Section 5

Question 1

Describe the muscle receptors and their function.

Question 2

Describe the three levels of neural input involved in motor control.

Question 3

How do skeletal muscles play a key role in proprioception, and can you provide an example to illustrate this concept?

Answer 3

Skeletal muscles contribute to proprioception, which is your awareness of your body in the environment. For example, in the activity mentioned, you can extend your arms overhead and, without looking, point your fingers towards each other to touch your fingertips together. This demonstrates how muscles communicate their positions to the central nervous system without relying on sight.

Question 4

What is the primary role of muscle spindles, and where are they located in the muscles?

Answer 4

Muscle spindles monitor changes in muscle length and are distributed throughout the muscles as a collection of specialized muscle cells known as intrafusal fibers. These fibers are found within spindle-shaped connective tissue and are located among the extrafusal fibers.

Question 5

What is the primary purpose of Golgi tendon organs, and where are they located?

Answer 5

Golgi tendon organs respond to changes in muscle tension and are receptors found at the junction of tendons and muscle fibers.

They respond to both stretch and contraction of the muscle.

When extrafusal fibers contract and pull on the tendons, the stretch activates Golgi tendon organ afferents, which relay this information to the brain. Most of this information is used subconsciously, and it’s related to muscle tension rather than muscle length, which is not consciously perceived.

Question 6

What are the two different kinds of muscle receptors that allow proprioception from muscles to occur?

Answer 6

Muscle spindles and golgi tendon organs.

Question 7

Contrast extrafusal fibers and muscle spindles.

Answer 7

In contrast to extrafusal fibers, which are innervated by alpha motor neurons, muscle spindles are innervated by gamma motor neurons.

Question 8

What is the function of the central region of a muscle spindle, and what kind of information do the sensory afferent fibers in this region transmit to the central nervous system (CNS)?

Answer 8

The central region of a muscle spindle contains sensory afferent fibers that are activated by stretch and transmit information on muscle length and the rate of stretch to the CNS.

Question 9

What are extrafusal fibers?

Answer 9

Regular muscle fibres

Question 10

What is the role of afferent neurons in motor control, and where do they generally occur?

Answer 10

Afferent neurons are involved in spinal reflexes and are generally found at the level of the spinal cord. They play a role in maintaining posture and protective movements such as the withdrawal reflex.

Question 11

What is the primary motor cortex, and what type of movements does it mediate?

Answer 11

The primary motor cortex contains fibers originating from pyramidal cells that descend and terminate directly on motor neurons or interneurons in the spinal cord. This system, known as the corticospinal motor system, mediates fine voluntary movements of body parts, particularly those involving the hands and fingers.

Question 12

What is the role of the brain stem in motor control, and how is it influenced by other motor regions?

Answer 12

The brain stem is part of the multineuronal motor system and is influenced by motor regions of the cortex, the cerebellum, and the basal nuclei. This system regulates overall body posture and involuntary movements of larger muscle groups.

Question 13

A collection of specialized muscle cells in which muscle spindles are
distributed.

Answer 13

Intrafusal Fibres

Question 14

The muscle receptor responsible for responding to muscle tension

Answer 14

Golgi Tendon Organs

Question 15

These are essential for maintaining posture and protective movements such as the withdrawal effect.

Answer 15

Spinal Reflexes

Question 16

The system that mediates fine voluntary movements of body parts such as the hands and fingers.

Answer 16

Corticospinal Motor System

Question 17

The muscle receptor responsible for responding to stretch.

Answer 17

Muscle spindles

Question 18

What is the key factor in the coordination of movement, and why is it important to balance excitatory and inhibitory inputs?

Answer 18

The coordination of movement, both voluntary and involuntary, depends on the balance of excitatory and inhibitory inputs on motor neurons. Damage to any level of the central nervous system (CNS) can affect the proper coordination of movement.

Question 19

Using your knowledge of how voluntary movement is controlled, describe how damage to the
brainstem nuclei would affect movement.

Answer 19

Damage to the brainstem nuclei would result in decreased input on motor neurons which are
responsible for the excitation of muscle fibres.

With decreased input on the motor neurons, voluntary movement would be hindered.

Question 20

Using your knowledge of how voluntary movement is controlled, describe how damage to
muscle spindle would affect movement.

Answer 20

Damage to a peripheral receptor, such as a muscle spindle receptor, would affect the detection of
muscle length. This would therefore hinder the ability of the afferent nerves to properly convey
information to the brainstem and therefore the primary motor cortex. Damage to muscle spindles
would therefore hinder the brain’s ability to coordinate purposeful muscle activity