Chapter 26: Initiation and Control of Coordinated Muscular Movements

Test Bank

Type: multiple choice question

Title: Chapter 26 - Question 01

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)?

Feedback: Subhead: The Motor Unit

Learning Objective: Differentiate between α motoneurons and γ motoneurons.

Bloom’s Level: 4. Analyzing

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.

Type: multiple choice question

Title: Chapter 26 - Question 02

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)?

Feedback: Subhead: The Motor Unit

Learning Objective: Differentiate between α motoneurons and γ motoneurons.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 03

3. Which of the following is true about α motoneurons?

Feedback: Subhead: The Motor Unit

Learning Objective: Name the elements that make up a motor unit.

Bloom’s Level: 2. Understanding

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.

Type: multiple choice question

Title: Chapter 26 - Question 04

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

Feedback: Subhead: The Motor Unit

Learning Objective: Name the elements that make up a motor unit.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 05

5. The most important means used to control muscle tension is

Feedback: Subhead: The Motor Unit

Learning Objective: Name the elements that make up a motor unit.

Bloom’s Level: 2. Understanding

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.

Type: multiple choice question

Title: Chapter 26 - Question 06

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

Feedback: Subhead: The Motor Unit

Learning Objective: Describe the two basic types of skeletal muscle fibers.

Bloom’s Level: 3. Applying

a. Fatigue quickly

b. Contract quickly

c. Poorly vascularized

d. High myoglobin content

e. Relatively low oxidative capacity

Type: multiple choice question

Title: Chapter 26 - Question 07

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

Feedback: Subhead: The Motor Unit

Learning Objective: Describe the two basic types of skeletal muscle fibers.

Bloom’s Level: 3. Applying

a. be large.

b. have high endurance capacity.

c. be highly vascularized.

d. have high myoglobin content.

e. have relatively high oxidative capacity.

Type: multiple choice question

Title: Chapter 26 - Question 08

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

Feedback: Subhead: The Motor Unit

Learning Objective: Describe the two basic types of skeletal muscle fibers.

Bloom’s Level: 2. Understanding

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.

Type: multiple choice question

Title: Chapter 26 - Question 09

9. 1a afferents are least active in terms of action potential firing to the spinal cord when the muscle is

Feedback: Subhead: The Motor Unit

Learning Objective: Describe the role of muscle spindles in muscle contraction.

Bloom’s Level: 3. Applying

a. stretched.

b. contracted.

c. relaxed.

d. generating great force.

e. heavily vascularized.

Type: multiple choice question

Title: Chapter 26 - Question 10

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

Feedback: Subhead: The Motor Unit

Learning Objective: Describe the process of temporal summation and spatial summation.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 11

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

Feedback: Subhead: The Motor Unit

Learning Objective: Explain the concept of the size principle of motor recruitment.

Bloom’s Level: 3. Applying

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)

Type: multiple choice question

Title: Chapter 26 - Question 12

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

Feedback: Subhead: The Motor Unit

Learning Objective: Explain the concept of the size principle of motor recruitment.

Bloom’s Level: 3. Applying

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

Type: multiple choice question

Title: Chapter 26 - Question 13

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

Feedback: Subhead: Spinal Reflexes

Learning Objective: Distinguish between agonists and antagonists and between extensor muscles and flexor muscles.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 14

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

Feedback: Subhead: Spinal Reflexes

Learning Objective: Distinguish between agonists and antagonists and between extensor muscles and flexor muscles.

Bloom’s Level: 2. Understanding

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.

Type: multiple choice question

Title: Chapter 26 - Question 15

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

Feedback: Subhead: Spinal Reflexes

Learning Objective: Describe the underlying mechanisms of the stretch reflex.

Bloom’s Level: 3. Applying

a. extrafusal muscle fibers.

b. 1a afferents.

c. intrafusal muscle fibers.

d. α motoneurons.

e. γ motoneurons.

Type: multiple choice question

Title: Chapter 26 - Question 16

16. The sensory receptors for the stretch reflex is contained

Feedback: Subhead: Spinal Reflexes

Learning Objective: Describe the underlying mechanisms of the stretch reflex.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 17

17. The flexor reflex is also often called the “withdrawal reflex”. This is because it

Feedback: Subhead: Spinal Reflexes

Learning Objective: Describe the two consistent features of the flexor reflex.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 18

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?

Feedback: Subhead: Spinal Reflexes

Learning Objective: Describe the two consistent features of the flexor reflex.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 19

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

Feedback: Subhead: Motor Control of Muscle Spindles

Learning Objective: Describe the role of fusimotor fibers in muscle contraction.

Bloom’s Level: 4. Analyzing

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.

Type: multiple choice question

Title: Chapter 26 - Question 20

20. Central (CNS) awareness of muscle stretch occurs because of

Feedback: Subhead: Motor Control of Muscle Spindles

Learning Objective: Describe the role of fusimotor fibers in muscle contraction.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 21

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

Feedback: Subhead: Motor Control of Muscle Spindles

Learning Objective: Explain the function served by coactivation of α and γ motoneurons.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 22

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

Feedback: Subhead: Generation of Coordinated Movements

Learning Objective: Describe where the central pattern generator for respiration is situated and how it generates the rhythm of breathing.

Bloom’s Level: 3. Applying

a. respiratory defense centers.

b. higher respiratory centers.

c. cardiovascular respiratory centers.

d. pulmonary respiratory centers.

e. brainstem respiratory centers.

Type: multiple choice question

Title: Chapter 26 - Question 23

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

Feedback: Subhead: Generation of Coordinated Movements

Learning Objective: Describe where the central pattern generator for respiration is situated and how it generates the rhythm of breathing.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 24

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

Feedback: Subhead: Generation of Coordinated Movements

Learning Objective: Explain how the level of carbon dioxide in the environment influences the rhythmicity of breathing.

Bloom’s Level: 3. Applying

a. bicarbonate.

b. oxygen.

c. water.

d. carbon dioxide.

e. protons.

Type: multiple choice question

Title: Chapter 26 - Question 25

25. Protons and carbon dioxide are linked in the CNS because

Feedback: Subhead: Generation of Coordinated Movements

Learning Objective: Explain how the level of carbon dioxide in the environment influences the rhythmicity of breathing.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 26

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)?

Feedback: Subhead: Generation of Coordinated Movements

Learning Objective: Discuss the experimental evidence for the role of a central mechanism in producing coordinated leg movements.

Bloom’s Level: 6. Creating

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

Type: multiple choice question

Title: Chapter 26 - Question 27

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

Feedback: Subhead: Generation of Coordinated Movements

Learning Objective: Discuss the experimental evidence for the role of a central mechanism in producing coordinated leg movements.

Bloom’s Level: 3. Applying

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

Type: multiple choice question

Title: Chapter 26 - Question 28

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?

Feedback: Subhead: Generation of Coordinated Movements

Learning Objective: Explain the role of sensory feedback in modulating respiration and locomotion.

Bloom’s Level: 6. Creating

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.

Type: multiple choice question

Title: Chapter 26 - Question 29

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

Feedback: Subhead: Organization of Descending Motor Control

Learning Objective: List six key directional terms that are used in discussing the nervous system.

Bloom’s Level: 2. Understanding

a. anterior.

b. posterior.

c. caudal.

d. dorsal.

e. inferior.

Type: multiple choice question

Title: Chapter 26 - Question 30

30. The origin of the corticospinal tract is in the

Feedback: Subhead: Organization of Descending Motor Control

Learning Objective: Discuss how the lateral and medial motor pathways differ in terms of their anatomy and function.

Bloom’s Level: 2. Understanding

a. cerebral cortex.

b. visual cortex.

c. frontal cortex.

d. lateral spinal cord.

e. medial spinal cord.

Type: multiple choice question

Title: Chapter 26 - Question 31

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

Feedback: Subhead: Organization of Descending Motor Control

Learning Objective: Discuss how the lateral and medial motor pathways differ in terms of their anatomy and function

Bloom’s Level: 2. Understanding

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.

Type: multiple choice question

Title: Chapter 26 - Question 32

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

Feedback: Subhead: Organization of Descending Motor Control

Learning Objective: Discuss how the lateral and medial motor pathways differ in terms of their anatomy and function

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 33

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.

Feedback: Subhead: Motor Cortex and the Execution of Voluntary Movement

Learning Objective: Explain why somatotopic maps show so much distortion in the representation of motor cells.

Bloom’s Level: 2. Understanding

a. diverse

b. large

c. old

d. dense

e. multifunctional

Type: multiple choice question

Title: Chapter 26 - Question 34

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

Feedback: Subhead: Motor Cortex and the Execution of Voluntary Movement

Learning Objective: Discuss why sensory feedback is essential for fixating and tracking objects with the eyes during head movements.

Bloom’s Level: 3. Applying

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

Type: multiple choice question

Title: Chapter 26 - Question 35

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

Feedback: Subhead: Motor Cortex and the Execution of Voluntary Movement

Learning Objective: Explain the role of directionally selective neurons in muscle movement.

Bloom’s Level: 1. Remembering

a. angle.

b. age.

c. activity.

d. proprioception.

e. direction.

Type: multiple choice question

Title: Chapter 26 - Question 36

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

Feedback: Subhead: The Cerebellum and Basal Ganglia

Learning Objective: Explain in general terms how the cerebellum participates in motor control.

Bloom’s Level: 3. Applying

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

Type: multiple choice question

Title: Chapter 26 - Question 37

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

Feedback: Subhead: The Cerebellum and Basal Ganglia

Learning Objective: Describe the synaptic organization of the cerebellar cortex.

Bloom’s Level: 4. Analyzing

a. excitatory.

b. inhibitory.

c. neither excitatory nor inhibitory.

d. both excitatory and inhibitory.

e. None of the above

Type: multiple choice question

Title: Chapter 26 - Question 38

38. Major inputs into the cerebellar cortex originate from

Feedback: Subhead: The Cerebellum and Basal Ganglia

Learning Objective: Describe the synaptic organization of the cerebellar cortex.

Bloom’s Level: 3. Applying

a. stellate and basket cells.

b. Purkinje cells.

c. granule cells.

d. Golgi cells.

e. cells comprising the inferior olive and pontine nuclei.

Type: multiple choice question

Title: Chapter 26 - Question 39

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

Feedback: Subhead: The Cerebellum and Basal Ganglia

Learning Objective: Explain the role played by mossy fibers and climbing fibers in the cerebellum.

Bloom’s Level: 3. Applying

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.

Type: multiple choice question

Title: Chapter 26 - Question 40

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

Feedback: Subhead: The Cerebellum and Basal Ganglia

Learning Objective: List five principle functions served by the basal ganglia.

Bloom’s Level: 3. Applying

a. cerebellum.

b. motor cortex.

c. corticospinal tract.

d. basal ganglia.

e. red nucleus.

Type: multiple choice question

Title: Chapter 26 - Question 41

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

Feedback: Subhead: The Cerebellum and Basal Ganglia

Learning Objective: Name the five key structures of the basal ganglia.

Bloom’s Level: 3. Applying

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

Type: multiple choice question

Title: Chapter 26 - Question 42

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

Feedback: Subhead: The Cerebellum and Basal Ganglia

Learning Objective: Name the five key structures of the basal ganglia.

Bloom’s Level: 3. Applying

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

Type: multiple choice question

Title: Chapter 26 - Question 43

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?

Feedback: Subhead: The Cerebellum and Basal Ganglia

Learning Objective: Discuss two diseases that are caused by disorders of the basal ganglia.

Bloom’s Level: 3. Applying.

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.

Type: essay/short answer question

Title: Chapter 26 - Question 44

44. Explain how a motor unit responds to increasingly stronger loads.

Feedback: Because muscle fibers from a single motor unit are spread throughout the muscle, contraction of a single motor unit would cause only a weak contraction of the entire muscle. As the load increases and more strength is required, therefore, contractions of the muscle must become increasingly stronger, requiring stimulation and recruitment of more motor units.

Subhead: The Motor Unit

Learning Objective: Name the elements that make up a motor unit.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 26 - Question 45

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

Feedback: Time and space are linked together by speed. That is, how fast does an epsp or ipsp travel from the postsynaptic site throughout the rest of the cell before it decays to baseline levels.

Subhead: The Motor Unit

Learning Objective: Describe the processes of temporal summation and spatial summation.

Bloom’s Level: 5. Evaluating

Type: essay/short answer question

Title: Chapter 26 - Question 46

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

Feedback: Besides considering that the input resistance is inversely proportional to its radius, one must also consider the length and thickness of the input dendrites, the distance between point of stimulation on the dendrites and the axon hillock, the thickness of the myelin on the axon, the length of the Nodes of Ranvier, and temporal and spatial summation of inputs to the postsynaptic neuron.

Subhead: The Motor Unit

Learning Objective: Explain the concept of the size principle and motor recruitment.

Bloom’s Level: 4. Analyzing

Type: essay/short answer question

Title: Chapter 26 - Question 47

47. Explain what happens to a muscle when it stretches.

Feedback: When a muscle stretches, not only are extrafusal muscle fibers activated, but also Type II sensory endings, wrapped around intrafusal muscle fibers, are activated, sending sensory signals to the spinal cord via 1a afferents.

Subhead: Spinal Reflexes

Learning Objective: Distinguish between agonists and antagonists and between extensor and flexor muscles.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 26 - Question 48

48. Explain the function of Golgi Tendon Organs.

Feedback: Golgi Tendon Organs respond when the muscle contracts by activating antagonist muscles during stretch; therefore, as a reflex, they help prevent injuries caused by overstretching. They work by sending inhibitory sensory signals to the spinal cord via 1b afferents. As such, they are also considered proprioceptors.

Subhead: Spinal Reflexes

Learning Objective: Describe the underlying mechanisms of the stretch reflex.

Bloom’s Level: 2. Understanding

Type: essay/short answer question

Title: Chapter 26 - Question 49

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

Feedback: The painful stimulus on the foot activates nociceptors, which then sends afferent action potentials to the spinal cord via sensory neurons, which then diverge upon entering the dorsal horn, where they will make polysynaptic contacts with interneurons in the dorsal, intermediate and ventral horns. These inter-neurons will then make secondary synaptic contacts with α motoneurons, which will then be sent to the periphery. Some of these inter-neurons are inhibitory and therefore, inhibit the following α motoneurons as they leave the ventral horn: Those that exit the spinal cord via the contra-lateral ventral horn will serve the contra-lateral leg. These descending motor neurons will then (1) inhibit the extensors in the ipsilateral thigh and the extensors in the contra-lateral hamstrings, and (2) stimulate the flexors in the ipsilateral hamstrings and the extensors in the contra-lateral thigh. These actions on the contra-lateral leg enable the person to more firmly plant that limb on the ground, thereby helping to ensure that balance is maintained. Meanwhile, ascending pathways are sent to the sensorimotor cortex in the brain to perceive the pain. In addition, the upper limbs might also be stimulated to grab a hold of something to reinforce maintenance of balance.

Subhead: Spinal Reflexes

Learning Objective: Describe the two consistent features of the flexor reflex.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 26 - Question 50

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.

Feedback: While carrying the initial load, both α and γ motoneurons are firing action potentials. When the load is suddenly increased, intrafusal muscle activation and spindle discharge is increased, which, then in turn, increases α motoneuron discharge and extrafusal muscle contraction. When the extrafusal discharge and contraction have caught up with that of the intrafusal muscles, a new level of increased contraction is established to accommodate the heavier load.

Subhead: Motor Control of Muscle Spindles

Learning Objective: Explain the function served by coactivation of α and γ motoneurons.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 26 - Question 51

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.

Feedback: Protons cannot cross the blood-brain barrier, but carbon dioxide easily does so. During times of poor respiration, carbon dioxide accumulates in the blood, travels to the CNS, and then crosses the blood-brain barrier, where, once on the CNS side, it can be converted into bicarbonate and protons, which then stimulate the chemosensitive area (aka., dorsal respiratory group) in the medulla.

Subhead: Generation of Coordinated Movements

Learning Objective: Explain how the level of carbon dioxide in the environment influences the rhythmicity of breathing.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 26 - Question 52

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?

Feedback: A treadmill is predictable and even. In real life, the terrain is often rugged and unpredictable, filled with obstacles that could cause you to lose balance, if the proper sensory feedback pathways were not functioning at optimal levels or you were simply not paying attention.

Subhead: Generation of Coordinated Movements

Learning Objective: Explain the role of sensory feedback in modulating respiration and locomotion.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 26 - Question 53

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

Feedback: The lateral cortiospinal tract originates in the lateral pre-central gyrus, decussate in the medulla and travel through the most lateral aspect of the contra-lateral spinal cord, which mediate the more distal limbs (hands, fingers); such somatotypy is seen in a somatotopic map in the grey matter of the spinal cord, where the most intermediate horns mediate motoneurons that will eventually innervate the muscles of the hands and fingers. In contrast, the ventral corticospinal tract originates more medially in the pre-central gyrus, but do not decussate, and travel ipsilateral through the spinal cord ventral column, where they mediate the more proximal limbs (upper and forearm); likewise, such somatotypy is revealed in the somatotopic map in the grey matter of the spinal cord, where the ventral horn medate motorneurons that will eventually innervate the muscles of the upper arm and forearms.

Subhead: Organization of Descending Motor Control

Learning Objective: Discuss how the lateral and medial motor pathways differ in terms of their anatomy and functions.

Bloom’s Level: 4. Analyzing

Type: essay/short answer question

Title: Chapter 26 - Question 54

54. Give examples of distortion of the somatotopic map.

Feedback: Activities and skills requiring fine motor coordination and dexterity are afforded large swaths of motor cortex, where neuronal is relatively high. Such examples may be playing the piano, typing, speaking, executed by fingers, tongue and lips. On the other hand, larger body parts, such as the torso and the legs are afforded relatively less cortical density and volume, as they require little-to-no fine motor skill.

Subhead: Motor Cortex and the Execution of Voluntary Movement

Learning Objective: Explain why somatotopic maps show so much distortion in the representation of motor cells.

Bloom’s Level: 3. Applying

Type: essay/short answer question

Title: Chapter 26 - Question 55

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.

Feedback: To track a fast-moving object, saccades occur: the eyes must move quickly and in tandem to bring the fovea to the image. To assist with this, the occipital-to-posterior parietal cortex and the frontal cortex (planning movements) converge on the superior colliculus for controlling vertical saccades and on the pontine reticular formation for controlling horizontal saccades. These, in turn, send afferents to the three cranial nerves (III, IV, VI) to move the eye. To track a slow-moving object, smooth pursuit also entails moving the eyes in tandem to track a moving object. But, in this case, the midtemproal and midsuperior temporal lobes stimulate the pontine nuclei; but involvement of the three cranial nerves is not absolutely necessary.

Subhead: Motor Cortex and the Execution of Voluntary Movement

Learning Objective: Discuss why sensory feedback is essential for fixating and tracking objects with the eyes during head movements.

Bloom’s Level: 4. Analyzing

Type: essay/short answer question

Title: Chapter 26 - Question 56

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?

Feedback: Orientation columns in the visual cortex respond to angles of an object seen with respect some point of references, such as the horizontal plane.

Subhead: Motor Cortex and the Execution of Voluntary Movement

Learning Objective: Explain the role of directionality selective neurons in muscle movement.

Bloom’s Level: 4. Analyzing

Type: essay/short answer question

Title: Chapter 26 - Question 57

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.

Feedback: Thinking of initiating a movement begins in higher cortical areas, such as the parietal or pre-frontal and frontal (a nonprimary motor cortex) cortices. These activate the primary motor cortex (pre-central gyrus), which then activates the brainstem (medullary and pontine nuclei), which, in turn, send axons to the spinal cord and then to the muscles of the body, as well as to the muscles of the head and neck (via separate pathways). The pre-central gyrus sends input to and receives input from the cerebellum and basal ganglia, which are involved in refinement and visual processing of the object (e.g., you are reaching for a pen) of our movement in relation to ourselves in space. In turn, both the cerebellum and basal ganglia also modulate the inputs into the brainstem and spinal cord sent to these two latter places by the pre-central gyrus. Because of all this interaction, we don’t only just perform the movement, but we can do so smoothly, competently, rather than clumsily.

Subhead: The Cerebellum and Basal Ganglia

Learning Objective: Explain in general terms, how the cerebellum participates in motor control.

Bloom’s Level: 4. Analyzing

Type: essay/short answer question

Title: Chapter 26 - Question 58

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.

Feedback: In PD, the decreased dopamine from the substantia nigra leads to decreased inhibition of the inhibition, leading to excessive inhibitory output, resulting in hypokinesia and bradykinesia via decreased thalamic signals to the cortex, finally resulting in decreased corticospinal outflow. In HD, there is decreased striatal (enkephalin) output and decreased inhibition of globus pallidus, leading to enhanced excitatory effects of indirect path, resulting in decreased inhibition via direct path and then hyperkinesis.

Subhead: The Cerebellum and Basal Ganglia

Learning Objective: Discuss two diseases that are caused by disorders of the basal ganglia.

Bloom’s Level: 4. Analyzing