Spinal reflexes, upper motor neurones and control of movement Flashcards Preview

Neurology > Spinal reflexes, upper motor neurones and control of movement > Flashcards

Flashcards in Spinal reflexes, upper motor neurones and control of movement Deck (36):
1

What do spinal interneurons receive input from?

Primary sensory axons
Descending axons from the brain
Collateral LMNs
Other interneurons

2

What are the different types of input that can be given to a spinal interneurons?

Excitatory
Inhibitory

3

What do inhibitory interneurons mediate?

Inverse myotatic response
Reciprocal inhibition

4

What is reciprocal inhibition?

Reflex results in contraction of extensor muscle whilst simultaneously relaxing the antagonist flexor muscle

5

Describe the pathway for reciprocal inhibtion

1a afferent from muscle spindle extensor makes an excitatory monosynaptic contact with alpha motor neuron innervating the homonymous muscle
Via polysynaptic pathway involving an inhibitory interneuron, the 1a fibre also inhibits the alpha motor neurone supplying the flexor muscle

6

What will excitatory interneurons mediate?

Flexor reflex
Crossed extensor reflex

7

What is the flexor reflex?

Noxious stimulus causes the limb to flex by:
Contraction of flexor muscles via excitatory interneurons
Relaxation of extensor muscle via excitatory and inhibitor internueons

8

What is the crossed extensor reflex?

Noxious stimulus causes the limb to extend via:
Contraction of extensor muscles via excitatory interneurons
Relaxation of flexor muscles via excitatory and inhibitory interneurons

9

What does the crossed extensor reflex enhance?

Postural support during withdrawal of a foot from a painful stimulus

10

What are the descending spinal tracts concerned with?

Control of movement
Muscle tone
Spinal reflexes
Spinal autonomic functions
Modulation of sensory transmission

11

Describe the lateral descending pathways

Under control from the cerebral cortex
Important for voluntary control of distal musculature

12

Describe the ventromedial pathways

Under control from brain stem
Important for posture and locomotion

13

Which pathways make up the lateral pathways?

Lateral corticospinal
Rubrospinal

14

Which pathways makeup the ventromedial pathways?

Pontine reticulospinal
Medullary reticulospinal
Lateral vestibulospinal tract
Tectospinal tract
Ventral corticospinal tract

15

Where do axons in the corticospinal tract decussate?

85% at medullary pyramids to form the lateral corticospinal tract
Remainder stay ipsilateral to form the ventral corticospinal tract to decussate more caudally

16

Where will axons of the corticospinal tract terminate?

Dorsolateral region of ventral horn of grey matter
Location of LMNs and interneurons controlling distal muscle particular flexors

17

Where are the cell bodies of the rubrospinal tract found?

Red nucleus - receives input from the motor cortex and cerebellum

18

Where will axons of the rubrospinal tract decussate?

Ventral tegmental decussation and descend the spinal cord ventrolateral to the lateral corticospinal tract terminating at the ventral horn

19

What is the function of the rubrospinal tract?

Exerts control over limb flexor muscles exciting LMNs of those muscles

20

What are lesions of the lateral columns associated with?

Loss of fractionated movements
Slowing and impairment of accuracy of voluntary movements
Little effect on posture

21

Where are cell bodies of the vestibulospinal tracts found?

Vestibular nuclei

22

Where will the vestibular nuclei receive input?

CN 8
Vestibular labyrinths
Cerebellum

23

Where will axons from the lateral vestibular nucleus descend?

Ipsilaterally as the lateral vestibulospinal tract as far as the lumbar spinal cord

24

What is the function of the lateral vestibulospinal tract?

Upright position
Balanced posture by facilitating extensor MNs of antigravity muscles

25

Where will axons from the medial vestibular nucleus descend?

Medial vestibulospinal tract as far as the cervical spinal cord

26

What is the function of the medial vestibulospinal tract?

Activates cervical spinal circuits that control neck and back muscles guiding head movement

27

Where do the cell bodies from the tectospinal tract reside?

Superior colliculus

28

What input does the tectospinal tract receive?

Retina
Visual cortex
Afferents conveying somatosensory and auditory info

29

Where will axons from the tectospinal tract run?

Decussate in dorsal tegmental decussation
Descend close to the midline to the cervical spinal cord

30

What is the function of the tectospinal tract?

Influences muscles of neck, upper trunk and shoulders

31

What is the function of the superior colliculus?

Map of the external world guiding the orientation of the head and eyes to visual stimulus

32

Where do the pontine and medullary reticulospinal tracts arise from?

Reticular formation

33

What is the course of the pontine reticulospinal tract?

Descends ipsilaterally

34

What is the function of the pontine reticulospinal tract?

Enhances antigravity reflexes
Helps to maintain a standing posture by facilitating contraction of extensors of lower limbs

35

What is the course of the medullary reticulospinal tract?

Descends bilaterally

36

What is the function of the medullary reticulospinal tract?

Opposes the action of the pontine tract
Releases antigravity muscles from reflex control