Descending Tracts in Euro Anatomy and Physiology

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Questions and Answers

What is the primary function of descending tracts?

Regulate the body's autonomic functions

Carry motor nerves from the brain to control skeletal muscles (correct)

Carry sensory information from the spinal cord to the brain

Control the activities of smooth muscles

Which tract supplies facial muscles involved in facial expressions?

Corticobulbar tract (correct)

Corticospinal tract

Tectospinal tract

Rubrospinal tract

What is the main characteristic of pyramidal tracts?

They are involved in posture maintenance only

They are involved in skilled involuntary movements

They do not pass through the pyramid of medulla

They pass through the pyramid of medulla (correct)

Which tract is involved in posture maintenance in response to head position?

Vestibulospinal tract Signup and view all the answers

Which tract crosses to the opposite side at the medullary pyramid?

Lateral corticospinal tract Signup and view all the answers

What is the primary function of the extrapyramidal tracts?

Involved in posture maintenance and skilled voluntary movements Signup and view all the answers

Which tract arises from the red nucleus in the midbrain?

Rubrospinal tract Signup and view all the answers

Which tract is involved in the movement of the head according to visual stimuli?

Tectospinal tract Signup and view all the answers

What is the origin of nerve fibers in the corticospinal tract?

Motor cortex Signup and view all the answers

Which tract gives rise to cranial nerves?

Cortical nuclear tract Signup and view all the answers

What is the primary function of the vestibulospinal tract?

Posture maintenance in response to head position Signup and view all the answers

Which tract is involved in inhibiting pain pathways?

Rapha spinal tract Signup and view all the answers

What is the characteristic of the lateral corticospinal tract?

Supplies distal muscles Signup and view all the answers

Which tract arises from the nucleus raphe magnus in the medulla?

Rapha spinal tract Signup and view all the answers

What is the characteristic of the tectospinal tract?

Involved in vision Signup and view all the answers

What is the characteristic of the reticulospinal tract?

Ipsilateral, does not decussate Signup and view all the answers

Study Notes

Descending Tracts in Euro Anatomy and Physiology

Descending tracts carry motor nerves from the brain, primarily from the cerebral cortex, and control the activities of skeletal muscles.
There are two types of descending tracts: pyramidal tracts and extrapyramidal tracts.

Pyramidal Tracts

Pyramidal tracts include corticospinal tract and corticobulbar tract.
Corticospinal tract:
- Nerve fibers arise from the cortex and descend to the anterior horn cells of the spinal cord.
- Divided into lateral corticospinal tract (80% of fibers) and anterior corticospinal tract (20% of fibers).
- Lateral corticospinal tract:
  - Crosses to the opposite side at the medullary pyramid.
  - Supplies distal muscles, involved in skilled movements.
- Anterior corticospinal tract:
  - Does not cross the midline.
  - Supplies proximal muscles, involved in posture maintenance.
Corticobulbar tract:
- Nerve fibers arise from the motor cortex and go to the cranial nerve nuclei in the brainstem.
- Supplies facial muscles, involved in facial expressions.

Extrapyramidal Tracts

Extrapyramidal tracts do not pass through the pyramid of medulla.
Involved in posture maintenance and skilled voluntary movements.
Four types of extrapyramidal tracts:
- Rubrospinal tract:
  - Arises from the red nucleus in the midbrain.
  - Crosses to the opposite side.
  - Supplies digital muscle groups, involved in skilled movements.
- Vestibulospinal tract:
  - Arises from the vestibular nuclei in the brainstem.
  - Receives input from the inner ear.
  - Helps maintain posture in response to head position.
- Reticulospinal tract:
  - Arises from the reticular formation in the pons and medulla.
  - Does not cross the midline.
  - Supplies proximal group of muscles, involved in posture maintenance.
- Tectospinal tract:
  - Arises from the tectum (superior colliculus) in the midbrain.
  - Crosses to the opposite side.
  - Involved in moment of the head according to visual stimuli.

Other Energy Pathways

Rafah spinal tract:
- Serotonergic, starts from the nucleus raphe magnus in the medulla.
- Inhibits pain pathways and helps in sensory motor coordination.
Certain spinal tract:
- Noradrenergic, starts from the nucleus locus coeruleus and nucleus subcoeruleus.
- Inhibits pain pathways and helps in sensory motor coordination.

Descending Tracts

Carry motor nerves from the brain, primarily from the cerebral cortex, to control skeletal muscles
Two types: pyramidal tracts and extrapyramidal tracts

Pyramidal Tracts

Include corticospinal tract and corticobulbar tract
Corticospinal tract:
- Nerve fibers arise from the cortex and descend to the anterior horn cells of the spinal cord
- Divided into lateral corticospinal tract (80% of fibers) and anterior corticospinal tract (20% of fibers)
- Lateral corticospinal tract:
  - Crosses to the opposite side at the medullary pyramid
  - Supplies distal muscles, involved in skilled movements
- Anterior corticospinal tract:
  - Does not cross the midline
  - Supplies proximal muscles, involved in posture maintenance
Corticobulbar tract:
- Nerve fibers arise from the motor cortex and go to the cranial nerve nuclei in the brainstem
- Supplies facial muscles, involved in facial expressions

Extrapyramidal Tracts

Do not pass through the pyramid of medulla
Involved in posture maintenance and skilled voluntary movements
Four types:
- Rubrospinal tract:
  - Arises from the red nucleus in the midbrain
  - Crosses to the opposite side
  - Supplies digital muscle groups, involved in skilled movements
- Vestibulospinal tract:
  - Arises from the vestibular nuclei in the brainstem
  - Receives input from the inner ear
  - Helps maintain posture in response to head position
- Reticulospinal tract:
  - Arises from the reticular formation in the pons and medulla
  - Does not cross the midline
  - Supplies proximal group of muscles, involved in posture maintenance
- Tectospinal tract:
  - Arises from the tectum (superior colliculus) in the midbrain
  - Crosses to the opposite side
  - Involved in moment of the head according to visual stimuli

Other Energy Pathways

Rafah spinal tract:
- Serotonergic, starts from the nucleus raphe magnus in the medulla
- Inhibits pain pathways and helps in sensory motor coordination
Certain spinal tract:
- Noradrenergic, starts from the nucleus locus coeruleus and nucleus subcoeruleus
- Inhibits pain pathways and helps in sensory motor coordination

Descending Tracts

Carry motor nerves from the brain, primarily from the cerebral cortex, to control skeletal muscles.
Divided into two categories: pyramidal tracts and extrapyramidal tracts.

Pyramidal Tracts

Consist of corticospinal tract and cortical nuclear tract.
Corticospinal tract:
- Nerve fibers arise from the cortex and descend to the anterior horn cells of the spinal cord.
- Longer than cortical nuclear tract.
- Gives rise to spinal nerves.
- Divided into lateral corticospinal tract (80% of fibers) and anterior corticospinal tract (20% of fibers).
- Lateral corticospinal tract:
  - Supplies distal muscles.
  - Involved in skilled movements.
- Anterior corticospinal tract:
  - Supplies proximal muscles.
  - Involved in posture maintenance.
Cortical nuclear tract:
- Nerve fibers arise from the motor cortex and go to cranial nerve nuclei in the brainstem.
- Ends near the cranial nerve nuclei.
- Gives rise to cranial nerves.

Extrapyramidal Tracts

Do not pass through the pyramid of medulla.
Involved in posture maintenance and skilled voluntary activities.
Examples:
- Rubra spinal tract:
  - Arises from red nucleus in the midbrain.
  - Decussates to the opposite side.
  - Supplies distal muscle groups.
- Vestibulospinal tract:
  - Arises from vestibular nuclei in the inner ear.
  - Receives input from the inner ear.
  - Helps maintain posture in response to head position.
- Reticulospinal tract:
  - Arises from reticular formation in the brainstem.
  - Ipsilateral, does not decussate.
  - Supplies proximal group of muscles.
- Tectospinal tract:
  - Arises from tectum or superior colliculus.
  - Involved in vision.
  - Decussates to the opposite side.
  - Helps in moment of the head according to visual stimuli.

Other Pathways

One-and-a-half pathway:
- Rapha spinal tract:
  - Serotonergic, starts from nucleus raphe magnus in the medulla.
  - Inhibits pain pathways.
  - Helps in sensory motor coordination.
- Cerulospinal tract:
  - Noradrenergic, starts from nucleus locus coeruleus and nucleus sub coeruleus.
  - Inhibits pain pathways.
  - Helps in sensory motor coordination.

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Description

Learn about descending tracts that carry motor nerves from the brain, controlling skeletal muscles, and the two types: pyramidal tracts and extrapyramidal tracts.