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AUDI 402 > Lesson 4: PNS > Flashcards

Lesson 4: PNS Flashcards

1
Q

Where do somatic nerve axons extend? What do they do there?

A

Into the spinal cord to synapse on a motor/inter/sensory neuron

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2
Q

What is a monosynaptic reflex?

A

One sensory neuron synapses directly on one motor neuron - a simple reflex

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3
Q

What is areflexia?

A

Absence of reflex

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4
Q

What are central pattern generators? What do they do?

A

Constantly active neurons at the spinal cord. They produce basic motor patterns without voluntary action

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5
Q

What is the viscera?

A

The internal organs of the body

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6
Q

What is the role of the autonomic nervous system, in term of information?

A

Carries info to and from the viscera

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7
Q

What is the covering of a peripheral nerve? 4 layers

A

Each axon: schwann cell sheath, then endoneurium. Axons bungled together by perineurium = fascicles. Epineurium layer over fascicles

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8
Q

What does a peripheral nerve consist of?

A

A bundle of fascicles

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9
Q

Which senses are the ‘special senses’? What’s different about them

A

Smell, vision, hearing, taste

They have specialized receptors - little sensory organs

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10
Q

What is the most common receptor type? What information does it conduct?

A

Bare nerve ending. It processes tissue damage or stretch as pain

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11
Q

What are muscle spindles? (Label). What are muscle spindles made of?

A

Mechanoreceptors. Small sensory organs, with a sensory area at its equator and small intrafusal fibres at each pole

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12
Q

What are the three roles of muscle spindles?

A

Spasticity following injury to the nervous system, monitoring the muscle length, monitoring rate of change in muscle length

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13
Q

What is the role of alpha-motor neurons?

A

Innervate the extrafusal fibers of the skeletal muscles

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14
Q

What is the primary role of gamma-motor neurons? (2)

A

To regulate the length of spindle fibers and modulate the excitability of the annulospiral primary endings

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15
Q

How do gamma-motor neurons differ from alpha-motor neurons in terms of structure?

A

There are fewer and smaller axonal processes

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16
Q

What happens when the ventral nerve root receives information to contract?

A

This information travels along the gamma-motor neurons –> Portions of the intrafusal muscle fibers contract, which stretches the central part of the muscle spindles –> afferent projections to spinal cord –> alpha-motor neurons to extrafusal muscles –> reflexive contraction of the extrafusal fibers of the muscle

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17
Q

What is the static role of the muscle spindle?

A

Modulate the length of a muscle

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18
Q

What is the dynamic role of the muscle spindle?

A

Modulate the rate of change in a muscle length

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19
Q

Why must gamma motor neurons reset?

A

So that the centre is constantly sensitive

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20
Q

Which tracks do gamma motor neurons receive input from?

A

The reticulospinal and vestibulospinal tracts

21
Q

What occurs during a monosynaptic stretch reflex?

A

Impulses along the afferent fibers –> dorsal horn –> alpha motor neuron

22
Q

What is reciprocal innervation?

A

When the contraction of one muscle is paired with the antagonist being relaxed

23
Q

What is co-contraction? What is the result?

A

Simultaneous contraction fo opposing muscles due to abnormal reflex activity. Results in no movement of the body part

24
Q

What is a motor unit?

A

A single alpha motor neuron and all the muscle fibres it innervates

25
Q

What is the difference between a sign and a symptom?

A

A symptom is reported by the patient, whereas a sign can be observed and measured

26
Q

What is neuropraxia? What is its outlook?

A

Light compression of the nerve - reversible

27
Q

What is axonotmesis? How is it healed?

A

Heavier compression - the axon is severed, but the Schwann cell sheath and fibrous coverings are intact. The axon regenerates from the point of the lesion

28
Q

What is neurotmesis? What are its consequences?

A

Severance of the axon and disruption or misalignment of the Schwann cell sheath = action potential can’t conduct, and degeneration of the axon distally from the lesion

29
Q

How quickly does a severed axon grow back?

A

1 mm/day

30
Q

What is the stapedius?

A

A small muscle that responds to loud sounds by contracting, to reduce the ossicle vibration

31
Q

What nerve innervates the stapedius?

A

The facial nerve

32
Q

What may cause innapropriate contraction of facial muscles in response to loud noises?

A

If the lesion to the facial nerve is before the branch that innervates the stapedius breaks off, the axon may regenerate in the wrong sheath

33
Q

What are the four symptoms of lower motor neuron lesions?

A

Areflexia, rapid muscle atrophy, flaccid paralysis, and abscence of muscle tone

34
Q

What are the two main causes for sensory neuron damage?

A

Damage to the disc protrusion at the root, or nutritional damage at the root

35
Q

What are the causes of damage to alpha motor neurons?

A

Poliomyelitis, nutritional damage, and autoimmune disease

36
Q

What is wallerian degeneration

A

Degeneration from the point of injury distally

37
Q

What is the treatment for a severed sheath? Why?

A

Surgical repairment of the nerve, as the sheath must remain aligned

38
Q

How does Polio affect the body?

A

It infects the alpha motor neuron cell body of the voluntary motor nerve (lower motor neuron)

39
Q

What has occurred in Myasthenia Gravis?

A

Receptors on the postsynpatic membrane of the muscle are destroyed by the immune system, resulting in a limited number of receptors

40
Q

What happens when there is damage to either the parasympathetic or sympathetic system?

A

Over-action of the unopposed function

41
Q

Where is acetylcholine?

A

In parasympathetic nerve endings of neuromuscular junctions

42
Q

Where is norepinephrine located?

A

In the sympathetic nerve endings

43
Q

Where does dopamine go, and what transports it there?

A

Into the basal nuclei, via the substantia nigra cells

44
Q

What disease is involved in irregular dopamine amounts?

A

Parkinson’s disease

45
Q

Where is GABA?

A

Basal nuclei

46
Q

What disease is associated with less GABA?

A

Huntington’s Chorea

47
Q

What is the role of enkephalins and endorphins?

A

Pain modulation

48
Q

What is the role of substance P?

A

Pain

AUDI 402 (14 decks)

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