Question

16. Which of the following explains the action of Epinephrine at the SA node?

a) It binds to Beta 1 receptors on the SA node increasing the strength of cardiac muscle contraction

b) It binds to muscarinic receptors on the SA node prolonging repolarization

c) It binds to beta 1 receptors on the SA node causing rapid opening of HCN causing the membrane increasing the frequency of action potentials

17. Which of the following describes the action of a cholinergic antagonist at the SA node?

a) It would decrease heart rate

b) It would increase heart rate

c) It would activate muscarinic receptors on the SA node

d) It would block Beta 1 receptors on the SA node

18. Atropine is a cholinergic antagonist drug. Which of the following describes its action?

a) It binds to Beta 1 receptors in the SA node, increasing heart rate

b) It will stimulate Beta 1 receptors on the SA node and increase heart rate

c) By blocking acetylcholine at its muscarinic receptor it increases heart rate

d) No answer text provided.

19. Action potential produced and propagated along an axon. Why?

a) Action potentials directly cause the phosphorylate calmodulin

b) Action potentials cause the opening of calcium ion channels at the axon tip

c) Action potentials directly cause the phosphorylate vesicles containing neurotransmitters

d) No answer text provided.

20. How will an increase strength of a stimuli at a receptor impact an action potential?

a) It will shorten the duration of the absolute refractory period of an action potential

b) It will increase the amplitude of an action potential

c) No answer text provided.

d) It will increase the frequency of an action potneital

ANSWERS ONLY - No need for explanation :)

Answer 1

16. C

Epinephrine binds with the beta 1 receptors on the heart and causes the rapid opening of the sodium channels which would then increase the frequency of action potentials resulting in increased heart rate.

Epinephrine doesn't bind to muscuranic receptors

17. B

Cholinergic antagonist will increase the heart rate (as cholinergic agonist will decrease the heart rate)

18. C

Atropine is an cholinergic antagonist and it blocks the muscuranic receptors on the heart and increase the heart rate

Atropine doesn't have any action on beta receptors

19. B

Axon potentials cause the opening of the calcium ion channels at the axon tip

20. B

Increase in the strength of the action potential will increase the amplitude of the action potential

Hope this helps.... Thank you!!!