Vagus (X) Nerve

VAGUS (X) NERVE

Q. 1

At the level of Arch of aorta, the relationship of left vagus nerve and left phrenic nerve‑

 A

Phrenic nerve anterior, vagus nerve posterior

 B

Phrenic nerve posterior, vagus nerve anterior

 C

Both in same plane anteroposteriorly

 D

Variable in relationship

Q. 1

At the level of Arch of aorta, the relationship of left vagus nerve and left phrenic nerve‑

 A

Phrenic nerve anterior, vagus nerve posterior

 B

Phrenic nerve posterior, vagus nerve anterior

 C

Both in same plane anteroposteriorly

 D

Variable in relationship

Ans. A

Explanation:

Phrenic nerve anterior, vagus nerve posterior


Q. 2

Bilateral cutting of vagus nerve causes ‑

 A

Decrease heart rate

 B

Decrease respiratory rate

 C

Increase heart rate

 D

Decreased BP

Q. 2

Bilateral cutting of vagus nerve causes ‑

 A

Decrease heart rate

 B

Decrease respiratory rate

 C

Increase heart rate

 D

Decreased BP

Ans. C

Explanation:

Ans. is ‘c’ i.e., Increase heart rate

Aortic nerve (a branch of vagus nerve) carries :‑

i) Baroreceptor afferent from Aortic sinus.

ii) Chemoreceptor afferent from Aortic bodies.

Bilateral sectioning of vagus nerve causes increase in heart rate and BP due to two reasons :‑

i) Abolition of baroreceptor discharge of aortic sinus on RVLM → causing increasing in sympathetic output.

ii)  Inhibition of nucleus ambiguous  → causing decreased parasympathetic tone.

Effect on chemoreceptors afferent is minimal as chemoreceptors are stimulate by low PO, and normally they have no dischange.



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