11.2

Question 1

What is a homunculus? (when talking about biopsychology)

Answer 1

A representation of the human body in the sensory or motor cortex; also any topographical representation of the body by a neural area

Question 2

Where in the body does the right primary motor cortex control movement?

Answer 2

The left side of the body

Question 3

How is the homunculus in the motor cortex distorted? (2 ways)

Answer 3

1. Sizes of neural representation of different parts is disproportionate (cortical magnification)
2. Motor homunculus is discontinuous - not a perfect spatial representation

Question 4

What is topographic organization?

Answer 4

Neural spatial representation of the body or areas of the sensory world perceived by a sensory organ

Question 5

Where are whole-body movements elicited in the brain?

Answer 5

The premotor cortex

Question 6

Where are more precise movements elicited in the brain?

Answer 6

M1 (primary motor cortex)

Question 7

What is the position-point theory?

Answer 7

A theory that states that the motor cortex has a map of where parts of the body can be in space so that when a part of the cortex is stimulated, the associated part of the body moves to the appropriate spatial position, regardless of its starting position

Question 8

How do motor neurons increase a movement’s force?

Answer 8

By increasing their firing rate and its duration

Question 9

What is the role(s) of motor cortex neurons?

Answer 9

Planning (timing and force) and initiating movements; simple coding for where we want the position to end (completing the movement)

Question 10

What happens in M1 when someone imagines movement?

Answer 10

It displays subthreshold activity

Question 11

What is subthreshold activity?

Answer 11

Activity that is not strong enough to produce a movement

Question 12

What is constraint-induced therapy?

Answer 12

A procedure in which restraint of a healthy limb forces a patient to use an impaired limb to enhance recovery of function

Question 13

What does constraint-induced therapy exemplify?

Answer 13

Plasticity in the motor cortex

Question 14

What are corticospinal tracts?

Answer 14

The main efferent pathway from the motor cortex to the brainstem to the spinal cord

Question 15

Why are corticospinal tracts also known as pyramidal tracts?

Answer 15

They form bumps (pyramids) on the ventral surface of the brainstem

Question 16

What happens at the pyramidal protrusion?

Answer 16

Axons cross hemispheres of the body (80% of them)

Question 17

What is the difference between the anterior corticospinal tract and the lateral corticospinal tract?

Answer 17

The anterior corticospinal tract is uncrossed whereas the lateral corticospinal tract is crossed.

Question 18

What do the anterior corticospinal tracts do?

Answer 18

Moves the muscles of the midline body (trunk) on the same side of the body

Question 19

What do the lateral corticospinal tracts do?

Answer 19

Moves the fingers and limbs on the opposite sides of the body

Question 20

What are the roles of interneurons?

Answer 20

Immediate feedback, involved in organizing complex movements

Question 21

What is the role of motor neurons?

Answer 21

Carrying all nervous system commands to the muscles

Question 22

Where in the spinal cord are spinal cord motor neurons (interneurons included) located?

Answer 22

Anterior horns

Question 23

What does an extensor muscle do?

Answer 23

Moves the limb away from the trunk

Question 24

What does a flexor muscle do?

Answer 24

Moves the limb in towards the trunk

Question 25

What is the main neurotransmitter at the neuromuscular junction?

Answer 25

Acetylcholine

Question 26

The ________ organization of the motor cortex is represented by a(n) ________, in which parts of the body that are capable of the most skilled movements (esp. the mouth, fingers, and thumbs) are regulated by _______ cortical regions

Answer 26

topographic; homunculus; larger

Question 27

________ theory states that the motor cortex has a map of where body parts can be in space, such that when a part of the cortex is stimulated, the associated body part moves to an appropriate special position

Answer 27

Position-point

Question 28

Many corticospinal-tract fibers cross to the opposite side of the spinal cord to form the ________ tracts; some stay on the same side to form _______ tracts

Answer 28

lateral; anterior

Question 29

The anterior corticospinal tracts carry instructions for ___________ movements, whereas the lateral corticospinal tracts carry instructions for ______ and ________ movements

Answer 29

midline; finger; arm

Question 30

Motor neuron axons in the spinal cord carry instructions to ________ that are arranged in pairs. One ______ a limb; the other ______ the limb

Answer 30

Muscles; extends; flexes

Question 31

What does the plan of movements in the motor cortex, as revealed by electrical stimulation, tell us about the brain's representation of movement?

Answer 31

M1 is organized into a set of functional categories that encode a movement lexicon, or dictionary. Used in different combinations, these few movements enable more complex movements

Question 32

What are the corticobulbar tracts?

Answer 32

Tracts responsible for head muscle movements. Goes from motor cortex to facial muscles