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Questions and Answers
What is the conus medullaris?
What is the conus medullaris?
Which structure follows the conus medullaris?
Which structure follows the conus medullaris?
Which of the following accurately describes the positioning of the spinal cord in adults?
Which of the following accurately describes the positioning of the spinal cord in adults?
What is the primary function of the spinal nerves?
What is the primary function of the spinal nerves?
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Which layer of the meninges is the innermost layer surrounding the spinal cord?
Which layer of the meninges is the innermost layer surrounding the spinal cord?
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What is the primary function of afferents in relation to motor neurons?
What is the primary function of afferents in relation to motor neurons?
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What occurs when there is a lesion within the upper motor neuron?
What occurs when there is a lesion within the upper motor neuron?
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Which of the following best describes Central Pattern Generators (CPGs)?
Which of the following best describes Central Pattern Generators (CPGs)?
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What is the role of the spinal cord in autonomic regulation?
What is the role of the spinal cord in autonomic regulation?
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What is a key distinction between upper and lower motor neurons?
What is a key distinction between upper and lower motor neurons?
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Which type of neuron is responsible for carrying sensory information to the spinal cord?
Which type of neuron is responsible for carrying sensory information to the spinal cord?
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In the context of spinal reflexes, what is a key feature of a monosynaptic reflex arc?
In the context of spinal reflexes, what is a key feature of a monosynaptic reflex arc?
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Which reflex is characterized by the withdrawal of a limb in response to a noxious stimulus?
Which reflex is characterized by the withdrawal of a limb in response to a noxious stimulus?
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What occurs during reciprocal inhibition in a stretch reflex?
What occurs during reciprocal inhibition in a stretch reflex?
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Which type of neuron is classified as a lower motor neuron?
Which type of neuron is classified as a lower motor neuron?
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What type of reflex occurs when a stimulus activates pain fibers and results in opposite limb extension?
What type of reflex occurs when a stimulus activates pain fibers and results in opposite limb extension?
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How many pairs of cervical spinal nerves are there?
How many pairs of cervical spinal nerves are there?
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Which part of the spinal reflex arc is primarily responsible for processing sensory input?
Which part of the spinal reflex arc is primarily responsible for processing sensory input?
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What is the primary function of gamma motor neurons?
What is the primary function of gamma motor neurons?
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What is a dermatome?
What is a dermatome?
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Where do lumbar and sacral nerves exit the spinal column?
Where do lumbar and sacral nerves exit the spinal column?
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Which structure in the spinal cord is responsible for motor neuron activity?
Which structure in the spinal cord is responsible for motor neuron activity?
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What characterizes myotomes?
What characterizes myotomes?
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What type of neurons are found in the posterior horn of the spinal cord?
What type of neurons are found in the posterior horn of the spinal cord?
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What is the primary function of the central canal of the spinal cord?
What is the primary function of the central canal of the spinal cord?
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Which of the following best describes the composition of white matter in the spinal cord?
Which of the following best describes the composition of white matter in the spinal cord?
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Study Notes
Spinal Cord Structure and Function
- The spinal cord extends from the medulla to L1/L2.
- It is located within the vertebral canal of the vertebral column.
- In adults, the spinal cord only occupies the upper two-thirds of the vertebral column.
- It is protected by the vertebral column, meninges and cerebrospinal fluid.
Intended Learning Outcomes
- Describe the gross anatomy and internal structure of the spinal cord.
- Identify the locations of the ascending and descending tracts within the spinal cord.
- Differentiate between upper and lower motor neurons.
- Describe the mechanism of spinal reflexes and their significance.
Gross Anatomy
- The spinal cord has two swollen regions: cervical and lumbar.
- The spinal cord ends between L1 and L2.
- The spinal cord is considerably shorter than the vertebral column.
Gross Anatomy - Details
- Conus Medullaris: Tapered end of the spinal cord (L1/L2).
- Filum Terminale: Delicate strand of fibrous tissue extending downwards from the conus medullaris.
- Cauda Equina: Lumbosacral nerve roots surrounding the filum terminale, resembling a horse's tail.
Meninges of the Spinal Cord
- Dura Mater: Outermost meninx.
- Arachnoid: Middle meninx.
- Pia Mater: Innermost meninx.
Clinical Connection - Spinal Tap
- A spinal tap (lumbar puncture) involves inserting a needle into the subarachnoid space to withdraw cerebrospinal fluid (CSF).
- This procedure is used for diagnostics, introducing medications and measuring CSF pressure.
- Access to the subarachnoid space during a spinal tap is facilitated by the space between vertebrae L3 and L4 or L4 and L5. Flexion of the spine further increases this space.
Spinal Nerves
- Spinal nerves connect the spinal cord to the rest of the body.
- They are composed of two bundles of axons (roots): posterior roots and anterior roots.
- Spinal nerves exit through intervertebral foramina.
- Spinal nerves from different levels combine to form peripheral nerves.
Spinal Segmentation
- There are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
- Cervical nerves exit above their corresponding vertebral body (C8 is an exception).
- All other spinal nerves exit through the intervertebral foramen below their corresponding vertebra.
- Lumbar and sacral nerves extend some distance before exiting their intervertebral foramina.
Dermatome
- A dermatome is an area of skin innervated by a single spinal nerve root.
Myotome
- A myotome is a group of muscles innervated by a single spinal nerve root.
- Used to assess muscle activity, particularly in cases of suspected nervous system damage.
- These contractions are performed isometrically, in mid-range.
Internal Structure of the Spinal Cord
- The spinal cord contains gray and white matter.
- Gray matter houses cell bodies of neurons and interneurons.
- White matter consists of myelinated axons.
White Matter Tracts
- Anterior Column
- Lateral Column
- Posterior Column
Descending Tracts
- Lateral corticospinal
- Rubrospinal
- Reticulospinal
- Vestibulospinal
- Anterior corticospinal
- Tectespinal
Ascending Tracts
- Posterior spinocerebellar
- Lateral spinothalamic
- Anterior spinocerebellar
- Spinotectal
- Anterior spinothalamic
- Fasciculus cuneatus
- Fasciculus gracilis
Types of Neurons in the Spinal Cord
- Sensory neurons
- Upper motor neurons
- Alpha (skeletomotor) neurons
- Gamma (fusimotor) neurons
- Interneurons
Motor Neuron
- Upper motor neuron: Entirely within the central nervous system (CNS).
- Lower motor neuron: Cell body in the CNS sending axons to innervate muscles.
Spinal Reflex
- A reflex is a fast, involuntary action in response to a stimulus.
- A reflex arc is the pathway of neural impulses involved in a reflex.
Classification of Reflexes
- Monosynaptic/polysynaptic
- Ipsilateral/contralateral
- Intra-segmental/inter-segmental
Spinal Reflexes - Examples
- Stretch reflex
- Flexor withdrawal reflex
- Crossed extension reflex
- Plantar reflex/Babinski sign
What does the spinal cord do?
- Motor control
- Sensory information transmission
- Autonomic regulation
- Central pattern generators (coordinating rhythmic movements like stepping).
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Description
Test your knowledge on the spinal cord's anatomy and physiology. This quiz covers the gross anatomy, internal structures, and functions of the spinal cord, including its protective mechanisms and neural pathways. Learn to identify key features and understand spinal reflexes through targeted questions.
