Lect 24 - neurophysiology 4; motor control

Flashcards for reviewing motor control, including movement planning, neural pathways, and reflexes.

Efferent Signals

CNS sends instructions to the rest of the body using these signals.

Function of Prefrontal Cortex in Movement

Planning the desired movement outcome.

Function of Premotor Cortex in Movement

Organising movement sequences to achieve the outcome.

Function of Primary Motor Cortex in Movement

Directing voluntary movement.

Function of Basal Nuclei

Influence posture and automatic movements; refine movements by selecting which to allow and which to inhibit.

Function of Cerebellum

Stores and facilitates learning, planning, and execution of motor programs; monitors sensory input; organises timing of muscle contractions.

Corticospinal Pathway

Pathway controlling movement of limbs and trunk.

Neuromuscular Junction (NMJ)

• synapse is huge

• only Ach as neurotransmittter

• inputs only excitatory —> no summation required

Motor Unit

A single lower motor neuron plus all the skeletal muscle fibres it innervates.

Small Motor Units

• motor neuron + few muscle fibres

• Motor units that can produce more precise movements.

Large Motor Units

• motor neuron + many muscle fibres

• Motor units that can produce more forceful movements.

Voluntary Movement

Type of movement with a 100+ ms latency and highly variable response time.

Reflex Movement

• 30-40ms letency

• consistent and reproducible

• protects muscle from teaering

Interneurons

connecter neuron that is neither sensory nor motor

Neuron-neuron synapse

• synapses are tiny

• variety of neurotransmitters

• inputs can be excitatory or inhibitory —> requires summation

the 7 steps of stretch reflex response

1. tendon tap causes sudden, fast stretch of quadriceps muscle

2. proprioceptors/stretch receptors within the muscle get stretched

3. Mechanically-gated Na⁺ channels open in membrane of dendritic endings of the stretch receptors

4. Na⁺ entry causes depolarisation leading to an action potential which propagates along the sensory axon to spinal cord

5. Synaptic transmission from sensory axon terminal causes depolarisation in motor neuron cell body

6. Action potential fires and propagates along motor axon to neuromuscular junction of quadriceps

7. Stimulates quadriceps to contract

the withdrawl reflex

1. nocireceptors activated

2. sensory neuron depolarises and action potential propogates to spinal cord

3. sensory neuron stimulates interneurons

4. excitatory interneurons stimulates flexors of motor neurons allows body to withdraw from stimulus

5. inhibatory interneurons stimulate extensors to relax the limb