6.1 Neuro Anatomy & Physiology - The Spinal Cord and Motor Control

Question 1

Fundamentally, what is the spinal cord?

Answer 1

A column of nervous tissue (2-way highway)

Question 2

What is the diameter of the spinal cord?

Answer 2

1mm

Question 3

What is the function of the spinal cord?

Answer 3

Connects brain to PNS

Question 4

Where does the spinal cord run to/from?

Answer 4

Brainstem to lumbar region

Question 5

What are the two main tracts of the spinal cord? What type of input do these two tracts carry?

Answer 5

Ascending tract: sensory/afferent
Descending tract: motor/efferent

Question 6

What type of input does the dorsal root carry?

Answer 6

Sensory input (afferent)

Question 7

What type of input does the ventral root carry?

Answer 7

Motor (efferent)

Question 8

What makes up grey matter?

Answer 8

• Cell bodies
• Neuroglia
• Unmyelinated axons

Question 9

How does CSF flow through the spinal cord?

Answer 9

Through the central canal

Question 10

What is the spinal nerve?

Answer 10

The joining of the ventral and dorsal roots at a distance away from the spinal cord itself. These two only branch apart near the spinal cord.

Question 11

What is a dorsal root ganglion?

Answer 11

Collection of sensory neuron cell bodies

Question 12

What is the grey commissure? What type of axons does it contain, and why does this make sense?

Answer 12

• Connects two sides of the spinal cord
• Unmyelinated axons; makes sense: grey

Question 13

What is the difference between somatic and visceral neurons?

Answer 13

Somatic: Conscious control
Visceral: Internal organs (viscera)

Question 14

What is the function of the neurons in the lateral horn of the spinal cord?

Answer 14

Autonomic functions

Question 15

What are the three white matter tracts/funiculi of the spinal cord?

Answer 15

• Dorsal
• Lateral
• Ventral

Question 16

What is the dorsal column responsible for?

Answer 16

Sensory function

Question 17

What is the lateral column responsible for?

Answer 17

Sensory and motor function

Question 18

What is the ventral column responsible for?

Answer 18

Sensory and motor function

Question 19

Which type(s) of muscles drive somatic muscle activity?

Answer 19

Skeletal

Question 20

Which type(s) of muscles drive visceral muscle activity?

Answer 20

Cardiac and smooth

Question 21

Which brain structures are commonly associated with motor movement?

Answer 21

Brain and spinal cord (CNS)

Question 22

Which brain structures add context and meaning to motor movement?

Answer 22

• Basal ganglia
• Cerebellum

Question 23

What are the two types of motor neurons?

Answer 23

Upper and lower

Question 24

Where are upper motor neurons found?

Answer 24

Motor cortex (pre-central gyrus)

Question 25

Where do lower motor neurons originate? What tracts do they make up?

Answer 25

Brainstem and spinal cord. They make up the descending tracts.

Question 26

In which two enlargements of the spinal cord can lower motor neurons be found? What do these correlate with?

Answer 26

- Cervical enlargement - Lumbar enlargement This correlates with the upper and lower limbs

Question 27

What muscle fibres do alpha motor neurons supply?

Answer 27

Extrafusal (main muscle mass)

Question 28

Which three sources do alpha motor neurons recieve input from?

Answer 28

- Muscle spindles - Spinal interneurons - Upper motor neurons

Question 29

What are the two types of lower motor neurons?

Answer 29

- Alpha - Gamma

Question 30

Which muscle fibres do gamma motor neurons supply?

Answer 30

Intrafusal muscle fibres/muscle spindles/proprioceptors

Question 31

What do intrafusal muscle fibres do?

Answer 31

Detect the amount and rate of change in muscle length. This information is then fed back to the spinal cord for processing

Question 32

What is the name of sensory inputs that are given to the motor unit?

Answer 32

Proprioceptive information/input

Question 33

What are the two sources of proprioceptive information in muscles?

Answer 33

- Muscle spindles - Golgi tendon organs

Question 34

What do golgi tendon organs detect? What kind of neurons do they sinapse with?

Answer 34

- They detect muscle tension - They synapse with inhibitory internurons, thus preventing further contraction and stopping the muscle from snapping.

Question 35

What can interneurons recieve input from?

Answer 35

- Descending upper motor + collaterals of lower motor neurons - Sensory axons - Other interneurons

Question 36

What is in Brodman's area 6? What do these structures do?

Answer 36

- Pre-motor areas - Supplementary motor areas Involved in planning and initiation of movement.

Question 37

How does the prefrontal cortex help with motor movement?

Answer 37

Important in planning and decision making

Question 38

How does the posterior parietal lobe help with motor movement?

Answer 38

Helps integrate sensory input with motor function

Question 39

What is another name for the pyramidal motor system? What is it involved in?

Answer 39

Corticospinal tract; motor planning and initiation

Question 40

Where do motor neurons decussate?

Answer 40

Lower medulla (pyramids)