Posture & movement Flashcards
How is posture controlled?
- With static and phasic reflexes
- primarily automatic, unconscious
- Reflex control due to constant shifts ( postural sway)
Describe how a static posture is brought about
sustained muscle contraction
Describe how a dynamic posture is brought about
Short term phasic reflexes
What is the role of pressure receptors in postural control?
- Maintainence of posture
- skin pressure receptors
- stand soles feet pressure receptors monitor distribution weight
- clinically if destroyed—> possible tabes dorsalis
State the hierarchy of control for movement control in terms of the three primary control areas in the brain
- Spinal cord
- Brain stem
- Cerebrum
State the 2 side circuits involved in control of movement
- cerebellum
- basal ganglia
State the 3 systems involved in control of feedback of movement
- vision
- vestibular
- propiception
Outline what happens at the start of movement and what is involved
- Initiation of voluntary movement
- Basal ganglia& supplementary motor area involvement
What is the supplementary motor area?
- 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
What could go wrong clinically at the start of movement
ABULIA:
- lesions in the supplementary motor area
- initiation of movement is nearly impossible
- Even though all other elements of the motor system are intact
Outline what happens during movement and what is involved
- 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
Outline what happens to stop movement & what is involved?
- Requires ‘brakes’ on before reach goal
- Basal ganglia and cerebellum involvement
- Relies on feedback to predict end point
Outline what happens after movement
- Return to resting state
- tone, posture, balance
List the:
a. ) function
b. ) clinical association
c. ) blood supply
…of the prefrontal cortex
a. ) Idea, motivation
b. ) head injury
c. ) ACA
List the:
a. ) function
b. ) blood supply
…of the premotor cortex
a. ) idea, motivation, conceptualization
b. ) MCA
List the:
a. ) function
b. ) blood supply
…of the posterior parietal cortex
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
List the:
a. ) function
b. ) blood supply
…of the supplementary motor area
- motor association cortex
- secondary motor cortex
a. ) plan, strategy, programme for movement
b. ) ACA
List the:
a. ) function
b. ) clinical association
c. ) blood supply
…of the cerebellum
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
List the:
a. ) function
b. ) clinical association
c. ) blood supply
…of the basal ganglia
a. ) amplitude settings, timing sequences, programming
b. ) Parkinson’s, Chorea, Athetosis, resting tremor
c. ) MCA- lenticulostriate A; ACA & anterior choroidal
Describe the basal ganglia
- has several nuclei
- Interconnected; 2 pathways- direct& indirect
Describe the functional roles of the supplementary & pre motor cortex; primary motor cortex and postural adjustments in control of movement
- Supplementary& pre motor cortex: Command
- Primary motor cortex: initiate
- Postural adjustments: then movement
List the:
a. ) function
b. ) clinical association
c. ) blood supply
…of the primary motor cortex
a. ) activate spinal motor neurones via cortico spinal tracts ( some decussate in the medulla)
b. )
c. )MCA
- Homunculus: single fasiculus to large muscle groups
List the:
clinical association
…of the corticospinal tract
- 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.
Describe the mechanism of spasticity
- 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)
What is the role of the spinal cord?
- activates muscles
- signal arrives anterior horn cell
- anterior ventral root
- common peripheral nerve
- muscle synapse; neuromuscular junction
Describe the sensory feedback involved in movement control
- Visual
- Vestibular
- Peripheral: Muscles (spindles); tendons (GTO); joints; cutaneous
Describe and define akinesia?
- NO MOVEMENT
- supplementary motor area, basal ganglia
- difficulty with tasks requiring cooperative movements both hands
- can not initiate movement
Describe and define bradykinesia and hypokinesia
- Bradykinesia( slow movement)
- Hypokinesia (decreased movement)
- Supplementary motor area, basal ganglia
- Clinical association= Parkinson’s
