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46 Cards in this Set

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  • Back
a calculation of mean arterial blood pressure is the product of which two factors?
cardiac output and total peripheral resistance (COxTPR=MAP)
how is TPR calculated from a series of parallel vascular beds?
adding the inverse of the resistances for each bed.
what is the RMP of a cardiac muscle cell?
approx. -90mV
are the proteins at the interior of a cardiac muscle cell positively or negatively charged?
negatively
what are the approximate concentrations of Na+, K+, and Ca++ in an average cardiac muscle cell?
Inside:
K+ = 145mM
Na+ = 5mM
Ca++ = 10^-7mM

Outside:
K+ = 4mM
Na+ = 140mM
Ca++ = 2mM
which two pumps are responsible for maintaining the extra- and intracellular ion concentrations? how many of each ion is exchanged in each of these two pumps?
Na+/K+ pump and Na+/Ca++ pump; 3Na+/2K+ and 3Na+/1Ca++
Which of the constitutive pumps on cardiac muscle cells requires ATP for energy?
Na+/K+ pump
what effect do proteins inside muscle cells have on cations?
attract cations into cell
at rest, is cardiac muscle cell permeability to K+ or Na+ greater? by how much?
K+ by almost 100 times
which, K+ or Na+, has a higher tendancy to leak from the cell at rest?
K+, due to large permeability
what does the Nernst equation determine?
the electrical equilibrium potential
why is the RMP much closer to the K+ equilibrium constant than to that of Na+?
Because the cell is much more permeable to K+
which equation accounts for both resting concentrations AND permeabilities in cells?
Goldman
what activity characterizes phase 0 in cardiac muscle cell action potentials? which type of channel is mostly responsible for this action?
rapid depolarization; tetrodotoxin-sensitive (fast) Na+ channels.
the small repolarization that characterizes phase 1 is the result of what 2 factors?
1) transient outward movement of K+
2) inactivation of the fast Na+ channel
phase 2 is also known as which phase in the cardiac muscle cell action potential?
plateau
which three events characterize phase 2 of the cardiac muscle cell action potential?
1) inward Ca++ current from L-type Ca++ channels, catecholamine-sensitive
2) increase in Na+ permeability via slow channel
3) decrease in K+ permeability , minimizing K+ loss from cell.
which event in phase 2 is often referred to as 'inward rectification'?
decrease in K+ permeability
phase 3 is characterized by which 3 events?
1) inactivation of slow Na+ channels
2) inactivation of L-type catecholamine-sensitive Ca++ channels
3) increase in K+ permeability
what is the main difference between action potentials in nerve cells and cardiac cells?
nerve cells have much shorter refractory period; cardiac cells need more refractory time to allow heart to beat in a regulated fashion
what is the definition of the absolute refractory period? what channel action characterizes this period?
a period during which no stimulus, regardless of how large, can produce a response; the inactivation of fast Na+ channels
what is the definition of the relative refractory period? what channel action characterizes this period?
a period during which a larger-than-normal stimulus is required to generate a new action potential; many (but not all) of the fast Na+ channels are reset
the supranormal period is characterized by _____ than normal stimuli which result in responses that are often _____ than normal.
lower; lower
what is tetany?
sustained uncontrolled muscle contractions
which 3 factors determine the time course of cardiac action potentials, both slow- and fast-response?
1) ion channel permeability
2) membrane potential
3) ion concentration gradients
while phase 4 in fast-type cardiac action potentials is characterized by a return to RMP, the phase 4 in slow-type AP's is characterized by what?
spontaneous depolarization
the unique action of phase 4 in slow-type cardiac action potentials is characterized by which 3 processes?
1) slowly decreasing K+ permeability
2) slow increase in Ca++ permeability
3) small increase in Na+ permeability (non-fast Na+ channels)
phases 0-2 in slow-type cardiac action potentials are characterized by which 2 processes?
1) Ca++ entry
2) slow Na+ channels
phase 3 (repolarization) in slow-type cardiac action potentials are characterized by which 3 processes?
1) inactivation of Ca++ channels
2) inactivation of Na+ channels
3) increased K+ permeability
which cells use the slow-type cardiac action potentials?
SA and AV nodes
which cells in the heart are responsible for the rate of the heart's beating?
SA node cells
does parasympathetic stimulation increase or decrease heart rate? sympathetic?
decreased; increased
trace blood through the heart from the superior and inferior vena cavae to the aorta
Superior/inferior vena cavae, bring blood into heart --> right atrium --> tricuspid valve --> right ventricle --> pukmonary artery --> lungs --> via pu,onary veins to left atrium (thin walled) --> left ventricle --> mitral valve --> aorta, rest of body.
what controls the size of the arteries which enter the capillaries?
smooth muscle
what is the approximate RMP of AV and SA node cells?
-55mV
what is the driving force for the Na+/Ca++ exchange pump? how many Na+ atoms are pumped for how many Ca++ atoms? in which direction?
Na+ gradient; 3 Na+ pumped inside cell for every 1 Ca++ pumped out of cell
the flow out K+ out of the cell is balanced by which force
attractive force from negatively charged proteins attracting K+ ions into cell
what happens if KCl is injected into someone's blood? why?
it would most likely cause an MI because all cells would contract at same time.
what is the action of ouabain and digitalis?
poisoning of Na+ pump
at what points during the fast-type cardiac AP are inactivation and activation gates of tetrodotoxin-sensitive Na+ channels open and closed?
initially, activation gate closed and inactivation gate closed. following stimulation, activation gates open, resulting in depolarization. immediately following depolarization, inactivation gates close, throwing cell into absolute refractory period. As many inactivation gates open and activation gates simultaneously close, the relative refractory period begins. Eventually, all channels have a closed activation and open inactivation channel open and the cell has been reset for another AP.
which channel which contributes significantly to fast-type cardiac AP plays nearly no role in slow-type AP's?
fast-type, tetrodotoxin-sensitive Na+ channel
what effect do sympathetic and parasympathetic stimulation have on slow-type cardiac AP's?
SYMPATHETIC stimulation makes a stronger, faster heartbeat and PARASYMPATHETIC stimulation makes a slower heartbeat.
in which cardiac chamber is the SA node located? the AV node?
right atrium; between atria and ventricles
why is it helpful that AV node rate is slightly slower than that of SA node?
so that ventricles have time to fill completely before contracting
why is conduction in Purkinje fibers so much quicker than that of AV or SA nodes?
because you want entire ventricle muscle to contract forcefully at the same moment
what is represented by the P wave in an ECG? QRS wave? T wave
P = atrial depolarization and contraction
QRS = ventricular depolarization and contraction
T = ventricular repolarization