Topic 8.7

Question 1

Where are grey and white matter in the SP?

Answer 1

White matter : superficial

Grey matter : inside

Question 2

How is the organization of motor neurons in the grey matter?

Answer 2

Musculotopic organization

Question 3

What are somatic motor neurons?

Answer 3

Neurons that project to skeletal muscle

Question 4

What are autonomic motor neurons?

Answer 4

Neurons that project to smooth muscle

Question 5

2 main lasses of somatic motor neurons

Answer 5

alpha and gamma

Question 6

What is a motor unit?

Answer 6

motor neuron + all the sk muscle fibers it supplies

Question 7

What does the main alpha motor neuron axon synapse with?

Answer 7

With extrafusal muscle fibers

Question 8

What is the size principle of motor innervation?

Answer 8

As more force is needed, a greater number of motor units are recruited, in an order according to the magnitude of their force output

Question 9

Which type of muscles have more / less alpha motor neuron innervation?

Answer 9

More : limb muscles

Less : muscles for manipulation

Question 10

What do gamma motor neurons synapse with?

Answer 10

with intrafusal muscle fibers

Question 11

What are the 3 types of inhibitory interneurons?

Answer 11

• Ia
• Ib
• Renshaw cell

Question 12

What is the role of the Ia interneuron?

Answer 12

inhibitor of antagonist muscles in reflex arch

Question 13

What is the role of the Ib interneuron?

Answer 13

Found in a reflex arch, where it is activated by a golgi tendon organ

Question 14

What do Renshaw cells do?

Answer 14

They can modulate the strength of firing rate of a motor neuron via recurrent inhibition

Question 15

3 examples of proprioceptive receptors

Answer 15

• muscle spindle
• gto
• joint receptors

Question 16

Where are muscle spindles especially abundant?

Answer 16

In muscles for fine movement (like extraocular muscles)

Question 17

2 types of intrafusal fibers

Answer 17

• nuclear chain fibre

- nuclear bag fibre

Question 18

Sensory innervation of muscle spindles

Answer 18

• Group Ia fibers (for both)

- Group II fibers (for nuclear chain fiber)

Question 19

What do sensory Ia fibers in muscle spindles?

Answer 19

Detect velocity of length change

Question 20

What do sensory II fibers in muscle spindles?

Answer 20

detect change of length of the muscle fiber

Question 21

Motor innervation of nuclear bag and nuclear chain fibre

Answer 21

Dynamic and static gamma motor neuron

Question 22

What does GTO sense?

Answer 22

Tension when we contract the muscles (stretch receptor)

Question 23

What type of afferent fibers innervate GTO?

Answer 23

type Ib afferent nerves

Question 24

What is a reflex?

Answer 24

an involuntary instantaneous response to an eliciting stimulus

Question 25

3 parts of the reflex arc?

Answer 25

- afferent limb - central component - efferent limb

Question 26

4 reflexes

Answer 26

- Stretch (myotatic) reflex - GT reflex (inverse myotatic) - Flexor withdrawal - Baby reflexes

Question 27

Types of synapses of group Ia afferent fibers (2)

Answer 27

- monosynaptic | - bisynaptic

Question 28

What maneuver allows better testing of myotatic reflex?

Answer 28

Jendrassik maneuver

Question 29

What type of reflex is the GTO reflex?

Answer 29

polysynaptic reflex

Question 30

Which muscle is relaxed in the GTO reflex?

Answer 30

The agonist / homonymous muscle (by inhibitory interneuron)

Question 31

Which fiber types can carry the noxious stimulus?

Answer 31

Type III, IV fibers - a delta axons

Question 32

What is the stimulus of the flexor withdrawal reflex?

Answer 32

pain (noxious stimulus)

Question 33

What is the portion of the reflex that crosses to the other side of SP called?

Answer 33

crossed-extension reflex

Question 34

4 baby reflexes

Answer 34

- positive support reflex - babinski reflex - palmar grasp reflex - labyrinthine head righting reflex

Question 35

What is babinski reflex?

Answer 35

big toe of baby's foot moves upward after the sole is stroked

Question 36

What is a spinal cord transection?

Answer 36

a tear within the sp as a result of a traumatic injury

Question 37

2 types of sp cord transection syndromes

Answer 37

- upper motor neuron syndrome | - lower motor neuron syndrome

Question 38

Symptoms of UMN (3)

Answer 38

- muscle weakness - hyperreflexia - tight muscles (hypertonia)

Question 39

Symptoms of LMN (3)

Answer 39

- weeakened reflexes - flaccid muscles (hypo / atonia) - muscle atrophy

Question 40

What is quadriplegia?

Answer 40

lesion at T1 or above

Question 41

When do we require mechanical ventilation?

Answer 41

if lesion above C4

Question 42

What is paraplegia?

Answer 42

Below the level of T1

Question 43

What is spinal shock?

Answer 43

loss of reflex, motor and sensory function below the level of a spinal cord injury