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LCRS > Neuroscience 8 - The peripheral nervous system > Flashcards

Neuroscience 8 - The peripheral nervous system Flashcards

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.
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2
Q

What is a myotome and a dermatome?

A
  1. Myotome - groups of muscles supplied by a single spinal nerve root.
  2. Dermatome - the skin that is mainly supplied by a single spinal nerve.
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3
Q

Where do somatic neurones originate from?

A

The primary motor cortex in the brain.

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4
Q

Is SNS autonomic or voluntary?

A

Can be both voluntary or autonomic (reflexive).

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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.

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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).
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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.
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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.

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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.
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10
Q

What are ganglia?

A

Cell bodies, synapses and dendrites in the PNS.

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11
Q

What is the dorsal and ventral root? And What do they join to form?

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).
  3. They both join to form a mixed spinal nerve.
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12
Q

What are rami?

A
  1. They are lateral branches of the spinal cord that carry both sensory and motor fibres.
  2. Not the same as ventral and dorsal root ganglia.
  3. Form plexus.
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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.
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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.

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15
Q

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

A
  1. Can determine the site of spinal damage by simple pin prick exam.
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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 of peripheral neuropathies? (6)

A

Has many causes.

  1. Metabolic.
  2. Toxic.
  3. Inflammatory.
  4. Traumatic.
  5. Genetic.
  6. Idiopathic.
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. Lacerations or ischemic injuries.
  4. Damage to epineurium - no nerve growth.
22
Q

What is electromyography (EMG)?

A
  1. It is a technique for evaluating and recording electrical activity produced by muscles.
  2. Involves placing a needle electrode in the muscle and another on the skin.
  3. Distinguish between muscle conditions that begin in the muscle and nerve disorders that cause muscle weakness.
23
Q

What are nerve conduction velocity tests?

A
  1. They measure the conduction velocity of nerves in the body.
  2. A nerve is stimulated and an electrode is placed downstream that measures the time taken for signal to reach - hence calculate the speed.
  3. Sower than normal could indicate damage to the nerve.
24
Q

What is Epineurium, Perineurium and Endoneurium?

A
  1. Epineurium - connective tissue that surrounds the nerve.
  2. Perineurium - connective tissue that surrounds the fascicle.
  3. Endoneurium - connective tissue that surrounds the axon.
25
Q

What are satellite cells?

A
  1. These cells support the neurons.

2. Equivalent of astrocytes but in the PNS.

26
Q

Are unmyelinated axons surrounded by Schwann cells?

A

Yes, they only have a single layer of membrane.

27
Q

Where is the cell body of the somatic sensory neuron?

A

Dorsal root ganglion.

28
Q

Where is the cell body of the autonomic sensory neuron?

A

Dorsal root ganglion, similar arrangement to somatic sensory.

29
Q

How are the neurons in the PNS grouped?

A

They are grouped based on the diameter, signal conduction velocity and myelination state.

30
Q

What do the spinal nerves exit the vertebra through?

A

Intervertebral foramina.

31
Q

What is the difference between the innervation of spinal and peripheral nerves on the skin?

A

Spinal nerves innervate in a stripey pattern (dermatomes) whereas peripheral nerves innervate in a patchy pattern.

32
Q

What is the clinical significance of myotomes?

A

Important part of neurological examination (e.g. testing for muscle weakness).

33
Q

Can long-distance axon regeneration and substantial functional recovery occur in the adult PNS nerves?

A

Yes

34
Q

What is the difference between an intramuscular EMG and surface EMG?

A
  1. Intramuscular EMG - involves inserting a needle electrode through the skin into the muscle.
  2. Surface EMG - placing electrodes on the skin over the muscle.
35
Q

What can a slower than normal nerve conduction study suggest?

A

Slower than normal speed could indicate nerve damage from direct trauma, diabetic or peripheral neuropathy, viral nerve infection or nerve entrapment diseases like the Carpal Tunnel Syndrome among other conditions.

36
Q

What is Somatosensory Evoked Potential (SEP)? How does it work?

A
  1. SEP are measured to assess whether sensations (pain, temperature and touch) in the periphery are being transmitted to the brain.
  2. Stimulating electrodes are placed on the arm and/or leg.
  3. Recording electrodes are placed on the head and/or spine.
37
Q

What is Somatosensory Evoked Potential (SEP) indicate?

A
  1. Evoked potentials in the recording electrodes can indicate the integrity of transmission at peripheral mechanoreceptors to the cerebral cortex.
  2. Combined with EMG and NCV tests to assess the patient for generalized disorders of the nervous system like multiple sclerosis (MS)

LCRS (22 decks)

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