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Control & Movement > Control L15 spinal reflexes > Flashcards

Control L15 spinal reflexes Flashcards

1
Q

What are three functions of the brain motor neurones?

A

Initiation of movements
Integration of neurones
Co-ordination of functions and movement

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2
Q

What are the 2 main functions of the spinal cord motor neurons?

A

Simple reflexes
Pattern generation

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3
Q

What structure is involved in initiation of movement in the motor cortex?

A

Basal ganglia

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4
Q

What structure is involved in sensory motor coordination in the brainstem cortex?

A

Cerebellum

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5
Q

What are 3 examples of spinal reflexes?

A

Myotactic stretch reflex
Inverse myotactic reflex
Crossed extensor/flexor withdrawal reflex

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6
Q

What is a reflex?

A

A fast, predictable, automatic response to a change in environment or stimulus

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7
Q

What are the 5 functional components of the reflex arc?

A

1 - receptor in the periphery stimulated
2 - action potential travels in the afferent axons
3 - signal integrated by relay neurone/interneuron in the spinal cord
4 - signal travels through the motor neurone to the effector
5 - response is initiated in the effector (muscle/gland)

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8
Q

What is a mono synaptic reflex?

A

A reflex where only 1 synapse is involved in integration

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9
Q

What is a polysynaptic reflex?

A

A reflex where 2 or more synapses are invoked e.g. afferent neuron —> interneuron —> efferent neuron

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10
Q

Which type of integration is rapid and which is slower but more complex?

A

Rapid = monosynaptic
Slower but more complex = polysynaptic

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11
Q

What are myotactic stretch reflexes?

A

Reflex where muscles contract in response to stretching within the muscle

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12
Q

What receptor is involved in the myotatic stretch reflex?

A

Muscle spindle receptors

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13
Q

What are the functions of the myotatic stretch reflex?

A

Antigravity/Posture
Movement
Muscle tone maintenance

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14
Q

What is an example of a reflex test that tests an agonist response to myotatic stretch reflex?

A

The patellar tap reflex

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15
Q

What is the sequence of events involved in the patellar tap reflex?

A
  1. Tap quad tendon which stretches quad muscle
  2. Muscle spindle is activated increasing the firing of impulses in 1a afferent neuron
  3. Afferent terminals synapse directly with and excite the alpha motor neuron (LMN)
  4. This increases alpha motor neuron efferent axon activity
  5. As a result the agonist homonymous muscle contracts (i.e. same muscle as afferent arose contracts)
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16
Q

What type of reflex is the myotatic stretch reflex?

A

Monosynaptic

17
Q

What level of the spinal cord does the patellar tap reflex work at?

A

L2-L4

18
Q

What are alpha motor neurones?

A

The LMN that leave the spinal cord and innervate the bulk of a muscle

19
Q

What is the antagonist response of the myotatic stretch reflex, the patellar tap reflex?

A

when the agonist muscles (extensor muscle group in this case) are innervated, there is reciprocal inhibition of antagonist muscle groups by the 1a inhibitory interneuron of the motor neurones (flexor group in this case)

20
Q

How does the addition of load cause a myotatic stretch reflex (e.g. in arm muscle group)?

A

The muscle spindle detects change in length of the muscle due to increased load and activates he 1a afferent neuron. This leads to direct excitation of agonist (in this case flexor) muscle group (in this case biceps) and indirect inhibition by the 1a inhibitory interneuron of the antagonist (extensor) muscle groups (in this case triceps brachii)

21
Q

What is the function of the inverse myotatic (Golgi tendon) stretch reflex?

A

A protective reflex to control the tension of an active muscle in response to contraction to avoid tendon damage I.e. tendon feedback and overload protection

22
Q

What receptor is involved in the inverse myotatic stretch reflex?

A

Golgi tendon organ receptor

23
Q

Where is the Golgi tendon organ located?

A

In between the muscle and it’s corresponding tendon?

24
Q

What is the sequence events in the inverse myotatic stretch reflex when there is increased muscle tension?

A
  1. Golgi tendon organ excitation leads to increased firing in the 1b afferent neuron
  2. This leads to indirect inhibition via an inhibitor interneuron of motor neurone which are innervating the homonymous muscles
  3. This causes the active muscle to relax
  4. Simultaneously there is indirect excitation of motor neurone innervating antagonist muscle groups so the inactive muscle contracts
25
Q

What is the crossed extensor/flexor withdrawal reflex?

A

When noxious (harmful/unpleasant) cutaneous stimulation causes flexion withdrawal from the offending stimulus. Simultaneously extension of the contralateral limb (crossed extensor) may occur for weight bearing.

26
Q

What are the functions of the crossed extensor/flexor withdrawal reflex?

A

Damage limitation by avoiding stimuli
Maintained balance on limb withdrawal

27
Q

What aid the sequences of events of the crossed extensor/flexor withdrawal reflex in the context of the lower limb e.g. trodden on something sharp?

A
  1. Sensation of pain leads to increased firing of A-delta and C afferent neurones
  2. In ipsilateral limb, there is polysynaptic activation of flexor muscles and polysynaptic inhibition of extensor muscles
  3. Simultaneously in the contralateral limb there is polysynaptic inhibition Of flexors and excitation of extensor muscles allowing autonomic maintenance of balance during the reflex
28
Q

What receptors are involved in the crossed extensor/flexor reflex?

A

Nociceptors/free nerve endings/pain receptors

29
Q

how are sensory afferent fibres organised?

A

In groups

30
Q

What reflexes use group 1 sensory afferent fibres?

A

Myotatic stretch reflex
Inverse myotatic reflex

31
Q

Which reflex uses group 3 and 4 sensory afferent fibres?

A

Flexor withdrawal reflex

32
Q

What efferent neurones are involved in all reflexes?

A

Alpha motor efferent neurone

Control & Movement (36 decks)

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