Spinal Cord Anatomy and Function

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Which of the following accurately describes the relationship between spinal segments and vertebrae in the thoracic region?

A spinal segment is typically two spines higher than its corresponding vertebra. (correct)
A spinal segment is typically one spine higher than its corresponding vertebra.
A spinal segment is typically located at the same vertebral level.
A spinal segment is typically three to four spines higher than its corresponding vertebra.

The cauda equina is formed due to the spinal cord being shorter than the vertebral column. Where is the cauda equina located?

Within the thoracic vertebral canal.
Below the termination of the spinal cord, extending into the lower lumbar and sacral vertebral canals. (correct)
Above the termination of the spinal cord, extending into the upper lumbar and thoracic vertebral canals.
Within the cervical vertebral canal.

What is the functional composition of a common spinal nerve after the dorsal and ventral roots combine?

A mix of afferent sensory and efferent motor fibers. (correct)
Primarily interneurons facilitating communication between sensory and motor neurons.
Exclusively efferent motor fibers.
Exclusively afferent sensory fibers.

What is the primary function of the ventral ramus of a spinal nerve?

Innervating the muscles, skin, and structures of the anterior trunk and limbs. (A) Signup and view all the answers

If a patient has damage to the brachial plexus, which of the following regions would MOST likely be affected?

Upper limb (C) Signup and view all the answers

What is the role of the denticulate ligaments in the spinal meninges?

To anchor the spinal cord to the dura mater, limiting lateral movement. (B) Signup and view all the answers

Which of the following describes the path taken by spinal nerve roots as they descend within the spinal canal to reach their respective intervertebral foramen, particularly below the cervical segments?

They take an increasingly oblique course. (A) Signup and view all the answers

Where are the cell bodies of efferent motor fibers located?

Spinal grey matter (B) Signup and view all the answers

Which of the following best describes the function of gamma motor neurons located in the ventral horn's Lamina IX?

They innervate intrafusal muscle fibers within muscle spindles, regulating muscle tone. (B) Signup and view all the answers

The spinocerebellar tract originates from which structure in the spinal cord?

Clarke's column (A) Signup and view all the answers

A patient has damage to the lateral part of the ventral horn in the cervical region of their spinal cord. Which of the following deficits would you most likely expect?

Difficulty controlling muscles in the upper limbs. (B) Signup and view all the answers

Which of the following structures contains preganglionic sympathetic neurons?

Lateral lamina VII in the thoracic and upper lumbar vertebrae (C) Signup and view all the answers

What is the primary function of the intersegmental/propriospinal fibers within the spinal cord?

Connecting adjacent or distant spinal cord segments for intersegmental communication (D) Signup and view all the answers

If a patient exhibits loss of fine touch and proprioception on the right side of their body, which spinal cord structure is most likely damaged?

Right dorsal columns (A) Signup and view all the answers

The phrenic nerve, which innervates the diaphragm, originates from which spinal cord segments?

C3-C5 (D) Signup and view all the answers

A lesion limited to the fasciculus cuneatus in the cervical spinal cord would result in loss of:

Proprioception and fine touch from the ipsilateral upper limb. (D) Signup and view all the answers

Why is it possible to extract cerebrospinal fluid (CSF) from the lower spinal cord, even though the spinal cord terminates at the L1/L2 vertebral level?

The arachnoid and dura mater extend down to the S2 vertebral level, creating a space containing CSF beyond the spinal cord's termination. (A) Signup and view all the answers

What is the fate of the meningeal root sleeves after the spinal roots fuse?

They become continuous with the epineurium of the spinal nerve. (C) Signup and view all the answers

What is the significance of the ventral median fissure and the dorsal median sulcus in the spinal cord?

They incompletely divide the spinal cord into halves and serve as anatomical landmarks. (C) Signup and view all the answers

Which of the following best describes the relationship between spinal segment level and the amount of white matter?

Higher spinal segments contain more white matter because ascending tracts accumulate fibers as they ascend. (C) Signup and view all the answers

The lateral horn of the spinal cord is associated with which function and spinal level?

Preganglionic sympathetic neurons in the thoracic and upper lumbar segments. (B) Signup and view all the answers

In the context of Rexed's laminae, where do cutaneous afferents primarily terminate?

Superficial laminae of the dorsal horn. (C) Signup and view all the answers

What is the primary function of the substantia gelatinosa, and which fibers provide input to it?

Pain modulation; receives input from Aδ and C fibers. (C) Signup and view all the answers

How does encephalin, found in high levels within the substantia gelatinosa, contribute to pain modulation?

By decreasing the release of substance P via opioid receptor binding. (D) Signup and view all the answers

A patient has a lesion affecting the fasciculus gracilis at the T4 level of the spinal cord. Which sensory deficit would you expect to find?

Loss of fine touch and proprioception on the left leg. (B) Signup and view all the answers

The ventral posterior nucleus of the thalamus is a key relay station for sensory information. Which of the following pathways does not directly synapse in this nucleus?

Spinocerebellar Tract (B) Signup and view all the answers

A patient suffers a stroke affecting the right side of the medulla oblongata. Which sensory deficit would you least expect?

Impaired proprioception on the right side of the body. (A) Signup and view all the answers

Following a spinal cord injury, a patient exhibits loss of pain and temperature sensation on the right side of the body, starting a few segments below the level of the injury. Which pathway is most likely affected?

Left Spinothalamic Tract (D) Signup and view all the answers

Where does the second-order neuron of the spinothalamic tract decussate?

Ventral white commissure (D) Signup and view all the answers

Which of the following describes the termination point of reticulothalamic fibers in the spinoreticulothalamic system?

Intralaminar thalamic nuclei (D) Signup and view all the answers

Which of the following body regions would be represented most laterally within the spinothalamic tract?

Foot (A) Signup and view all the answers

The spinocerebellar tracts primarily transmit impulses from which of the following?

Muscle spindles (D) Signup and view all the answers

Which of the following statements accurately describes the pathways of the dorsal and ventral spinocerebellar tracts?

Ventral tract fibers decussate in the spinal cord and ascend contralaterally, while dorsal tract fibers ascend ipsilaterally. (A) Signup and view all the answers

A patient exhibits decreased muscle tone and difficulty maintaining posture. Which component of the stretch reflex is MOST likely affected?

Gamma motor neurons controlling the contraction of intrafusal muscle fibers (D) Signup and view all the answers

In the flexor reflex, what role do interneurons play in the withdrawal of a limb from a noxious stimulus?

They relay the signal from primary afferent neurons to alpha motor neurons, ultimately activating flexor muscles. (A) Signup and view all the answers

The ventral spinocerebellar tract enters the cerebellum through the superior cerebellar peduncle, while the dorsal spinocerebellar tract enters through the inferior cerebellar peduncle. Where do the fibers of both these tracts ultimately terminate?

The Vermis of the cerebellar cortex (A) Signup and view all the answers

During a neurological examination, a doctor taps the patellar tendon, and the patient's lower leg extends. Which of the following components is directly responsible for causing the contraction of the quadriceps muscle in this reflex?

Alpha motor neurons (D) Signup and view all the answers

A person steps on a sharp object. Which of the following BEST describes the sequence of events that occurs in the flexor reflex?

Activation of afferent fibers → activation of alpha motor neurons → stimulation of flexor muscles → withdrawal of the limb (B) Signup and view all the answers

Which statement accurately describes reciprocal innervation in the context of the stretch reflex?

Afferent fibers from the stretched muscle activate inhibitory interneurons, which inhibit the antagonist muscles. (D) Signup and view all the answers

How does the activation of gamma motor neurons affect the sensitivity of the stretch reflex?

It lowers the threshold of stretch receptors, making the muscle more responsive to stretch. (D) Signup and view all the answers

Coordination of limb flexion around multiple joints relies on which of the following mechanisms within the spinal cord?

Collateralisation of primary afferents and interneurons to distribute signals across multiple spinal segments. (B) Signup and view all the answers

The extensor plantar response involves what specific movements of the toes upon stimulation of the sole?

Dorsiflexion of the big toe and splaying out of the other toes. (B) Signup and view all the answers

In a crossed extensor reflex, what action occurs in the contralateral limb when the flexor reflex is activated in a weight-bearing limb?

Extension, to support the body's weight. (B) Signup and view all the answers

Why is it safe to insert needles into the lower spinal canal for procedures like lumbar punctures?

The spinal cord terminates at a higher level, leaving only spinal nerves in the lower spinal canal. (D) Signup and view all the answers

Which of the following is a key characteristic of spondylosis that leads to spinal nerve compression?

Degenerative changes in the spinal joints, leading to nerve compression. (A) Signup and view all the answers

A patient presents with neck pain radiating down the arm and hand, accompanied by paraesthesia and muscle weakness. Loss of tendon reflexes is also noted. Which condition is most likely indicated by these symptoms?

Cervical spinal nerve compression. (C) Signup and view all the answers

Which spinal cord segments are primarily tested when assessing the quadriceps reflex (knee jerk)?

L3 and L4 (B) Signup and view all the answers

What is the primary cause of sensory ataxia in tabes dorsalis, and how is it clinically assessed?

Damage to lumbosacral dorsal spinal roots and dorsal columns, leading to unsteady gait exacerbated when eyes are closed (Romberg's sign). (B) Signup and view all the answers

Spinal Cord Segmentation

The spinal cord's organization from head (rostral) to tail (caudal), divided into cervical, thoracic, lumbar, sacral, and coccygeal segments.

Cervical & Lumbar Enlargements

Enlargements of the spinal cord at cervical (C4-T1) and lumbar (L1-S3) regions to innervate the upper and lower limbs, respectively.

Conus Medullaris

The conically shaped termination of the spinal cord, usually around the L1-L2 vertebral level.

Filum Terminale

A strand of connective tissue that extends from the conus medullaris to the first coccygeal vertebra.