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Exercise 30

Decreasing heart rate is under the control of what nervous division?

parasympathetic division

What is the resting heart rate of the average person?

70 to 80 beats per minute

Are there more sodiem ions inside or outside a cardiac muscle cell during the resting membrane potential?

more sodium ions outside

What happens to sodium ions when a membrane depolarizes?

sodium channels open; sodium inflow

What happens to the heart when an action potentail is generated in the SA node?

The impluse is conducted throughout the heart and the heart contracts which is myocardial contraction

The movement of electrochemical impulses in the myocarduim is called .... conduction.


What effect do calcium slow channels have on shortening or lengthing the contraction time of the heart muscle?

lengthening - makes calcium channels more permeable and repolarization accures

Beta-adrenergic blockers bind to norepinephrine sires, preventing these neurotransmitters from having an effect. What effect would the use of "beta blocker" have on heart rate?

Beta blockers cause calcium channels to open, decreasing the threshold and causeing more rapid firing of the SA node. Which will lower the heart rate.

What heart sound is produced by the closeure of the atrioventricular valves in the heart?


A heart murmur is normally caused by what event?

imperfect closure of valves (atrioventricular and similunar valves)

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