Dr Gawad Physiology Course Online Exams – Descending Tracts

1. Functions of the Extrapyramidal system include all of the following except:

Control of muscle tone

Swinging of the arms during walking

Posture and equilibrium

Type writing

The extrapyramidal system is responsible for controlling muscle tone, swinging of the arms during walking, and maintaining posture and equilibrium. However, it is not involved in the specific motor skills required for typing, such as fine motor control and coordination of finger movements. Therefore, the correct answer is type writing.

Explanation

The extrapyramidal system is responsible for controlling muscle tone, swinging of the arms during walking, and maintaining posture and equilibrium. However, it is not involved in the specific motor skills required for typing, such as fine motor control and coordination of finger movements. Therefore, the correct answer is type writing.

2. Stroke of precentral gyrus will cause:

Loss of equilibrium

Loss of fine movements

Loss of muscle tone

Loss of swinging of arms

A stroke affecting the precentral gyrus, which is responsible for motor control, can result in the loss of fine movements. This is because the precentral gyrus contains the primary motor cortex, which controls voluntary movements of the body. When damaged, it can lead to difficulties in executing precise and coordinated movements, such as writing, buttoning a shirt, or picking up small objects. Other symptoms of a stroke in this area may include weakness or paralysis on one side of the body, difficulty with speech or swallowing, and changes in muscle tone.

Explanation

A stroke affecting the precentral gyrus, which is responsible for motor control, can result in the loss of fine movements. This is because the precentral gyrus contains the primary motor cortex, which controls voluntary movements of the body. When damaged, it can lead to difficulties in executing precise and coordinated movements, such as writing, buttoning a shirt, or picking up small objects. Other symptoms of a stroke in this area may include weakness or paralysis on one side of the body, difficulty with speech or swallowing, and changes in muscle tone.

3. The cranial motor nuclei which receive innervation only from the contralateral corticobular tract are:

Trigeminal & vagus

Vagus & glossopharyngeal

Facial and hypoglossal

Facial and glossopharyngeal

The cranial motor nuclei that receive innervation only from the contralateral corticobular tract are the facial and hypoglossal nuclei. The trigeminal and vagus nuclei receive innervation from both ipsilateral and contralateral corticobular tracts. The vagus and glossopharyngeal nuclei receive innervation from both ipsilateral and contralateral corticobular tracts. The facial and glossopharyngeal nuclei receive innervation from both ipsilateral and contralateral corticobular tracts.

Explanation

The cranial motor nuclei that receive innervation only from the contralateral corticobular tract are the facial and hypoglossal nuclei. The trigeminal and vagus nuclei receive innervation from both ipsilateral and contralateral corticobular tracts. The vagus and glossopharyngeal nuclei receive innervation from both ipsilateral and contralateral corticobular tracts. The facial and glossopharyngeal nuclei receive innervation from both ipsilateral and contralateral corticobular tracts.

4. Primary motor area (area 4) characterized by all of the following except:

The body is represented in an inverted manner

Cortical representation of any part of the body in area 4 is directly proportional to its size

It is an area of high excitability

It facilitates the spinal reflexes as, stretch reflex

The primary motor area (area 4) is characterized by the following: the body is represented in an inverted manner, it is an area of high excitability, and it facilitates the spinal reflexes such as the stretch reflex. However, the cortical representation of any part of the body in area 4 is not directly proportional to its size.

Explanation

The primary motor area (area 4) is characterized by the following: the body is represented in an inverted manner, it is an area of high excitability, and it facilitates the spinal reflexes such as the stretch reflex. However, the cortical representation of any part of the body in area 4 is not directly proportional to its size.

5. Premotor area 6, which is false:

It is of low excitability

Initiates gross movements on the contralateral limbs

Nvolved in the selection of appropriate motor plans for voluntary movements.

Shares together with the cerebellum in initiation of automatic associated involuntary movements

The premotor area 6 is not involved in the initiation of automatic associated involuntary movements. This area is actually involved in the selection of appropriate motor plans for voluntary movements. It is responsible for planning and organizing movements, rather than controlling involuntary movements.

Explanation

The premotor area 6 is not involved in the initiation of automatic associated involuntary movements. This area is actually involved in the selection of appropriate motor plans for voluntary movements. It is responsible for planning and organizing movements, rather than controlling involuntary movements.

6. Regarding the difference between pyramidal and extrapyramidal tracts, which is true:

Pyramidal pathway from the cortex to the spinal cord involves multiple neurons and synapses than extrapyramidal

Only some of pyramidal fibers cross to opposite side

Pyramidal functions later on in life

None of the above

The statement "pyramidal functions later on in life" is the correct answer because it accurately reflects the difference between pyramidal and extrapyramidal tracts. The pyramidal pathway, which involves the corticospinal tract, is responsible for voluntary motor movements and develops later in life. In contrast, the extrapyramidal tracts are involved in involuntary movements and are present from birth. The other options in the question are not accurate explanations of the difference between the two tracts.

Explanation

The statement "pyramidal functions later on in life" is the correct answer because it accurately reflects the difference between pyramidal and extrapyramidal tracts. The pyramidal pathway, which involves the corticospinal tract, is responsible for voluntary motor movements and develops later in life. In contrast, the extrapyramidal tracts are involved in involuntary movements and are present from birth. The other options in the question are not accurate explanations of the difference between the two tracts.

7. Lesion of lateral column will lead to the following motor deficit:

Paralysis of fine movement muscles on the same side of the lesion

Paralysis of respiratory muscles on ipsilateral side

Paralaysis of hypoglossal nreve supplied muscles on the opposite side

None of the above

A lesion of the lateral column refers to damage or injury to the lateral column of the spinal cord. The lateral column contains motor fibers that control voluntary movements of the body. Therefore, if there is a lesion in this area, it will result in paralysis of the fine movement muscles on the same side of the lesion. This means that the muscles responsible for precise and delicate movements on the same side as the lesion will be unable to function properly.

Explanation

A lesion of the lateral column refers to damage or injury to the lateral column of the spinal cord. The lateral column contains motor fibers that control voluntary movements of the body. Therefore, if there is a lesion in this area, it will result in paralysis of the fine movement muscles on the same side of the lesion. This means that the muscles responsible for precise and delicate movements on the same side as the lesion will be unable to function properly.