circulatory system part 3 Flashcards
Control of contraction:
vertebrate heart is what?
myogenic
cradiomyocytes do what?
produce spontaneous rhythmic depolarization (do not require nerve signal)
cardiomyocytes function how?
electrically coupled via gap junctions to ensure coordinated contractions
AP’s pass directly from cell to cell
pacemaker cells are what are where?
cells are in the sinus venosus in fish
in the right atrium vertebrates (SA node)
pacemaker cells are derived from what?
cardiomyocytes
pacemaker charactersitics
small with few myofibrils, mitoch, or other organelles
do not contract
have unstable resting potential that drifts up
What are If channels?
Funny current inward Na+ allows influx produces pacemaker potential
what are T-type channels?
Ca+ channels does not require much to depolarize to activate and will activate L-type
What are L-type channels
long lasting has long AP’s
Control of Pacemaker cells
Increase in heart rate
norepinephrine released from sympathetic neurons and epinephrine released from adrenal cortex
more pacemaker (Funny) and Ca+ channels open
rate of depolarization and frequency of AP’s increase
Decrease in heart rate
Vagus nerve
Ach released from parasympathetic neurons
more K+ channels Open
pacemaker cells hyperpolarize
time for depolarization takes longer, frequency of AP’s decrease
At rest Vagus parasympathetic influence is dominant over sympathetic
Extended AP’s
AP’s in cardiomyocytes differ from those in skeletal muscles
What is the plateu phase?
extended depolarization that corresponds to refractory period and that lasts as long as the contractions
caused by Ca+ entry via L-type channels
prevents tetnus
