Spinal Cord Organisation and Nerves

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Questions and Answers

Which of these statements regarding the organization of the spinal cord is NOT true?

  • The dorsal roots are associated with the dorsal root ganglia, while the ventral roots are not.
  • The dorsal horn of the spinal cord houses motor neurons, while the ventral horn houses sensory neurons. (correct)
  • The spinal cord is not uniform in shape, with enlargements in the cervical and lumbosacral regions.
  • The white matter of the spinal cord contains myelinated axon fibers, while the gray matter contains neurons and glial cells.

Which of the following statements correctly describes the role of the dorsal and ventral roots in the spinal cord?

  • The dorsal roots contain sensory neuron axons, while the ventral roots contain motor neuron axons. (correct)
  • The dorsal roots contain both sensory and motor neuron axons, while the ventral roots contain only sensory neuron axons.
  • The dorsal roots contain motor neuron axons, while the ventral roots contain sensory neuron axons.
  • The dorsal roots contain both sensory and motor neuron axons, while the ventral roots contain only motor neuron axons.

Which of the following structures is NOT directly involved in protecting the spinal cord?

  • Intervertebral disc (correct)
  • Dura mater
  • Vertebral arch
  • Arachnoid mater

What is the function of the dorsal root ganglia (DRG)?

<p>To contain the cell bodies of sensory neurons that receive information from the body. (B)</p> Signup and view all the answers

Which of the following statements correctly describes the location of the epidural space?

<p>Between the dura mater and the vertebral canal. (A)</p> Signup and view all the answers

Which of the following statements correctly describes the function of the ventral ramus of a spinal nerve?

<p>It supplies sensory, motor, and sympathetic innervation to the anterolateral parts of the trunk and limbs. (C)</p> Signup and view all the answers

Which of the following neuron types is NOT found in the gray matter of the spinal cord?

<p>Dorsal root ganglia sensory neurons (C)</p> Signup and view all the answers

Which of the following statements accurately describes the relationship between the roots and rootlets of spinal nerves?

<p>Rootlets join to form roots, which then join to form spinal nerves. (A)</p> Signup and view all the answers

Which of the following structures is responsible for connecting the vertebral body to the vertebral arch?

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

Which of the following statements accurately describes the relationship between the Spinothalamic tract and the Dorsal Column Pathway?

<p>The Spinothalamic tract synapses in the ventral posterior thalamic nuclei, while the Dorsal Column Pathway synapses in the dorsal column nuclei, specifically the nucleus cuneatus (N.C.) and nucleus gracilis (N.G.). (C), The Spinothalamic tract ascends on the contralateral side of the spinal cord, while the Dorsal Column Pathway ascends on the ipsilateral side. (D)</p> Signup and view all the answers

A patient sustains a spinal cord injury that completely severs the dorsal column nuclei on the left side of the brainstem. Which of the following sensory deficits would this patient most likely experience?

<p>A loss of discriminative touch and conscious proprioception on the left side of the body. (D)</p> Signup and view all the answers

Which of the following statements is TRUE regarding somatotopic mapping in the Spinothalamic tract?

<p>Somatotopic mapping in the Spinothalamic tract is based on the distribution of sensory receptors in different body regions, which is not necessarily correlated with the distribution of motor neurons. (A)</p> Signup and view all the answers

A patient experiences a stroke affecting the left ventral posterior thalamic nuclei. Which of the following sensory deficits would this patient most likely experience?

<p>A loss of pain and temperature sensation on the right side of the body. (A)</p> Signup and view all the answers

Which of the following statements accurately describes the role of projection interneurons in the Spinothalamic tract?

<p>Projection interneurons receive input from ascending sensory fibers and project to other spinal cord segments, modifying the transmission of sensory information. (E)</p> Signup and view all the answers

How many pairs of spinal nerves are associated with the spinal cord segments?

<p>30 pairs (A)</p> Signup and view all the answers

Which vertebra is associated with two pairs of spinal nerves?

<p>C1 (B)</p> Signup and view all the answers

Which type of axons do C1 spinal nerves contain?

<p>Only motor axons (B)</p> Signup and view all the answers

From where do the C2 spinal nerves arise?

<p>Below C1 vertebra (D)</p> Signup and view all the answers

What is the total number of cervical vertebrae?

<p>7 (D)</p> Signup and view all the answers

How many thoracic vertebrae are present in the spinal column?

<p>12 (C)</p> Signup and view all the answers

Which spinal nerves contain both motor and sensory axons?

<p>C3 spinal nerves (A)</p> Signup and view all the answers

What structure anchors the spinal cord to the coccyx?

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

At which vertebral level does the spinal cord typically terminate?

<p>L1/L2 (D)</p> Signup and view all the answers

Which of the following statements is true about the lumbosacral enlargement?

<p>It contains less compact spinal cord segments than cervical segments. (C)</p> Signup and view all the answers

Where do the spinal nerve roots from L2 to S5 travel before emerging as spinal nerves?

<p>In the cauda equina (B)</p> Signup and view all the answers

Which of these structures fuse to form the filum terminale?

<p>Pia mater (B)</p> Signup and view all the answers

What is the function of the cauda equina?

<p>To route lower spinal nerves to their exit points (A)</p> Signup and view all the answers

Which anatomical regions are associated with the spinal cord enlargements?

<p>Lumbosacral and cervical enlargements (D)</p> Signup and view all the answers

What are the spinal segments in the lumbar enlargement primarily responsible for?

<p>Supplying the lower limbs (C)</p> Signup and view all the answers

What happens after the spinal cord ends at the conus medullaris?

<p>Spinal nerve roots continue downwards as part of the cauda equina (B)</p> Signup and view all the answers

Which segment of the spine does NOT contain a notable enlargement?

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

What is the primary function of the spinothalamic tract?

<p>Pain, temperature, itch, and simple touch sensation (C)</p> Signup and view all the answers

Where does the enlarged subarachnoid space, also known as the lumbar cistern, primarily occur?

<p>Between L1/L2 and S2/S3 vertebral levels (A)</p> Signup and view all the answers

Which descending tract is primarily involved in conscious movement?

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

What is the anatomical relationship between the cauda equina and the filum terminale?

<p>The filum terminale anchors the cauda equina to the coccyx (C)</p> Signup and view all the answers

In which region of the spinal cord does the grey matter specifically take the shape of a 'fat butterfly'?

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

What purpose does the reticulospinal tract serve in the spinal cord?

<p>Muscle tone and reflex control (B)</p> Signup and view all the answers

Which of the following describes the configuration of grey and white matter through the cervical levels?

<p>Thin grey matter with a resemblant butterfly shape (D)</p> Signup and view all the answers

What is the primary purpose of a lumbar puncture?

<p>To collect cerebral spinal fluid (CSF) (B)</p> Signup and view all the answers

Which ascending tract is responsible for transmitting sensory information about discriminative touch?

<p>Dorsal column medial lemniscus pathway (A)</p> Signup and view all the answers

In which section of the spinal cord does the ratio of white to grey matter visibly increase?

<p>Cervical levels (D)</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 are responsible for transmitting signals between the spinal cord and the rest of the body.

Dorsal Root

The dorsal root of a spinal nerve carries sensory information from the body to the spinal cord.

Ventral Root

The ventral root of a spinal nerve carries motor commands from the spinal cord to the muscles.

Dorsal Root Ganglion (DRG)

The dorsal root ganglion (DRG) is a cluster of nerve cell bodies located near the dorsal root of the spinal nerve. It contains sensory neurons that transmit signals from the body to the spinal cord.

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30 Pairs of Spinal Nerves

There are 30 pairs of spinal nerves, each associated with a specific segment of the spinal cord, providing the point of connection between the central nervous system and the body.

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Vertebrae and Spinal Nerves

Each vertebra is associated with a pair of spinal nerves, which project from the spinal cord, except for the C1 vertebra which has two pairs.

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C1 Spinal Nerve

The C1 spinal nerves are unique in that they contain only motor axons, while the remaining spinal nerves (from C2 onwards) contain both motor and sensory axons.

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Vertebral Column

The bony structure that protects the spinal cord. It is made up of individual vertebrae stacked on top of each other.

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Epidural space

The space between the dura mater and the vertebral canal, filled with fat and small veins.

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Meninges: Dura, Arachnoid, Pia

These three meninges surround and protect the spinal cord, providing a protective barrier and support.

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Subarachnoid Space

A fluid-filled space between the arachnoid and pia mater, containing cerebrospinal fluid (CSF) and small blood vessels.

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Cervical Enlargement

The region of the spinal cord where the spinal nerves for the arms originate, forming the brachial plexus.

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Lumbosacral Enlargement

The area of the spinal cord where lumbar and sacral nerve roots originate. It's larger than other areas because it needs to accommodate the larger nerve roots for the legs and lower body.

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Cauda Equina

The collection of nerve roots that extend from the end of the spinal cord and run downwards within the vertebral column.

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Conus Medullaris

The end of the spinal cord, located at the level of the 1st and 2nd lumbar vertebrae.

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Filum Terminale

A thin, fibrous extension of the pia mater that attaches the spinal cord to the coccyx.

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Lumbar Cistern

The space within the vertebral column, below the conus medullaris, filled with cerebrospinal fluid.

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Long Spinal Nerve Roots

Nerve roots that are longer than others due to the spinal cord ending higher up than the vertebral column.

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Spinal Cord Ending

The point where the spinal cord ends at the L1/L2 vertebral level.

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Compression of Nerve Roots

Nerve roots extending from the spinal cord are compressed due to less space in the lumbar and sacral regions compared to other regions.

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Lumbar and Sacral Nerves

Lumbar and sacral nerves are responsible for providing motor and sensory innervation to the legs, feet, and lower body.

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Spinothalamic Tract

A pathway in the spinal cord that transmits sensory information about pain, temperature, itch, and crude touch to the brain.

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Dorsal Column Pathway

A pathway in the spinal cord that transmits sensory information about fine touch, pressure, vibration, and proprioception (body awareness) to the brain.

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Projection Interneuron

A type of neuron that transmits sensory information from the body to the spinal cord.

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Decussation

The process by which nerve fibers cross over from one side of the body to the other as they ascend to the brain.

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Lumbar puncture

A procedure where a needle is inserted into the lumbar cistern to sample cerebrospinal fluid or administer medications.

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Epidural injection

A procedure where a needle is inserted into the epidural space, the space between the dura mater and the vertebral bone.

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White to grey matter ratio

The proportion of white matter (axons) and gray matter (neuronal cell bodies) changes along the spinal cord.

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Lumbar enlargement

The lumbar enlargement is due to the increased need for neurons to control the lower limbs.

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Sacral region (spinal cord)

The part of the spinal cord that controls the sacrum and lower limbs.

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Study Notes

Spinal Cord Organisation

  • The spinal cord is a complex structure
  • Each segment of the spinal cord gives rise to a pair of spinal nerves
  • There are 30 pairs of spinal nerves
  • The spinal cord segments are organised from C1-C8, then T1-T12, L1-L5, and S1-S5
  • Cervical vertebrae: C1 to C7
  • Thoracic vertebrae: T1 to T12
  • Lumbar vertebrae: L1 to L5
  • Sacral vertebrae: S1 to S5 (fused)
  • Coccyx: 3-4 small fused vertebrae

Spinal Nerves and Vertebrae

  • Exceptionally the C1 vertebra is associated with 2 pairs of spinal nerves
  • C1 spinal nerves contain motor axons only
  • These arise from the spinal cord above the C1 vertebra
  • C2 spinal nerves contain motor and sensory axons and arise from the spinal cord below C1
  • The pattern continues, with subsequent spinal nerves containing both motor and sensory axons, arising from the spinal cord below the preceding nerve

Spinal Cord Protection

  • The spinal cord is protected within the vertebral column
  • The subarachnoid space is between the arachnoid and pia and contains CSF and small blood vessels

Spinal Cord Rootlets, Roots and Nerves

  • Note: rootlets form roots, roots form nerves
  • Dorsal root ganglia (DRG) position on the dorsal root
  • Ventral roots are not associated with a ganglion

Organisation of a Vertebral Section

  • Dorsal ramus supplies sensory, motor, and sympathetic innervation to the back
  • Ventral ramus supplies sensory, motor and sympathetic innervation to the anterolateral parts of trunk and limbs

White and Grey Matter in the Spinal Cord

  • Grey matter contains neurons and glia
  • Dorsal rootlets
  • Dorsal horn
  • Lateral horn
  • Intermediate zone
  • Ventral horn
  • White matter contains myelinated axon fibre tracts

The Cauda Equina and Lumbar Cistern

  • The spinal cord ends at the conus medullaris (vertebral level L1/L2)
  • The pia surrounding the spinal cord forms the filum terminale
  • L2 to S5 spinal nerve roots and the coccygeal nerve run caudally to emerge at their appropriate vertebral level forming the cauda equina.
  • The dura and subarachnoid space enlarges between L1/L2 and S2/S3, forming the lumbar cistern.

Clinical Interventions Associated with the Spinal Cord

  • Epidural injection is into the epidural space, outside of the dura mater
  • Lumbar puncture inserts a spinal needle between the 3rd and 4th lumbar vertebrae to collect CSF.

Ratio of White to Grey Matter

  • The ratio of white to grey matter in the spinal cord changes along the rostrocaudal axis
  • Cervical levels have a skinny top butterfly shape
  • Thoracic levels have an underweight butterfly shape
  • Lumbar levels have a well-proportioned butterfly shape
  • Sacral levels have a fat butterfly shape

Major Ascending and Descending Axon Tracts

  • Different tracts, such as Spinothalamic, Dorsal Column-Medial Lemniscus, and Spinocerebellar, transmit different types of sensory information
  • Pyramidal and Non-Pyramidal tracts are motor pathways

Spinothalamic Tract

  • Transmits pain, temperature, itch, and simple touch sensations.
  • Originates in the DRG and crosses over (decussates) in the spinal cord.
  • Enters the brain through the ventral posterior thalamic nuclei.

Dorsal Column Pathway

  • Carries fine touch and conscious proprioception.
  • Ascends ipsilaterally in the dorsal columns.

Pyramidal Motor Pathway (Corticospinal Tracts)

  • Responsible for voluntary movements.
  • Upper and Lower motor neurons.
  • 90% of pyramidal tracts decussate (cross over) in the medulla.

Spinocerebellar Pathway

  • Carries non-conscious proprioceptive information.
  • Ascends ipsilaterally to the cerebellum
  • Little decussation occurs

Spinal Cord Grey Matter

  • Divided into regions called laminae
  • Each lamina has a specific function relating to either nociception, mechanoreception, proprioception or visceral sensation, and motor coordination involving somatic or visceral organs.

Somatic Motor Functions Associated with Spinal Nerves

  • Specific spinal nerve levels control different body parts and actions (e.g., T1-hands, T2-T5 chest muscles, L1-hip muscles, S1-toe muscles)

Spinal Cord Lesions and Somatic + Autonomic Motor Function Impairment

  • Spinal cord lesions can lead to specific motor (and autonomic) function loss at certain spinal levels.
  • The level of the injury determines which body parts and functions are affected.

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