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Questions and Answers
What is the highest center for the control of voluntary movements?
What is the highest center for the control of voluntary movements?
Which type of motor neurons directly influences involuntary contraction or movement of skeletal muscles?
Which type of motor neurons directly influences involuntary contraction or movement of skeletal muscles?
What type of reflex involves motor neurons of the spinal cord?
What type of reflex involves motor neurons of the spinal cord?
Which structure is responsible for voluntary movement and is under conscious control?
Which structure is responsible for voluntary movement and is under conscious control?
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What connects the cerebral motor cortex to skeletal muscles?
What connects the cerebral motor cortex to skeletal muscles?
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Which neurons are located in the anterior horn of the spinal cord?
Which neurons are located in the anterior horn of the spinal cord?
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Which of the following types of neurons are considered upper motor neurons?
Which of the following types of neurons are considered upper motor neurons?
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Involuntary movements of skeletal muscles are primarily controlled by which part of the central nervous system?
Involuntary movements of skeletal muscles are primarily controlled by which part of the central nervous system?
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What is the primary function of the extrapyramidal system?
What is the primary function of the extrapyramidal system?
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Which of the following tracts is NOT part of the extrapyramidal system?
Which of the following tracts is NOT part of the extrapyramidal system?
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From which area does the rubrospinal tract originate?
From which area does the rubrospinal tract originate?
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What type of movements are primarily regulated by the pyramidal system?
What type of movements are primarily regulated by the pyramidal system?
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Which tract originates from the vestibular nuclei?
Which tract originates from the vestibular nuclei?
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The descending motor pathway that travels through the medullary pyramids is known as what?
The descending motor pathway that travels through the medullary pyramids is known as what?
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Which of the following best defines the term 'extrapyramidal tracts'?
Which of the following best defines the term 'extrapyramidal tracts'?
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Which vestibular nuclei contribute to the vestibulospinal tracts?
Which vestibular nuclei contribute to the vestibulospinal tracts?
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What is the main function of the lateral vestibulospinal tract?
What is the main function of the lateral vestibulospinal tract?
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What type of movements do the tectospinal and reticulospinal tracts primarily facilitate?
What type of movements do the tectospinal and reticulospinal tracts primarily facilitate?
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What reflex is primarily maintained by the medial vestibular nuclei?
What reflex is primarily maintained by the medial vestibular nuclei?
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Which sensory inputs are involved in activating the tectospinal tract?
Which sensory inputs are involved in activating the tectospinal tract?
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What is the primary role of the tectospinal tract?
What is the primary role of the tectospinal tract?
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What is the primary function of the pyramidal tract?
What is the primary function of the pyramidal tract?
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Which tract originates from the red nucleus and is involved in motor functions?
Which tract originates from the red nucleus and is involved in motor functions?
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Which reflex is primarily associated with the reticulospinal tract?
Which reflex is primarily associated with the reticulospinal tract?
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Which tracts do NOT pass through the medullary pyramids?
Which tracts do NOT pass through the medullary pyramids?
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What type of movements are primarily associated with the extrapyramidal system?
What type of movements are primarily associated with the extrapyramidal system?
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Which anatomical structures are involved in the vestibular system's function for equilibrium?
Which anatomical structures are involved in the vestibular system's function for equilibrium?
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Which of the following statements accurately reflects the role of the reticulospinal tract?
Which of the following statements accurately reflects the role of the reticulospinal tract?
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Which movement reflex does the tectospinal tract primarily assist with?
Which movement reflex does the tectospinal tract primarily assist with?
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What is the primary function of the tectospinal tract?
What is the primary function of the tectospinal tract?
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What input does the rubrospinal tract primarily receive?
What input does the rubrospinal tract primarily receive?
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Which area is NOT involved in the coordination of eye movements?
Which area is NOT involved in the coordination of eye movements?
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What is the role of the medial longitudinal fasciculus?
What is the role of the medial longitudinal fasciculus?
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Which type of eye movement is characterized by fast redirections of gaze?
Which type of eye movement is characterized by fast redirections of gaze?
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What is an outcome of upper motor neuron lesions above the midbrain?
What is an outcome of upper motor neuron lesions above the midbrain?
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Which cranial nerves are associated with eye movement control?
Which cranial nerves are associated with eye movement control?
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Which pathway is responsible for both dorsolateral and ventromedial motor functions?
Which pathway is responsible for both dorsolateral and ventromedial motor functions?
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What is the purpose of smooth pursuit eye movements?
What is the purpose of smooth pursuit eye movements?
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What area of the brain initiates saccades?
What area of the brain initiates saccades?
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How do the upper motor neurons contribute to eye movement?
How do the upper motor neurons contribute to eye movement?
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Which function is NOT associated with the rubrospinal tract?
Which function is NOT associated with the rubrospinal tract?
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What is the primary aim of binocular vision?
What is the primary aim of binocular vision?
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What happens during conjugate eye movements?
What happens during conjugate eye movements?
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Study Notes
Extrapyramidal System
- The extrapyramidal system is a collection of descending motor pathways in the brainstem.
- Responsible for unconscious movements (supraspinal reflexes).
- Includes four key tracts:
- Tectospinal tract: originates in the tectum (midbrain) and controls head and neck movements in response to sensory stimuli.
- Rubrospinal tract: originates in the red nucleus (midbrain) and mainly controls flexor muscles. It receives input from the pyramidal system (cortex) and the cerebellum.
- Reticulospinal tract: originates in the reticular formation (brainstem) and influences postural reflexes and gait control. It is primarily involved in extensor muscle tone.
- Vestibulospinal tract: originates in the vestibular nuclei (brainstem) and controls head and body balance. It is essential for maintaining posture and balance via reflexes.
Brainstem Structures
- The brainstem is composed of three regions:
- Midbrain: Contains the tectum, tegmentum, and a base. The tectum is involved in visual and auditory reflexes. The tegmentum houses the red nucleus, reticular formation, and substantia nigra. The base includes the cerebral peduncles.
- Pons: Bridges the cerebellum with the rest of the brain. Contains the pontine nuclei, reticular formation, and sensory pathway nuclei.
- Medulla: Contains the pyramids, olives, reticular formation, and nuclei of cranial nerves (VIII-XII). The pyramids are critical for the corticospinal tract.
Body Movement
- Movements of the body are a combination of voluntary and involuntary actions.
- Voluntary movements are controlled by the cerebral motor cortex and are initiated through the pyramidal pathway.
- Involuntary movements, or reflexes, are controlled by spinal cord and brainstem motor neurons.
Supraspinal Reflexes
- Proprioceptive reflexes: These reflexes are triggered by sensory information from the body, such as stretching of muscles or tendons. They help to maintain posture and body position.
- Stereotyped supraspinal reflexes: These are preprogrammed movements that are triggered by specific stimuli, such as the startle reflex or the withdrawal reflex from a painful stimulus.
The Reticulospinal Tract
- Plays a key role in postural reflexes and gait control.
- It receives input from the basal ganglia, motor cortex, and cerebellum.
- It influences muscle tone, particularly in extensor muscles, to maintain upright posture.
The Vestibulospinal Tracts
- Originate in the vestibular nuclei, which receive information from the vestibular system (inner ear).
- The lateral vestibulospinal tract (LVST) controls antigravity muscles (extensors) in response to gravity, maintaining balance.
- The medial vestibulospinal tract (MVST) stabilizes the head during movements, especially rotational movements.
The Tectospinal Tract
- Controls reflexive head and neck movements in response to sensory stimuli, including visual, auditory, tactile, temperature, and pain.
- It is crucial for steering the body during gait, aligning the visual axis in the direction of movement.
The Rubrospinal Tract
- A flexor-biased tract that receives input from the motor cortex and cerebellum.
- Plays a role in fine motor control and coordination.
Damage to the Pyramidal System
- Upper motor neuron lesions above the midbrain can lead to symptoms like spasticity (increased muscle tone), hyperreflexia (overactive reflexes), and Babinski sign.
- Upper motor neuron lesions below the midbrain can cause similar symptoms, but with some variations.
Anatomical Division of Descending Motor Pathways
- Motor pathways in the spinal cord are located in the lateral and anterior funiculi.
- Two major pathways exist:
- Dorso-lateral pathways: primarily involved in voluntary movements, especially limb movements.
- Ventro-medial pathways: primarily involved in posture and trunk movements.
Co-ordination of Cortical and Brainstem Motor Activity
- This coordinated activity is essential for movements like gaze, which involves the simultaneous movement of both eyes.
Gaze
- It is the synchronized movement of both eyes to focus on a single point in the environment.
- Gaze control involves both cortical and brainstem activity, particularly the oculomotor (III), trochlear (IV), and abducens (VI) cranial nerves.
Medial Longitudinal Fasciculus (MLF)
- A pathway that interconnects the nuclei of the oculomotor, trochlear, abducens, and vestibular nerves.
- It ensures coordinated eye movements and relays information regarding head movements from the vestibular system to the oculomotor system.
Types of Eye Movements
- Conjugate movements: both eyes move in the same direction.
- Vergence movements: both eyes move in opposite directions, converging or diverging to focus on objects at different distances.
Fast and Slow Conjugate Eye Movements
- Saccades: fast eye movements that redirect gaze to bring a new object into focus. They are initiated by cortical and subcortical centers and coordinated by brainstem gaze centers, specifically the Paramedian Pontine Reticular Formation (PPRF) for horizontal and rostal Midbrain Reticular Formation (rMRF) for vertical saccades, respectively.
- Smooth pursuit movements: slower eye movements that help maintain a visual target on the fovea as the object or the observer moves. They involve visual and motor cortex, cerebellar, and vestibular feedback.
Initiation of Saccades
- The initiation of saccades is regulated by the frontal eye field (FEF), supplementary eye field, and parietal eye field, which project to the contralateral PPRF for horizontal saccades and the rMRF for vertical saccades.
Coordination of Horizontal Conjugate Eye Movements
- The left PPRF controls the movement of both eyes to the left.
- The right PPRF controls the movement of both eyes to the right.
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Description
Explore the extrapyramidal system, a network of motor pathways in the brainstem responsible for unconscious movements. Learn about the key tracts involved, including the tectospinal, rubrospinal, reticulospinal, and vestibulospinal tracts. Understand their roles in reflexes, posture, and balance.
