CV a&p Flashcards
do skeletal myocytes or ventricular myocytes contain more mitochondria?
ventricular myocytes contain more mitochondria
normal ventricular RMP and what regulates it
-90mV, regulated by potassium
what does hypocalcemia and hypercalcemia do to threshold potential respectively?
hypocalcemia decreases TP (cells depol more easily bc its closer to RMP)
hypercalcemia increases TP
the wave of depolarization throughout the heart is regulated by gap junctions or t tubules?
gap junctions
equilibrium potential
no net movement across cell membrane. inside potential equals outside potential
which equation relates to equilibrium potential
nernst equation
automaticity
ability to generate AP spontaneously ex) SA node and HR
excitability
ability to respond to electrical stimulus by depolarizing and firing an AP. ex) conduction and contractile CV cells
conductance
ability to transmit electrical current. ions are charged and therefore require an open channel.
open ion channel increases conductance of that ion (duh)
lusitropy
rate of myocardial relaxation
dromotropy
conduction velocity through heart
RMP is determined by 3 things
chemical force (concentration gradient)
electrostatic counter force
Na/K/ATPase
what is the primary determinant for RMP
K. the nerve cell continually leaks this at rest
decreased serum K makes RMP more
negative, cells become more resistant to depol
increased serum K makes RMP more
positive, cells depol more easily
what is the primary determinant of threshold potential
calcium
a cell depolarizes when what enters the cell
Na or Ca2+
what happens during repolarization
K leaves the cell or Cl- enters the cell
resistant to subsequent depol during refractory period
hyperpolarization
movement of cells membrane potential to a more negative value beyond baseline RMP.
purpose of Na/K/ATPase
restores ionic balance towards RMP
1. removes Na that enters the cell during depol
2. returns K that has left the cell during repot
for every _______ ions the Na/K/ATPase pump removes, ___________ ions go back into the cell
for every 3 Na ions it removes, 2 K ions go back into cell
what happens during cardioplegia with high K
Na channels get locked in their closed inactive state
5 phases of myocyte AP
0: depol (Na in)
1: initial repol (K in, Cl- out)
2: plateau (K in, Ca2+ out)
3: repol (K out)
4: maintenance of trans membrane potential (K+ out and Na/K/ATPase fx
what’s the point of the plateau phase in a cardiac myocyte (that neurons dont have)
gives myocytes time to contract and eject SV