CNS Spinal Cord

Question 1

Components of Spinal cord

Answer 1

*Runs from medulla oblongata to L1 or L2
*Functions
- Connects PNS inferior to head with brain
*White matter
- Sensory/motor pathways up to and from brain
*Gray matter
- Reflex center

Question 2

What are the Meningeal Layers of Spinal Cord?

Answer 2

*Dura mater
*Arachnoid mater
*Pia mater

Question 3

What are the spaces of the Meningeal Layers?

Answer 3

Epidural space
* Fat filled space around dura mater
* Location for epidural anesthesia (birth)
Subarachnoid space
* Contains CSF

Question 4

What are Spinal Cord Enlargements?

Answer 4

Bulges of the spinal cord indicate regions where a larger number of neurons are entering/leaving the spinal cord
* Cervical enlargement (upper limbs)
* Lumbar enlargement (lower limbs)

Question 5

Anatomy of the Spinal Cord: White Matter

Answer 5

White matter
* Myelinated (and some unmyelinated axons) create columns
- Transport sensory info to brain
- Transport motor info away from brain

Question 6

Classifications of white mater - direction

Answer 6

White matter is classified based on the direction they carry the nerve impulse
* Ascending tracts
- Exclusively sensory neuron axons
* Descending tracts
- Exclusively motor neuron axons
* Commissural tracts
- Interneurons that carry information from one side of spinal cord to the other side

Question 7

What are the divisions of White matter?

Answer 7

White matter
* Divided into 3 major columns on each side of spinal cord called funiculi (“long ropes”)
- Dorsal funiculus
- Lateral funiculus
- Ventral funiculus

Question 8

Gray matter of spinal cord

Answer 8

*Gray matter: neuronal cell bodies,
dendrites, glia, nonmyelinated axons
*Types
- Ventral horns
- Lateral horns
- Dorsal horns

Question 9

What are Ventral horns?

Answer 9

• Neurons associated with motor
  functions leave spinal cord here

Question 10

What are Lateral horns?

Answer 10

Lateral horns
* Visceral motor neurons (ANS)
* Only found in thoracic and upper lumbar regions of spinal cord

Question 11

What are Dorsal horns?

Answer 11

Dorsal horns
* Sensory neurons enter spinal cord here

Question 12

Organization of Gray Matter in Spinal Cord

Answer 12

Four classes of neurons in PNS travel to/from specific regions of
spinal cord
*Somatic sensory and visceral sensory
*Somatic motor
*Visceral motor

Question 13

Somatic sensory and visceral sensory neurons

Answer 13

Somatic sensory and visceral sensory
* Sensory cell bodies are located in dorsal root ganglia
* Dorsal root to dorsal horns

Question 14

What are Somatic motor neurons?

Answer 14

Somatic motor
* Cell bodies are in ventral horns
* Axons exit via ventral root

Question 15

what are Visceral motor neurons?

Answer 15

Visceral motor
* Cell bodies from lateral horns exit through ventral root

Question 16

Types of Spinal Roots?

Answer 16

*Dorsal roots transport sensory into spinal cord
*Ventral roots transport motor away from spinal cord
*Spinal nerves are made of both ventral and dorsal roots (= mixed)

Question 17

What are examples of Ascending Pathways?

Answer 17

Example of a sensory pathway:
1. Sensory receptors are activated
2. Sensory neurons synapse with interneurons within the dorsal horn of spinal cord gray matter
3. Interneurons transport signal via ascending tracts to thalamus
4. Ascending tracts to somatosensory cortex

Question 18

What are Descending Pathways?

Answer 18

Example of motor pathway:
1. Primary motor cortex initiates a response
2. Interneurons transport signal to appropriate region of spinal cord
3. Interneurons synapse within ventral horns with motor neuron
4. Motor neuron transports signal to cells of action (ex. Skeletal muscle fibers)

Question 19

What is the Reflex Arc?

Answer 19

*An automatic and rapid motor response
*Doesn’t require input from brain

Question 20

Types of Reflex Arcs?

Answer 20

*Monosynaptic reflex
*Polysynaptic reflex

Question 21

What are Monosynaptic reflex?

Answer 21

Monosynaptic reflex
* Axon terminals of sensory neurons directly synapse on motor neuron within spinal cord
* Number of neurons involved = 2
* Number of synapses involved = 1

Question 22

What are Polysynaptic reflex?

Answer 22

Polysynaptic reflex
* Axon terminals of sensory neurons connected via one or more interneurons to a motor neuron
* Number of neurons involved = 3+ (or
more)
* Number of synapses involved = 2+ (or
more)