Spinal cord

Question 1

What is the role of the upper motor systems?

Answer 1

Send info to spinal cord and brain stem; initiate voluntary movements

Question 2

Where are the upper motor systems located?

Answer 2

Motor cortex and brainstem; either directly or under the influence of other brain areas that control movements

Question 3

What are the lower motor systems?

Answer 3

Grey matter of spinal cord and brainstem; contain lower motor neurones and lower circuit neurones

Question 4

How long and thick is the spinal cord?

Answer 4

44cm long; 6-13mm thick

Question 5

Where is the spinal cord situated in spinal column?

Answer 5

Vertebral foramen

Question 6

Where does the spinal cord end, and why?

Answer 6

L1/L2; spinal cord cells don’t grow more as body grows

Question 7

In a cross section of the spinal cord, what is the middle part which looks like an H?

Answer 7

Neurones and other cells (grey matter)

Question 8

In a cross section of the spinal cord, what is the outside of the cord?

Answer 8

Fibres (white matter)

Question 9

Within the spinal segment, what is the anterior part of the cord called?

Answer 9

Ventral horn; contains motor nuerones

Question 10

Within the spinal segment, what is the posterior part of the cord called?

Answer 10

Dorsal horn; contains sensory neurones

Question 11

What is a neural prosthesis?

Answer 11

A system to bypass the output from the damaged spinal cord; in order to do this we have to decode the signals from the brain

Question 12

What is a motor pool?

Answer 12

All the motor neurones that innervate a single muscle; each fibre innervated by a single neurone

Question 13

Why do the cervical and lumbar spine have more motor pools?

Answer 13

More controlled movements, thus more muscles

Question 14

Why does the thoracic spine have fewer motor pools?

Answer 14

Less controlled movements, thus fewer muscles

Question 15

What is the somatotopic organisation of lower motor neurones?

Answer 15

Proximal muscle neurones located medially; distal muscle neurones located laterally

Question 16

What is a motor unit?

Answer 16

A single neurone innervating multiple muscle fibres

Question 17

What are the distinguishing characteristics of slow motor unit?

Answer 17

Small motor neurones
Innervate relatively few muscle fibres
Generate small forces
Innervate small, slow twitch muscle fibres

Question 18

What are the distinguishing characteristics of fast fatiguable motor unit?

Answer 18

Large motor neurones
Innervate larger, more powerful units
Generate more force
Innervate larger, fast fatiguable muscle fibres

Question 19

What are the distinguishing characteristics of fast fatigue-resistant motor unit?

Answer 19

Motor units of intermediate size

Not as fast as FF units but less fatiguable

Question 20

How does physical activity affect types of motor unit?

Answer 20

Due to muscle plasticy, different training can change the type of muscle fibre present in the exercised muscle; paralysis transforms slow twitch fibres to fast twitch

Question 21

What is implication of more neurones innervating a single muscle?

Answer 21

Finer movements

Question 22

What are reflexes?

Answer 22

Actions produced at the level of the spinal cord

Question 23

What is the patellar reflex?

Answer 23

Monosynaptic

Question 24

What is the withdrawal reflex?

Answer 24

Polysynaptic