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25 Cards in this Set

  • Front
  • Back
the coupling of electrical stimulation with mechanical force happens via:
calcium enters the myocyte during Phase__ depolarization
L-type voltage-dependent calcium channels located in ____ and ____
sarcolemma and T tubules
L-type voltage-gated calcium channels open in response to local ____
AP. Thus, calcium diffuses into cytosol from ECF across T-tubule membrane during cardiac AP.
calcium binds to troponin and initiates:
a contraction
in cardiac contractile cells, the L-type calcium channels are located primarily in the _________. these voltage gated channels are opened in response to a local AP.
Calcium diffused into the cytosol from the ECF across the T tubule mumbrane during a cardiac AP.
this small amount of entering calcium triggers the opening of nearby calcium release channels in the adjacent lateral sacs of the sarcoplasmic reticulum. in this way, calcium entering the cytosol from the ECF induces a much larger release of calcium into the cytosol from the intracellular stores.
the resultant local bursts of calcium from the sarcoplasmic reticulum collectively increase the cytosolic calcium pool sufficiently to turn on the contractile machinery.
this extra supply of calcium from the sarcoplasmic reticulum is responsible for the long period of cardiac contraction. this increased contractile time ensures adequate time to eject the blood.
the role of calcium within the cytosol is to bind with the troponin-tropomyosin complex and physically pull it aside so that the cross-bridge cycling and contraction can take place.
in cardiac muscle, the exent of cross bridge activity varies with the amount of cytosolic calcium. various regulatory factors can alter the amount of cytosolic calcium.
removal of calcium from the cytosol by energy dependent mechanisms in both the plasma membrane and sarcoplasmic reticulum restores the blocking action of troponin and tropomyosin, so that:
contraction ceases and the heart muscle relaxes.
some drugs alter cardiac function by:
changing calcium movement across myocardial cell membranes
force of contractions
rise in ECF calcium levels:
prolongs plateau of AP
the more calcium released:
the stronger the contraction (to a certain extent)
involuntary contraction of muscle
refractory period:
the time after AP during which excitable tissue's membrane is unresponsive
cardiac tissue must contract in a responsive, controlled, and reliable manner to create the pressure difference that drives blood thru the cardiovascular system.
the cardiac cycle is the time period from the start of one ventricular contraction to the beginning of the next.
mechanical events of the cardiac cycle include:
contraction, relaxation, and the resultant changes in blood flow. these result from rhythmic changes in cardiac electrical activity.
the cardiac cycle =
alternate periods of systole and diastole
contraction and emptying
relaxation and filling
heart murmurs are:
abnormal heart sounds
heart murmurs are usually assoc. with:
heart disease. murmurs in young people that are not assoc with heart disease are called functional murmurs.
heart murmurs result from:
turbulent flow rather than laminar flow.
the turbulent flow of heart murmurs is caused by:
1. stenotic valves: stiff, narrowed valve; doesnt open sufficiently
2. insufficient, leaky valves: valve that doesnt close completely; usually scarring of valve edges-> dont fit together properly

rheumatic fever is often a culprit for both