Motor Pathways and Cerebellum Overview
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Questions and Answers

What is the role of the mesencephalic nucleus in sensory processing?

  • It processes touch and pressure sensations.
  • It is involved in temperature sensations.
  • It processes pain sensations.
  • It is responsible for proprioception. (correct)

In Brown-Sequard syndrome, which type of sensory information is lost on the same side as the lesion?

  • Only pain sensation.
  • Pain and temperature sensations.
  • Proprioception and touch. (correct)
  • Only proprioception.

How does the spinothalamic tract relay pain and temperature sensations?

  • It crosses over at the level of the brainstem.
  • It remains ipsilateral until reaching the cerebral cortex.
  • It decussates at the level of the first-order neurone.
  • It decussates at the level of the second-order neurone. (correct)

What is the primary effect on motor pathways in Brown-Sequard syndrome?

<p>Upper motor neurone signs occur only on the same side as the lesion. (D)</p> Signup and view all the answers

Which organisation of sensory pathways is disrupted in Brown-Sequard syndrome?

<p>Both sensory and motor pathways on the same side of the lesion. (C)</p> Signup and view all the answers

What is the primary role of upper motor neurones?

<p>To initiate voluntary muscle contraction (B)</p> Signup and view all the answers

What anatomical structure is primarily involved in the decussation of corticospinal tract fibers?

<p>The medulla (D)</p> Signup and view all the answers

Which of the following accurately describes the lateral corticospinal tract?

<p>It manages fine and skilled voluntary movements (B)</p> Signup and view all the answers

Where do lower motor neurones originate from?

<p>The ventral horn of the spinal cord (A)</p> Signup and view all the answers

What is the major function of the cerebellum in motor control?

<p>To coordinate muscle movements (C)</p> Signup and view all the answers

Why are axons of upper motor neurones described as passing through the corona radiata?

<p>They travel from the brain to the spinal cord (A)</p> Signup and view all the answers

Which part of the brain is primarily responsible for the integration of movement and position feedback?

<p>The cerebellum (A)</p> Signup and view all the answers

What is a positive sign of the Babinski reflex?

<p>Big toe moves upward with other toes fanning out (D)</p> Signup and view all the answers

What does the motor homunculus represent?

<p>The targets of motor regions in the primary motor cortex (A)</p> Signup and view all the answers

Which neurotransmitter is primarily used by first-order neurons in sensory pathways?

<p>Glutamate (A)</p> Signup and view all the answers

Where do the axons of second-order neurons synapse in the sensory pathway?

<p>Ventral posterior nucleus of the thalamus (A)</p> Signup and view all the answers

Which pathway is responsible for transmitting sensory input of discriminative touch and proprioception?

<p>Dorsal column pathway (B)</p> Signup and view all the answers

In which structure does the fasciculus gracilis terminate?

<p>Nucleus gracilis (B)</p> Signup and view all the answers

What condition is indicated by lower motor neurone lesions?

<p>Hyporeflexia or areflexia and muscle atrophy (C)</p> Signup and view all the answers

What is the correct order of neuron types in the sensory pathways from the peripheral region to the somatosensory cortex?

<p>First-order, second-order, third-order (C)</p> Signup and view all the answers

Which of the following symptoms is NOT associated with LMN lesions?

<p>Increased muscle tone (D)</p> Signup and view all the answers

Where does the fasciculus cuneatus terminate?

<p>At the nucleus cuneatus (D)</p> Signup and view all the answers

What occurs at the sensory decussation?

<p>Second-order axons decussate to the opposite side (D)</p> Signup and view all the answers

What is the primary function of the spinothalamic tract?

<p>Relay sensory input of pain and temperature (A)</p> Signup and view all the answers

Which of the following tracts is responsible for unconscious proprioception?

<p>Dorsal spinocerebellar tract (D)</p> Signup and view all the answers

What type of information does the trigeminothalamic tract convey?

<p>Sensory input from cranial nerve afferents (A)</p> Signup and view all the answers

What is the role of the second-order neurones in the somatosensory pathways?

<p>They ascend to the thalamus after decussating (D)</p> Signup and view all the answers

To which areas do the third-order axons extend?

<p>Brodmann areas 1, 2, and 3 (C)</p> Signup and view all the answers

Which tract monitors the state of spinal reflex arcs in the lower limbs?

<p>Ventral spinocerebellar tract (D)</p> Signup and view all the answers

What is the primary function of the medial/ventral corticospinal tract?

<p>Control of axial muscles for posture and swallowing (C)</p> Signup and view all the answers

The corticobulbar tract is essential for which function?

<p>Activation of skeletal muscles in the head and neck (B)</p> Signup and view all the answers

Where do the axons of the upper motor neurons in the corticobulbar tract travel to?

<p>Along the internal capsule to the brainstem (C)</p> Signup and view all the answers

Extrapyramidal tracts originate from which part of the brain?

<p>Vestibular nuclei, reticular nuclei, and basal ganglia (B)</p> Signup and view all the answers

What is a common symptom associated with Parkinson's disease?

<p>Inability to move voluntary muscles (B)</p> Signup and view all the answers

What effect do upper motor neuron lesions have on muscle tone?

<p>Result in increased muscular tone and hyperreflexia (D)</p> Signup and view all the answers

What is the primary role of the basal ganglia in movement control?

<p>Inhibiting involuntary or inappropriate movements (C)</p> Signup and view all the answers

The descending vestibulospinal tract influences which aspect of movement?

<p>Posture and balance through spinal motor neurons (B)</p> Signup and view all the answers

Flashcards

Spinothalamic Tract

The sensory pathway that transmits information about pain and temperature from the body to the brain.

Medial/Ventral Corticospinal Tract

A pathway in the spinal cord that carries nerve impulses from the motor cortex to the muscles of the trunk and head, allowing for voluntary movement.

Dorsal Column Pathway

The sensory pathway that transmits information about touch, pressure, and proprioception from the body to the brain.

Corticobulbar Tract

A pathway that connects the motor cortex to cranial nerve nuclei in the brainstem, controlling the movement of facial muscles, swallowing, and other head and neck functions.

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Brown-Sequard Syndrome

A neurological condition caused by damage to one side of the spinal cord, leading to specific motor and sensory deficits.

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Hemiplegia

A neurological condition characterized by paralysis or weakness on one side of the body.

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Extrapyramidal Tracts

A group of brain structures that regulate movement, posture, and muscle tone. They help initiate and coordinate movements while suppressing unwanted movements.

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Decussation

The point where the axons of neurons cross from one side of the nervous system to the other.

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Parkinson's Disease

A neurological disorder caused by dopamine deficiency, leading to muscle rigidity, tremors, slow movements, and gait disturbances.

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Upper Motor Neuron Lesions

A loss of muscle control that affects upper motor neurons, resulting in increased muscle tone, spasticity, and exaggerated reflexes.

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Akinesia

The ability to initiate and execute voluntary movements.

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Bradykinesia

Extremely slow movements, usually associated with Parkinson's disease.

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Festinating Gait

A rapid, small-stepped gait often seen in Parkinson's disease, where the individual takes short, hurried steps to maintain balance.

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Babinski Reflex (+ve Sign)

A neurological sign indicating damage to the upper motor neuron (UMN), characterized by upward movement of the big toe and fanning outward of other toes when the sole of the foot is stroked.

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Babinski Reflex (-ve Sign)

A neurological sign indicating normal functioning of the upper motor neuron (UMN), characterized by downward flexion of the toes when the sole of the foot is stroked.

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Lower Motor Neuron Lesion (LMN)

A neurological condition affecting the lower motor neurons (LMN), characterized by reduced muscle tone, muscle weakness, and a diminished or absent reflex.

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Lower Motor Neurons (LMN)

Neurons directly responsible for transmitting signals from the spinal cord to muscles, controlling voluntary movement.

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Muscle Spindles

Specialized sensory receptors located in muscles that detect changes in muscle length and rate of change, sending signals to the brain about body position and movement.

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Golgi Tendon Organs

Specialized sensory receptors located in tendons that detect changes in muscle tension, sending signals to the brain about muscle force and load.

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Somatosensory Cortex

The region of the brain responsible for processing sensory information received from the body.

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Dorsal Column-Medial Lemniscus Pathway

This pathway carries sensory information about fine touch, pressure, vibration, and proprioception from the body to the brain.

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Sensory Decussation

The point where the axons of second-order neurons cross to the opposite side of the brainstem.

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Medial Lemniscus

A bundle of nerve fibers that carries sensory information from the body up to the thalamus.

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Ventral Spinocerebellar Tract

A tract that carries proprioception from the lower limbs to the cerebellum, helping to coordinate movement.

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Rostral Spinocerebellar Tract

A tract that carries proprioception from the upper limbs to the cerebellum, helping to coordinate movement.

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Trigeminothalamic Tract

This pathway carries sensory information from the face, head, and oral cavity to the brain.

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What is the difference between upper and lower motor neurons?

Upper motor neurons (UMNs) originate from the cerebral cortex, while lower motor neurons (LMNs) originate from the ventral horn of the spinal cord or cranial nerve nuclei.

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What is a motor homunculus?

The motor homunculus is a map that shows the areas of the primary motor cortex that control different parts of the body.

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What is the role of the cerebellum in movement?

The cerebellum coordinates movement by integrating motor input from the cortex and sensory input from proprioceptors, which provide information about the body's position and movement.

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What is the corticospinal/pyramidal tract?

The corticospinal/pyramidal tract is a pathway that starts in the brain and travels down to the spinal cord. It includes Upper Motor Neurons (UMNs) that control movement.

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Where are the cell bodies of upper motor neurons (UMNs) in the corticospinal tract located?

The cell bodies of UMNs in the corticospinal tract are found in the primary motor cortex, secondary motor cortex, and a small part of the somatosensory cortex.

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What is decussation of the pyramids?

Most of the fibers from one side of the cerebral cortex cross over to the other side at the medulla, which is the lower part of the brainstem. This is known as decussation.

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What is the lateral corticospinal tract?

Approximately 85-90% of corticospinal fibers decussate and form the lateral corticospinal tract. This is responsible for fine, skilled voluntary movements.

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What is the function of the lateral corticospinal tract?

The lateral corticospinal tract controls fine, skilled voluntary movements such as finger movement and influences reflex arcs that control distal ends of limbs.

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Study Notes

Motor Pathways

  • Innervation of skeletal muscle involves upper and lower motor neurons
  • Upper motor neurons originate in the cerebral cortex
  • Lower motor neurons originate from the spinal cord's ventral horn or cranial nerve nuclei
  • Upper motor neuron axons synapse with lower motor neurons or interneurons, traveling from the cerebral cortex to the spinal cord
  • Motor homunculus illustrates the targets of different regions within the primary motor cortex of the cerebral cortex, relating to different body parts

Role of Cerebellum

  • The cerebellum coordinates movement by combining motor input from the motor cortex with proprioceptor sensory input (position, speed, limb movement)
  • Feedback to the motor cortex via the thalamus refines movement coordination

Corticospinal/Pyramidal Tract

  • Neuronal pathway from brain to spinal cord
  • Cell bodies of upper motor neurons located in primary motor cortex, secondary motor cortex, and part of somatosensory cortex
  • Axons travel through the corona radiata and internal capsule to the brainstem
  • At the medulla, axons form the pyramid, hence the name
  • Most fibers decussate (cross to the opposite side) at the pyramid
  • Lateral corticospinal tract (85-90%): descends the spinal cord, synapses with interneurons or lower motor neurons, controlling fine movements, including reflexes of distal limbs
  • Medial/ventral corticospinal tract (10-15%): doesn't decussate, controls axial muscles (trunk, head), often involves bilateral muscle contraction

Corticobulbar Tract

  • Pathway from cerebral cortex to cranial nerve nuclei in the brain
  • Same origin as corticospinal tract, including primary and secondary motor cortexes and part of somatosensory cortex
  • Axons travel through corona radiata and internal capsule to the brainstem
  • Synapses with lower motor neurons of cranial nerve nuclei (III, IV, V, VI, VII, IX, X, XI, XII), innervating facial and masticatory muscles

Extrapyramidal Tracts

  • Tracts originating from parts of the brain other than the motor cortex (vestibular nuclei, reticular nuclei, basal ganglia)
  • Control movement, posture, and muscle tone
  • Vestibular nuclei: influence spinal motor neurons via descending vestibulospinal tract
  • Reticular nuclei: influence spinal motor neurons via descending reticulospinal tract
  • Basal ganglia: influence lower motor neurons of brainstem and spinal cord, inhibiting involuntary or inappropriate movements

Parkinson's Disease

  • Disorder of basal ganglia, caused by dopamine deficiency
  • Symptoms include akinesia (inability to move), muscular rigidity, bradykinesia (slow movement), festinating gait, and postural instability

Sensory Pathways

  • Sensory information from peripheral body regions (excluding the head) travels to the somatosensory cortex via three neurons: first-order, second-order, and third-order
  • First-order neurons: cell bodies in dorsal root ganglion, use glutamate for neurotransmission.
  • Second-order neurons: cell bodies in dorsal horn or medulla. Axons ascend and synapse with third-order neurons in the thalamus' ventral posterior nucleus
  • Third-order neurons: cell bodies in thalamus. Extend axons to the primary somatosensory cortex
  • Dorsal column pathway: delivers discriminative touch (e.g., pressure, vibration), and proprioception
  • Spinothalamic tract: delivers pain, temperature, and crude touch
  • Spinocerebellar tract: delivers sensory input to the cerebellum

Trigeminothalamic Tracts

  • Sensory input from afferent axons in cranial nerves to the somatosensory cortex
  • First-order axons, carrying sensory info (e.g., pain, temperature, touch, proprioception) travel to nuclei in the brainstem where they synapse
  • From these nuclei second-order neurons extend to the thalamus and synapse with third-order nuclei
  • Information is relayed to somatosensory cortex

Brown-Sequard Syndrome

  • Hemi-lesion (damage) in spinal cord
  • Disrupts motor and sensory pathways
  • Upper motor neuron signs (e.g., muscle weakness, hemiplegia) appear ipsilaterally (same side) below the lesion
  • Lower motor neuron signs (e.g., damage to lower motor neurons) may occur on the same side, at the vertical level of the lesion.
  • Proprioception and touch are lost on the side of the lesion
  • Pain and temperature sensation are lost on the opposite side of the lesion

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Motor and Sensory Pathways Lecture 19 PDF

Description

This quiz explores the structure and functions of motor pathways in the nervous system, including upper and lower motor neurons, and the role of the cerebellum in movement coordination. Understand how the corticospinal tract facilitates communication between the brain and spinal cord, and the significance of the motor homunculus in mapping body part control in the primary motor cortex.

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