Neuroscience: Motor Areas and Anatomy Quiz

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Questions and Answers

A lesion in the motor-hand area would primarily cause what deficit?

Weakness of the hand on the same side of the lesion.

Weakness of the leg on the same side of the lesion.

Weakness of the leg on the opposite side of the lesion.

Weakness of the hand on the opposite side of the lesion. (correct)

Which artery primarily supplies the motor-hand area?

Anterior communicating artery

Middle cerebral artery (correct)

Posterior cerebral artery

Anterior vertebral artery

Where is the area for the legs and feet located in the precentral gyrus (PCG)?

Anterior to the motor-hand area.

Near the motor-hand area, towards the vertex. (correct)

In between the motor-hand area and the trunk area.

Posterior to the motor-hand area.

Which of the following describes the location of the superior frontal gyrus?

Runs parallel to the interhemispheric fissure. Signup and view all the answers

The superior frontal sulcus forms what, in conjunction with the precentral sulcus, when trying to locate the motor-hand area?

An imaginary arrow Signup and view all the answers

What is the visible appearance of cerebrospinal fluid (CSF) in a T1-weighted MRI scan?

Black Signup and view all the answers

Which area of the precentral gyrus is primarily responsible for controlling movements of the mouth and tongue?

Ventrolateral region Signup and view all the answers

Which motor fibers are the most direct to internal capsule without any obstacle course?

Hand motor fibers Signup and view all the answers

What is the centrum semiovale mainly formed by?

White matter converging motor fibers Signup and view all the answers

Which of the following best describes the spatial arrangement of the motor fibers?

Arranged in a logical order representing the body Signup and view all the answers

Where do the face and tongue motor fibers primarily target?

Brainstem cranial nerves. Signup and view all the answers

What anatomical structure must face and tongue motor fibers arch to reach the internal capsule?

The insula. Signup and view all the answers

What becomes black in a T1 weighted MRI scan?

Gray matter Signup and view all the answers

What consequence may occur if blood pressure gets high in the area described?

Bleeding and paralysis of the arm, legs, and face Signup and view all the answers

Which area is allocated for the arms and legs according to the description?

Most posterior Signup and view all the answers

What types of tracts are described for the arms and head?

Corticospinal for arms and corticobulbar for head Signup and view all the answers

What is noted about the distribution of motor functions among individuals?

Variations can lead to different levels of control over the mouth and face Signup and view all the answers

What is the significance of the fibers twisting in the internal capsule?

It represents the arrangement of different motor areas for better efficiency Signup and view all the answers

What happens to the muscle controlled by a destroyed lower motor neuron?

The muscle shrinks and atrophies. Signup and view all the answers

Where is the oculomotor nucleus complex located?

In the midbrain beneath the aqueduct of Sylvius. Signup and view all the answers

What is a plausible cause of the electric fan propeller not spinning if no external damages are visible?

There could be internal mechanical failure. Signup and view all the answers

Which cranial nerve nucleus is responsible for motor control of the tongue?

Hypoglossal nucleus (CN 12) Signup and view all the answers

What anatomical structure denotes the diamond shape at the level of the pons?

Fourth ventricle. Signup and view all the answers

Which anatomical structure is responsible for both pain perception and balance?

Pons Signup and view all the answers

What is the primary function of the diencephalon in relation to the nervous system?

All forms of sensory integration Signup and view all the answers

Lesions interrupting long tracts will have different effects depending on their location. Which location will likely affect visual perception?

Cerebral Cortex Signup and view all the answers

Which statement regarding decussation is correct?

Decussation refers to connections crossing over to the opposite side. Signup and view all the answers

Which region is responsible for autonomic functions such as swallowing and phonation?

Medulla Signup and view all the answers

What is the consequence of a lesion occurring before the decussation of long tracts?

Ipsilateral sensory deficits Signup and view all the answers

Which of the following observations is essential in assessing an unconscious patient?

Check the pupils and extraocular movements Signup and view all the answers

In the context of neurological lesions, what does Occam's razor suggest about diagnosis?

The simplest explanation is usually the correct one. Signup and view all the answers

What is the primary function of the corticospinal tract?

Control of essential muscle functions Signup and view all the answers

Where does the majority of the corticospinal tract fibers decussate?

At the cervicomedullary junction Signup and view all the answers

What percentage of corticospinal fibers descend uncrossed?

10% Signup and view all the answers

In which portion of the body are the arm fibers located relative to the leg fibers in the corticospinal tract?

Lateral to the leg fibers Signup and view all the answers

Which structure is part of the lower motor neuron pathway impacted by the corticospinal tract?

Brainstem Signup and view all the answers

What type of movements does the lateral corticospinal tract primarily control?

Limbs movements Signup and view all the answers

Why is it important for the corticospinal tract to have a degree of redundancy?

To maintain consistent muscle innervation Signup and view all the answers

What should be assessed when evaluating problems in muscle function?

Function of upper or lower motor neurons Signup and view all the answers

Which part of the corticospinal fibers descends as the anterior corticospinal tract?

Uncrossed fibers Signup and view all the answers

Which type of muscle activity is least likely to be paralyzed due to corticospinal tract control?

Swallowing Signup and view all the answers

Study Notes

Overview of Motor Cortex Anatomy

The corticospinal and corticobulbar tracts originate in the sensorimotor cortex, located on the banks of the central sulcus.
55% of the fibers originate in the frontal lobe, and 35% from the parietal lobe.
The precentral gyrus (PCG) has a 1:1 representation of body muscles.
Fine motor movements involve more neurons than gross movements.
More important movements have more neurons assigned.
The PCG is part of the frontal lobe, responsible for voluntary muscle activation and connected to the corticospinal tract.
It runs transversely from the brain's apex towards the Sylvian fissure.
The central sulcus is a helpful landmark for identifying the PCG.
The motor-hand area is often seen as a "knob" or bump within the PCG (an inverted omega).
The shape of the PCG can vary between individuals (inverted omega or epsilon shaped).

Corticospinal and Corticobulbar Tracts

Corticospinal tracts contain upper motor neuron axons controlling arm and leg muscles. They end in the spinal cord.
Corticobulbar fibers originate in the sensorimotor complex (face, eye, mouth, tongue areas) and end on brainstem motor nuclei.
Corticobulbar fibers control muscles in the head and neck.
Approximately 50% of corticobulbar fibers decussate, synapsing on the opposite side lower motor neurons in the brainstem.
The remaining 50% stay ipsilateral.
Corticospinal fibers decussate (cross) at the cervicomedullary junction to form the lateral corticospinal tract (controlling limbs).
10% of corticospinal fibers descend uncrossed as the anterior corticospinal tract (controls axial muscles).

Lower Motor Neurons

Lower motor neurons are organized, with specific nuclei controlling specific muscles.
Brainstem nuclei include the oculomotor (eye), trochlear (superior oblique), abducens (lateral rectus), hypoglossal (tongue), and ambiguus (swallowing) nuclei.
Different spinal cord areas control different movement types: medial columns for posture and axial muscles; lateral columns for finer movements in the limbs.
Damage to lower motor neurons results in flaccid paralysis.

Lesions and Clinical Correlations

Damage to specific areas can cause weakness in corresponding body parts.
Upper motor neuron lesions result in contralateral weakness or paralysis.
Lower motor neuron lesions result in ipsilateral weakness.
Strokes in different artery regions affect different body parts.
Anterior cerebral artery stroke affects legs, middle cerebral artery stroke affects face and hands.
Stroke localization is crucial for determining the cause of weakness or paralysis.
Assessment of reflexes (hyporeflexia, hyporeflexia, or areflexia) is important in diagnosing upper/lower motor neuron issues.

Tracts and Pathways

Corticospinal and corticobulbar axons follow specific pathways (centrum semiovale, corona radiata, internal capsule, cerebral peduncles) to reach their target muscles.
These pathways' arrangement maintains a spatial representation of the body (homunculus).
Lateral ventricles, caudate nucleus, putamen, and globus pallidus are important structures for corticospinal tract fibers.
Leg fibers are furthest back in the internal capsule; hand fibers are middle; and face and tongue fibers are closest to the genu and more medial.
There are "back-up" fibers in these tracts, which may help recovery from some types of damage.

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Description

Test your knowledge on the anatomical features and functions of motor areas in the brain, particularly focusing on the precentral gyrus. This quiz covers lesion effects, arterial supply, and the spatial organization of motor fibers. Ideal for neuroscience students and professionals.