Spinal Cord Structure and Function Quiz
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Questions and Answers

What is the primary function of projection interneurons?

  • To ascend the spinal cord to higher nervous system regions (correct)
  • To anchor the spinal cord to the vertebral column
  • To connect sensory neurons with local circuit interneurons
  • To transmit information only within the spinal cord

Where does the spinal cord end in the vertebral column?

  • At the conus medullaris (correct)
  • At the lumbar cistern
  • At the cauda equina
  • At the brachial plexus

What structure stabilizes the spinal cord by anchoring it to the coccyx?

  • Cauda equina
  • Lumbar cistern
  • Conus medullaris
  • Filum terminale (correct)

What is characterized by the spinal nerves that leave the cervical enlargement?

<p>They make up the brachial plexus. (D)</p> Signup and view all the answers

What is a key characteristic of the lumbosacral enlargement compared to other segments of the spinal cord?

<p>It is more compressed than the cervical and thoracic segments. (A)</p> Signup and view all the answers

What type of neuron is classified as the first order neuron in proprioception?

<p>Proprioceptive DRG neuron (C)</p> Signup and view all the answers

In the proprioceptive circuit, where do the first order neurons connect?

<p>Lamina VII of the dorsal horn (D)</p> Signup and view all the answers

Which structure does the second order neuron in the proprioception pathway originate from?

<p>Nucleus of Clarke (D)</p> Signup and view all the answers

What happens to 90% of motor neuron axons at the junction of the medulla and spinal cord?

<p>They undergo decussation (B)</p> Signup and view all the answers

What does the lateral corticospinal tract primarily innervate?

<p>Limb muscles (B)</p> Signup and view all the answers

Which order neuron connects to the ipsilateral cerebellum?

<p>Third order neuron (C)</p> Signup and view all the answers

What is the primary function of Golgi tendon organs?

<p>Detect muscle tension (B)</p> Signup and view all the answers

Where do lower motor neurons reside in the spinal cord?

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

What type of neuron is the first order neuron in the dorsal column medial lemniscus pathway?

<p>Pseudounipolar neuron (B)</p> Signup and view all the answers

Where do the axons from first order neurons in the dorsal column terminate?

<p>In the nucleus cuneatus and nucleus gracilis (D)</p> Signup and view all the answers

Which pathway conveys non-conscious proprioception?

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

Which nuclei do second order neurons in the dorsal column medial lemniscus pathway project from?

<p>Nucleus cuneatus and nucleus gracilis (C)</p> Signup and view all the answers

What is the final destination of axons projected from third order neurons in the dorsal column medial lemniscus pathway?

<p>Primary sensory cortex (B)</p> Signup and view all the answers

What is the primary purpose of a lumbar puncture?

<p>To analyze cerebrospinal fluid for various conditions (B)</p> Signup and view all the answers

At which vertebral levels is a lumbar puncture ideally performed?

<p>Between the 3rd and 4th lumbar vertebrae (D)</p> Signup and view all the answers

Which statement best describes the ratio of white to grey matter in the lumbar region of the spinal cord?

<p>Well-proportioned ratio of white to grey matter (A)</p> Signup and view all the answers

What function does the spinothalamic tract primarily serve?

<p>Conduction of sensory information related to pain and temperature (D)</p> Signup and view all the answers

Which statement is correct about the first order neuron in the spinothalamic tract?

<p>It is a small diameter nociceptive unipolar neuron (A)</p> Signup and view all the answers

What type of neurons are found in the dorsal root ganglia (DRG)?

<p>Pseudo unipolar neurons (B)</p> Signup and view all the answers

How many pairs of spinal nerves do humans have?

<p>31 pairs (C)</p> Signup and view all the answers

What is the function of the ventral root of a spinal nerve?

<p>To allow motor neurons to exit the spinal cord (C)</p> Signup and view all the answers

Which section of the spine has the highest number of vertebrae?

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

What is the function of the spinous process in vertebrae?

<p>To serve as an attachment point for muscles (D)</p> Signup and view all the answers

What kind of structure is the arachnoid layer of the meninges described as?

<p>Web-like and fluid-filled (D)</p> Signup and view all the answers

Which portions of the spine are fused vertebrae found?

<p>Sacral and coccyx (C)</p> Signup and view all the answers

Which vertebrae are located in the neck region?

<p>C1 to C7 (C)</p> Signup and view all the answers

What is the primary function of the dorsal root?

<p>To transmit sensory information to the spinal cord (A)</p> Signup and view all the answers

Which part of the spinal nerve supplies motor innervation to the back?

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

Where are preganglionic sympathetic neurons located in the spinal cord?

<p>In the intermedio-lateral horn of T1 to L2 (B)</p> Signup and view all the answers

What type of axons does the ventral root primarily contain?

<p>Motor neuron axons (D)</p> Signup and view all the answers

What does the subarachnoid space contain?

<p>Cerebrospinal fluid and small blood vessels (B)</p> Signup and view all the answers

Which part of the spinal cord is most pronounced in the thoracic region?

<p>Lateral horn (B)</p> Signup and view all the answers

Which of the following is NOT a function of the spinal nerve?

<p>Supplies parasympathetic innervation (A)</p> Signup and view all the answers

Which of the following correctly describes white matter in the spinal cord?

<p>Is primarily composed of myelinated axon fiber tracts (C)</p> Signup and view all the answers

Flashcards

Spinal Nerves

Each segment of the spinal cord gives rise to a pair of spinal nerves, which carry sensory and motor information to and from the body.

Dorsal Root Ganglion (DRG)

The dorsal root ganglion (DRG) is a cluster of nerve cell bodies that contains the sensory neurons responsible for transmitting information from the body to the spinal cord.

Pseudo-Unipolar Sensory Neurons

Sensory neurons are pseudo-unipolar, meaning they have two axons: one that projects to the periphery (PNS) and another that projects to the spinal cord (CNS).

Ventral Root

The ventral root allows motor neurons to exit the spinal cord through the spinal nerve and travel to skeletal muscles to control movement.

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Vertebrae

The spinal column is made up of 33 bones called vertebrae, which are divided into five regions: cervical, thoracic, lumbar, sacral, and coccyx.

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Vertebral Body

The vertebral body is the thick, bony cylinder structure that forms the front portion of each vertebra. It provides strength and stability to the spine.

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Vertebral Arch

The vertebral arch is the bony structure that forms the back portion of each vertebra. It encloses the spinal cord and provides protection to the spinal nerves.

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Meninges

The meninges are three layers of protective tissue that surround the spinal cord: dura mater, arachnoid mater, and pia mater.

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Projection Interneurons

Interneurons found in all grey matter regions whose axons project to distant areas of the nervous system, often sensory in nature.

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Local Circuit Interneurons

Interneurons found within the same spinal cord level, involved in local computations and communication between sensory and motor neurons.

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Conus Medullaris

The tapered end of the spinal cord, located at the vertebral level L1/L2.

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Filum Terminale

A fibrous extension of the pia mater that anchors the spinal cord to the coccyx, providing stability.

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Lumbar Cistern

The enlarged subarachnoid space below the conus medullaris, extending to the level of S2/S3, containing the cauda equina.

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Pia mater

The innermost membrane that tightly surrounds the spinal cord.

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Subarachnoid space

The space between the arachnoid and pia mater containing cerebrospinal fluid (CSF) and small blood vessels.

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Epidural space

The space above the meninges, containing small veins and fat.

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Dorsal root

The bundle of axons carrying sensory information from the body to the spinal cord.

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Preganglionic sympathetic neuron axons

The axons of neurons that originate in the spinal cord and synapse in the sympathetic ganglia.

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Postganglionic sympathetic neuron axons

The axons of neurons that carry signals from the sympathetic ganglia to target organs.

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Lumbar Puncture (spinal tap)

The cerebrospinal fluid (CSF) surrounding the spinal cord is extracted through a needle inserted into the lumbar cistern, between the 3rd and 4th lumbar vertebrae.

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Spinal Cord Grey/White Matter Distribution

The ratio of white to grey matter in the spinal cord changes along its length. Cervical regions have less grey matter, resembling a thin butterfly. The ratio increases towards the lumbar and sacral regions, producing a more robust butterfly shape.

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Spinothalamic Tract

The spinothalamic tract transmits pain, temperature, itch, and simple touch sensations from the body to the brain.

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Pseudo-unipolar Neuron

A sensory neuron with a single axon that branches into two processes. One projects to the periphery, while the other projects to the spinal cord.

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Decuessation

The process where nerve fibers cross over to the opposite side of the brain or spinal cord.

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Dorsal Column-Medial Lemniscus (DCML) Pathway

The Dorsal Column-Medial Lemniscus (DCML) pathway is responsible for transmitting information about discriminative touch and conscious proprioception from the body to the brain. It involves a chain of three neurons: the first-order neuron, the second-order neuron, and the third-order neuron. This pathway allows us to perceive fine details about textures, shapes, and the position of our limbs in space.

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First-Order Neuron in DCML Pathway

The first-order neuron in the DCML pathway is a pseudounipolar neuron located in the dorsal root ganglion (DRG). This neuron receives sensory input from the body and sends its axon up the spinal cord through the dorsal column.

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Second-Order Neuron in DCML Pathway

The second-order neurons in the DCML pathway reside in the nucleus cuneatus (NC) and nucleus gracilis (NG) in the medulla. They receive input from the first-order neurons and transmit information contralaterally to the thalamus.

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Third-Order Neuron in DCML Pathway

The third-order neurons in the DCML pathway are located in the ventral posterior nucleus (VPL) of the thalamus. They receive input from the second-order neurons and project to the primary sensory cortex, where conscious perception of touch and proprioception occurs.

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Spinocerebellar Pathway

The spinocerebellar pathway transmits non-conscious proprioceptive information from the body to the cerebellum. This pathway plays a key role in coordinating movement and maintaining balance.

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Golgi Tendon Organ

A proprioceptive sensory receptor located within tendons that detects changes in muscle tension.

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First Order Neuron (Golgi Tendon Organ)

A large, heavily myelinated sensory neuron in the dorsal root ganglion that detects muscle tension and sends information to the spinal cord.

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Lamina VII

The deepest layer of the dorsal horn in the spinal cord, where the first-order neuron from the Golgi tendon organ synapses with a premotor neuron.

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Premotor Neuron

A neuron located in Lamina VII that receives input from the Golgi tendon organ and projects to motor neurons to regulate muscle contraction.

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Nucleus of Clarke

A specialized nucleus located within Lamina VII from C8-L3, where a branch of the first-order neuron from the Golgi tendon organ makes a synapse.

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Second Order Neuron (Nucleus of Clarke)

A neuron located in the Nucleus of Clarke that carries proprioceptive information from the Golgi tendon organ to the cerebellum.

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Lateral Cuneate Nucleus

A nucleus located in the medulla oblongata that receives proprioceptive information from the cerebellum.

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Spinocerebellar Tract

The pathway that carries proprioceptive information from the Golgi tendon organ to the cerebellum, allowing for unconscious coordination of movement.

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Study Notes

Spinal Cord Structure and Function

  • Spinal cord segments give rise to pairs of spinal nerves.
  • 31 pairs of spinal nerves.
  • Dorsal root ganglia (DRG) contain sensory neuron cell bodies.
  • Sensory neurons are pseudo-unipolar, having two axons that extend peripherally and centrally.
  • Peripherally projecting axons carry sensory information to skin and muscles.
  • Centrally projecting axons relay sensory information to the central nervous system (CNS).
  • Ventral roots contain motor neurons that exit the spinal cord and travel to skeletal muscles.

Vertebrae and Spinal Nerves

  • Humans have 32-33 vertebrae.
  • Vertebrae are categorized as cervical (7), thoracic (12), lumbar (5) sacral (5), coccygeal (3-4).
  • Cervical vertebrae are in the neck.
  • Thoracic vertebrae are in the upper back and connected to ribs.
  • Lumbar vertebrae are in the lower back.
  • Sacral vertebrae are fused in the pelvis.
  • Coccygeal vertebrae are small fused vertebrae.
  • Each vertebra has a pair of spinal nerves associated with it.
  • Spinal nerves emerge from the spinal cord between vertebrae
    • e.g., c1 nerves emerge above c1.

Spinal Cord Meninges

  • Three meninges surround and protect the spinal cord.
  • Dura mater, arachnoid, pia mater.
  • Dura mater is the tough, outer layer.
  • Arachnoid is a web-like structure filled with cerebrospinal fluid (CSF).
  • Pia mater is a delicate layer that wraps around the spinal cord.
  • CSF and small blood vessels are in the subarachnoid space between arachnoid and pia.

Spinal Cord Organization

  • Dorsal root, ventral root, spinal nerve.
  • Dorsal root subdivides into dorsal rootlets that carry sensory information.
  • Ventral root carries motor information.
  • Both roots merge to form a spinal nerve.
  • Grey matter is organized into different regions within the spinal cord such as dorsal horn, ventral horn, intermediate zone and lateral horn.

White and Gray Matter

  • White matter: myelinated axon tracts, mostly on the outside of the spinal cord.
  • Grey matter: contains neurons and glia, mostly on the inside of the spinal cord.
  • Important: White and grey matter are split into different regions (dorsal horns, ventral horns, intermediate zone etc.)

Spinal Cord Enlargements

  • Cervical enlargement: Contains nerves for upper limbs.
  • Lumbosacral enlargement: Contains nerves for lower limbs.

Cauda Equina and Lumbosacral Cistern

  • After spinal cord ends, the remaining spinal nerves form the cauda equina.
  • Lumbosacral cistern is an expanded subarachnoid space below the spinal cord.

Clinical Interventions

  • Epidural injection: for pain relief, usually near birth.
  • Lumbar puncture (spinal tap): sample of CSF, in enlarged lumbar cistern, useful in medical diagnosis.

Ascending Tracts

  • Spinothalamic tract: carries sensory information about pain, temperature, and touch.

Descending Tracts

  • Pyramidal motor pathway: for voluntary movement; consists of lateral and anterior corticospinal tracts.

Non-pyramidal Motor Pathways

  • Responsible for conscious muscle control and reflexes (balance and posture).
  • Reticulospinal and vestibulospinal tracts.

Spinal Cord Laminae

  • Gray matter is divided into 10 distinct regions called laminae.
  • Each lamina has specific functions related to sensory and motor input/output.

Spinal Nerves

  • Each segment of spinal cord gives rise to 2 spinal nerves.
  • Each spinal nerve branches into dorsal ramus and ventral ramus.
  • Dorsal rami innervate, supply, the back muscles and skin.
  • Ventral rami innervate the rest of the body, including the limbs.

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Spinal Cord Anatomy PDF

Description

Test your knowledge on the spinal cord's structure and its functional significance. This quiz covers spinal cord segments, spinal nerves, and the vertebral column. Understand the role of sensory and motor neurons as well as the categorization of vertebrae.

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