Chapter 8 Help Pg 199-211

Question 1

Neural signals are conducted from the primary motor cortex to the motor neurons of the spinal cord over four different pathways. Two pathways descend in the ______ region of the spinal cord, and two descend in the _____ region of the spinal cord.
What do they do?

Answer 1

Dorsolateral,
Ventromedial,

Signals conducted over these pathways act together in the control of voluntary movement.

Question 2

Medullary pyramids are two bulges on the _____ surface of the _____.

Answer 2

Ventral, medulla

Question 3

The dorsolateral corticospinal tract descends from the primary motor cortex through ___________, then decussates and continues to descend in the contralateral dorsolateral spinal white matter. Most notable among the neurons of the dorsolateral corticospinal tract are the ________– extremely large pyramidal neurons of the primary motor cortex.

Answer 3

Medullary pyramids,

Betz cells

Question 4

Most axons of the dorsolateral corticospinal tract synapse on small interneurons of the ___________, which synapse on the ________ of the distal muscles of the wrist, hands, fingers, and toes.

Answer 4

Spinal gray matter,

Motor neurons

Question 5

Primates and the few other mammals that are capable of moving their digits independently have __________ tract neurons that synapse directly on digit ________ neurons.

Answer 5

Dorsolateral corticospinal,

motor

Question 6

A second group of axons that descends from the primary motor cortex synapses in the _________ of the midbrain. The axons of neurons in the ________ then decussate and descend through the _________, where some of them terminate in the nuclei of the cranial nerves that control the muscles of the _____. The rest continue to descend in the _________ portion of the spinal cord. This pathway is called the ___________.

Answer 6

Red nucleus,
Red nucleus,
Medulla,
Face,
Dorsolateral,

Dorsolateral corticorubrospinal tract (rubro refers to the red nucleus)

Question 7

The axons of the ___________ tract synapse on the interneurons that in turn synapse on motor neurons that project to the distal muscles of the arms and legs.

Answer 7

Dorsolateral corticorubrospinal

Question 8

Betz cells are in the _________ tract.

Answer 8

Dorsolateral corticospinal

Question 9

There are two major divisions of the dorsolateral motor pathway, one direct (__________) and one indirect (___________).

Answer 9

Direct = the corticospinal tract
Indirect = the corticorubrospinal tract

Question 10

The direct ventromedial pathway is the _________, and the indirect one is called the _________.

Answer 10

Ventromedial corticospinal tract,

Ventromedial cortico-brainstem-spinal tract

Question 11

The long axons of the ventromedial corticospinal tract descend ipsilaterally from the ____________ directly into the _______ areas of the ________. As each axon of the ventromedial corticospinal tract descends, it branches diffusely and innervates the ________ in several different spinal segments on both sides of the __________.

Answer 11

Primary motor cortex,
Ventromedial,
Spinal white matter,
Interneuron circuits,
Spinal gray matter

Question 12

Which four brain stem structures interact with the ventromedial cortico-brainstem-spinal tract?

Answer 12

1-The tectum,

2-The vestibular nucleus,

3-The reticular formation,

4-The motor nuclei of the cranial nerves that control the muscles of the face.

Question 13

The _______ receives auditory and visual information about spatial location.
The _______ receives information about balance from receptors in the semicircular canals of the inner ear.
The _______ (among other things) contains motor programs that regulate complex species-typical movements such as walking, swimming, and jumping.

Answer 13

Tectum,
Vestibular nucleus
Reticular formation

Question 14

The tectum

Answer 14

Receives auditory and visual information about spatial location.

Question 15

Vestibular nucleus

Answer 15

Receives information about balance from receptors in the semicircular canals.

Question 16

Reticular formation (with regards to the ventromedial cortico-brainstem-spinal tract)

Answer 16

Contains motor programs that regulate complex species-typical movements such as walking, swimming, and jumping.

Question 17

The __________ comprises motor cortex axons that feed into a complex network of brain stem structures. The axons of some of the neurons of this complex brain stem motor network then descend _________ into the ventromedial portion of the _________. Each side carries signals from both hemispheres, and each neuron synapses in the interneurons of several different spinal cord segments that control the proximal muscles of the ________ and _______.

Answer 17

Ventromedial cortico-brainstem-spinal tract,
Bilaterally,
Spinal cord,
Trunk,
Limbs

Question 18

The descending dorsolateral and ventromedial pathways are similar in that each is composed of two major tracts, one whose axons descend directly to the _______ and another whose axons synapse in the _______ on neurons that in turn descend to the _______.

Answer 18

Spinal cord,
Brain stem,
Spinal cord

Question 19

The two dorsolateral tracts differ from the two ventromedial tracts in two major respects:

Answer 19

• the two ventromedial tracts are much more diffuse. Many of their axons innervate interneurons on both sides of the spinal gray matter and in several segments, whereas the axons of the two dorsolateral tracts terminate in the contralateral half of one spinal cord segment, sometimes directly on a motor neuron.
• the motor neurons activated by the two ventromedial tracts project to proximal muscles of the trunk and limbs (e.g., shoulder muscles), whereas the motor neurons activated by the two dorsolateral tracts project to distal muscles (e.g., finger muscles).

Question 20

Because all four of the descending motor tracts originate in the __________, all are presumed to mediate __________; however, major differences in their routes and destinations suggest that they have __________.

Answer 20

Cerebral cortex,
Voluntary movement,
Different functions

Question 21

What happened to the monkeys when scientists transected the left and right dorsolateral corticospinal tracts, just above the decussation of the tracts?

Answer 21

The monkeys could stand, walk, and climb quite normally; however, their ability to use their limbs for other activities was impaired.

Reaching movements were impaired (especially in the first few days), they never regained the ability to move their fingers independently of one another, and never regained the ability to release objects from their grasp. Oddly, they could release grasp on bars of cage when climbing, meaning that the same response performed in different contexts can be controlled by different parts of the central nervous system.

Question 22

The two ventromedial tracts are involved in the control of _______ and ________ and they can exert control over the limb movements involved in such activities.

Answer 22

Posture,

Whole-body movements (e.g., walking and climbing)

Question 23

Both dorsolateral tracts control the movements of the _______. This redundancy was presumably the basis for the good recovery of limb movement after the initial lesions of the corticospinal dorsolateral tract. However, only the _________ division of the dorsolateral system is capable of mediating independent movement of the digits.

Answer 23

Limbs,

Corticospinal

Question 24

_________ are the smallest units of motor activity. Each contains a single ________ and all of the individual skeletal muscle fibers that it innervates.

Answer 24

Motor units,

Motor neuron

Question 25

When the _______ fires, all the muscle fibers of its unit contract together. Motor units differ appreciably in the number of muscle fibers they contain; the units with the ______ fibers- those of the fingers and face- permit the _____ degree of selective motor control.

Answer 25

Motor neuron,
Fewest,
Highest

Question 26

A skeletal muscle comprises hundreds of thousands of threadlike muscle fibers bound together in a tough membrane and attached to a bone by a _______.

Answer 26

Tendon

Question 27

_________, which is released by motor neurons at neuromuscular junctions, activated the _________ on each muscle fiber and causes the fiber to contract.

Answer 27

Acetylcholine,

Motor end-plate

Question 28

________ is the only method that muscles have for generating force, thus any muscle can generate force in only ________.

Answer 28

Contraction,

One direction

Question 29

All of the motor neurons that innervate the fibers of a single muscle are called its ________.

Answer 29

Motor pool

Question 30

Although an oversimplification, skeletal muscle fibers are often considered to be of two basic types:

Answer 30

Fast and slow

Question 31

Fast muscle fibers

Answer 31

Those that contract and relax quickly. Capable of generating great force, but fatigue quickly because they are poorly vascularized (have fewer blood vessels, which give them a pale color).

Question 32

Slow muscle fibers

Answer 32

Slow and weaker, but capable of sustained contraction because they are more richly vascularized (and hence much redder).

Question 33

Two types of muscle contraction:

Answer 33

Isometric contraction

Dynamic contraction

Question 34

Isometric contraction

Answer 34

Activation of a muscle can increase the tension that it exerts on two bones without shortening and pulling them together; this is termed isometric contraction.

Question 35

Dynamic contraction

Answer 35

Activation of a muscle can shorten and pull them together; this is termed dynamic contraction.

Question 36

The tension of a muscle can be increased by increasing the number of ________ in its motor pool that are ________, by increasing the firing rates of those already firing, or more commonly a _______.

Answer 36

Neurons,
Firing,
A combination of both.

Question 37

The activity of skeletal muscles is monitored by two kinds of receptors:

Answer 37

Golgi tendon organs

Muscle spindles

Question 38

________ are imbedded in the tendons, which connect each skeletal muscle to bone; ________ are embedded in the muscle tissue itself.

Answer 38

Golgi tendon organs,

Muscle spindles

Question 39

Golgi tendon organs respond to _______, but they are completely insensitive to changes in _______.

Answer 39

Increases in muscle tension (i.e., to the pull of the muscle on the tendon),

muscle length.

Question 40

Muscle spindles respond to changes in _______, but they do not respond to changes in _______.

Answer 40

Muscle length,

Muscle tension.

Question 41

Under normal conditions, the function of the Golgi tendon organs is to provide the central nervous system with information about _______, but they also serve a protective function. When the contraction of a muscle is so extreme that there is risk of damage, the Golgi tendon organs excite _______ in the spinal cord that cause the muscle to ______.

Answer 41

Muscle tension,
Inhibitory interneurons,
Relax

Question 42

_______ act to bend or flex a joint, and _______ act to straighten or extend it.

Answer 42

Flexors,

Extensors

Question 43

Any two muscles whose contraction produces the same movement, be it flexion or extension, are said to be _______. Those that act in opposition, like triceps and biceps, are said to be ________.

Answer 43

Synergistic muscles,

Antagonistic muscles

Question 44

The leg extension that happens as a result of the tap on the knee that is often done by doctors with a rubber headed hammer.

Answer 44

Patellar tendon reflex

Question 45

Stretch reflex

Answer 45

A reflex elicited by a sudden external stretching force on a muscle (like the patellar tendon reflex).

Question 46

(Patellar tendon reflex) The rap on the knee _______ stretches the _______ of the thigh muscle and elicits a burst of firing in their _______ neurons. The burst of firing in the ________ neurons triggers a burst of firing in the thigh muscle _______ neurons, which causes the thigh muscle to _______.

Answer 46

Tendon,
Spindles,
Afferent,
Spindle afferent,
Motor,
Contract

Question 47

The reflex that occurs after touching something painful.

Answer 47

Withdrawal reflex

Question 48

The leg extension that happens as a result of the tap on the knee that is often done by doctors with a rubber headed hammer.

Answer 48

Patellar tendon reflex

Question 49

Stretch reflex

Answer 49

A reflex elicited by a sudden external stretching force on a muscle (like the patellar tendon reflex).

Question 50

Unlike the stretch reflex, the ______ reflex is not monosynaptic.

Answer 50

Withdrawal

Question 51

________ refers to the fact that antagonistic muscles are innervated in a way that permits a smooth, unimpeded motor response: when one is ________, the other relaxes.

Answer 51

Reciprocal innervation,

Contracted

Question 52

“Bad news” of a sudden painful event in the hand arrives in the ______ of the spinal cord and has two effects: the signals excite both ______ and ______ interneurons.

Answer 52

Dorsal horn,
excitatory,
Inhibitory

Question 53

Movements are quickest when there is simultaneous excitation of all ______ and complete inhibition of all ______; however, this is not the way voluntary movement is normally produced. Most muscles are always ______ to some degree, and movements are produced by adjustment in the level of relative cocontraction between ______.

Answer 53

Agonists,
Antagonists,
Contracted,
Antagonists

Question 54

Cocontraction

Answer 54

the simultaneous contraction of agonist and antagonist muscles around a joint.

Question 55

Movements produced by cocontraction are _____, and they can be stopped with precision by a slight increase in the contraction of the _____ muscles.

Answer 55

Smooth,

Antagonistic

Question 56

Recurrent collateral inhibition

Answer 56

A system of negative feedback which allows Renshaw cells to inhibit a neuron by communicating through a branched axon loop returning to the cell body. This system hinders repetitive firing of a single motor neuron.

What is RECURRENT COLLATERAL INHIBITION? definition of RECURRENT COLLATERAL INHIBITION (Psychology Dictionary)

Question 57

Each motor neuron branches just before it leaves the _______, and the ranch synapses on a small _______ interneuron, which _______ the very motor neuron from which it receives its input.

Answer 57

Spinal cord,
Inhibitory,
Inhibits

(The inhibition produced by these local feedback circuits is called recurrent collateral inhibition)

Question 58

What are the small inhibitory interneurons that mediate recurrent collateral inhibition?

Answer 58

Renshaw cells

Question 59

What is motor equivalence?

Answer 59

The fact that the same basic movement can be carried out in different ways involving different muscles.

For example, if you wrote your name with your toe, your signature would still retain many of its typical characteristics.

Question 60

Motor equivalence suggests that specific central sensorimotor programs for signing your name are not stored in the ________ that directly control your preferred hand; general programs are stored higher in your ________ and then are adapted to the situation as required.

Answer 60

Neural circuits,

Sensorimotor hierarchy

Question 61

Response chunking hypothesis

Answer 61

The idea that practice combines the central sensorimotor programs that control individual responses into programs that control sequences of responses (chunks of behavior).

(In a novice typer, each letter is individually controlled, rather than an expert who would see the words as a chunk)

Question 62

The Jenkins and colleagues brain-imaging studies found that:

Answer 62

the more someone practiced something, the less the association areas and the cerebellum were involved in executing the process.

Question 63

What is sensory feedback?

Answer 63

Sensory feedback is feedback provided within the sensory systems where information from sensory receptors is returned along the afferent pathways so the brain can monitor the consequence of actions