5.2 Organisation of the spinal cord

Question 1

How many pairs of spinal nerves are in each area?

Answer 1

8 C
12 T
5 S
1 Co

Question 2

What are the meninges layers?

Answer 2

Pia (innermost), arachnoid and dura

Question 3

What layer of meninges contains the CSF?

Answer 3

Arachnoid

Question 4

What are the dentate ligaments?

Answer 4

Thickenings of the pia mater that anchor the spinal cord into the dural sheath

Question 5

Where do the large fibres run?

Answer 5

Come in more medial and synapse deeper - they have a variety of different endings which will form collaterals with interneurons, direct with motor, synapse with projecting neurons going elsewhere

Question 6

Where do smaller fibres run?

Answer 6

first synapse in the superficial horn and will ascend or descend several levels before synapsing again

Question 7

What is the rexed laminae?

Answer 7

Regions of the grey matter related to the kinds of cells present

Question 8

How does the stretch (myotatic reflex) work?

Answer 8

Stretch is sensed by afferent 1a fibres which synapse on alpha motor neurons innervating the same muscle group that is stretched contracting the muscle and alleviating passive stretch

Question 9

How does reciprocal inhibition work?

Answer 9

Stretch information carried by 1a afferent fibres is also passed onto internurons in layer 4, these inhibit alpha motor neurons that innervate opposing muscle groups

Question 10

What muscles fibres are activated in autogenic inhibition?

Answer 10

1b (fast)

Question 11

What is thought to occur in UMN damage?

Answer 11

poorly controlled 1a (myotatic) and 1b (autogenic inhibition) reflexes don’t behave normally and the poor coordination between the 2 arises from inappropriate descending inputs. The stretch reflex is prolonged and exaggerated which is eventually overcome by a prolonged and exaggerated revers myotatic reflex

Question 12

What is involved in the withdrawal reflex?

Answer 12

Flexor reflex and crossed extensor reflex

Question 13

What information does the spinothalamic pathway transmit?

Answer 13

Pain and temperature

Question 14

What information does the dorsal column system transmit?

Answer 14

fine touch and proprioception

Question 15

What information does the spinocerebellar system transmit and what are the sibdivisions

Answer 15

Proprioceptive information, concerning muscle tension and stretch to the cerebellum
Dorsal - GTI and spindles
Ventral - GTI only

Question 16

What information does the cuneo-cerebellar system transmit and what is it the equivalent of?

Answer 16

information from GTI and spindles of the upper limb

Equivalent of dorsal spinocerebellar