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CM - Control > L15 - Spinal reflexes > Flashcards

L15 - Spinal reflexes Flashcards

1
Q

what is a reflex?

A

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

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2
Q

what are the components of the reflex arc?

A
  1. sensory receptor
  2. sensory neuron
  3. integration centre (monosynaptic or polysnaptic)
  4. motor neuron
  5. effector organ (muscle or gland)
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3
Q

what is a monosynaptic integration centre?

A

1 synapse, rapid (no interneurons)

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4
Q

what is a polysynaptic integration centre?

A

2 or more synapses, slower but more complex

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5
Q

what is the myotatic stretch reflex?

A

muscle contraction in response to stretching/change in length within the muscle

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6
Q

what is the sensory receptor within the myotatic stretch reflex?

A

muscle spindle

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7
Q

what are the functions of the myotatic stretch reflex?

A
  • antigravity - posture - movement
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8
Q

the patellar tap reflex is what type of reflex?

A

myotatic stretch reflex

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9
Q

what is the sequence of events for the agonist response of the patellar tap reflex?

A
  1. tap quadriceps tendon
  2. activation of muscle spindle = firing of 1a afferent
  3. 1a afferent synapses directly with alpha motor neuron (monosynaptic)
  4. contraction of agonist
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10
Q

what type of sensory afferent is excited in the patellar tap reflex?

A

1a afferent

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11
Q

what type of sensory afferent is excited in a myotatic stretch reflex?

A

1a afferent

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12
Q

what is reciprocal inhibition?

A

Reciprocal inhibition describes the process of muscles on one side of a joint relaxing to accommodate contraction on the other side of that joint. e.g. quads contract so hamstrings have to relax

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13
Q

during a myotatic stretch reflex, is the innervation of the agonist direct or indirect?

A

direct excitation of motor neurone innervating agonist

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14
Q

during a myotatic stretch reflex, is the innervation of the antagonist direct or indirect?

A

indirect inhibition via 1a inhibitory interneuron innervating antagonist

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15
Q

what is the inverse myotatic stretch reflex?

A

controls the tension of an active muscle, in response to muscle contraction to avoid tendon damage?

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16
Q

which type of reflex controls the tension of an active muscle to avoid damage?

A

inverse myotatic stretch reflex

17
Q

what is the sensory receptor of the inverse myotatic stretch reflex?

A

Golgi tendon organ

18
Q

what is the function of the inverse myotatic stretch reflex?

A
  • tension feedback - overload protection
19
Q

describe the sequence of events of the inverse myotatic stretch reflex?

A

(muscle is under great tension)

  1. Golgi tendon organ excitation = firing of 1b afferent
  2. synapses with inhibitory interneuron
  3. decreased motor neuron activity / same muscle is relaxed
20
Q

during the inverse myotatic reflex, is the innervation of the agonsit direct or indirect?

A

indirect inhibition via inhibitory interneuron - innervating homonymous muscle = relaxation

21
Q

during the inverse myotatic reflex, is the innervation of the antagonsit direct or indirect?

A

indirect excitation of motor neurones innervating antagonist muscle groups (contract)

22
Q

what is the crossed extensor/flexor withdrawal reflex?

A

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

23
Q

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

A
  • damage limitation of avoidance
  • maintained balance on limb withdrawal
24
Q

what is the sensory receptor within the crossed extensor/flexor withdrawal reflex?

A

cutaneous nociceptor

25
Q

what is a nociceptor?

A

A nociceptor is a sensory neuron that responds to damaging or potentially damaging stimuli by sending “possible threat” signals to the spinal cord and the brain. features in the crossed extensor/flexor withdrawal reflex

26
Q

activation of the cutaneous nociceptor results in increased activity of which type of afferent fibre?

A

A-delta C afferent

27
Q

with reference to the crossed extensor/flexor withdrawal reflex, what happens to the ipsilateral flexors?

A

Polysynaptic activation of ipsilateral flexors.

28
Q

with reference to the crossed extensor/flexor withdrawal reflex, what happens to the ipsilateral extensors?

A

Polysynaptic inhibition of ipsilateral extensors.

29
Q

with reference to the crossed extensor/flexor withdrawal reflex, what happens to the contralateral flexors?

A

Polysynaptic inhibition of contralateral flexors.

30
Q

with reference to the crossed extensor/flexor withdrawal reflex, what happens to the contralateral extensors?

A

Polysynaptic excitation of contralateral extensors.

CM - Control (20 decks)

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