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Questions and Answers
Excitation contraction coupling in the myocardial cells is the process where the depolarization wave is propagated over the cardiac muscle fibers then spreads through T-tubules → release of ______ from the terminal cisternae of sarcoplasmic reticulum.
Excitation contraction coupling in the myocardial cells is the process where the depolarization wave is propagated over the cardiac muscle fibers then spreads through T-tubules → release of ______ from the terminal cisternae of sarcoplasmic reticulum.
Ca++
The released ______ binds to troponin C.
The released ______ binds to troponin C.
Ca++
The strength of cardiac muscle contraction is directly proportional to the concentration of ______ in the extracellular fluid.
The strength of cardiac muscle contraction is directly proportional to the concentration of ______ in the extracellular fluid.
calcium
Extracellular calcium enters via L-type Ca++ channels during action potential along ______.
Extracellular calcium enters via L-type Ca++ channels during action potential along ______.
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At the end of plateau of cardiac muscle, Ca++ influx is suddenly stopped and active pumping (reuptake) of Ca++ occurs into SR by Ca++ ATP ase, and outside the cell through T tubules by ______-Ca++ exchanger.
At the end of plateau of cardiac muscle, Ca++ influx is suddenly stopped and active pumping (reuptake) of Ca++ occurs into SR by Ca++ ATP ase, and outside the cell through T tubules by ______-Ca++ exchanger.
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According to Starling's law, an increase in venous return leads to an increase in initial length (EDV) which results in an increase in ______.
According to Starling's law, an increase in venous return leads to an increase in initial length (EDV) which results in an increase in ______.
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Within certain limits, the greater the initial length of the cardiac muscle fibers, the greater the ______.
Within certain limits, the greater the initial length of the cardiac muscle fibers, the greater the ______.
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Positive inotropic agents lead to an increase in ______.
Positive inotropic agents lead to an increase in ______.
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Vagal tone reduces SAN rhythm from 120 beat/min to 70 beat/min, blocking vagus with atropine results in an increase in ______.
Vagal tone reduces SAN rhythm from 120 beat/min to 70 beat/min, blocking vagus with atropine results in an increase in ______.
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Marked increase in extracellular K+ may stop the heart in ______.
Marked increase in extracellular K+ may stop the heart in ______.
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Study Notes
Excitation-Contraction Coupling in Myocardial Cells
- Depolarization wave spreads through cardiac muscle fibers, initiating contraction.
- Signal travels via T-tubules, leading to calcium release from sarcoplasmic reticulum terminal cisternae.
- Released calcium ions bind to troponin C, facilitating muscle contraction.
Calcium's Role in Contraction Strength
- Strength of cardiac muscle contraction is directly proportional to extracellular calcium concentration.
- Calcium enters myocardial cells through L-type calcium channels during the action potential phase.
Calcium Handling and Reuptake
- At the end of the plateau phase of cardiac muscle action potential, calcium influx ceases.
- Active reuptake of calcium into the sarcoplasmic reticulum occurs via calcium ATPase.
- Calcium is also extruded from the cell through T-tubules utilizing the sodium-calcium exchanger.
Starling's Law and Cardiac Function
- According to Starling's Law, increased venous return results in enhanced end-diastolic volume (EDV).
- Greater initial length of cardiac muscle fibers correlates with increased contraction strength.
- Allows the heart to adjust its output in response to varying levels of venous return.
Effects of Inotropic Agents and Autonomic Regulation
- Positive inotropic agents enhance the strength of muscle contractions by increasing calcium availability.
- Vagal tone reduces the heart rate from 120 beats per minute to approximately 70 beats per minute.
- Atropine administration blocks vagal effects, causing an increase in heart rate.
Effects of Extracellular Potassium Levels
- Significant increases in extracellular potassium can lead to cardiac arrest.
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Description
Test your knowledge on the ability of the cardiac muscle to convert chemical energy into mechanical energy for pumping blood. Explore topics like excitation-contraction coupling in myocardial cells and the process of cross bridge cycling for contraction.
