cardiology E4

what does it mean for the systemic circulatory system to be in parallel? what does this allow for?

means that blood goes directly to a tissue and then goes directly back to the heart; does not go from one tissue to another

allows for blood to be shunted to the appropriate tissue in the appropriate amount

TISSUE METABOLISM DICTATES FLOW

the R/L ventricles pump the _________ amount of blood

same

describe the valves of the heart, the structure, and function

left AV (bicuspid) and right AV (tricuspid) have chordae tendineae to prevent prolapsing; LUB

aortic SL and pulmonary SL do not have chords; balloon out with leakproof seam

five steps of systole and diastole

1. late diastole: heart is relaxed and filling passively

2. atrial systole: top off

   1. S1

3. isovolumic ventricle systole: vents contracting but pressure has not increased enough to overcome aorta

4. ventricular ejection: vents > aortic pressure

5. ventricular relaxation (early diastole): ventricles relaxing and are empty

end systolic volume

65mL

remaining volume in the heart; reaches this at the end of ventricular systole when blood has been ejected into the aorta. accompianied with heart sound 2 of SL valves and dicrotic notch. remains at 65mL during early diastole.

end diastolic volume

135mL

isovolumetric ventricular contraction; accompanied by heart sound 1 of AV valves

autorhythmic cells

• unstable resting potential

• pacemaker potential followed by action potential

• inward Na+ current

• inward Ca2+ current

• outward K+ current

• resting membrane of -60mV

steps of pacemaker cell depolarization

1. Na+ funny channels cause a slow depolarization towards threshold (40)

2. Na+ channels close and t-type Ca2+ channels open, bringing the membrane to threshold

3. transient channels close and L-type Ca2+ channels open during rising phase

4. peak - ca2+ close and k+ open

5. repolarization due to k+ flow out of the cell

6. hyperpolarization causes funny sodium channels to open again

contracile cells

• connected by gap junctions (immediate electrical signal conduction) and intercalated discs (tightly bind)

• resting membrane potential -90

• stable resting membrane potential

• long plateau caused by calcium

• absolute refractory period

steps of contractile cell action potential

• pm potential causes immediate firing of contractile cells and Na+ channels to open

• steep depolarization caused by Na+ influx

• peak - na+ channels close, transient k+ channels open for a blip

• t K+ channels close, L-type calcium channels open and cause plateau

  • L-type calcium channels close and K+ channels open, repolarization

purpose of plateau

allows calcium influx into the cell, which triggers opening of ryanodine receptors on SR and causes further intracellular calcium release. this causes cross bridging and contraction!

longer plateau = longer contraction