Test Guide Unit 6 Human Physiology

Human Physiology Digestive System Organs ❖ Mouth - Mechanical (tongue and teeth) + chemical digestion (salivary amylase) ❖ Esophagus - No digestion occurs ❖ Stomach - hydrochloric acid (pH = 2-3) activates enzyme pepsinogen into pepsin, which breaks down proteins ❖ Small intestine - contains amylases, lipases, proteases (all digestion is finished in the duodenum, or first 10 inches) ➢ Has villi and microvilli (fingerlike projections that absorb nutrients efficiently) ❖ Liver - has many functions ➢ Produces bile ➢ Neutralizes acids in food from stomach ➢ Makes cholesterol, nitrogenous waste, and urea ➢ Detoxifies the blood (alcohol + drugs) ❖ Gallbladder - stores bile for liver ❖ Pancreas - makes digestive enzymes for small intestine + makes sodium bicarbonate to neutralize stomach acid ❖ Large intestine (colon) - no digestion ➢ undigested waste is removed ➢ Water is reabsorbed ➢ Vitamins (B, K, folic acid) are produced ❖ Rectum - temporarily stores feces until it is removed from the body Gas Exchange ❖ Happens in tiny air sacs in lungs (alveoli) ❖ Negative pressure lets humans breathe (expanding chest decreases pressure in lungs + draws air in) ❖ Hemoglobin molecules transport oxygen in the blood; carbon dioxide dissolves into blood plasma Blood Clotting ❖ Starts when clotting factors are released ❖ Platelets release thromboplastin which changes prothrombin into thrombin ➢ This causes fibrinogen to change into fibrin; fibrin makes up the clot Path of Blood ❖ Right atrium ❖ Right atrioventricular valve (also called tricuspid valve) ❖ Right ventricle ❖ Pulmonary semilunar valve ❖ Pulmonary artery ❖ Lungs ❖ Pulmonary vein ❖ Left atrium ❖ Left atrioventricular valve (also called bicuspid valve) ❖ Left ventricle ❖ Aortic semilunar valve ❖ Aorta ❖ All cells in body ❖ Returns to heart through vena cava ➢ *Arteries transport blood away from heart (high pressure), veins transport blood toward heart (low pressure) Hormones ❖ Steroid hormones - can pass through cell membrane + bind to receptor inside cell ➢ This creates a hormone-receptor complex that triggers a response from nucleus ❖ Polypeptide hormones - cannot pass through cell membrane; binds to receptor on surface of cell ➢ 2nd messenger is triggered in cytoplasm, which finally triggers a response from nucleus Feedback Mechanisms ❖ Negative feedback - maintains homeostasis ❖ Positive feedback - enhances a response that already exists Nervous System ❖ In vertebrates: ➢ Central nervous system (CNS) - brain + spinal cord ➢ Peripheral nervous system (PNS) - all nerves outside of CNS ■ Sensory: carries information from nerve endings/sensory receptors ■ Motor: consists of 2 systems ● Somatic system - controls voluntary muscles ● Autonomic system - controls involuntary muscles ◆ Sympathetic: ➢ Increased heartbeat + breathing ➢ Glycogen converted to glucose by liver ➢ Fight-or-flight response ➢ Adrenaline raises blood sugar levels ➢ Increased gas exchange ◆ Parasympathetic: ➢ Opposite functions of sympathetic ➢ Decreases heartbeat + breathing ➢ More digestion ➢ Calms body down ❖ Basic unit of nervous system: neuron ➢ When axon is polarized (at rest) sodium and potassium stay on opposite sides of membrane ➢ impulse/action potential passes through an axon and causes a wave of depolarization (makes sodium flow in, potassium flow out). ➢ The sodium-potassium pump then restores neuron’s resting potential during the refractory period. ❖ Impulse travels along axon electrically; across synapse chemically ➢ Vesicles release neurotransmitters that travel across synapses Eye Parts ❖ Cones - photoreceptors that can detect differences in color; located in retina ❖ Cornea - clear covering that protects eye + lets light into eye ❖ Humor - fluids that the eyeball is filled with; maintains eye shape ❖ Iris - controls amount of light that enters eye ❖ Lens - focuses light directly onto retina ❖ Pupil - hole in middle of iris ❖ Retina - turns light into nerve impulses that carry information to brain through optic nerve ❖ Rods - photoreceptors that are sensitive but don’t detect color; located in retina Ear Parts ❖ Auditory canal - the ear canal (where sound enters the ear) ❖ Cochlea - part of the inner ear that is filled with fluid; sends nerve impulses to brain ❖ Ear bones - includes stirrup, hammer, anvil ❖ Eustachian tube - makes sure pressure between environment and inner ear is equal ❖ Oval window - sends pressure waves to cochlea ❖ Semicircular canals - helps maintain balance, filled with fluid ❖ Tympanum - eardrum that vibrates when sound waves hit it Excretion ❖ Basic unit of kidney: nephron ❖ Nephron functions: ➢ Filtration of glucose, salts, vitamins, urea, etc. from the blood; happens in Bowman’s capsule + is nonselective ➢ Secretion is active and selective uptake of molecules that were not filtered into Bowman’s capsule ➢ Reabsorption is when water + nutrients filtered into nephron are absorbed into capillaries, both passive and active transport, happens in the tubule, loop of Henle, and collecting tubule ➢ Excretion is when metabolic wastes are removed from the body