43. Also please explain how ions control contraction of cardiac muscles
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The answer is (2)
During hyperpolarization K+ is depleted from approximately 3% of the total cardiac muscle volume, and that the replenishment of K+ occurs primarily by K+ diffusion from a much larger fraction of the extracellular space.
Like a neuron, a given myocardial cell has a negative membrane potential when at rest. Stimulation above a threshold value induces the opening of voltage-gated ion channels and a flood of cations into the cell. The positively charged ions entering the cell cause the depolarization characteristic of an action potential. Like skeletal muscle, depolarization causes the opening of voltage-gated calcium channels and the release of Ca2+ from the t-tubules. This influx of calcium causes calcium-induced calcium release from the sarcoplasmic reticulum, and free Ca2+ causes muscle contraction. After a delay, potassium channels reopen, and the resulting flow of K+ out of the cell causes repolarization to the resting state.
Regards
The answer is (2)
During hyperpolarization K+ is depleted from approximately 3% of the total cardiac muscle volume, and that the replenishment of K+ occurs primarily by K+ diffusion from a much larger fraction of the extracellular space.
Like a neuron, a given myocardial cell has a negative membrane potential when at rest. Stimulation above a threshold value induces the opening of voltage-gated ion channels and a flood of cations into the cell. The positively charged ions entering the cell cause the depolarization characteristic of an action potential. Like skeletal muscle, depolarization causes the opening of voltage-gated calcium channels and the release of Ca2+ from the t-tubules. This influx of calcium causes calcium-induced calcium release from the sarcoplasmic reticulum, and free Ca2+ causes muscle contraction. After a delay, potassium channels reopen, and the resulting flow of K+ out of the cell causes repolarization to the resting state.
Regards