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Biological Sciences
Peter A.Bowler

e109 lecture notes 10/31/12 Cardiovascular system (Ch. 14) -atria contract together, then ventricles contract together -volume of blood leaving left ventricle = volume of blood leaving right ventricle *know difference btwn pulmonary and systemic circulation -cardiac output = volume of blood leaving either ventricle per unit time -the volume of blood leaving the left ventricle (per contraction) must equal the volume of blood leaving the right ventricle (per contraction) even though the systemic circulation has a much larger total volume that the pulmonary circulation -the volume of blood leaving either atrium per contraction = the volume of blood leaving either ventricle (per contraction) 1. RA  2. RV  pulmonary circulation 1. LA 2. LV  systemic circulation 2. contraction of RAand LA (let’s say 100 mL each)—if these amounts weren’t equal, you would get a buildup of circulation in the system 3. RV and LV send out 100 mL in circulation 4. The net transfer is going to be the same between the two circuits of the system One way valves -Cusps of right AV (tricuspid) valve: between an atrium and a ventricle (blood goes from atrium to ventricle) -Cusp of leftAV (bicuspid) valve (*tricuspid vs. bicuspid doesn’t matter) -Pulmonary semilunar valve: connects the right ventricle to pulmonary circulation -Aortic semilunar valve -During ventricular contraction, the AV valves remain closed to prevent black flow to the atria -flow of blood doesn’t reverse in the system because of one-way valves and mechanical stops: can only open in one direction -Fig 14.7 Cardiac muscle cells What is the relationship between this figure 14-8 and the heart as a whole -this is the zoomed in version of the walls of the muscular heart chambers -cardiac cells are uninucleate, branched, and connect to each other through intercalated disks Intercalated disks -desosomes (hold cells together, transmit force) -gap junctions (electrical signals transmitted between cells b/c of the continuity) 2 types of cells in the heart: 1) 99% cardiac muscle cells (contractile) 2) 1% autorhythmic cells (pacemakers) –important in generating heart beat The events of contraction in a CARDIAC muscle cell and how are they different/similar to contraction in skeletal and smooth muscle cells (Review-Table 12.3) 1. cardiac muscle: action potential enters from the adjacent cell [can do this b/c of intercalated disks—spreads to all adjacent cardiac cells in the vicinity] a. skeletal muscle: action potential generated when the cell is depolarized by AcH that is released from the neurotransmitter that stimulated it. It doesn’t just contracts, but only when it is stimulated by a neurotransmitter/motor neuron; doesn’t have intercalated disks and not like cardiac muscle b. smooth muscle: some smooth muscles are connected by gap junctions 2. cardiac muscle: T-tubule (transverse tubule)-- a. skeletal muscle: same b. smooth muscle: no T tubules 3. cardiac muscle: Voltage-gated Ca2+ channels open. Ca2+ enters the cell a. skeletal: no not like skeletal b/c Ca2+ didn’t come rushing in from the ECF (outside). It only entered from the sarcoplasmic reticulum b. smooth: it is like some smooth muscle cells 4. cardiac muscle: Ca2+ induces release of more Ca2+ through ryanodine receptor- channels. a. skeletal: not triggered by increase of Ca2+ b. smooth: somewhat like cardiac c. all three do get an increase in Ca2+ in the cytoplasm though 5. cardiac muscle: Ca2+ signal initiates contraction a. true for all 6. cardiac muscle: Ca2+ binds to troponin to initiate contraction a. skeletal: exactly the same b. smooth: does not have troponin, but Ca2+ is a necessary part of contraction 7. cardiac muscle: Relaxation occurs when Ca2+ unbinds from troponin a. skeletal: same b. smooth: not 8. cardiac muscle: Ca2+ is pumped back into SR for storage
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