anat

Nervous System

1. Action Potential

   • All-or-nothing principle: Neuron fires fully or not at all.

   • Steps: Resting → Depolarization (Na+ in) → Repolarization (K+ out) → Refractory.

2. CNS vs. PNS

   • CNS: Brain/spinal cord (integration).

   • PNS: Nerves outside CNS (sensory/motor).

3. Neurons

   • Most common: Multipolar (e.g., motor).

   • Structure: Dendrites (receive), cell body, axon (transmit), myelin (insulate).

   • Types: Sensory (afferent), motor (efferent), interneurons.

4. Reflex Arc

   • Example: Knee-jerk.

   • Path: Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector.

5. Senses

   • Vision:

     • Most acute: Fovea (cones).

     • Accommodation: Lens changes shape.

     • Disorders: Myopia, hyperopia, cataracts.

   • Taste/Smell: Chemoreceptors.

Cardiovascular System

1. Blood

   • Cell types:

     • Erythrocytes (RBCs: O₂/CO₂).

     • Leukocytes (WBCs: immunity).

     • Platelets (clotting).

   • Plasma: Liquid (water, proteins, electrolytes).

   • Normal pH: 7.35–7.45.

2. Blood Vessels

   • Arteries: Oxygenated blood from heart.

   • Veins: Deoxygenated blood to heart (valves).

   • Capillaries: Gas/nutrient exchange.

3. Heart

   • Path: RA → RV → Lungs → LA → LV → Body.

   • Pacemaker: SA node.

   • Sounds: "Lub-dub" (valves closing).

   • Layers: Pericardium, myocardium, endocardium.

Respiratory System

1. Pulmonary Ventilation

   • Inspiration: Diaphragm contracts (volume up, pressure down).

   • Expiration: Diaphragm relaxes (volume down, pressure up).

2. Key Structures

   • Epiglottis: Covers trachea.

   • Larynx: Voice box.

   • Pleural membrane: Reduces friction.

3. Lung Volumes

   • Tidal volume:

     • Normal breath (
       {\approx}500
       mL).

   • Vital capacity: Max inhale/exhale.

4. CO₂ Role: Regulates blood pH (bicarbonate).

Digestive System

1. Path of Food

   • Mouth → Esophagus → Stomach → Small intestine → Large intestine → Anus.

2. Key Organs

   • Liver: Bile, detoxifies.

   • Gallbladder: Stores bile.

   • Pancreas: Enzymes (amylase, lipase), insulin.

3. Absorption

   • Nutrients: Small intestine (villi).

4. Teeth

   • Adult: 32.

   • Structure: Enamel, dentin, pulp.

5. Terms

   • Bolus: Chewed food + saliva.

   • Chyme: Partially digested food from stomach.