5. Can cardiac muscle be tetanized? Why or why not? What is the physiological si

Question

5. Can cardiac muscle be tetanized? Why or why not? What is the physiological significance of this for the heart? (1 pt) Compare and contrast excitation contraction coupling in skeletal and cardiac muscle. Be sure that you make clear any differences between the two and the significance of those differences. (1 pt) 6. 7. (a) Resting heart rate in healthy individuals is often around 70 beat per minute. Considering that the SA node depolarizes at a rate much faster than this (ex. 100 times per minute), what is the physiological reason for a resting heart rate of 70 beats per minute? (1 pt) (b) Crash carts in hospitals contain drugs such as epinephrine and atropine for advanced cardiac life support. Describe the mechanism of action for each of these drugs and indicate why would they be used? (1 pt)

Explanation / Answer

5. No, cardiac muscle cannot be tetanized. The longer refractory period in cardiac muscle cells prevents them from getting tetanized. This results in a relatively long relaxation period due to which the heart Chambers can refill with blood.

6.

Cardiac muscle skeletal muscle Has its own excitability (AV node, SA node, Bundle of His). Excited by motor nerve. Action potential transmits to the contractile muscles via gap junction. Acetylcholine binds to muscle membrane and produce an action potential. Action potential propagate along T tubules Action potential propagates along T tubules. Action potential activates dihydropyridine receptors on T tubules and cause an influx of extracellular Ca2+ into the muscle cell. Action potential stimulates dihydropyridine on T tubules and does not cause an influx of extracellular Ca2+ into the muscle cell. Increased intracellular Ca2+ ions activate rynodine receptors and release Ca2+ ions from sarcoplasmic reticulum. Activated dihydropyridine receptors mechanically stimulate rynodine receptors and release Ca2+ ions from sarcoplasmic reticulum. Ca2+ binds to troponin C and begins muscle contaction. Ca2+ binds to troponin C and begins muscle contaction.

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