Week 8 - The Anatomy of the Brainstem & Spinal Cord Flashcards
What is the termination level of the spinal cord in adults?
Approximately the level of the disc between vertebrae L1 and L2
Common variations exist where the spinal cord has terminated as high as vertebra TXII and as low as between LII and LIII.
What is the conus medullaris?
The cone-shaped distal end of the spinal cord
It originates a bunch of nerve roots known as the cauda equina.
What is the cauda equina?
A bunch of nerve roots originating from L2-L5, S1-S5, and C1
It innervates the pelvis and lower limbs.
How many pairs of mixed spinal nerves are attached along the spinal cord?
31 pairs
These include 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves, and 1 coccygeal nerve.
What are the anterior and posterior roots of spinal nerves responsible for?
- Anterior roots are motor roots
- Posterior roots are sensory roots.
What is the significance of the cervical and lumbosacral enlargements?
They accommodate the many motor neurons required for the upper and lower limbs, respectively.
What are the denticulate ligaments?
Pial tissue sheets that anchor the spinal cord within the dural sac.
What are the main components of the spinal cord’s arterial supply?
- 1 anterior spinal artery
- 2 posterior spinal arteries
The anterior spinal artery originates from the vertebral artery.
What is the artery of Adamkiewicz?
The largest medullary artery that usually arises on the left side in the lower thoracic upper lumbar region (T9-L1).
How many anterior and posterior spinal veins are there typically?
3 anterior and 3 posterior spinal veins.
What is the shape of the spinal cord gray matter when transversely sectioned?
Shaped like a butterfly or an H.
What is the role of the substantia gelatinosa?
It modulates the activity of pain and temperature afferent fibers.
What are the three funiculi in each half of the spinal cord?
- Dorsal (posterior) funiculus
- Lateral funiculus
- Anterior (ventral) funiculus
What do laminae I-IV in the spinal cord gray matter primarily receive?
Exteroceptive inputs such as pain, temperature, and tactile touch.
What is the function of lamina VI in the spinal cord?
Involved in the integration of somatic motor processes
Present only in cervical and lumbar segments.
What type of neurons are found in lamina VIII and IX?
Alpha and gamma motor neurons.
True or False: The ventral horn of the gray matter reaches the ventral surface.
False.
What does the gray commissure connect?
The two sides of the gray matter.
What is the role of neurons in the medial aspect of the ventral horn?
They receive afferents from the vestibulospinal and reticulospinal systems and innervate axial musculature.
Fill in the blank: The gray matter of the spinal cord consists primarily of _______.
[neuronal cell bodies, dendrites, and myelinated and unmyelinated axons]
What is the somatotopic arrangement of neurons in the ventral horn of the spinal cord?
Neurons are located according to the muscles they innervate:
- Extensor muscles - ventral
- Flexor muscles - dorsal
- Axial and limb girdle muscles - medial
- Distal extremity muscles - lateral
This arrangement allows descending pathways to preferentially influence distal musculature activity.
Where are the motor phrenic neurons located in the spinal cord?
Lamina IX of the cervical spinal cord (C3-C5)
These neurons provide innervation to the diaphragm.
What type of neurons are located in lamina IX of the thoracic segments?
Thoracic respiratory motor neurons
They innervate the intercostal, rib cage, and other back muscles.
What is the function of lamina X in the spinal cord?
It surrounds the central canal and is a site for the convergence of somatic and visceral afferents
About 10%-15% of preganglionic sympathetic neurons are located in laminae VII and X.