lecture 23 - motor control

Question 1

What is a reflex movement?

Answer 1

A rapid, reproducible automatic motor response to external stimulus.

Question 2

Are reflex movements reproducible or irreproducible?

Answer 2

Reproducible

Question 3

What parts of the nervous system are involved in reflex movement?

Answer 3

A simple neural circuit involving peripheral nerves, motor neurons and the spinal cord (no higher brain centres)

Question 4

What are the overall steps in a stretch reflex (5)?

Answer 4

Receptor stimulation, sensory neuron activation, information processing in spinal cord (CNS), motor neuron activation, response by peripheral effector.

Question 5

What occurs at the receptor stimulation step of a stretch reflex?

Answer 5

Mechanically gated ion channels are activated when the muscle spindle is stretched.

Question 6

What occurs at the sensory neuron activation step of a stretch reflex?

Answer 6

The mechanically gated ion channels trigger an action potential that travels via a sensory neuron to the dorsal root ganglia.

Question 7

What occurs at the information processing step of a stretch reflex?

Answer 7

Sensory info received from sensory neuron and processed in lower structures of CNS (spinal cord) before a monosynaptic (single synapse) is initiated to active motor neuron.

Question 8

What occurs at the motor neuron activation step of the stretch reflex?

Answer 8

Motor neuron activated by single synapse (MONOSYNAPTIC) and leaves ventral horn, reaching a peripheral effector muscle fibre.

Question 9

What occurs at the effector response in a stretch reflex?

Answer 9

Neuro-muscular synapse occurs, generating muscle contraction, causing a stretch.

Question 10

What are the afferent components of the stretch reflex?

Answer 10

Receptor stimulation, sensory neuron activation, CNS processing.

Question 11

What are the efferent components of the stretch reflex?

Answer 11

Motor neuron activation, peripheral effector response (e.g. muscle contraction)

Question 12

What type of neuron is the sensory neuron in reflex movements?

Answer 12

Unipolar.

Question 13

What are the locations of the components of the sensory neuron in a reflex arc of a stretch reflex?

Answer 13

Input zone at muscle fibre, cell body in posterior/dorsal root ganglion, output in dorsal root

Question 14

What are locations of the components of a motor neuron in stretch reflex?

Answer 14

Input/cell body in ventral horn, axon exits through ventral root to the periphery where output zone is at a neuro-muscular junction.

Question 15

What are the overall steps in a withdrawal reflex (5)?

Answer 15

Receptor stimulation, sensory neuron activation, info processing in CNS (and transmission to higher centres), activation of motor neuron, peripheral effector response.

Question 16

What occurs at the receptor stimulation step in withdrawal reflex?

Answer 16

A painful stimulus is detected by sensory receptors (e.g. in the skin).

Question 17

What occurs at the sensory neuron activation step in the withdrawal reflex?

Answer 17

Signal from sensory receptor is received by sensory neuron and transmitted to posterior/dorsal root ganglion.

Question 18

What occurs at the CNS information processing component of the withdrawal reflex?

Answer 18

Synapse between sensory neuron and excitatory interneuron in posterior root ganglia. Excitatory interneuron then transmits a signal both to higher levels of the CNS (brain) and to a a motor neuron.

Question 19

What occurs at the motor neuron activation step of the withdrawal reflex?

Answer 19

Motor neuron transmits information from an excitatory interneuron to a peripheral effector.

Question 20

What occurs at the peripheral effector activation step of the withdrawal reflex?

Answer 20

Motor neuron activates a a muscle fibre (effector) at a neuromuscular junction, causing the muscle to withdraw from the source of the painful stimulus.

Question 21

What is the function of the cerebral cortex, in terms of movement planning and execution?

Answer 21

Plans and initiates voluntary motor activity

Question 22

What is the function of the basal nuclei, in terms of movement planning and execution?

Answer 22

To modify voluntary and reflexive motor patterns at the subconscious level.

Question 23

What is the function of the thalamus and midbrain, in terms of movement planning and execution?

Answer 23

Control reflexes on response to visual and auditory stimuli.

Question 24

What is the function of the cerebellum, in terms of movement planning and execution?

Answer 24

Coordinates complex motor patterns through feedback loops.

Question 25

What is the function of the brain stem and spinal cord, in terms of movement planning and execution?

Answer 25

Controls simple cranial and spinal reflexes

Question 26

What is the function of the pons and medulla oblongata, in terms of movement planning and execution?

Answer 26

Controls balance reflexes and complex respiratory reflexes

Question 27

What is the function of the hypothalamus, in terms of movement planning and execution?

Answer 27

Controls reflex motor patterns related to eating, drinking, sexual activity and respiratory reflexes.

Question 28

What regions of the brain have the greatest level of motor complexity?

Answer 28

Cerebral cortex, cerebellum, basal nuclei

Question 29

What regions of the brain have the least level of motor complexity?

Answer 29

Brain stem/ spinal cord, pons and medulla oblongata, hypothalamus.

Question 30

What part of the brain is responsible for the learning of motor programmes?

Answer 30

Cerebellum.

Question 31

What are motor programmes?

Answer 31

Learned patterns of complex neural activity associated with specific movements

Question 32

What neurons allow the body to sense its own movement, action, position and location?

Answer 32

Proprioceptive sensory neurons

Question 33

Where is information from proprioceptive sensory neurons received to coordinate movement?

Answer 33

The cerebellum

Question 34

What part of the brain controls postural movements for balance and body position?

Answer 34

Cerebellum

Question 35

What is ataxia?

Answer 35

Loss of bodily movement control

Question 36

What do disorders of the cerebellum typically lead to?

Answer 36

Ataxia

Question 37

What are the key types of ataxia (4)?

Answer 37

Drunken gait, tremor, dysarthria, dysmetria

Question 38

What is dysarthria?

Answer 38

A form of ataxia, affecting speech

Question 39

What is dysmetria?

Answer 39

A form of ataxia, resulting in an inability to judge distance

Question 40

Where does the desire to initiate a voluntary movement typically arise?

Answer 40

The frontal cortex/frontal lobes

Question 41

What information, which goes into planning movements, is processed in the frontal cortex?

Answer 41

Intentions, memories and experiences, risk, personality, emotion, environment.

Question 42

What is the process in which movements are generated when the brain decides to initiate a voluntary movement?

Answer 42

Descending pathways (corticospinal tracts) are activated. The tracts cross at the medulla to opposite side of the body and terminate at interneurons and motorneurons, which activate skeletal muscle in the periphery.

Question 43

How does the motor cortex control the amount of force generated by a muscle during voluntary movement?

Answer 43

By controlling the frequency of action potential firing (summation) and altering the number of motor units activated (recruitment)