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MCAT Biology Lecture 7


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Path of blood
Left ventricle, aorta, arteries, arterioles, capillaries. Venules, veins, superior and inferior vena cava right atrium.
Right venticle, pulmonary arteries, arterioles, capillaries of lungs. Venules, veins, pulmonary veins, left atrium.
sinoatrial node (SA node)
autorhythmic pacer of heart in right atrium.
atrioventricular node (AV node)
recieves action potential from SA node, but is slow to contract. Delays ventrical contraction so atria can finish before ventricals contract.
artery contractions
arteries wrapped around with smooth muscle innervated by sympathetic nervous system. used to reroute blood and regulate bloodpressure.
domeshaped muscle, skeletal, below lungs. Allows breathing.
throat, passage way for food/air.
systole, diastole
ventricles contracting, relaxation of heart and then contraction of atria.
bundle of His
conductive fibers in the ventricle wall. potential branches via Purkinje fibers that fork off bundle, allowing for uniform and strong contraction throughout heart.
vagus nerve
innervates SA node, slows contractions down. parasympathetic.
venules, veins
veins contain much more blood by volume than arteries. Blood slowest in capillaries, next slowest in veins. Veins have valves to prevent backflow.
microscopic blood vessels, one cell thick. Use pinocytosis, diffusion or transport, fenestrations, or movement through cell spaces. Initially hydrostatic pressure more than osmotic, water flows out. At end, reverse is true. 10% fluid loss to interstitium -> lymph.
nasal cavity
filters moistens warms air. Coarse hair at front. Mucus from goblet cells traps/moistens. Cilia move mucus and dust back to pharynx for swallowing or spit.
behind epiglottis. voice box, contains vocal cords. stimulates coughing if nongaseous material enters.
in front of esophagus. ringed cartilage covered by ciliated mucous cells that move dust towards pharynx.
lt and rt split off trachea, branch into bronchioles which terminate in alveoli.
grapelike clusters where gas exchange takes place.
4 polypeptide subunits, each with a heme group--with iron in the center. Each can combine with one O2, forming oxy hemoglobin. cooperativity, a cascade effect.
oxygen saturation of hemoglobin depends on:
lower O2 affinity if high CO2 pressure, low pH (high H+), high temperature, BPG.
CO2 carried in blood in 3 ways:
physical solution
bicarbonate ion -- the main one!
carbamino compounds
carbonic anhydrase
enzyme to catalyse reversible rx:

CO2+H2O -> HCO3- + H+
A few extra ideas about respiratory system
chemoreceptors monitor CO2 levels in blood and increase breathing rate when they go up. pH and O2 are monitored by peripheral chemoreceptors as well.
Low pH is a result of high CO2 (in acidic form).
lymphatic system
collects excess interstitial fluid and returns to blood. Also large particles. Flow goes through lymph nodes which fight infection. Lymph system is open. Many lymph nodes contain lymphocytes throughout system.
blood composition
blood is connective tissue. centrifuged blood composed of plasma, buffy coat of white blood cells, red blood cells.
plasma composition
proteins, albumin, immunoglobulins (antibodies), fibrinogen(clotting), water, iopns, urea, ammonia etc.
red blood cells, no organelles. Live 120 days, burst in spleen or liver and are broken down.
white blood cells. Have organelles, no hemoglobin. Protect vs foreign invaders.
orgin of blood cells
stem cells in bone marrow
parts of membrane bound cytoplasm torn from megakaryocytes.. megakaryocytes remain in marrow. Platelets function in clotting.
dilation of blood vessels, increased capillary permeability, swelling of tissue cells, migration of macrophages and granulocytes to inflamed area. Impedes spread of infection.
steps in bacterial infection
inflammation, macrophages and neutrophils engulf bacteria. Interstitial goes into lympathic system and lymphocytes are in lymph nodes. Macrophages present antigens to B lympocytes. B lymphocytes use helper T cells to differentiate into memory and plasma cells. plasma cells make antibodies which go into blood and attack bacteria. Memory cells are for secondary response.
types of acquired immunity
humoral or B-Cell
cell mediated or T-cell
primary vs secondary response
2ndary result of memory cells, 20 days to full activation vs 5 days
humoral immunity effective vs:
bacteria, fungi, parasitic protozoans, viruses, blood toxins.
steps in infected cell situation
cell mediated immunity:
T-lymphocytes, mature in thymus where they are tested against self antigens. Differentiate into helper T, memory T, supressor T and killer(cytotoxic) T cells. Killer T cells bond to antigen carrying cells, puncture the cell. Attack transplanted tissue and cancer.

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