Deck 26: Initiation and Control of Coordinated Muscular Movements

Question 1

If a skeletal muscle fiber is excised from the body, mounted between two immovable plates, and then concentrically stretched (lengthened), which will respond more than the other (in terms of firing action potentials)?

A) A (alpha) motoneurons will respond more than γ motoneurons.
B) Γ motoneurons will respond more than α motoneurons.
C) A (alpha) and γ motoneurons will respond to the same extent.
D) Neither α nor γ motoneurons will respond in this artificial setup.
E) It depends on how much stretch is employed.

Answer 1

E

Question 2

In physical movements that require a lot of stretching (e.g., yoga), which of the following will respond more than the other (in terms of firing action potentials)?

A) A (alpha) motoneurons will respond more than γ motoneurons.
B) Γ motoneurons will respond more than α motoneurons.
C) A (alpha) and γ motoneurons will respond to the same extent.
D) Neither α nor γ motoneurons will respond in this artificial setup.
E) It depends on how much stretch is employed.

Answer 2

B

Question 3

Which of the following is true about α motoneurons?

A) They make synaptic contact with intrafusal muscle fibers.
B) They make synaptic contact with joints, thereby regulating the force that the muscle is capable of exerting.
C) They sense stretch of the muscle.
D) They are the presynaptic endings that comprise the neuromuscular junction.
E) They are the postsynaptic endings that comprise the neuromuscular junction.

Answer 3

D

Question 4

The ratio of the number of α motoneurons to the number of muscle fibers it innervates is associated with how

A) large the muscle is.
B) many muscle fibers there are.
C) complex the α motor neuron is.
D) often the muscle is used.
E) much dexterity the movement requires.

Question 5

The most important means used to control muscle tension is

A) increased use of extrafusal muscle fibers.
B) increased use of intrafusal muscle fibers.
C) recruitment of more motor units.
D) recruitment of more mitochondria.
E) recruitment of more Golgi Tendon Organs.

Question 6

In endurance training (e.g., running, swimming), which of the following best describes the characteristics of the muscles used?

A) Fatigue quickly
B) Contract quickly
C) Poorly vascularized
D) High myoglobin content
E) Relatively low oxidative capacity

Question 7

The muscles on which strength training (e.g., power-lifting, weight-lifting, resistance training) depends would

A) be large.
B) have high endurance capacity.
C) be highly vascularized.
D) have high myoglobin content.
E) have relatively high oxidative capacity.

Question 8

Skeletal muscle fibers can be grouped into two basic types. These are known as

A) extrafusal and intrafusal muscle fibers.
B) α and γ motoneurons.
C) slow-twitch and fast-twitch muscle fibers.
D) myotatic and spinal muscle fibers.
E) striated and unstriated muscle fibers.

Question 9

1a afferents are least active in terms of action potential firing to the spinal cord when the muscle is

A) stretched.
B) contracted.
C) relaxed.
D) generating great force.
E) heavily vascularized.

Question 10

In temporal summation, postsynaptic neurons may respond to input from presynaptic neurons if such input

A) occurs all on the same postsynaptic site.
B) all occur on different postsynaptic sites.
C) occur in rapid succession.
D) are all excitatory.
E) are all subthreshold.

Question 11

Which of the following muscles would experience the least amount of motor recruitment?

A) Latissimus dorsi (found in the back)
B) Pectoralis major (found in the chest)
C) Rectus femoris (found in the thigh)
D) Adductor pollicis (found in the hand)
E) Superior oblique (abducts the eyes)

Question 12

The greater the force needed, the greater the _______ in gradually increasing _______.

A) motor unit recruitment; neuron size
B) motor unit recruitment; muscle size
C) motor unit recruitment; motor unit size
D) spatial summation; neuron size
E) temporal summation; neuron size

Question 13

In the myotatic knee-jerk reflex, what would happen if the α motoneurons to the hamstrings were severed?

A) The lower leg would tremor.
B) The thigh would tremor.
C) The Golgi tendon organ would experience exaggerated stretch.
D) The intrafusal muscle fibers would extensively.
E) The extrafusal muscle fibers would stop firing.

Question 14

Reciprocal innervation means that contraction of one muscle set is accompanied by

A) relaxation of an antagonistic muscle.
B) stimulation of a downstream muscle.
C) stimulation of its downstream Golgi tendon organs.
D) inhibition of an antagonistic muscle.
E) stimulation of an antagonistic muscle.

Question 15

When the monosynaptic stretch reflex is first initiated, the first thing to respond is

A) extrafusal muscle fibers.
B) 1a afferents.
C) intrafusal muscle fibers.
D) α motoneurons.
E) γ motoneurons.

Question 16

The sensory receptors for the stretch reflex is contained

A) deep within the extrafusal muscle fibers.
B) deep within the intrafusal muscle fibers.
C) in the muscle spindles.
D) within the Golgi tendon organs.
E) surrounding the Golgi tendon organs.

Question 17

The flexor reflex is also often called the "withdrawal reflex". This is because it

A) is a polysynaptic reflex arc.
B) is life-preserving or causes avoidance of an aversive stimulus.
C) causes the animal to withdraw into isolation.
D) involves each side of the body, one at a time.
E) involves both sides of the body, sequentially.

Question 18

Which of the following about the flexor reflex would most likely be different in someone who steps on a sharp object with one foot vs. someone who touches a hot stove with their hand?

A) Stepping on a sharp object would involve only α, but not γ, motoneurons.
B) Stepping on a sharp object would involve only γ, but not α, motoneurons.
C) Stepping on a sharp object would likely require the use contralateral leg, but touching a hot stove would not require using the contralateral hand to maintain balance.
D) Stepping on a sharp object would involve the upper limbs as well, but touching a hot stove would not likely involve the lower limbs to maintain balance.
E) Stepping on a sharp object would require higher-order cerebral centers to help maintain balance, but touching a hot stove would not.

Question 19

Recordings of extrafusal muscle tension and accompanying sensory discharge from muscle spindles reveal that

A) stimulation of α motoneurons is required to elicit a response from fusiform γ efferents.
B) fusiform efferents respond when extrafusal muscle fibers are relaxed.
C) fusiform efferents respond only if extrafusal muscle fibers are stimulated.
D) intrafusal muscle fibers' work load is proportional to that of the extrafusal muscle fibers.
E) intrafusal muscle fibers exhibit either maximum tension or none at all, depending on the tension experienced by the extrafusal muscle fibers.

Question 20

Central (CNS) awareness of muscle stretch occurs because of

A) stimulation of α motoneurons.
B) stimulation of γ motoneurons.
C) relaxation of α motoneurons.
D) relaxation of γ motoneurons.
E) stimulation of both α and γ motoneurons.

Question 21

One of the main benefits of α and γ motoneuron coactivation is to

A) provide constant feedback to the brain regarding muscle tension and length.
B) prevent injury to the muscle because if stretched too much, it will resist stretch.
C) provide greater flexibility of the muscle.
D) provide the muscle with greater strength.
E) allow the muscle to hypertrophy.

Question 22

Medullary and pontine respiratory centers are considered to be primitive centers, controlling baseline levels of respiration, which, however, can be modulated by emotions, changes in environmental temperature and innate defense (e.g., sneezing, coughing). These are considered to be

A) respiratory defense centers.
B) higher respiratory centers.
C) cardiovascular respiratory centers.
D) pulmonary respiratory centers.
E) brainstem respiratory centers.

Question 23

Regarding the inspiratory center in the medulla (aka the dorsal respiratory group), action potential frequency is

A) inversely proportional to rate of exhalation.
B) proportional to the rate of exhalation.
C) inversely proportional to the rate of inhalation.
D) proportional to the rate of inhalation.
E) proportional to the depth of inhalation.

Question 24

The chemical signal in the CNS that causes changes in respiratory rate and/or depth is

A) bicarbonate.
B) oxygen.
C) water.
D) carbon dioxide.
E) protons.

Question 25

Protons and carbon dioxide are linked in the CNS because

A) protons cannot cross the blood-brain-barrier, while carbon dioxide can.
B) carbon dioxide cannot cross the blood-brain-barrier, while protons can.
C) bicarbonate cannot cross the blood-brain-barrier, while protons can.
D) protons cannot cross the blood-brain-barrier, while bicarbonate can.
E) water cannot cross the blood-brain-barrier.

Question 26

In the experiments in which the cat's mesencephalic locomotor region was transected, strength of stepping was proportional to strength of electrical stimulation applied to this nucleus but had no effect on speed. What is a plausible way to centrally control stepping speed (running)?

A) Stimulating the basal ganglia
B) Stimulating the deep cerebellar nuclei
C) Stimulating the motor cortex
D) Inhibiting the deep cerebellar nuclei
E) Inhibiting the basal ganglia

Question 27

Which of the following scenarios most illustrate that complex motor movements are genetically programmed, rather than learned.

A) A human baby taking its first steps
B) Juvenile birds trying to fly for the first time
C) Birds teaching their offspring singing
D) Kitten stalking and catching a mouse
E) A dog running when you call him

Question 28

You placed a person in an air-tight chamber with a treadmill set at first and comfortable walking speed, but then gradually inclined so that to maintain the same speed, walking intensity had to increase. At this point, then, if the ambient levels of carbon dioxide was gradually raised to levels that are just high enough to raise its levels in the blood, but not enough to cause unconsciousness or kill the person, what would be the probable resulting respiratory rate?

A) It would not change.
B) It would gradually increase throughout the duration of the experiment.
C) It would gradually decrease throughout the duration of the experiment.
D) it would increase and then gradually decrease as carbon dioxide levels rose.
E) It would decrease and then gradually increase as carbon dioxide levels rose.

Question 29

When a person is on all four limbs, with knees and hands touching the floor, the back is

A) anterior.
B) posterior.
C) caudal.
D) dorsal.
E) inferior.

Question 30

The origin of the corticospinal tract is in the

A) cerebral cortex.
B) visual cortex.
C) frontal cortex.
D) lateral spinal cord.
E) medial spinal cord.

Question 31

Which of the functions is characteristic of the ventral corticospinal tract?

A) It mediates control of only distal muscles.
B) It descends all the way to the lumbar spinal cord.
C) It descends in the ipsilateral ventral column.
D) It terminates unilaterally in the spinal cord.
E) It mediates control of the viscera.

Question 32

Which of the following represents a key feature of the reticulospinal tract?

A) It controls locomotion, balance and posture.
B) It is one of the major lateral descending pathways.
C) It descends only as far as the cervical spinal cord.
D) It controls fine motor skills of the distal limbs.
E) It controls crude motor skills of the proximal limbs.

Question 33

The somatotopic map represents not only what part of the precentral gyrus houses neurons that will ultimately lead to serving a particular body part, but also how _______ those neurons are.

A) diverse
B) large
C) old
D) dense
E) multifunctional

Question 34

Which of the following scenarios best illustrate the use of saccades?

A) Watching goldfish swim around in their bowl from half a meter away
B) Watching a chase scene on TV
C) Watching a football game from high up in the bleachers
D) Watching a football game from the third row
E) Watching an opera from the balcony

Question 35

Experiments by Georgopoulos showed that visually guided arm movements are initiated by corticospinal neurons that were selective for

A) angle.
B) age.
C) activity.
D) proprioception.
E) direction.

Question 36

Which projection from the cerebellum indicates that it is involved in fine motor control?

A) To the motor cortex
B) To the vestibular nuclei
C) To the reticular nuclei
D) To the sensorimotor cortex
E) To the spinal cord

Question 37

Based on the network of synaptic connections among the many different neuron types (e.g., granule, Purkinje, basket) within the cerebellar cortex, it can be fairly stated that overall, the net functional effect of the cerebellum is

A) excitatory.
B) inhibitory.
C) neither excitatory nor inhibitory.
D) both excitatory and inhibitory.
E) None of the above

Question 38

Major inputs into the cerebellar cortex originate from

A) stellate and basket cells.
B) Purkinje cells.
C) granule cells.
D) Golgi cells.
E) cells comprising the inferior olive and pontine nuclei.

Question 39

Mossy fibers and climbing fibers play major roles in involving the cerebellum in coordinating

A) eye movements and equilibrium/balance.
B) gross motor control and equilibrium/balance.
C) gross motor control and hearing.
D) hearing and eye movements.
E) gross motor control and hearing.

Question 40

One of the main hallmark clinical symptoms of Parkinson's Disease is uncontrolled tremors throughout the body. This strongly indicates that this disease involves the

A) cerebellum.
B) motor cortex.
C) corticospinal tract.
D) basal ganglia.
E) red nucleus.

Question 41

Which of the following best matches the structure and neurons with the correct neurotransmitter they use?

A) Substantia nigra and GABA
B) Globus pallidus and glutamate
C) Subthalamic nucleus and glutamate
D) Caudate nucleus and dopamine
E) Subthalmic nucleus and GABA

Question 42

Which of the following describes the action of dopamine on striatal neurons of the direct and indirect paths, respectively?

A) Facilitates activity, suppresses activity
B) Facilitates activity, no effect on activity
C) Suppresses activity, facilitates activity
D) No effect on activity, facilitates activity
E) Suppresses activity, no effect on activity

Question 43

The amino acid, tyrosine, is the first precursor in the biosynthetic pathway that ultimately produces dopamine, which has been drastically decreased in Parkinson's Disease. Why cannot one simply consume large amounts of tyrosine to make up for the loss?

A) The amount of tyrosine needed to produce enough dopamine is toxic.
B) Tyrosine does not easily cross the blood brain barrier.
C) Tyrosine is converted into something else in the periphery before it reaches the CNS.
D) The neurons that convert tyrosine into dopamine have been destroyed.
E) It is impossible to target tyrosine directly to the neurons that produce dopamine from tyrosine.

Question 44

Explain how a motor unit responds to increasingly stronger loads.

Question 45

Although temporal and spatial summation are treated as separate phenomenon in textbooks, explain how they really are not, and rather, interact.

Question 46

What variables would you have to consider in predicting how a postsynaptic neuron will respond, given a certain size?

Question 47

Explain what happens to a muscle when it stretches.

Question 48

Explain the function of Golgi Tendon Organs.

Question 49

Draw/write out the flexor reflex steps of someone who steps on a nail with one bare foot.

Question 50

You are carrying a small stack of books (a moderate load) in your arms. Suddenly, someone tosses another book on top of the stack you are already carrying. Explain how α and γ motoneuron coactivation works to prevent you from dropping all the books when the weight unexpectedly increased.

Question 51

In the ubiquitous reaction, H₂O + CO₂ ↔ H₂CO₃ ↔ HCO₃^- + H⁺, found in the blood, explain how a build-up of protons in the blood leads to increased carbon dioxide in the CNS.

Question 52

What is one possible, yet profound, reason why treadmill experiments to study locomotion, such as those described in your textbook, have little real-life application?

Question 53

How do the topographies of the medial and lateral pathways correlate with the functions that they mediate?

Question 54

Give examples of distortion of the somatotopic map.

Question 55

Despite the fact that the musculature represented in the motor cortex (Fig. 26.17.B) shows the eyes, movement of the eyes are is not controlled by the motor cortex (but rather, by cranial nerves III, IV and VI). Explain the difference, then, between tracking a fast-moving object vs. one that is moving slowly. In both cases, assume that the object is close enough so that the head must move to keep the object on the retina.

Question 56

Which other cortex of another sensory modality is histologically arranged in a way that is analogous to neurons in the motor cortex that guide the limbs in a specific direction?

Question 57

Describe or draw the inter-relationships in how the motor cortex, pre-frontal cortex, basal ganglia, cerebellum, spinal cord and brainstem are involved a movement.

Question 58

Compare Parkinson's Disease (PD) and Huntington's Disease (HD) in terms of neurotransmitters and the how the various structures in the basal ganglia react.