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Biology 241 - Accelerated General Human Physiology » Summer 2021 » Lab Q12

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Question #1

Acetylcholine opens potassium channels in the membrane of the pacemaker cells. In this way, acetylcholine hyperpolarizes the membrane, which:

A. moves it farther from threshold so that action potentials (and heart contractions) take place at a slower rate.

B. does not change relative to threshold, so it has no effect on action potential production and heart contractions.

C. moves it closer to threshold so that action potentials (and heart contractions) take place at a faster rate.

Question #2

What is the effect of adrenaline on the amplitude of each contraction and the cardiac output?

A. The contraction amplitude increases and the cardiac output increases.

B. The contraction amplitude decreases and the cardiac output increases.

C. The contraction amplitude increases and the cardiac output decreases.

D. The contraction amplitude decreases and the cardiac output decreases.

Question #3

What is the effect of cooling on heart rate?

A. decreases heart rate due to depolarization of pacemaker cells

B. decreases heart rate due to hyperpolarization of pacemaker cells

C. decreases heart rate due to slowing the rate of ion channels opening and closing

D. increases heart rate due to depolarization of pacemaker cells

Question #4

Cardiac muscle has different characteristics than skeletal muscle. Which of the following describe cardiac muscle, BUT NOT skeletal muscle?

A. has a refractory period and has sarcomeres

B. uses calcium for cross-bridge cycling and recruitment of muscle cells

C. can initiate an action potential intrinsically and action potential lasts about 300ms

Question #5

The prolonged refractory period in the cardiac action potential is produced by:

A. open voltage-gated potassium channels.

B. open voltage-gated calcium channels.

C. closed voltage-gated potassium channels.

D. open voltage-gated sodium channels.

Question #6

Extra ventricular contractions should not happen normally. What is this called when the heart begins to contract with extra ventricular contractions without the correct rhythm?

A. recruitment

B. summation

C. muscle twitch

D. fibrillation

Question #7

The length of the cardiac myocytes will increase if:

A. the end diastolic volume decreases.

B. the end diastolic volume increases.

C. the end systolic volume decreases.

D. the end systolic volume increases.

Question #8

What action best describes Starling's Law of the Heart?

A. The atria restrict blood flow and prevent ventricle expansion.

B. As myocytes stretch, force of contraction increases

C. Cardiac myocytes have limited compliance, so they do not overstretch.

D. The veins contract to restrict blood flow back to the heart.

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