Motor systems

what are the brain areas involved in a motor plan

spinal cord

brainstem

cerebellum

primary motor cortex

precentral gyrus

peripheral neurons

effector

what neurotransmitter do motor fibres use

acetylcholine

What are key brain structures involved in movement?

Primary motor cortex (M1), premotor cortex, supplementary motor area (SMA), basal ganglia, cerebellum, and brainstem motor nuclei.

What is one method to infer or observe motor system functioning using imaging?

Functional MRI (fMRI) can track changes in blood flow related to motor activity during movement tasks.

What is one behavioral method to assess motor system function?

Observing motor performance in tasks such as reaching, grasping, or reflex testing.

describe the speed vs. accuracy trade off of movements

The faster you try to move, the less accurate you become — and the more accurate you try to be, the slower your movement tends to be.

what mechanism prioritizes accuracy in movement

closed loop control mechanism

what mechanism prioritizes speed in movement

open loop control mechanism

what are the properties of closed loop control mechanism

constantly compares what one wants to do vs. what one is actually doing and makes real time adjustments

what are the properties of open loop control mechanism

pre-planned movement and executed without ongoing corrections

what is reflex

simple, unvarying, unlearned response to sensory stimuli like touch, pressure, and pain

what is motor plan

set of muscle commands established before the action occurs

what is a way to study reflexes

electromyography (EMG)

what is electromyography

records the electrical activity of muscles

electrodes placed over several muscles gives a record of timing and strength of contraction of muscles involved in a movement

what are the 2 main types of striated muscle fibers

fast twitch

slow twitch

what are fast twitch striated muscle

contract rapidly but fatigue quickly

what are slow twitch striated muscle fibres

contract slowly but resistant to fatigue

how to muscles work

work via contractions of individual muscle fibres

What is one way in which divergence plays a role in motor control?

A single upper motor neuron can synapse onto multiple lower motor neurons, allowing broad coordination of muscle groups.

How does the spinal cord show evidence of learning and memory?

Through central pattern generators (CPGs)—networks in the spinal cord that can learn rhythmic motor patterns like walking, even without input from the brain.

What is flaccid paralysis and what causes it?

Flaccid paralysis involves loss of muscle tone and reflexes, caused by lower motor neuron damage (e.g., ventral horn or peripheral nerve injury).

What is spastic paralysis and what causes it?

Spastic paralysis involves increased muscle tone and exaggerated reflexes, caused by upper motor neuron damage (e.g., corticospinal tract lesions).

What is the corticospinal tract?

A major motor pathway from the cortex to the spinal cord that controls voluntary movement, crossing over at the medulla.

How does a reflex differ from a motor plan?

Reflexes are simple and unlearned; motor plans are pre-set sequences adjusted by feedback.

What is the innervation ratio?

Number of muscle fibers per motor neuron; low = fine control, high = gross movement.

What is a central pattern generator (CPG)?

Spinal circuits that produce rhythmic movements (e.g., walking) without brain input.

What are the two types of motor neurons involved in movement?

Upper motor neurons (UMNs) and lower motor neurons (LMNs).

Where do upper motor neurons (UMNs) originate and where do they travel?

UMNs originate in the cortex and travel down the spinal cord via the corticospinal tract.

Where do lower motor neurons (LMNs) originate and what do they do?

LMNs originate in the spinal cord and directly innervate muscles to cause movement.