thirst, hunger, sleep, and connecting the nervous system to the endocrine system via the pituitary gland.COLLEGE B. The Spinal Cord ❑The spinal cord is a long bundle of nerve tissue that extends from the brainstem down the vertebral column. ❑ Function: It serves as the primary pathway for: -Transmitting motor commands from the brain to the body. -Relaying sensory information from the body to the brain. ❑Reflex Arc: It is the control center for reflex actions (rapid, involuntary responses) that bypass the brain, allowing for immediate reaction to stimuli.CO DIVISIONS OF THE NERVOUS SYSTEM ❑The nervous system is structurally divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The PNS is further subdivided based on function.

A. Central Nervous System ❑The CNS includes the brain and spinal cord along with various centers that integrate all the sensory and motor information in the body.COLL B. Peripheral Nervous System ❑ The PNS is a vast network of nerves consisting of bundles of axons that link the body to the brain and the spinal cord. a. afferent nerves (also called sensory nerves) which are composed of afferent neurons (also called sensory neurons) that collect sensory information from the body and transmit it to the CNS. b. efferent nerves (also called motor nerves) which are composed of efferent neurons (also called motor neurons) that carry commands from the CNS to the bodyCOLL ❑ Acts as the communication link, relaying information between the CNS and the body's organs, muscles, and glands. ❑ The PNS is divided into two functional subdivisions: 1. Somatic Nervous System (SNS) ❑ The somatic system has voluntary control of our movements via skeletal muscle. ❑ Components: Sensory (Afferent) neurons- carry signals to the CNS; Motor (Efferent) neurons carry signals from the CNS to skeletal muscles.CO ❑ The PNS is divided into two functional subdivisions: 2. Autonomic Nervous System (ANS) ❑ The autonomic system has involuntary control of internal organs, blood vessels, and smooth and cardiac muscles. ❑ The ANS affects heart rate, digestion, respiratory rate, salivation, perspiration, pupil diameter, urination, and sexual arousal.COLLEG

The ANS is classically divided into three subsystems: 1. Parasympathetic nervous system : the parasympathetic system is responsible for stimulation of “rest-anddigest” activities that occur when the body is at rest, including sexual arousal, salivation, lacrimation (tears), urination, digestion, and defecation.COLLEGE 2. Sympathetic nervous system: The sympathetic nervous system is responsible for stimulating activities associated with the “fight-or-flight” response: mobilizing the systems of the body for escape or attacking sources of danger 3. Enteric nervous system: A network of neurons governing the function of the gastrointestinal tract; sometimes considered a third division of the ANS.COLLEGE GE The Role of Nervous System in Animal Behavior and Coordination 1. Core Functions and Behavior

2. Role in Innate Behaviors ❑ Reflexes: These are simple, fast, involuntary responses mediated by a reflex arc E.g. The suckling reflex in newborn mammals (e.g., puppies, human infants) is an innate motor pattern that ensures immediate feeding and survival upon contact with the mother. ❑ Fixed Action Pattern (FAPs): More complex, multi-step innate behaviors. Once triggered by a key stimulus, the action runs to completion. E.g. A female Greylag Goose will use her bill to repeatedly roll an egg (or any egg-like object) back into the nest if it rolls out. The sight of the egg outside the nest is the single stimulus that triggers this complex, unchangeable motor sequence. 3. Role in Learned Behaviors ❑ Habituation: A simple form of learning where the nervous system decreases its response to a repeated, irrelevant stimulus. E.g. Prairie dogs initially sound an alarm call at the sound of human footsteps. If no danger follows the sound repeatedly, their nervous system habituates (modifies the neural circuit) and they stop issuing the alarm. ❑ Imprinting: A highly specialized, rapid form of learning that occurs during a critical period in early development. E.g. Newly hatched ducklings and geese follow the first large moving object they see (usually their mother). This visual information is quickly and permanently 'imprinted' into their neural memory structures.C 4. Role in Coordination and Navigation ❑ Balance and Fine Motor Control: The cerebellum processes sensory information from muscles, joints, and the inner ear to adjust movement in real-time. E.g. The sophisticated neural circuitry in the large cerebellum of birds is essential for calculating the rapid, precise changes in wing position required for coordinated flight maneuvers. ❑ Long-Distance Navigation: Complex brain structures integrate multiple sensory inputs for migration. E.g. Migratory birds (like the Arctic Tern) use the hippocampus (a memory center) to store map-like representations of familiar landmarks and routes, while also using specialized neural circuits to sense the Earth's magnetic field for compass orientation.

UNIT XIV: REPRODUCTIVE SYSTEM ❑ The reproductive system is essential for producing offspring and involves a complex set of organs, ducts, and glands, largely regulated by hormones. MALE REPRODUCTIVE SYSTEM ❑ The male system produces, maintains, and transports sperm and semen, and secretes male sex hormones (androgens). EXTERNAL GENITALIA 1. Penis – the organ for copulation and urination. Contains erectile tissue (corpora cavernosa and corpus spongiosum) that fills with blood to allow for erection. 2. Scrotum – A loose pouch-like sac of skin hangs behind the penis and contains the testes. It acts as a thermoregulator to keep the testes at a slightly lower temperature than the body, which is essential for normal sperm development. INTERNAL GENITALIA 1. Testes (Testicles) – the paired gonads responsible for producing sperm (spermatogenesis) and the primary male sex hormone, testosterone. They contain coiled seminiferous tubules where sperm production occurs. 2. Epididymis – A coiled tube adjacent to the testis where immature sperm travel for maturation and storage.CO 3. Vas deferens (Ductus Deferens) – muscular tubes that transport mature sperm from the epididymis to the ejaculatory ducts. 4. Urethra – A tube that runs through the penis and carries both urine from the bladder and semen from the ejaculatory ducts out of the body.COLLE 5. Ejaculatory duct – Formed by the joining of the vas deferens and seminal vesicles, they pass through the prostate and empty into the urethra.COLLEG ACCESSORY GLANDS ❑ Produce seminal fluid (semen) to nourish and protect the sperm.

1. Seminal Vesicles – Produce a fluid rich in fructose (energy for sperm), mucus, and prostaglandins. 2. Prostate Gland – Produces a thin, milky fluid containing enzymes and citrate that helps liquefy the ejaculate. 3. Bulbourethral Glands (Cowper’s Glands) - Secrete a clear mucus that lubricates the urethra and neutralizes residual acidity from urine.CO FEMALE REPRODUCTIVE SYSTEM ❑ The female system produces the ovum (egg cell), receives sperm, protects and nourishes the developing fetus, and secretes female sex hormones. EXTERNAL GENITALIA: 1. Clitoris – It is the most sensitive part of the external genitalia, primarily for sexual arousal. 2. Vaginal opening – entrance to the vagina and serves for childbirth, menstruation, and intercourse. 3.Urethral opening–the exit point for urine to leave the body.COLL 4. Labia majora and minora – Folds of skin that enclose and protect the other external organs. 5. Vulva – The collective term for the external female genital organs. 6. Mons pubis - a rounded, fleshy mound of fatty tissue that covers the pubic bone and is covered with pubic hair after puberty.COLLEGE OF INTERNAL GENITALIA: 1. Ovaries – The paired gonads that produce ova and the female sex hormones, estrogen and progesterone. 2. Fallopian tubes (Oviducts) – narrow tubes attached to the uterus that serve as pathways for the ovum. Fertilization by sperm typically occurs here.CO 3. Uterus (Womb) – A hollow, muscular, pear-shaped organ where a fertilized egg implants and the fetus develops during pregnancy. The main body is the corpus, which expands during pregnancy.  The lower, narrow part is the cervix, which opens into the vagina.

4. Vagina – A muscular canal that connects the cervix to the outside of the body; it receives the penis during copulation and serves as the birth canal. TYPE OF REPRODUCTIVE SYSTEM ❑ Reproduction is the biological process by which organisms create new individuals. The two main types are asexual and sexual reproduction.COLLEGE SEXUAL REPRODUCTION ❑ Involves two parents (typically male and female), although some organisms are hermaphrodites. ❑ Offspring are genetically unique due to the combination of genes from both parents. ❑ Involves the fusion of gametes (sperm and egg) to form a zygote. ❑ This genetic variation is advantageous for species survival in a changing environment.CO ASEXUAL REPRODUCTION ❑ Involves a single parent ❑ Offspring are genetically identical clones of the parent. ❑ Does not involve the fusion of gametes (sex cells) or a change in chromosome number. TYPES OF ASEXUAL PROCESSES  Binary Fission - The parent cell splits into two approximately equal-sized daughter cells. E.g. Amoeba, bacteria  Budding – A new individual develops from an outgrowth (or bud) on the parent's body and then separates. E.g. Hydra, yeastCOL  Fragmentation - The parent's body breaks into distinct pieces, each of which can regenerate to form a new complete organism. E.g. Sea stars (starfish), Planaria (flatworms)  Parthenogenesis – An egg develops into a complete individual without fertilization by sperm. The offspring can be either haploid or diploid. E.g. Some species of rotifers, aphid certain fish, amphibians, and reptiles (Komodo dragons) BEHAVIOR OF ANIMALS ❑ Reproductive behavior encompasses the actions and strategies used by animals to locate, court, mate with, and provide care for offspring.COL COURTSHIP AND MATE SELECTION

❑ Function: To attract a mate, synchronize reproductive cycles, and allow the female to assess the male's fitness. ❑ Peacock (Bird): The male (peacock) displays his elaborate, colorful tail feathers (train) in a grand fan to attract the female (peahen). This visual signal advertises his health and genetic quality. ❑ Fiddler Crab (Crustacean): The male has one enormously enlarged claw, which he waves vigorously in a complex pattern to attract females and warn off rival males.COLLEGE OF A TERRITORIALITY AND COMPETITION ❑ Function: To secure and defend an area that provides necessary resources (food, nesting site) for successful reproduction. ❑ Elephant Seals (Mammal): Large dominant males ("beachmasters") establish and defend territories on breeding beaches, controlling access to large harems of females. This leads to intense, sometimes bloody, physical combat between males.COLLEGE PARENTAL CARE ❑ Function: Behaviors exhibited after mating to increase the survival rate of the offspring. ❑ Killdeer (Bird): The parent bird uses a distraction display (known as the "brokenwing display") to lure predators away from the nest. ❑ Emperor Penguins (Bird): Males provide extreme care by incubating the single egg through the harsh Antarctic winter without food, balancing it on their feet under a fold of skin (the brood pouch).