W19-L9: Functional Organisation of Spinal Cord

Question 1

Where do spinal nerve exit the spinal cord, above or below their corresponding vertebral body?

Answer 1

Above for cervical, below for thoracic, lumbar and sacral

Question 2

As you head more rostral in the spinal cord the amount of white matter

Answer 2

Increases

Question 3

T/F: There are local intra-spinal communication as well as ascending/descending tracts

Answer 3

True

Question 4

What are the two groups of ventral motor neurones?

Answer 4

Medial and Lateral groups

Question 5

Where do lateral ventral motor neurones innervate?

Answer 5

More distal muscle, medial is more proximal, ventral is more ventral muscles and dorsal more dorsal

Question 6

motor neurone pool

Answer 6

cluster of motor neurone cell bodies relating to a single muscle in the spinal cord (column of cells)

Question 7

How much does a motor neurone innervate?

Answer 7

motor neurone does a collection of muscle fibres, from 2-100

Question 8

motor unit

Answer 8

collective term for muscle fibres and the motor neurone that innervates them

Question 9

Muscle Spindle

Answer 9

also called intra-fugal fibres, can contract but main job is to detect stretch, in parallel with muscle fibres and transmits by group I and II axons

Question 10

What motor neurone innervates muscle spindles

Answer 10

gamma motor neurones (so it can contract to respond to muscle position)

Question 11

Tendon Organ

Answer 11

responds to how much force is going through the tendon,

in series with the fibres, transmitted by I b afferent neurone

Question 12

Monosynaptic stretch reflex complexity

Answer 12

Simple as it involves a single central synapse, is the most important sign in neurology

Question 13

Monosynaptic stretch reflex function

Answer 13

Reflex maintains posture, when a load is applied

Question 14

Monosynaptic stretch reflex mechanism

Answer 14

signal travels through dorsal root and makes an excitatory synapse with the motor neurone that innervates the same muscle, and also with an interneurone which is inhibitory to the motor neurone innervating opposing muscle

Question 15

Golgi tendon organ reflex

Answer 15

Too much force through a muscle causes stimulation of an inhibitory interneurone which synapses with the motor neurone of the same muscle, and stimulation of an excitatory interneurone which synapses with the motor neurone of the antagonistic muscle

Question 16

Golgi tendon organ reflex function

Answer 16

When load is too much protects the muscle and causes the load to be dropped

Question 17

multi-segmental reflex

Answer 17

ipsilateral to painful stimulus you want to activate flexor to withdraw foot and extensor muscles are inhibited to allow flexion to occur, also to support the body the contralateral leg’s extensor is excited
and the flexor is inhibited

Question 18

Short propriospinal neurones

Answer 18

Lateral ipsilateral neurones that tend to be shorter and are involved in smaller finer muscle reflexes

Question 19

Long propriospinal neurones

Answer 19

Medial bilateral interneurones that are longer and deal with larger postural muscles

Question 20

T/F: A limb can direct itself to the stimulus without the brain, all within the spinal cord

Answer 20

True

Question 21

lower motor neurone

Answer 21

neurone that innervates muscle

Question 22

upper motor neurone

Answer 22

neurone that effects the excitability of the LMN (functional term)

Question 23

upper motor neurone clinical sign

Answer 23

increased muscular response and therefore

larger reflex

Question 24

upper motor neurone injury mechanism

Answer 24

most of descending motor control is inhibitory so loss causes increased excitability beneath the region of the lesion