Clinical Neuroscience Week 4 - The Spinal Cord (Hard)
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Questions and Answers

What term describes the inhibition of antagonist muscles to enhance prime muscle movement?

  • Central pattern generator
  • Flexor withdrawal
  • Reciprocal inhibition (correct)
  • Muscle synergy

    • How do muscle synergies function in movement?

  • By controlling multiple muscle groups simultaneously. (correct)
  • By activating only one muscle group at a time.
  • By isolating movements to enhance strength.
  • By promoting involuntary muscle contractions.

    • Which type of reflex is characterized by flexion of one limb in response to a painful stimulus?

  • Flexor withdrawal reflex (correct)
  • Postural reflex
  • Patellar reflex
  • Stretch reflex

    • What is the main purpose of stepping pattern generators in the spinal cord?

    <p>To generate rhythmic walking patterns. (B)</p> Signup and view all the answers

    What can result from lesions in the brain affecting coordinated muscle action?

    <p>Pathological or abnormal synergy. (A)</p> Signup and view all the answers

    What distinguishes the flexor withdrawal reflex from the stretch reflex?

    <p>It involves multiple spinal segments. (A)</p> Signup and view all the answers

    What enables the spinal cord to produce rhythmic movement patterns independently of the brain?

    <p>Central pattern generators. (B)</p> Signup and view all the answers

    What is the role of inhibitory interneurons in muscle activation?

    <p>To prevent antagonist muscle opposition. (B)</p> Signup and view all the answers

    Which of the following describes a model that incorporates both reflexive and sensory feedback mechanisms in generating movement?

    <p>Combined model. (B)</p> Signup and view all the answers

    What impact does a spinal cord injury have on voluntary movement?

    <p>Limits the ability to adapt to movement changes. (A)</p> Signup and view all the answers

    What is the function of the autonomic division of the peripheral nervous system?

    <p>Regulates involuntary functions (C)</p> Signup and view all the answers

    Which group of axons is known for innervating nociceptive and temperature receptors?

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

    How are dermatomes different from peripheral nerves in terms of their function?

    <p>Dermatomes are well-defined areas linked to specific spinal roots. (D)</p> Signup and view all the answers

    Which class of axons is responsible for innervating extrafusal muscle fibers?

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

    What symptom is most likely associated with an injury to the lower motor neurons?

    <p>Localized strength loss (A)</p> Signup and view all the answers

    Which classification criterion is NOT used for peripheral nerve classification?

    <p>Functionality area (C)</p> Signup and view all the answers

    What defines a myotome?

    <p>A muscle group controlled by a single spinal nerve root (D)</p> Signup and view all the answers

    Which of the following reflects the impact of upper motor neuron injury on muscle strength?

    <p>Global weakness affecting multiple muscles (B)</p> Signup and view all the answers

    What is the primary role of Schwann cells in the peripheral nervous system?

    <p>Forming myelin around axons (D)</p> Signup and view all the answers

    Which characteristic is shared by Group A and Group C axons?

    <p>Both carry nociceptive information (B)</p> Signup and view all the answers

    Which structure of gray matter is located most dorsally?

    <p>Dorsolateral fasciculus (C)</p> Signup and view all the answers

    What is the primary role of the dorsal horn in the spinal cord?

    <p>To process incoming sensory information (B)</p> Signup and view all the answers

    Which component of spinal white matter is primarily responsible for transmitting pain signals?

    <p>Lateral spinothalamic tract (C)</p> Signup and view all the answers

    In which spinal cord region is more gray matter typically found?

    <p>Cervical region (B)</p> Signup and view all the answers

    What is the consequence of an injury to the anterior spinal artery?

    <p>Severe motor deficits (D)</p> Signup and view all the answers

    What type of reflex is characterized by a monosynaptic pathway?

    <p>Stretch reflex (D)</p> Signup and view all the answers

    Which component provides blood supply to the posterior third of the spinal cord?

    <p>Posterior spinal arteries (A)</p> Signup and view all the answers

    Where do sensory neurons synapse in the spinal cord after muscle spindle detection during a stretch reflex?

    <p>Ventral horn and dorsal horn (D)</p> Signup and view all the answers

    What type of signals do upper motor neurons send to the spinal cord?

    <p>Excitatory signals for skeletal muscle contraction (B)</p> Signup and view all the answers

    The lateral horns of the spinal cord are primarily associated with which system?

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

    A lesion in the lateral horn of the spinal cord would most likely impact which of the following functions?

    <p>Autonomic regulation of internal organs (D)</p> Signup and view all the answers

    Which of the following statements accurately describes the relationship between the spinal cord and the vertebral column?

    <p>The spinal cord ends at the level of L1/L2 in adults, with nerve roots continuing as the cauda equina (C)</p> Signup and view all the answers

    A patient presents with weakness and atrophy in their right arm. Which of the following spinal cord structures is most likely affected?

    <p>Right ventral horn (A)</p> Signup and view all the answers

    What is the primary functional difference between the dorsal and ventral horns of the spinal cord?

    <p>The dorsal horn receives sensory input, while the ventral horn transmits motor output (C)</p> Signup and view all the answers

    Which of the following is NOT true about the cauda equina?

    <p>It is directly connected to the brain via ascending and descending tracts (A)</p> Signup and view all the answers

    A patient experiences a loss of sensation in their left leg. Which of the following pathways is most likely affected?

    <p>Left dorsal column (C)</p> Signup and view all the answers

    Which of the following is characteristic of a lower motor neuron lesion?

    <p>Muscle atrophy (B)</p> Signup and view all the answers

    Why are the cervical and lumbar regions of the spinal cord larger than the thoracic region?

    <p>These regions control more complex motor functions (B)</p> Signup and view all the answers

    What is the primary reason for the inability of nerves in the central nervous system to regenerate effectively?

    <p>Formation of glial scars (D)</p> Signup and view all the answers

    Which mechanism aids in the regeneration process of peripheral nerves?

    <p>Chemicals secreted by Schwann cells (B)</p> Signup and view all the answers

    In Amyotrophic Lateral Sclerosis (ALS), which feature is typically associated with upper motor neuron loss?

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

    What does Wallerian degeneration describe?

    <p>The degeneration of the distal portion of a nerve after injury (B)</p> Signup and view all the answers

    What is a common feature of lower motor neuron diseases, such as those seen in ALS?

    <p>Intrinsic muscle wasting (B)</p> Signup and view all the answers

    Why is the prognosis for individuals diagnosed with ALS generally poor?

    <p>It is a fatal neurodegenerative disease (B)</p> Signup and view all the answers

    Which statement is true regarding the recovery timeline of peripheral nerves after injury?

    <p>Regeneration will plateau usually within the first year. (B)</p> Signup and view all the answers

    What condition is primarily characterized by a loss of motor neuron control and strength?

    <p>Amyotrophic Lateral Sclerosis (C)</p> Signup and view all the answers

    Which of the following is a rehabilitative implication following a peripheral nerve injury?

    <p>Muscles may still strengthen depending on nerve recovery. (D)</p> Signup and view all the answers

    What role do Schwann cells play in the injury response of peripheral nerves?

    <p>They provide a pathway for new nerve growth. (D)</p> Signup and view all the answers

    Flashcards

    Spinal Cord Structure

    Consists of gray and white matter with specific functions.

    Gray Matter

    Region in the spinal cord with neuron cell bodies; includes dorsal, lateral, and ventral horns.

    White Matter

    Region in the spinal cord containing myelinated axons, organized into columns.

    Dorsal Horn

    Part of the gray matter where sensory information enters the spinal cord.

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    Lateral Horn

    Gray matter region found only in the thoracic area, involved in sympathetic functions.

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    Ventral Horn

    Area in gray matter housing motor neuron cell bodies for lower motor neurons.

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    Cauda Equina

    Bundle of spinal nerves below the spinal cord proper, within the thecal sac.

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    Cervical Nerves

    Eight cervical nerves exit above their corresponding vertebra, unique to the cervical region.

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    Anterior Gray Horn

    The section of gray matter in the spinal cord responsible for motor neuron output.

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    Spinothalamic Tract

    A pathway that transmits pain and temperature sensations from the body to the brain.

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    Fasciculus Gracilis

    A tract that carries fine touch and proprioception information from the lower body to the brain.

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    Stretch Reflex

    A rapid, involuntary response to a muscle being stretched.

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    Anterior Spinal Artery

    An artery supplying blood to the anterior two-thirds of the spinal cord.

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    Posterior Spinal Artery

    Arteries supplying blood to the posterior third of the spinal cord.

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    Stepping Pattern Generators

    Neural circuits in the spinal cord that control rhythmic limb movements.

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    Monosynaptic Reflex

    A reflex involving a single synapse between sensory and motor neurons.

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    Cerebellum

    Brain region that coordinates voluntary movements and maintains posture.

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    Reciprocal Inhibition

    The process where the activation of one muscle inhibits the contraction of its antagonist muscle.

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    Muscle Synergies

    Coordinated activation of muscle groups working together for efficient movement.

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    Flexor Withdrawal Reflex

    A protective reflex causing withdrawal of a limb from a painful stimulus.

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    Central Pattern Generators (CPG)

    Neural circuits that produce repetitive rhythmic outputs like walking or running.

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    Polysynaptic Reflex

    A reflex involving multiple spinal segments that coordinate muscle responses across limbs.

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    Pathological Synergies

    Abnormal muscle patterns due to neurological impairment, limiting movement functionality.

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    Upper Motor Neurons (UMN)

    Nerve cells that originate in the brain and send signals to lower motor neurons in the spinal cord.

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    Lower Motor Neurons (LMN)

    Nerve cells that directly innervate skeletal muscles to control voluntary movements.

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    Selectivity in Movement Control

    The ability to control specific muscle movements, affected by neurological conditions.

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    Peripheral Nervous System

    Nerves outside the brain and spinal cord, not enclosed by bone.

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    Myelin

    A protective sheath around axons, composed of Schwann cells, enhancing signal transmission.

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    Lesion

    Localized damage in a specific region, causing focused weakness or sensory loss.

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    Somatic Division

    Part of the PNS that transmits sensory and motor information between skin, muscles, and the brain.

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    Autonomic Division

    Regulates involuntary functions such as heart rate and digestion through sympathetic and parasympathetic systems.

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    Dermatome

    Area of skin innervated by a single nerve root entering the spinal cord.

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    Peripheral Nerve vs Dermatome

    Peripheral nerves have broader distribution across the body; dermatomes are specific skin areas linked to nerve roots.

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    Myotome

    Muscle group innervated by a specific nerve root, producing a common motion.

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    Upper Motor Neuron

    Neurons in the brain or spinal cord affecting muscle strength globally, typically resulting in increased muscle tone and exaggerated reflexes.

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    Lower Motor Neuron

    Neurons that directly innervate muscles; localized weakness occurs; muscle tone may decrease or remain normal.

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    Sciatic Nerve Injury

    Damage to the sciatic nerve affects message transmission from spinal cord, leading to muscle atrophy and altered sensation.

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    Atrophy

    Muscle wasting that occurs in a specific pattern due to nerve injury.

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    Dermatome Mapping

    Sensation loss in a pattern according to skin segment innervation by a spinal nerve.

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    Hypo-reflexive Response

    Decreased reflex action due to impaired nerve communication.

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    Amyotrophic Lateral Sclerosis (ALS)

    A neurodegenerative disease causing muscle strength loss and motor control issues without known cause.

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    Upper Motor Neuron Signs

    Symptoms like spasticity or hyperreflexia indicating damage to CNS motor pathways.

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    Lower Motor Neuron Symptoms

    Features like muscle weakness and wasting due to peripheral nerve issues.

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    Regeneration in Peripheral Nervous System

    Peripheral nerves can regenerate post-injury due to Schwann cells promoting healing.

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    Glial Scar

    Scar formed in the CNS after injury, inhibiting nerve regeneration.

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    Wallerian Degeneration

    Process where the distal part of a nerve degenerates after injury, facilitating regeneration.

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    Study Notes

    Spinal Cord Anatomy

    • 31 pairs of spinal nerves exist.
    • The spinal cord ends approximately at L1/L2 in adults.
    • Cervical and lumbar regions of gray matter are enlarged compared to the thoracic region.
    • Three-order neural pathways exist, with tracts named for their origin and destination.

    Spinal Cord Internal Structure

    • Gray Matter:
      • Dorsal horn: Sensory information entry point.
      • Lateral horn: Located only in the thoracic region, responsible for sympathetic information.
      • Gray commissure: Connects the sides of the spinal cord.
      • Ventral horn: Contains motor outputs and lower motor neuron cell bodies.
    • White Matter:
      • Dorsal column: Receives sensory information.
      • Lateral column: Involved in some motor functions, but also autonomic.
      • Anterior column: Involved in motor output.

    Spinal Cord Longitudinal Organization

    • Regional differences: Gray and white matter distribution varies across spinal regions (cervical, thoracic, lumbar, sacral).
    • Cervical enlargement accommodates large amount of nerves to the arms; lumbar enlargement accommodates nerves of the legs.
    • Thoracic region contains lateral horn due to the sympathetic nervous system.
    • As you descend, the white matter disperses and the tracts exit.

    Spinal Cord Blood Supply

    • Supplied by the aorta, subclavian artery, vertebral arteries (cervical), intercostal, radicular arteries (thoracic and lumbar).
    • Two posterior and one anterior spinal artery.
    • Anterior spinal artery injury primarily causes motor deficits; posterior artery stroke primarily affects sensory tracts.

    Spinal Cord Reflexes

    • Reflexes are basic, withdrawal, and reciprocal inhibition.
    • Stepping pattern generators exist.
    • Descending systems (upper motor neurons): Brain signals to spinal cord to assist movement.
    • Motor cortex: Plans, initiates, and directs voluntary movements.
    • Brainstem centers: Control basic movements and posture.
    • Basal ganglia: Aids gait initiation.
    • Cerebellum: Aids sensory-motor coordination.

    Stretch Reflex

    • Monosynaptic: Rapid response.
    • Description: Muscle spindles detect stretch, triggering sensory neuron activation.
    • Synapses occur on alpha motor neurons (quadriceps contraction) and inhibitory interneurons (reciprocal inhibition of antagonist muscles, like the hamstrings).
    • Purpose: Prevent muscle damage, provide precise information about muscle state, enhance efficiency by preventing opposing muscle contraction.

    Reciprocal Inhibition

    • Antagonist muscles are inhibited when a muscle is activated.
    • Muscle synergies are coordinated muscle contractions for efficient movement.

    Flexor Withdrawal Reflex

    • Protective reflex in response to noxious stimuli.
    • Causes flexion in one limb and extension in the contralateral limb.
    • Polysynaptic (involves multiple spinal segments).

    Stepping Pattern Generators

    • Networks of spinal interneurons that generate rhythmic leg movements (like walking).
    • Can be produced without brain input (in animal models).
    • Still needs cortical influence for complex movements like balancing.

    Peripheral Nervous System

    • Upper motor neuron (UMN) vs. Lower motor neuron (LMN): UMN lesions cause global weakness and hypertonia; LMN lesions cause isolated weakness and hypotonia.
    • Nerve Structure: Myelinated axons (Schwann cells) form peripheral nerves which are outside the brain and spinal cord.
    • Nerve Lesions: Focal presentation (specific region affected), unlike global CNS lesions.

    Peripheral Nerve Classification

    • Classified by axon diameter, myelin thickness, conduction velocity, and function (sensory, motor, or both).
    • Axons are categorized by size and myelin presence.

    Dermatomes

    • Area of skin innervated by a single dorsal root.
    • Helpful for localizing spinal cord or nerve damage.

    Myotomes

    • Muscle groups controlled by specific spinal nerve roots. (specific muscles controlled by specific nerves)

    Upper Motor vs. Lower Motor Neuron Pathology

    • UMN: Global weakness, hypertonia, hyperreflexia, and more global sensory loss.
    • LMN: Isolated weakness, hypotonia, atrophy, hyporeflexia, and more focal sensory loss.

    Amyotrophic Lateral Sclerosis (ALS)

    • Progressive neurodegenerative disease affecting both UMNs and LMNs leading to muscle weakness.
    • Idiopathic; genetics and environment likely play a role.
    • Fatal; little to no regeneration in CNS neurons.
    • Supportive treatments exist to help maintain function but no cure.

    Spinal Cord Regeneration

    • Peripheral: Schwann cells promote regeneration.
    • Central: Glial scar formation inhibits regeneration.
    • CNS neurons have limited regeneration capacity, and if they do, it's usually not very impactful or useful. Peripheral nerves regenerate slowly, often at a rate of millimeter/day but can still impact muscle function if the nerve has been repaired.

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    Description

    Test your knowledge on spinal cord anatomy, including the organization of gray and white matter, spinal nerves, and neural pathways. This quiz covers key concepts related to the structure and function of the spinal cord's internal elements.

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