Lecture 8

Question 1

Ventral horn parts

Answer 1

Dorsolateral part
- Distal muscles
- Fine movements

Ventromedial part
- Proximal muscles
- Posture

Question 2

Alpha motor neurons

Answer 2

The neurons that attach to the muscles that are involved in voluntary movement

Question 3

Diseases that affect Alpha Motor Neurons

Answer 3

1. ALS
2. Poliomyelitis: viral infection that selectively attacks AMN’s

Question 4

The stretch reflex

Answer 4

This is to keep posture.
The muscle spindle senses stretching. Activates AMN and the muscle contracts.
Gamma motor neuron contracts muscle spindle during voluntary movements so that they stay short enough to sense stretching when muscles are short.

Question 5

Crossed extensor reflex

Answer 5

When one limb flexes, the other extends

Question 6

Fully automatic and highly coordinated movement patterns

Answer 6

• Walking
• Swallowing
• Breathing
• Orienting

Question 7

Withdrawal reflex

Answer 7

When you sense pain in your hand in pull it away quickly.

Question 8

Golgi tendon reflex

Answer 8

Protects the muscle from excessively heavy loads by causing the muscle to relax and drop the load. The golgi tendon causes relaxation of the muscle.

Question 9

Extrapyramidal systems (involuntary)

Answer 9

1. Rubrospinal tract: distal limb muscles, precise movement
2. Tectospinal tract: receives visual and auditory info. Reflex orienting response.
3. Vestibulospinal tract: head position to maintain balance and posture.
4. Reticulospinal tract: reflexes, state of arousal

Question 10

Pyramidal systems (voluntary)

Answer 10

1. Corticobulbar tract: move facial muscles and throat
2. Corticospinal tract: move all non facial muscles

Question 11

Damage to corticospinal tract

Answer 11

• Paralysis/paresis
• Spasticity/flaccidity
• Change in reflexes

Question 12

Cerebellum role in motor system

Answer 12

• Fine tuning of movements
• Timing of automated movement sequences, motor memory
• Maybe also timing in general

Question 13

Cerebellum parts

Answer 13

• Spinocerebellum: balance, walking, affected by alcohol
• Neocerebellum: control of fine movements
• Vestibulocerebellum: coordination of eye movements with body movements

Question 14

Cerebellar ataxia

Answer 14

Endpoint tremor, slurred speech

Question 15

Basal Ganglia anatomy

Answer 15

• Striatum (Caudate nucleus and Putamen)
• Globus Pallidus (Externa and Interna)
• Substantia Nigra
• Subthalamic nucleus

Question 16

Role of the Basal Ganglia in the motor system

Answer 16

The basal ganglia inhibits most of the movements sent out by the motor area. Only the most active response gets let through.

Question 17

Parkinson’s Disease

Answer 17

Tremor of hands, Rigidity, Bradykinesia
Medication: L-dopa, Stem cells, DBS
Cause: no dopamine production in the substantia nigra

Question 18

Motor cortex parts

Answer 18

• M1: direct motor control
• PMC (and PPC): externally guided, stimulus driven action
• SMA (and PFC): internally guided action

Question 19

Hemiplegia

Answer 19

Half sided paralysis due to lesions of upper motor neurons coming from M1

Question 20

Apraxia

Answer 20

• Loss of motor skill
• Lesions in SMA, PMC, PPC
• Ideomotor apraxia: rough idea of movements can be executed
• Ideational apraxia: no idea what to do, uses wrong tools

Question 21

Motor tuning in M1 and PMC

Answer 21

Individual motor neurons encode vector of movement, they are tuned for the direction of limb movement.
Tuning is fairly broad.
Actual movement is the vector sum of population of M1 cells.

Question 22

Affordance competition hypothesis

Answer 22

Sensory inputs create many potential motor responses (affordances). Depending on needs and potential payoffs, one of these has to be selected.

Question 23

Premotor cortex

Answer 23

Encodes population vectors of multiple potential actions, until colour cue is given to perform one action and not the other.

Question 24

Posterior Parietal Cortex (PPC)

Answer 24

Translating movement from retinal to hand, head or body centered reference frames.