cardiovascular physiology

Question 1

conducting cells

Answer 1

special cardiocytes that initiate and distribute action potentials in heart

Question 2

nodes

Answer 2

clusters of autorythmic cells that generate spontaneous action potentials in heart

Question 3

what happens to a autorhythmic cell in node with unstable resting potential

Answer 3

Na+ leaks in causing gradual depolarization “prepotential.” this causes gated Ca++ channels to open and a influx of Ca++ (depolarization). Ca++ channels closes as K+ voltage channels open causing an efflux of K+ (repolarization)

Question 4

has unstable resting potential

Answer 4

autorhythmic cells in nodes

Question 5

how does action potential spread along conducting pathways

Answer 5

through gap junctions at intercalated discs

Question 6

what nodes does the parasympathetic n.s innervates and what does it do

Answer 6

Acetylcholine slows heart down

Question 7

what nodes does the sympathetic n.s innervated and what does it do

Answer 7

norepinephrine speeds heart up

Question 8

why does the pacemaker firing trigger all-or-none contraction of a whole heart

Answer 8

because all cells are connected by gap junctions at the intercalated discs

Question 9

cardiac muscle anatomy and its functions (5)

Answer 9

gap junctions at intercalated discs (allows ions to move from cell to cell)
desmosomes (anchoring proteins prevent separation of contracting cells)
many mitochondria (cardiac muscle very fatigue resistant)
myofibrils branch
t-tubules trigger release of calcium from sarcoplasmic reticulum