L24 Motor Control

Flashcards for HUBS 191 Lecture 24: Neurophysiology 4 - Motor Control

Prefrontal Cortex (decision maker)

Brain region involved in decisions to move and planning the desired movement outcome. eg i want to sit 10 rows up.

Premotor Cortex (step by step)

Brain region involved in organizing movement sequences to achieve the desired outcome. eg, walk to stairs, climb stairs, walk down aisle, sit.

Primary Motor Cortex (unconcious)

Brain region involved in directing voluntary movement. e.g. activate knee and hip flexors to step up, activate tibialas anterior to dorciflex etc.

Basal Nuclei

Brain region that influences posture and automatic movements and refines movements by selecting which to allow and which to inhibit by altering sensitivity of

Cerebellum (posture and balance)

Brain region that stores and facilitates learning, planning, and execution of motor programs eg walking; monitors proprioceptors and balnce to compare actual movement to planned movement. Organises timing of muscle contractions and modifies ongoing activity.

Corticospinal Pathway

Controls movement of limbs and trunk.

Neuromuscular Junction (NMJ)

The communication point between nerves and skeletal muscle via chemical synapse, where ACh (excitory) is released. Only one neuron per muscle fibre so no summation needed cause no inhibitory local potential.

Motor Unit

A single lower motor neuron plus all the skeletal muscle fibers it innervates. Small MU has more control but less power. Large MU has less control and more power.

Voluntary Response

Movement with a 100+ ms latency, requires complex processing, time can be reduced with training.

voluntary response pathway

sensory receptors to somatosensory cortex through dorsal column pathway, then from brain back through the motor neurons through corticospinal pathway.

Reflex Response

Rapid, reproducible, automatic motor response to external stimulus with a ~30-40ms latency; involves a simple neural circuit and is not generally trainable.

Stretch reflex response pathway

stimulus, proprioceptors/stretch receptors in muscle deform, MG Na+ channels open in dendritic endings of receptors. Na+ entry = depolarisation = AP through sensory axon to spinal chord. Synapse to motor neuron, AP fires to NMJ of quads causing contraction

Inhibitory interneuron (connector)

Also stimulated by sensory neuron (during stretch reflex pathway) preventing activation (opposition to quad reflex) of motor neuron innervating hamstrings.

Stretch Reflex

A reflex response to sudden muscle stretch that protects the muscle from tearing.

Withdrawal reflex pathway

Nociceptors activate, sensory neuron depolarises = AP to spinal chord. Stimulates interneurons = excitation of motor neurons stimulating flexors, and inhibits motor neurons stimulating extensors.