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Phrenic nerve

Is the phrenic nerve (C3-C5) part of the parasympathetic division.
I just realised that parasympathetic fibres originate from CIII, CVII, CIX and CX.

Does this mean that the phrenic nerve is NOT part of the parasympathetic division? If it is then what about the fibres CIV and CV?

Thanks
Reply 1
The phrenic nerve from the anterior rami of C3-5 is predominantly concerned with sensory and motor innervation of the diaphragm. It is involved in inspiration via pulling down on the central tendon. It's been a little while since secondary for me so if you want any more explained let me know but as I understand it conveys sympathetic fibres. Can I just ask if you are confusing the crainal nerves seeing as after C8 spinal nerves become T1- (possibly comfusing the 12 cranial nerves CNI-XII e.g. Vagus CNX?).

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Original post by jadpan
The phrenic nerve from the anterior rami of C3-5 is predominantly concerned with sensory and motor innervation of the diaphragm. It is involved in inspiration via pulling down on the central tendon. It's been a little while since secondary for me so if you want any more explained let me know but as I understand it conveys sympathetic fibres. Can I just ask if you are confusing the crainal nerves seeing as after C8 spinal nerves become T1- (possibly comfusing the 12 cranial nerves CNI-XII e.g. Vagus CNX?).

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If it arises from the cranium why would it carry sympathetic fibres (which arise from T1-L2)? thank you
Reply 3
Can I ask what you are learning this for as that will help me explain, I find this a little tricky as a med student but simply put:
Parasympathetic=rest and digest
Sympathetic=fight or flight.
Looking back revising I am not sure the phrenic really carries anything more than sensory and motor fibres.
Really this topic gets pretty complicated to explain in a few sentences! Can you explain why you think sympathetic fibres only arise T1-L2 as this isnt something I have ever read, there are 31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 cocygeal) each have a posterior root containing afferent sensory fibres and an anterior roor containing efferent motor fibres.
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Original post by jsmith6131
Is the phrenic nerve (C3-C5) part of the parasympathetic division.
I just realised that parasympathetic fibres originate from CIII, CVII, CIX and CX.

Does this mean that the phrenic nerve is NOT part of the parasympathetic division? If it is then what about the fibres CIV and CV?

Thanks


The phrenic nerve does not contain parasympathetic nerve fibres as far as I know. It does have sympathetic nerve fibres in it, however (SNS is generally thoracolumbar, but not solely so).

You're getting confused between cervical sections of the spinal cord, and the cranial nerves. Cranial nerves III, VII, IX and X have parasympathetic components to them (parasympathetic nerves originate cranioscrally, generally). This is unrelated to the cervical segments (the fact that the numbers there go up to 10, but there are only 8 cervical spinal cord segments should have tipped you off!).

The fact that the phrenic nerve contains both somatic and sympathetic nerve fibres is what allows for autonomous breathing and voluntary breathing. If I choose, I can hold my breath, or breathe in a strange pattern. But if I stop thinking about it, my sympathetic nervous system takes over and regulates breathing for me (via the respiratory centre in the pontomedullary region).
Original post by Hype en Ecosse
The phrenic nerve does not contain parasympathetic nerve fibres as far as I know. It does have sympathetic nerve fibres in it, however (SNS is generally thoracolumbar, but not solely so).

You're getting confused between cervical sections of the spinal cord, and the cranial nerves. Cranial nerves III, VII, IX and X have parasympathetic components to them (parasympathetic nerves originate cranioscrally, generally). This is unrelated to the cervical segments (the fact that the numbers there go up to 10, but there are only 8 cervical spinal cord segments should have tipped you off!).

The fact that the phrenic nerve contains both somatic and sympathetic nerve fibres is what allows for autonomous breathing and voluntary breathing. If I choose, I can hold my breath, or breathe in a strange pattern. But if I stop thinking about it, my sympathetic nervous system takes over and regulates breathing for me (via the respiratory centre in the pontomedullary region).




thanks...I never knew this :smile:

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