Question

A person has cold, painful fingertips because of excessively constricted blood vessels in the skin. Which of the following alterations in autonomic function is most likely to be involved?

a. Low concentration of circulating epinephrine

b. High sensitivity of arterioles to norepinephrine

c. High sensitivity of arterioles to nitric oxide

d. Low parasympathetic nerve activity

e. Arterioles insensitive to epinephrine

Answer 1

Answer:

Option D (Low parasympathetic nerve activity)

Explanation: The two branches of the peripheral nervous system include the somatic neural system which innervates the voluntary parts of the body whereas the second branch is the autonomic nervous system which controls the functioning of the involuntary activities of the body. It has two branches; the sympathetic nervous system and the parasympathetic nervous system which opposes the functioning of each other.

Given in the question that the person is experiencing a cold, and painful fingertips because of the excessively constricted blood vessels in the skin. This effect is called as the Raynaud Phenomenon commonly abbreviated as RP. Since there is a constriction in the blood vessels it clearly is establishing the fact that there is the involvement of the sympathetic nervous system.

Sympathetic nervous system releases the neurotransmitters like epinephrine which constricts the blood flow through the blood vessels thereby increasing the blood pressure.

Condition A: when there is a low concentration of the circulating epinephrine; this signifies that the blood vessels cannot effectively get constricted due to the low concentration of the epinephrine. This thus will not be able to lead to a condition of extremely constricted blood vessels

Condition B: High sensitivity of arterioles to norepinephrine; norepinephrine opposes the functioning of the epinephrine. Thus as the blood vessels are extremely sensitive to epinephrine; this means they would immediately be made to exhibit vasodilation is response to the neurotransmitter released. This the causes the vasodilation

Condition C: High sensitivity of arterioles to Nitric oxide; Nitric oxide (NO) is known to trigger and induce vasodilation. Thus, the blood vessels sensitive to the nitric oxide are made to undergo vasodilation

Condition D: Low parasympathetic nerve activity; as parasympathetic nerves are known to oppose the functioning of the sympathetic nervous system; this means that the blood vessels will not be vasodilated due to which they will be made to constrict to the maximum levels thus increasing the blood flow within them

Condition E: Arterioles insensitive to epinephrine; as the arterioles are insensitive to the epinephrine; this signifies that the neurotransmitter would fail to exhibit its property of causing vasoconstriction due to which the blood pressure will not increase within the fingers.

Hence, option D is the correct option