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Questions and Answers
What is the primary function of projection interneurons?
What is the primary function of projection interneurons?
Where does the spinal cord end in the vertebral column?
Where does the spinal cord end in the vertebral column?
What structure stabilizes the spinal cord by anchoring it to the coccyx?
What structure stabilizes the spinal cord by anchoring it to the coccyx?
What is characterized by the spinal nerves that leave the cervical enlargement?
What is characterized by the spinal nerves that leave the cervical enlargement?
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What is a key characteristic of the lumbosacral enlargement compared to other segments of the spinal cord?
What is a key characteristic of the lumbosacral enlargement compared to other segments of the spinal cord?
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What type of neuron is classified as the first order neuron in proprioception?
What type of neuron is classified as the first order neuron in proprioception?
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In the proprioceptive circuit, where do the first order neurons connect?
In the proprioceptive circuit, where do the first order neurons connect?
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Which structure does the second order neuron in the proprioception pathway originate from?
Which structure does the second order neuron in the proprioception pathway originate from?
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What happens to 90% of motor neuron axons at the junction of the medulla and spinal cord?
What happens to 90% of motor neuron axons at the junction of the medulla and spinal cord?
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What does the lateral corticospinal tract primarily innervate?
What does the lateral corticospinal tract primarily innervate?
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Which order neuron connects to the ipsilateral cerebellum?
Which order neuron connects to the ipsilateral cerebellum?
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What is the primary function of Golgi tendon organs?
What is the primary function of Golgi tendon organs?
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Where do lower motor neurons reside in the spinal cord?
Where do lower motor neurons reside in the spinal cord?
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What type of neuron is the first order neuron in the dorsal column medial lemniscus pathway?
What type of neuron is the first order neuron in the dorsal column medial lemniscus pathway?
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Where do the axons from first order neurons in the dorsal column terminate?
Where do the axons from first order neurons in the dorsal column terminate?
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Which pathway conveys non-conscious proprioception?
Which pathway conveys non-conscious proprioception?
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Which nuclei do second order neurons in the dorsal column medial lemniscus pathway project from?
Which nuclei do second order neurons in the dorsal column medial lemniscus pathway project from?
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What is the final destination of axons projected from third order neurons in the dorsal column medial lemniscus pathway?
What is the final destination of axons projected from third order neurons in the dorsal column medial lemniscus pathway?
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What is the primary purpose of a lumbar puncture?
What is the primary purpose of a lumbar puncture?
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At which vertebral levels is a lumbar puncture ideally performed?
At which vertebral levels is a lumbar puncture ideally performed?
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Which statement best describes the ratio of white to grey matter in the lumbar region of the spinal cord?
Which statement best describes the ratio of white to grey matter in the lumbar region of the spinal cord?
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What function does the spinothalamic tract primarily serve?
What function does the spinothalamic tract primarily serve?
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Which statement is correct about the first order neuron in the spinothalamic tract?
Which statement is correct about the first order neuron in the spinothalamic tract?
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What type of neurons are found in the dorsal root ganglia (DRG)?
What type of neurons are found in the dorsal root ganglia (DRG)?
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How many pairs of spinal nerves do humans have?
How many pairs of spinal nerves do humans have?
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What is the function of the ventral root of a spinal nerve?
What is the function of the ventral root of a spinal nerve?
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Which section of the spine has the highest number of vertebrae?
Which section of the spine has the highest number of vertebrae?
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What is the function of the spinous process in vertebrae?
What is the function of the spinous process in vertebrae?
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What kind of structure is the arachnoid layer of the meninges described as?
What kind of structure is the arachnoid layer of the meninges described as?
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Which portions of the spine are fused vertebrae found?
Which portions of the spine are fused vertebrae found?
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Which vertebrae are located in the neck region?
Which vertebrae are located in the neck region?
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What is the primary function of the dorsal root?
What is the primary function of the dorsal root?
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Which part of the spinal nerve supplies motor innervation to the back?
Which part of the spinal nerve supplies motor innervation to the back?
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Where are preganglionic sympathetic neurons located in the spinal cord?
Where are preganglionic sympathetic neurons located in the spinal cord?
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What type of axons does the ventral root primarily contain?
What type of axons does the ventral root primarily contain?
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What does the subarachnoid space contain?
What does the subarachnoid space contain?
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Which part of the spinal cord is most pronounced in the thoracic region?
Which part of the spinal cord is most pronounced in the thoracic region?
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Which of the following is NOT a function of the spinal nerve?
Which of the following is NOT a function of the spinal nerve?
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Which of the following correctly describes white matter in the spinal cord?
Which of the following correctly describes white matter in the spinal cord?
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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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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.
