Gray Matter

Question 1

Gray Matter - Composition and Division

Answer 1

Central canal
Somas (cell bodies) surrounding the central canal and unmyelinated axons.
Division:
- Posterior (dorsal) gray horn
- Anterior (ventral) gray horn
- Lateral gray horn
- Posterior and anterior gray commissure
Somas organized into groups called nuclei:
- Sensory nuclei
- Motor nuclei

Question 2

Which type of nuclei is present at each of the horns and commissure?

Answer 2

Dorsal horn: somatic sensory nuclei, visceral sensory nuclei.
Ventral horn: somatic motor nuclei
Lateral horn: in thoracic and lumbar segments: visceral motor nuclei.
Posterior and anterior commissure: axons crossing laterally from one side to the other.

Question 3

Somatic - Function

Answer 3

Supplies and receives fibers (neurons) to and from the skin, skeletal muscles, joints and tendons.

Question 4

Visceral - Function and Division

Answer 4

Supplies and receives fibers (neurons) to and from smooth muscles, cardiac muscles and glands (autonomic nervous system).
Parasympathetic division: important for control of normal body functions (normal operation of digestive system).
Sympathetic division: fight or flight; important in helping us cope with stress.

Question 5

Lamina Classification Based on Cytostructure of Neurons

Answer 5

First 4 lamina: Exteroceptive sensation in dorsal horn.
Lamina 5 and 6: Proprioceptive sensations.
Lamina 7: Acts as a relay between muscle spindle and cerebellum.
Lamina 8-10: alpha and gamma motor neurons in ventral horn.

Question 6

Rexed Lamina 1 - Classification

Answer 6

Tip of posterior horn.
Respond to noxious and thermal stimuli.
Sends info to brain by contralateral spinothalamic tract. Nucleus gracilis and cuneatus.

Question 7

Rexed Lamina 2 - Classification (function, correspondence)

Answer 7

Involved in sensation of noxious and non-noxious stimuli. Help interpretate incoming signals as painful or not. Pain due to tissue injury or not.
Sends info to lamina III and IV.
Corresponds to substantia gelatinosa.

Question 8

Rexed Lamina 3 - Classification

Answer 8

Involved in proprioception and light touch.
Partially corresponds to nucleus proprius.

Question 9

Rexed Lamina 4 - Classification (correspondence, tracts)

Answer 9

Involved in non-noxious sensory information relay and processing.
Connect to lamina II and detect light touch.
Partially corresponds to nucleus proprius.
Projects to thalamus via contralateral and ipsilateral spinothalamic tract.

Question 10

Rexed Lamina 5 - Classification (tracts to and from brain)

Answer 10

Relays sensory info to brain via contralateral and spinothalamic tracts.
Receives descending info from brain via corticospinal and rubrospinal tracts.
Receive nociceptive info from visceral organs. Referred pain.

Question 11

Rexed Lamina 6 - Classification (neurons, function, tracts)

Answer 11

Many cells are interneurons participating in spinal reflexes.
Receives sensory info from muscle spindles (proprioception).
Sends info to brain via ipsilateral spinocerebellar pathways.

Question 12

Rexed Lamina 7 - Classification

Answer 12

Zona intermedia.
Receives info from lamina 2 and 6 and visceral afferent fibers.
Relays motor info to the viscera.

Question 13

Rexed Lamina 8 - Classification (location, tracts and function)

Answer 13

Base of ventral horn.
Descending vestibulospinal and reticulospinal fibers terminate.
Cells involved in modulating motor output to skeletal muscles.

Question 14

Rexed Lamina 9 - Classification

Answer 14

Two types of cells:
Alpha MN: giving rise to ventral root fibers to supply skeletal muscle fibers.
Gamma MN: giving rise to intrafusal muscle fibers.

Question 15

Rexed Lamina 10 - Classification

Answer 15

Involved in communication between spinal levels.
Axons cross over from one side of the spinal cord to the other.

Question 16

Spinal Cord Nuclei Classification - Marginal Zone (MZ)

Answer 16

Located at tip of dorsal horn.
Relay pain and temperature sensation to the brain.

Question 17

Spinal Cord Nuclei Classification - Substantia Gelatinosa (SG)

Answer 17

Located at the top of the dorsal horn.
Relay pain, temperature and light touch sensation to brain.

Question 18

Spinal Cord Nuclei Classification - Nucleus Proprius (NP)

Answer 18

Located in neck of dorsal horn.
Relays mechanical and temperature sensation to the brain.

Question 19

Spinal Cord Nuclei Classification - Dorsal Nucleus of Clark (DNC) (location, function and spinal segments)

Answer 19

Most dorsomedial nuclei.
Relays unconscious proprioceptive info to the brain.
Only found in spinal segments C8-L3.

Question 20

Spinal Cord Nuclei Classification - Interomediolateral Nucleus (IMN) (location, function to and from brain)

Answer 20

Located in the intermediate column and lateral horn.
Relays sensory info from viscera to brain, and autonomic signals from brain to visceral organs.

Question 21

Spinal Cord Nuclei Classification - Lateral MN and Medial MN (location, innervation)

Answer 21

Alpha and Gamma MNs.
Located in ventral horn.
Composed of motor neurons that innervate visceral and skeletal muscles.