Sensorimotor System

Question 1

Reflex

Answer 1

A simple, stereotyped, unlearned response to a particular stimulus

Question 2

Movement

Answer 2

A single relocation of body part

Question 3

Act

Answer 3

A complex, sequential behavior

Question 4

Motor plan

Answer 4

A set of muscle commands that are established before the action occurs

Question 5

High level of motor control hierarchy

Answer 5

Association and secondary motor cortex establish a goal of movement and the best strategy to accomplish it

Question 6

Middle level of motor control hierarchy

Answer 6

Primary motor cortex is involved in the sequence of muscle contraction to accomplish a goal, while the basal ganglia and cerebellum modulate activity of organized control systems to make movement more effective and controlled

Question 7

Lower level of motor control hierarchy

Answer 7

Brain stem integrates motor commands from above and relays back sensory information to the forebrain, while the spinal cord involves the activation of motor neurons that generate movement and adjustments in response to sensory information

Question 8

Antagonistic muscles

Answer 8

Muscles that oppose the action of another (ex: triceps and biceps)

Question 9

Synergistic muscles

Answer 9

Muscles that assist in synergy with an antagonistic muscle

Question 10

Fast-switch muscles

Answer 10

Muscles that contract greater force but fatigue faster because there’s less blood flow to the area (ex: jumping)

Question 11

Slow-switch muscles

Answer 11

Muscles that contract weaker force but sustains contractions because there’s more blood flow to the area (ex: walking)

Question 12

Muscle signal pathway

Answer 12

1. Lower motor neuron in the ventral spinal cord send their axons out the ventral roots to the periphery
2. The axons split into axon collateral branches that come into contact with muscle fibers, allowing an action potential to reach the muscle
3. Lower motor neurons connect to a muscle allowing upper motor neurons to connect to lower motor neurons (neuromuscular junction)
4. Acetylcholine is released to allow for muscle contraction at axon collaterals

Question 13

Motor unit

Answer 13

A single motor neuron and all the muscle fibers it innervates

Question 14

Muscle spindle

Answer 14

A capsule buried in other muscle fibers that contain intramural fibers responding to muscle stretch

Question 15

Golgi tendon organ

Answer 15

Sensory organs embedded in tendons that are sensitive to muscle tension so that pressure builds in the tendon

Question 16

When muscles are relaxed, what is the activation of muscle receptors?

Answer 16

No tension so no Golgi tendon organ activity, and no stretch, so no muscle spindle activity

Question 17

When muscles are lengthened, what is the activation of muscle receptors?

Answer 17

Tension so Golgi tendon organ is activated, and stretch so no muscle spindle activity

Question 18

When muscles are contracted, what is the activation of muscle receptors?

Answer 18

Tension so Golgi tendon organ is activated, but no stretch so no muscle spindle activity

Question 19

Reciprocal innervation definition

Answer 19

Activating one muscle by contraction simultaneously inhibits another antagonistic muscle

Question 20

Reciprocal innervation pathway

Answer 20

1. A weight dropped into the hand stretches the bicep muscle
2. The stretch excites the muscle spindle, which sends action potentials to the dorsal spinal cord
3. The action potential synapse onto motor neurons in the spinal cord that cause the biceps to contract, restoring the arm to its original position
4. The muscle spindle also excites interneurons that inhibit triceps motor neurons through GABA, causing the triceps to relax when the biceps contract

Question 21

Pyramidal system pathway

Answer 21

1. Large pyramidal neurons in the primary motor cortex (M1) are upper motor neurons that encode the extent, direction, and speed of movement
2. Descending motor pathways connect with the ventral horn of the spinal cord
3. Motor pathways synapse on the lower motor neurons

Question 22

How are the neurons in the primary motor cortex organized?

Answer 22

They’re organized somatopically (like homunculus) and contraleterally

Question 23

Lateral corticospinal system

Answer 23

Controls distal muscles and individual or fine movements of the arms and legs

Question 24

Ventral corticospinal system

Answer 24

Controls proximal limb muscles and whole body movements

Question 25

Supplementary motor cortex

Answer 25

Initiates preplanned movement in the moment before you move

Question 26

Premotor cortex

Answer 26

Incorporates context and intent to signal the preparation of movement

Question 27

Posterior parietal association cortex

Answer 27

PPAC; provides spatial representation of the body in space, with multimodal input from visual, auditory, and motor neurons

Question 28

Apraxia

Answer 28

The inability to perform movements on command so that movements are performed when not conscious of it from damage to PPAC

Question 29

Neglect

Answer 29

Failing to respond to visual, auditory, and somatosensory stimuli from damage to the PPAC

Question 30

Prefrontal cortex

Answer 30

Evaluates the consequences of actions and develops strategy to determine which is the best or right approach to movement

Question 31

Mirror neurons

Answer 31

Neurons activated when an individual makes goal-directed movements and when observing someone doing goal-directed movements

Question 32

Extrapyramidal systems

Answer 32

Systens regulating and fine-tuning motor commands

Question 33

Cerebellum functioning in extrapyramidal systems

Answer 33

Integrates and coordinates activity of sensorimotor system structures to correct deviations from intended movements

Question 34

Basal ganglia functioning in extrapyramidal systems

Answer 34

Modulates conscious and proprioceptive movements