What's the difference between Vagus and Phrenic Nerves?

[chilenoctm]

Could anyone explain to me the difference between the vagus and phrenic nerves??

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[pepocho]

Structure-wise or function-wise?

Structure-wise : Vagus nerve is the Cranial nerve X ( or ten), it is primarily known for its parasympathetic functions. It is also known as the "wandering" cranial nerve because it has a zillion little nerves branching off of it
Courtesy of WikiPedia: The phrenic nerve originates mainly from the 4th cervical nerve,[trochlear cranial nerve] but also receives contributions from the 5th and 3rd cervical nerves [trigeminal and optic cranial nerve respectively] (C3-C5) in humans.[1] Thus, the phrenic nerve receives innervation from parts of both the cervical plexus and the brachial plexus of nerves.

Functionwise:
Vagus Nerve is known to have a huge number of functions. Go ahead and check out its wikipedia page for functions, its a lengthy paragraph, and I am sure that is not all its function. Like mentioned before, Vagus nerve is more known for its parasympathetic functions. For example, the vagus nerve innervates the heart and it is one of the primary function (if not the primary reason) why the heart is able to have a resting rate of 60-80 bpm (whereas the Sinoatrial node has an instrinsic rate of 100bpm). If the vagus nerve were to be cut from the heart, theoretically the heart will begin beating 100 bpm.

Phrenic nerve- Its most important function is the innervation of the diaphragm. It controls the contraction of it and allows us to breath.


TL;DR

Vagus- cranial nerve X, important parasympathetic cranial nerve
Phrenic nerve- innervates diaphragm, controls breathing

 

[akinetopsia]

They both run bilaterally down the neck and thorax. Right vagus/left vagus; right phrenic/left phrenic. Vagus n. runs inside the carotid sheath with the common carotid artery(and internal carotid artery), internal jugular vein and deep cervical lymph nodes on each side. Some people remember this by thinking "CVI" for the contents of the carotid sheath minus the lymph nodes. To remember the origin of the phrenic nerves, think "C3-C4-C5 Keeps you alive" i.e. breathing, even though it originates primarily from the C4 root, and the left phrenic nerve pierces the diaphragm.

 

[Jepstein30]

the better question is.. why are you studying this for the MCAT?

seriously no point.. way too detailed. You only need vary basic anatomy/physiology.. no where near this much.