Posture & movement

Question 1

How is posture controlled?

Answer 1

• With static and phasic reflexes
• primarily automatic, unconscious
• Reflex control due to constant shifts ( postural sway)

Question 2

Describe how a static posture is brought about

Answer 2

sustained muscle contraction

Question 3

Describe how a dynamic posture is brought about

Answer 3

Short term phasic reflexes

Question 4

What is the role of pressure receptors in postural control?

Answer 4

• Maintainence of posture
• skin pressure receptors
• stand soles feet pressure receptors monitor distribution weight
• clinically if destroyed—> possible tabes dorsalis

Question 5

State the hierarchy of control for movement control in terms of the three primary control areas in the brain

Answer 5

• Spinal cord
• Brain stem
• Cerebrum

Question 6

State the 2 side circuits involved in control of movement

Answer 6

• cerebellum

- basal ganglia

Question 7

State the 3 systems involved in control of feedback of movement

Answer 7

• vision
• vestibular
• propiception

Question 8

Outline what happens at the start of movement and what is involved

Answer 8

• Initiation of voluntary movement

- Basal ganglia& supplementary motor area involvement

Question 9

What is the supplementary motor area?

Answer 9

• A part of the primate cerebral cortex that contributes to the control of movement.
• Located on the midline surface of the hemisphere just in front of (anterior to) the primary motor cortex

Question 10

What could go wrong clinically at the start of movement

Answer 10

ABULIA:

• lesions in the supplementary motor area
• initiation of movement is nearly impossible
• Even though all other elements of the motor system are intact

Question 11

Outline what happens during movement and what is involved

Answer 11

• Monitoring control messages and actual position
• cerebellum involvement
• compares signal from cerebrum with that from periphery and detects mismatches —> error correction
• smooth movement coactivation alpha/gamma

Question 12

Outline what happens to stop movement & what is involved?

Answer 12

• Requires ‘brakes’ on before reach goal
• Basal ganglia and cerebellum involvement
• Relies on feedback to predict end point

Question 13

Outline what happens after movement

Answer 13

• Return to resting state

- tone, posture, balance

Question 14

List the:

a. ) function
b. ) clinical association
c. ) blood supply

…of the prefrontal cortex

Answer 14

a. ) Idea, motivation
b. ) head injury
c. ) ACA

Question 15

List the:

a. ) function
b. ) blood supply

…of the premotor cortex

Answer 15

a. ) idea, motivation, conceptualization

b. ) MCA

Question 16

List the:

a. ) function
b. ) blood supply

…of the posterior parietal cortex

Answer 16

a. ) analyses sensory info; related to postulated movement particularly visual; activates supplementary motor area premotor cortex; to plan and write ‘programme’ for movement
b. ) MCA

Question 17

List the:

a. ) function
b. ) blood supply

…of the supplementary motor area

Answer 17

• motor association cortex
• secondary motor cortex
  a. ) plan, strategy, programme for movement
  b. ) ACA

Question 18

List the:

a. ) function
b. ) clinical association
c. ) blood supply

…of the cerebellum

Answer 18

a. ) balance, coordination, motor memory, error correction if there’s a mismatch, monitors, compares motor cortex command( the plan) with proprioceptive feedback ( what is actually happening
b. ) cerebellar pathologies, multiple sclerosis, ataxia
c. ) Basilar artery supplies the 3 cerebellar arteries

Question 19

List the:

a. ) function
b. ) clinical association
c. ) blood supply

…of the basal ganglia

Answer 19

a. ) amplitude settings, timing sequences, programming
b. ) Parkinson’s, Chorea, Athetosis, resting tremor
c. ) MCA- lenticulostriate A; ACA & anterior choroidal

Question 20

Describe the basal ganglia

Answer 20

• has several nuclei

- Interconnected; 2 pathways- direct& indirect

Question 21

Describe the functional roles of the supplementary & pre motor cortex; primary motor cortex and postural adjustments in control of movement

Answer 21

• Supplementary& pre motor cortex: Command
• Primary motor cortex: initiate
• Postural adjustments: then movement

Question 22

List the:

a. ) function
b. ) clinical association
c. ) blood supply

…of the primary motor cortex

Answer 22

a. ) activate spinal motor neurones via cortico spinal tracts ( some decussate in the medulla)
b. )
c. )MCA
- Homunculus: single fasiculus to large muscle groups

Question 23

List the:
clinical association

…of the corticospinal tract

Answer 23

• Acute: initial post pathology- contralateral flaccid paralysis
• Chronic: between 2days- 6months; motor cortex reorganisation (neuroplasticity); extrapyramidal pathways take control
• Spasticity: velocity dependent resistance to passive movement.

Question 24

Describe the mechanism of spasticity

Answer 24

• Changes gamma motor neurone & regulatory interneurones leads to increased alpha motor neurone activity; this leads to a much increased stretch reflex
• Happens if you lose the descending pathway(i.e the disinhibition pathway)

Question 25

What is the role of the spinal cord?

Answer 25

• activates muscles
• signal arrives anterior horn cell
• anterior ventral root
• common peripheral nerve
• muscle synapse; neuromuscular junction

Question 26

Describe the sensory feedback involved in movement control

Answer 26

• Visual
• Vestibular
• Peripheral: Muscles (spindles); tendons (GTO); joints; cutaneous

Question 27

Describe and define akinesia?

Answer 27

• NO MOVEMENT
• supplementary motor area, basal ganglia
• difficulty with tasks requiring cooperative movements both hands
• can not initiate movement

Question 28

Describe and define bradykinesia and hypokinesia

Answer 28

• Bradykinesia( slow movement)
• Hypokinesia (decreased movement)
• Supplementary motor area, basal ganglia
• Clinical association= Parkinson’s