Motor

Question 1

What coordinates movement

Answer 1

The cerebellum, inputs to brainstem

Question 2

Where do lower motor neurons input to

Answer 2

The ventral horn of the spinal cord, mapping based on side and proximal to distal

eg. motor neurons for left hand will input to the left ventral horn closer to the edge (as hand is more distal)

Question 3

Motor unit & recruitment

Answer 3

All muscle fibers innverated by one motor neuron (many fibers: one neuron but one fiber has one neuron)

Recruited from smallest -> biggest units, biggest 50% of units do 75% of max contraction

Question 4

Types of motor neurons

Answer 4

Alpha: innervates extrafusal muscle fibers (for contraction)

Gamma (muscle spindle) : innervate intrafusal muscle fibers that contract to regulate the tension level to reset sensitivity for sensory neurons detecting stretch

Question 5

Stretch reflex circuitry

Answer 5

Passive stretch -> detected by muscle spindle -> dorsal horn of spinal cord

From dorsal horn:
To motor neurons for synergist muscle to cause contraction
To interneurons to inhibit antagonising muscles motor neuron

Question 6

golgi tendon organs

Answer 6

Force detectors, between muscle and tendons

Only synapse with interneurons

Question 7

Descending motor control

Answer 7

Cerebral cortex motor neurons:
Lateral white matter of spinal cord, control lower motor neurons in lateral ventral horn (skilled movements)

Brainstem motor neurons:
Anterior-medial white matter of spinal cord, controls posture and balance

Question 8

Superior colliculus

Answer 8

Sensory integration area in 3D map of out space, orienting where sound comes from, uses vision to detect “looming” meaning we are falling to maintain posture

in the colliculospinal tract

Question 9

Primary motor cortex & premotor area

Answer 9

Premotor: more complex movement (harder to stimulate movement but when you do its multijoint/bilateral)

Primary motor cortex: not compounded movements, mapped to areas of the body

They share a pathway to brainstem

Question 10

what do motor maps represent

Answer 10

map of where the body can move to, purpose/function

Question 11

Basal ganglia role

Answer 11

Selection of complex patterns of voluntary movement & learning (evaluate sucess of these actions)
Initiating movement

Question 12

Basal ganglia overall rule

Answer 12

Direct pathway: D1 receptors (excitatory), increases cortical activity (selects patterns of movement)

Indirect pathway: D2 receptors (inhibitory), decreased activity

Therefore: dopamine = movement
as excites direct pathway by activating D1 receptors and inhibits indirect pathway by activating D2 receptors

Question 13

Parkinsons disease

Answer 13

Degeneration of substantia nigra cells
Leads to: more tonic inhibition of thalamus

-> inability to initiate movement
Resting tremor that disappears for voluntary movements

Question 14

Huntingtons disease

Answer 14

Loss of brain tissue in caudate
Leads to: less inhibition from caudate, leads to increased inhibition of internal globus pallidus so LESS inhibition of thalamus

-> symptoms are spontaneous movement

Question 15

what is ataxia

Answer 15

Inability to follow a path (unsteady & overcorrected movements), due to cerebellar dysfunction