Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MD2002 > Reflexes 2 > Flashcards

Reflexes 2 Flashcards

1
Q

what are 3 main features of muscle reflexes?

A
  1. they are automatic and fast
  2. they do not require conscious intervention for movement control
  3. they produce stereotyped response to a given stimulus (which means they can be used for diagnosis)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are features of a monosynaptic reflex arc?

A

+ sensory receptor
+ afferent component (sensory input)
+ central component (spinal processing)
+ efferent component (motor output)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are features of polysynaptic reflex arc?

A

one or more interneurons connect afferent (sensory) and efferent (motor) signals

+ sensory receptor
+ afferent component (sensory input)
+ central component (spinal processing)
+ efferent component (motor output)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the two classes of reflexes?

A
  1. intrasegmental

2. intersegmental

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what does it mean if a reflex is classified as intrasegmental?

A

the reflex arc is restricted to one or two spinal cord segments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what does it mean if a reflex is classified as intersegmental?

A

the reflex arc involves a number of spinal cord segments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what does the central portion of the spindle provide?

A

provides the sensory output for muscle length, however it is sensitive only over a relatively small change in length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

when is the spindle less sensitive?

A

when the muscle is completely contracted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the steps of the muscle reflex mechanism?

A
  1. activation of sensory receptors
  2. conduction to CNS along nerve fibres from receptors
  3. transmission across neuron/neuron synapses in CNS
  4. conduction from CNS along nerve fibres to muscle
  5. activation of muscle contractile machinery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the structure of muscle spindles?

A
  • extrafusal fibres
  • intrafusal fibres (2 types, bag and chain, depending on nuclei location)
  • nucleated portion of intrafusal fibres
  • spindle capsule
  • gamma motor neuron (efferent)
  • Grp II sensory fibre (afferent)
  • Grp 1A sensory fibre (afferent)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the 3 portions of the spindle fibre?

A

1x less elastic/contractile sensory portion (central)

2x contractile (gamma MNs) and elastic portion (ends)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are features of the central portion of the spindle?

A
  • provides sensory output for muscle length

- sensitive only over a relatively small change in length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe spindle sensitivity when almost completely contracted:

A
  • spindle sensitivity is at the most compressed part of its range and is LESS SENSITIVE

to prevent this:
- length of spindle adjusted to keep it within its most sensitive range by extending or shortening contractile spindle ends

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how is the CNS involved in adjusting the length of the spindle?

A

CNS activates the gamma motor efferents to the spindle in concert with the alpha motor neuron activation of the extrafusal muscle fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the 2 types of spindle fibres?

A
  1. chain fibres

2. bag fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are features of chain fibres?

A
  • innervated by both 1 A and II sensory nerve fibres
  • most common fibre type in spindle
  • so called because fibres’ nuclei are arranged in central portion
17
Q

what are features of bag fibres?

A
  • only innervated by type 1A fibres
  • only 1 or 2 per spindle
  • so called because of swelling in the equatorial region which houses the nuclei
18
Q

what info do 1A fibres provide?

A

info about rate of change in length

19
Q

what info do type II fibres provide?

A

info about total length

20
Q

what are features of mechanism of reciprocal innervation?

A
  1. influence of spindle sensory nerve fibres from one (homonymous) muscle on motor neurones projecting to antagonist muscles
  2. the effect is opposite to that on their own muscle
  3. relaxes antagonist muscles and facilitates shortening oh homonymous muscle
  4. requires involvement of a local inhibitory neuron in the reflex onto the antagonist muscles
21
Q

what is the definition of reciprocal innervation?

A

innervation so that the contraction of a muscle or set of muscles (as of a joint) is accompanied by the simultaneous inhibition of an antagonistic muscle or set of muscles

22
Q

what happens when a voluntary signal for muscular contraction leaves the spinal cord?

A
  • it travels to both intrafusal (via gamma MNs) and extrafusal (via alpha MNs) causing both sets of fibres to contract
  • spindle fibre ends shorten in concert with extrafusal fibres, which keeps central position constant in length, so anulospiral sensory endings do not detect a change in muscle length
23
Q

what happens in voluntary muscle lengthening?

A
  • actually passive but involves inhibition
  • intrafusal ends inhibited (excited less)
  • can stretch but no change in centre so no change in signal
24
Q

what are functional features of anulospiral endings?

A
  • if anulospiral endings do not change their length, there is no change in sensory nerve activity
  • only unpredicted changes in muscle length alter extension of anulospiral endings
  • therefore unpredicted changes in muscle length cause a change in sensory nerve activity
25
Q

what do muscle spindles monitor?

A
  • muscle length
  • rate of change in length
  • duration of change
26
Q

what do muscle spindles do?

A

mediate monosynaptic and polysynaptic stretch reflexes

27
Q

how do muscle spindles lie in relation to extrafusal fibres?

A

parallel

28
Q

how is length monitoring achieved?

A

by activation of both principal (group 1A) sensory fibres and secondary (group II) sensory fibres on both bad and chain intrafusal fibre types

29
Q

how is rate of change in length and duration achieved?

A

by activation of only principal (group 1A) sensory fibres on both bad and chain intrafusal fibre types

30
Q

what is the purpose of stretch reflexes?

A

to minimise unexpected changes in muscle length

31
Q

what is the role of gamma MNs in relation to spindle sensitivity

A
  • gamma MNs automatically produced: cause contraction of ends of intrafusal muscle fibres
  • adapts working range of intrafusal fibres

MD2002 (85 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions