Spinal Cord Anatomy and Meninges
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Questions and Answers

What is the function of the subarachnoid space?

  • It serves as a protective barrier against infections.
  • It facilitates the exchange of nutrients between tissues.
  • It is filled with cerebrospinal fluid. (correct)
  • It anchors the spinal cord to the vertebrae.

Which portion of white matter is located between the anterolateral sulcus and the anterior median fissure?

  • Anterior funiculus (correct)
  • Lateral funiculus
  • Posterior funiculus
  • Dorsolateral funiculus

What is the outermost layer of the meninges?

  • Pia mater
  • Subdural space
  • Dura mater (correct)
  • Arachnoid mater

What structure provides support through the subarachnoid space to the dura mater?

<p>Denticulate ligaments (B)</p> Signup and view all the answers

What is contained within the epidural space?

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

Which term describes the space between the dura mater and the bone?

<p>Epidural space (C)</p> Signup and view all the answers

What is the pia mater primarily known for?

<p>Giving rise to denticulate ligaments (A)</p> Signup and view all the answers

What do the denticulate ligaments connect?

<p>Dura mater and pia mater (A)</p> Signup and view all the answers

Which regions contain the cell bodies of the motor neurons and interneurons that innervate the lower limbs and trunk?

<p>Lumbar and sacral regions (B)</p> Signup and view all the answers

What characterizes the ventral horns at the cervical and lumbar enlargements?

<p>They are larger because they contain motor neurons for limb muscles. (A)</p> Signup and view all the answers

What is the main function of the lateral horn found in thoracic segments?

<p>To house pre-ganglionic sympathetic neurons. (D)</p> Signup and view all the answers

How are the Rexed laminae organized within the grey matter of the spinal cord?

<p>They are numbered from dorsal to ventral with Roman numerals. (B)</p> Signup and view all the answers

Which lamina is located around the central canal of the spinal cord?

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

What is the primary role of Radicular neurons in the spinal cord?

<p>To give rise to roots, including somatic motoneurons. (A)</p> Signup and view all the answers

Which structure is found only in specific portions of the spinal cord?

<p>Nucleus dorsalis (medial region of lamina VII) (A)</p> Signup and view all the answers

Why do the enlargements have a less lamellar organization in their ventral horns?

<p>Motor neurons are clustered rather than organized in layers. (C)</p> Signup and view all the answers

What type of motoneurons innervate intrafusal muscle fibers?

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

Which symptom is NOT commonly associated with Amyotrophic Lateral Sclerosis (ALS)?

<p>Impaired urinary function (A)</p> Signup and view all the answers

How does the contractile component of intrafusal muscle fibers differ from that of extrafusal muscle fibers?

<p>It is located only at the extremities in intrafusal fibers. (C)</p> Signup and view all the answers

Which type of reflex involves 1a inhibitory interneurons?

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

What typically leads to death in patients with Amyotrophic Lateral Sclerosis (ALS)?

<p>Failure of respiratory muscles (B)</p> Signup and view all the answers

Which of the following is a characteristic of extrafusal muscle fibers?

<p>Contractile components are present throughout their length (B)</p> Signup and view all the answers

In the patellar tendon reflex, what triggers the response?

<p>Tapping the patellar tendon (B)</p> Signup and view all the answers

Which statement about beta motoneurons is true?

<p>They innervate both extrafusal and intrafusal muscle fibers. (C)</p> Signup and view all the answers

What is primarily observed during the evaluation of motor weakness?

<p>Dorsiflexion of the great toes (A)</p> Signup and view all the answers

What is the correct term for the termination of the spinal cord?

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

Where is the subarachnoid space located for lumbar punctures?

<p>Between L3 and L4 or L4 and L5 (D)</p> Signup and view all the answers

What structure is referred to as the cauda equina?

<p>Spinal nerves below the conus medullaris (C)</p> Signup and view all the answers

What is the normal cerebrospinal fluid pressure in the lumbar cistern?

<p>8-15 mm of Hg (D)</p> Signup and view all the answers

What does cauda equina syndrome involve?

<p>Compression of multiple lumbosacral nerve roots (B)</p> Signup and view all the answers

What is the significance of the filum terminale?

<p>It connects the conus medullaris to the coccyx (D)</p> Signup and view all the answers

How does the white matter structure of the spinal cord change along its length?

<p>It decreases caudally (D)</p> Signup and view all the answers

What is a key clinical concern regarding the segmental veins?

<p>They can allow metastasis of tumors to the vertebrae. (D)</p> Signup and view all the answers

Which of the following symptoms is NOT associated with meningitis?

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

What does the presence of a clear tumbler against a rash in meningococcal septicaemia signify?

<p>The rash indicates blood vessel damage. (A)</p> Signup and view all the answers

What is a typical symptom associated with nerve root compression?

<p>Back pain and referred pain. (A)</p> Signup and view all the answers

Which condition is most likely to cause compression of nerve roots?

<p>Herniation of the nucleus polposus. (D)</p> Signup and view all the answers

When does the pain from a herniated disc typically increase?

<p>With stretching of the affected nerve root. (D)</p> Signup and view all the answers

What is a potential effect of compression of nerve roots on muscle function?

<p>Weakness and decreased reflex responses. (C)</p> Signup and view all the answers

What causes the pain related to posterior root fibers when affected by a prolapsed disc?

<p>Compression of the root fibers themselves. (A)</p> Signup and view all the answers

What happens to the hamstrings when the quadriceps contracts?

<p>They relax due to inhibition. (B)</p> Signup and view all the answers

Which type of interneurons are responsible for inhibiting motoneurons that extend the leg during a withdrawal reflex?

<p>Inhibitory interneurons (C)</p> Signup and view all the answers

What is the function of central pattern generators in the spinal cord?

<p>To generate rhythmic locomotion (A)</p> Signup and view all the answers

During the withdrawal reflex, how does the body ensure balance when retracting the stimulated leg?

<p>The other leg extends. (C)</p> Signup and view all the answers

What is the pathway of the stimulus from the sole of the foot during the withdrawal reflex?

<p>It first reaches the dorsal horn of the spinal cord. (D)</p> Signup and view all the answers

What role do 1a fibres play in reflex actions involving the quadriceps?

<p>They excite inhibitory interneurons. (B)</p> Signup and view all the answers

What type of reflex is characterized by the leg retracting and flexing when stepping on something pointy?

<p>Flexion withdrawal reflex (C)</p> Signup and view all the answers

What happens when the stimulus exits via the ventral root in reflex actions?

<p>It generates excitatory and inhibitory signals from the same axon. (C)</p> Signup and view all the answers

Flashcards

Posterior Funiculus

The region of white matter located between the median posterior sulcus and the dorsolateral sulcus in the spinal cord.

Lateral Funiculus

The region of white matter located between the dorsolateral sulcus and the anterolateral sulcus in the spinal cord.

Anterior Funiculus

The region of white matter located between the anterolateral sulcus and the anterior median fissure in the spinal cord.

Pia Mater

The innermost and thinnest layer of the meninges, a protective membrane surrounding the spinal cord and brain.

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Arachnoid Mater

The middle layer of the meninges, located between the pia mater and the dura mater.

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Subarachnoid Space

The space located between the arachnoid mater and the pia mater, filled with cerebrospinal fluid.

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Dura Mater

The outermost layer of the meninges, a tough protective membrane surrounding the spinal cord and brain.

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Denticulate Ligaments

Extensions of the pia mater that traverse the subarachnoid space and connect to the dura mater, helping stabilize the spinal cord.

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Segmental Veins

Veins that drain tissues of the breast, lungs, and prostate gland. They lack valves, allowing cancer cells to travel and metastasize to the vertebral column.

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Plexus of Batson

A network of veins within the vertebral column, facilitating the spread of cancer cells from the segmental veins.

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Meningitis

A serious infection of the meninges (protective membranes around the brain and spinal cord), characterized by fever, headache, vomiting, stiff neck, and sensitivity to light.

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Kernig's Sign

Stiffness of the hamstrings, preventing full leg extension when the hip is flexed at 90 degrees.

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Brudzinski's Sign

Flexion of the knees when the neck is flexed, indicating meningeal irritation.

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Meningococcal Septicaemia

A condition where bacteria multiply in the bloodstream, causing widespread inflammation and damage to blood vessels, leading to a characteristic rash and potential organ dysfunction.

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Intervertebral Disc Herniation

A protrusion of the nucleus pulposus (inner part of an intervertebral disc) through the annulus fibrosus (outer ring), often causing pain and compression of nerve roots.

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Nerve Root Compression

A condition where a nerve root is squeezed or compressed, typically by a herniated disc, leading to pain, numbness, weakness, and decreased reflexes in the affected area.

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Spondylosis

Degenerative disease of the spine characterized by inflammation, bony growths, and degeneration of the joint capsule.

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Osteophytes

Bony outgrowths that often occur in spondylosis, indicating degeneration of the spine.

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Conus Medullaris

The lowermost end of the spinal cord, marking the transition to the spinal nerves.

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Cauda Equina

Bundle of spinal nerves extending from the conus medullaris, resembling a horse's tail.

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Lumbar Cistern

Space within the spinal canal containing cerebrospinal fluid, extending from L2 to S2.

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Lumbar Puncture

Procedure performed in the lumbar cistern, typically between L3-L4 or L4-L5, to obtain cerebrospinal fluid and/or administer anesthesia.

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Cauda Equina Syndrome

A pattern of neurological symptoms caused by compression of multiple nerve roots in the cauda equina.

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Epidural Anesthesia

Method of administering anesthesia to the epidural space, located outside the dura mater, often used for labor pain relief.

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What are intrafusal muscle fibers?

Specialized muscle fibers that detect muscle stretch and send sensory information to the spinal cord.

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What are gamma motor neurons?

Type of motor neuron that innervates intrafusal muscle fibers, helping to regulate muscle spindle sensitivity.

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What is Amyotrophic Lateral Sclerosis (ALS)?

A debilitating neurodegenerative disease affecting both upper and lower motor neurons, leading to progressive muscle weakness, atrophy, and eventually paralysis.

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What are interneurons?

Type of neuron found in the spinal cord that plays a role in reflexes by connecting sensory and motor neurons.

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What is a 1a inhibitory interneuron?

A type of interneuron that inhibits the motor neuron responsible for muscle contraction in the stretch reflex.

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What are 1a sensory fibers?

The largest sensory nerve fibers that transmit information about muscle stretch from the muscle spindle to the spinal cord.

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What is the stretch reflex?

A reflex triggered by stretching a muscle, causing it to contract. It involves the muscle spindle, sensory neurons, interneurons, and motor neurons.

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What is Cauda Equina Syndrome?

A neurological disorder caused by compression of the nerve roots in the cauda equina, leading to severe pain, numbness, weakness, and bowel/bladder dysfunction.

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What are Rexed laminae?

The grey matter of the spinal cord is organized into 10 layers, called Rexed laminae, which are numbered from dorsal to ventral (I to X).

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Where is lamina I found?

Lamina I, also known as the posteromarginal nucleus, is present throughout the entire length of the spinal cord.

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Where is lamina VII located?

Lamina VII, specifically the medial region known as the nucleus dorsalis, is only found in specific segments of the spinal cord.

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Why are the ventral horns larger in certain regions?

The ventral horns are larger in the cervical and lumbar regions due to the presence of motor neurons innervating the limb muscles.

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What is unique about the thoracic spinal cord?

The thoracic spinal cord has a lateral horn, in addition to the ventral and dorsal horns, which houses pre-ganglionic sympathetic neurons.

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What are radicular neurons?

Radicular neurons are responsible for generating the roots of the spinal nerves, which include both somatic motor neurons and visceromotor neurons.

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Why is the organization of the ventral horns different in enlargements?

The ventral horns have a less lamellar organization in the enlargements due to the presence of motor neuron clusters for limb innervation.

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Where is lamina X found?

Lamina X is located around the central canal of the spinal cord.

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Reciprocal Inhibition

A reflex where a stimulus triggers both contraction of a muscle and relaxation of its antagonist.

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Flexion Withdrawal reflex

A reflex that is activated when a part of the body encounters a painful stimulus, causing the affected limb to withdraw quickly.

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Central Pattern Generators

A neural circuit in the spinal cord responsible for generating rhythmic patterns of muscle activity, particularly for movements like walking.

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Recurrent Inhibition

A type of inhibition where a neuron inhibits its own activity by sending a collateral branch to an inhibitory interneuron, which in turn feeds back to the original neuron.

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Mono-synaptic Excitation

In the context of the knee-jerk reflex, the Ia afferent fibers from the muscle spindle synapse directly on the motoneurons controlling the quadriceps muscle, causing its contraction.

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Inhibitory Interneurons

In the context of the knee-jerk reflex, Ia afferent fibers also excite inhibitory interneurons that target the hamstrings, the antagonistic muscle to the quadriceps, causing its relaxation.

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Ia Afferent Fiber Branching

The Ia afferent fibers from the muscle spindle in the knee-jerk reflex branch within the spinal cord, with one branch exciting the quadriceps motoneurons and the other branch activating inhibitory interneurons that target the hamstrings.

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Ia Afferent Fiber Role in Knee-Jerk Reflex

The Ia afferent fibers, responsible for transmitting sensory information from muscle spindles, play a crucial role in the knee-jerk reflex by activating both excitatory and inhibitory pathways within the spinal cord.

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Study Notes

Spinal Cord Anatomy

  • The spinal cord runs from the foramen magnum to the first lumbar vertebra (L1/L2)
  • Its position makes it vulnerable to damage from vertebral column strain
  • It's connected to the body through spinal nerves
  • Each spinal cord segment has four spinal roots and two spinal nerves
  • 31 (or 33) segments in total (varying classifications)
    • 8 cervical
    • 12 thoracic
    • 5 lumbar
    • 5 sacral
    • 1 coccygeal (or 3)
  • Cervical and lumbar enlargements accommodate more neurons for upper/lower limb innervation (larger diameter area)
  • The spinal cord has grooves for arteries (anterior median fissure, anterolateral sulcus, dorsolateral sulcus, and median posterior sulcus)
  • The spinal cord roots exit at intervertebral foramina
  • The spinal cord has nerve roots exiting at oblique angles due to the longer vertebral column

Spinal Cord Meninges

  • Pia mater(innermost), arachnoid mater (middle), dura mater (outermost) surround and protect the cord
  • The epidural space between the dura and the vertebra houses adipose tissue and venous plexuses.
  • The subarachnoid space contains cerebrospinal fluid (CSF)
  • Branches from the pia mater extend to the dura mater, called denticulate ligaments

Spinal Cord Internal Structure

  • The white matter decreases towards the caudal end (lower part of the spinal cord)
  • Grey matter has different areas of function and cell clusters (different laminae), varying in location and size
    • Laminae are numbered to label different sections
  • The internal structure of the spinal cord contains cell bodies, axons, of interneurons, and motor neurons
  • Ventral (anterior) and dorsal (posterior) horns are for motor and sensory neurons respectively
  • Lateral horns are in the thoracic and upper lumbar regions and contain pre-ganglionic sympathetic neurons
  • The cauda equina is the collection of spinal nerves extending below the conus medullaris and is located in the lumbar cistern

Spinal Cord Blood Supply

  • The anterior spinal artery supplies the anterior 2/3 of the spinal cord.
  • Posterior spinal arteries supply the posterior section and are connected to segmental arteries.
  • The artery of Adamkiewicz, originating frequently from the posterior intercostal arteries, is crucial for lower 2/3 of the spinal cord supply, as it anastomoses with other arteries.

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