Neuroscience 8 - The peripheral nervous system Flashcards Preview

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Flashcards in Neuroscience 8 - The peripheral nervous system Deck (23)
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1
Q

What are the 4 types of neuron in the PNS? And what are their functions?

A
  1. Somatic sensory - carries information from skin/muscle/joints.
  2. Somatic motor - controls striated muscle.
  3. Autonomic sensory - brings sensory information from the internal organs.
  4. Autonomic motor - controls glands or smooth muscle.
2
Q

What is a myotome and a dermatome?

A
  1. Myotome - the muscle that a spinal nerve innervates.

2. Dermatome - the skin that a spinal nerve innervates.

3
Q

Where do somatic neurones originate from?

A

The primary motor cortex in the brain.

4
Q

Is SNS autonomic or voluntary?

A

Can be both voluntary or autonomic (reflexive).

5
Q

Where do autonomic neurones originate from?

A

From the visceral nuclei in the hypothalamus and leave via the autonomic nuclei in the brain stem or spinal cord.

6
Q

What are the 2 divisions of the ANS?

A
  1. Sympathetic - formed by neurones leaving from spinal nerves T1 - L2 (fight or flight).
  2. Parasympathetic - formed by neurones leaving from cranial and sacral nerves (resting and digesting).
7
Q

What are pre and post ganglionic neurones?

A
  1. Pre-ganglionic neurones originate from the brain stem or spinal cord.
  2. Post-ganglionic neurones originate from autonomic ganglia to target organ/tissue.
8
Q

How many pairs of nerves does the PNS consist of? And what are they split into?

A

There are 43 pairs of nerves in the PNS. Split into 12 cranial nerves and 31 spinal nerves.

9
Q

What are the 5 differences between ANS and SNS?

A
  1. SNS has voluntary effectors and ANS has involuntary effectors.
  2. SNS has single motor neurone from spinal cord to target whereas ANS has 2 neuones (ganglionic synapse).
  3. SNS is always stimulatory whereas ANS is both stimulatory and inhibitory.
  4. SNS uses ACh but ANS uses ACh + NE.
  5. SNS does not fire at rest but ANS has a baseline firing.
10
Q

What are ganglia?

A

Cell bodies, synapses and dendrites in the PNS.

11
Q

What is the dorsal and ventral root?

A
  1. The dorsal root is posteriorly located and brings afferent signals from periphery to CNS (sensory).
  2. The ventral root is anteriorly located and brings efferent signals from CNS to periphery (motor).
12
Q

What are rami?

A

They are lateral branches of the spinal cord that carry both sensory and motor fibres. Not the same as ventral and dorsal root ganglia.

13
Q

What are the groups of neurones in the PNS?

A
  1. A group - Have large diameters and are myelinated (high conduction velocity) - alpha, beta, delta and gamma types.
  2. B group - Have smaller diameters but myelinated (low conduction velocity) - autonomic information.
  3. C group - small diameters and not myelinated (low conduction velocity) - dull, aching burning pain and temperature sensation.
14
Q

What are nerve plexuses?

A

They are networks of intersecting spinal nerves. They include the cervical, brachial, lumbar, sacral, celiac and coccygeal plexuses.

15
Q

What is the clinical relevance of dermatomes being innervated by spinal and peripheral nerves?

A

Spinal nerves innervate in a stripey pattern whereas peripheral nerves innervate in a patchy pattern.

16
Q

What are peripheral neuropathies?

A
  1. It is progressive damage affecting PNS nerves.
  2. May impair:
    - Sensation (sensory nerves), tingling numbness.
    - Movement (motor nerves), weakness of hand + feet.
    - Involuntary functions (autonomic nerves), change heart rate and blood pressure.
17
Q

What are causes or peripheral neuropathies? (5)

A

Has many causes.

  1. Metabolic.
  2. Toxic.
  3. Inflammatory.
  4. Traumatic.
  5. Genetic.
18
Q

What is mononeuropathy and polyneuropathy?

A
  1. Mononeuropathy is single nerve affected.

2. Polyneuropathy is when multiple nerves are affected.

19
Q

What is neuropraxia?

A
  1. Selective demyelination of axon sheath causing a reversible conduction block.
  2. Endoneurium and axon still intact.
20
Q

What is axonotmesis?

A
  1. Demyelination and axon loss.
  2. Epineurium and perineurium still intact.
  3. Damage occurs slightly below and proximal to the site of injury.
21
Q

What is neurotmesis?

A
  1. Most severe type of nerve injury.
  2. Complete nerve division and disruption.
  3. Damage to epineurium - no nerve growth.
22
Q

What is electromyography?

A

It is a technique for evaluating and recording electrical activity produced by muscles. Involves placing a needle electrode in the muscle and another on the skin.

23
Q

What are nerve conduction velocity tests?

A
  1. They measure the conduction velocity of nerves in the body. A nerve is stimulated and an electrode is placed downstream that measures the time taken for signal to reach - hence calculate the speed.
  2. Sower than normal could indicate damage to the nerve.