Neuroscience: Central Nervous System Tracts

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Questions and Answers

Which nerve from the sacral plexus is primarily responsible for supplying the foot?

  • Tibial nerve (correct)
  • Femoral nerve
  • Radial nerve
  • Fibular nerve

What characterizes visceral reflexes compared to somatic reflexes?

  • Require higher brain functions for execution
  • Control skeletal muscles only
  • Involve voluntary muscle activation
  • Control smooth and cardiac muscles, and glands (correct)

What is a common cause of sciatic nerve injury?

  • Trauma from sports injuries
  • Herniated intervertebral disc or osteoarthritis (correct)
  • Chemical exposure
  • Excessive exercise

Which type of reflex involves the highest complexity and speed?

<p>Polysynaptic reflexes (C)</p> Signup and view all the answers

Which component of the muscle spindle is responsible for adjusting the sensitivity of the spindle?

<p>Gamma motor neuron (D)</p> Signup and view all the answers

The term 'wrist drop' is associated with injury to which nerve?

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

Which statement correctly describes the characteristics of muscle cells?

<p>All muscle cells have contractility and elasticity. (C)</p> Signup and view all the answers

What describes the stretch (myotatic) reflex?

<p>Causes contraction when a muscle is stretched to maintain balance (B)</p> Signup and view all the answers

Which nerve supplies the medial and anterior compartments of the leg?

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

What is a primary function of beta-3 adrenergic receptors?

<p>Lipolysis in adipocytes. (D)</p> Signup and view all the answers

Which of the following is NOT a function of skeletal muscle tissue?

<p>Support the vascular system. (C)</p> Signup and view all the answers

Which neurotransmitter is released by the autonomic nervous system alongside acetylcholine and norepinephrine?

<p>Substance P. (C)</p> Signup and view all the answers

What role do the arrector muscles play in the autonomic nervous system?

<p>They are affected only by sympathetic fibers. (D)</p> Signup and view all the answers

What is a characteristic feature of muscle spindles?

<p>They contain sensory endings that respond to stretch. (C)</p> Signup and view all the answers

Which is a common outcome of decreased blood flow as controlled by the autonomic nervous system?

<p>Decreased glandular secretion. (D)</p> Signup and view all the answers

What is a key characteristic of polysynaptic reflexes?

<p>They require multiple interneurons to connect sensory and motor pathways. (C)</p> Signup and view all the answers

What is the primary motor function of the Accessory Nerves (XI)?

<p>Neck and upper back movement (A)</p> Signup and view all the answers

Which of the following nervous functions is NOT associated with the Glossopharyngeal Nerves (IX)?

<p>Facial expression control (A)</p> Signup and view all the answers

What role does the coccygeal ligament play in the spinal cord?

<p>Anchors the spinal cord to prevent longitudinal movement (C)</p> Signup and view all the answers

Which structure is primarily responsible for detecting changes in muscle length?

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

In the context of spinal reflexes, which characteristic defines a polysynaptic reflex?

<p>Allows for multiple routes of neural communication (D)</p> Signup and view all the answers

Which of the following components is NOT a part of the gray matter in the spinal cord?

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

During the epidural block procedure, which type of anesthesia is administered?

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

From which region does the lumbosacral enlargement provide nerves?

<p>Pelvic region and lower limbs (D)</p> Signup and view all the answers

Flashcards

Beta-1 receptors

Increase metabolic activity in skeletal and cardiac muscles.

Beta-2 receptors

Relax smooth muscles, widening airways.

Beta-3 receptors

Trigger lipolysis (fat breakdown) releasing nutrients into the bloodstream.

ANS effects on glands

Often happen indirectly through effects on blood vessels; increased blood flow, increased secretion; decreased blood flow, decreased secretion.

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Additional neurotransmitters in ANS

ANS fibers may release neurotransmitters beyond ACh and NE, including enkephalins, substance P, and more.

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Skeletal muscle regeneration

Minimal repair ability, myosatellite cells are stem cells but cannot develop into a new muscle cell to replace a dead one.

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Muscle Excitability

Muscle's ability to respond to chemical, stretch, or electrical stimuli.

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Universal Muscle Characteristics

All muscle cells share excitability, conductivity, contractility, extensibility, and elasticity.

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Radial nerve injury

Damage to the radial nerve, often caused by crutch use, resulting in wrist drop (fingers and hand chronically flexed).

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Sciatic nerve injury

Injury to the sciatic nerve, often due to herniated disc or osteoarthritis, causing sharp pain traveling from the gluteal region down the leg to the ankle.

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Visceral Reflexes

Reflexes that control smooth and cardiac muscles, glands, and adipose tissue (not muscular system).

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Spinal Reflexes (Monosynaptic)

The fastest and least complex spinal reflexes, involving a single synapse between sensory and motor neurons.

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Stretch Reflex

A reflex where a stretched muscle contracts to resist the stretch and maintain balance.

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Muscle Spindle (Intrafusal Fibers)

Specialized muscle fibers within a muscle spindle that detect stretch and trigger the stretch reflex.

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Femoral Nerve

Major nerve of the lumbar plexus, supplying the anterior and medial thigh compartments.

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Sciatic Nerve Branches (Fibular and Tibial)

Two major branches of the sciatic nerve that serve the foot and leg.

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Facial Nerves (VII)

Sensory nerves for taste and motor nerves for facial expressions.

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Vestibulocochlear Nerves (VIII)

Sensory nerves responsible for hearing and balance.

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Glossopharyngeal Nerves (IX)

Sensory and motor nerves for taste and head/neck functions.

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Vagus Nerves (X)

Sensory nerves for the internal organs (viscera), and motor nerves for digestion and breathing.

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Accessory Nerves (XI)

Motor nerves controlling neck and upper back muscles.

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Hypoglossal Nerves (XII)

Motor nerves for tongue movement.

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Spinal Cord Enlargements

Thicker areas of the spinal cord, supplying nerves to limbs (upper and lower).

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Epidural Anesthesia

Temporary sensory block (and sometimes motor paralysis), performed in the epidural space to control pain, commonly during childbirth.

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Study Notes

Tracts in the Central Nervous System (CNS)

  • Tracts are bundles of nerve fibers in the CNS.
  • Three types: projection, commissural, and association tracts.
  • Projection tracts extend vertically between the cerebrum and lower brain/spinal cord centers.
  • Commissural tracts cross from one cerebral hemisphere to the other, allowing communication between the two sides of the cerebrum. Most pass through the corpus callosum.
  • Association tracts connect different regions within the same cerebral hemisphere. Long association fibers connect different lobes, while short association fibers connect gyri within a lobe.

Disconnection Syndrome

  • Cutting the corpus callosum (to treat severe epilepsy) can cause a disconnection syndrome.
  • Each hemisphere becomes aware of the other, but the hemispheres are disconnected from each other.
  • For example, an item held in the left hand might not be able to be verbally identified.

Language Areas in the Brain

  • Posterior speech area (Wernicke area): Usually in the left hemisphere, responsible for recognizing spoken and written language. Located posterior to the lateral sulcus.
  • Motor language area (Broca area): Usually in the left hemisphere, controls the muscles of the larynx, tongue, cheeks, and lips for speaking and hand movements for signing. Located in the inferior prefrontal cortex.
  • Aphasia is a disorder of language. It can be caused by lesions of the Wernicke or Broca areas.
    • Nonfluent aphasia: approximated words, difficulty with specific word formation, but can produce similar sounding substitutes.
    • Fluent aphasia: words are made up , nonsensical, or gibberish

Hemisphere Differences

  • Left hemisphere is usually the categorical hemisphere and is specialized for spoken and written language, in 96% of right-handed people and 70% of left-handed people.

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