CNS Spinal Cord Flashcards
(22 cards)
Components of Spinal cord
*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
What are the Meningeal Layers of Spinal Cord?
*Dura mater
*Arachnoid mater
*Pia mater
What are the spaces of the Meningeal Layers?
Epidural space
* Fat filled space around dura mater
* Location for epidural anesthesia (birth)
Subarachnoid space
* Contains CSF
What are Spinal Cord Enlargements?
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)
Anatomy of the Spinal Cord: White Matter
White matter
* Myelinated (and some unmyelinated axons) create columns
- Transport sensory info to brain
- Transport motor info away from brain
Classifications of white mater - direction
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
What are the divisions of White matter?
White matter
* Divided into 3 major columns on each side of spinal cord called funiculi (“long ropes”)
- Dorsal funiculus
- Lateral funiculus
- Ventral funiculus
Gray matter of spinal cord
*Gray matter: neuronal cell bodies,
dendrites, glia, nonmyelinated axons
*Types
- Ventral horns
- Lateral horns
- Dorsal horns
What are Ventral horns?
- Neurons associated with motor
functions leave spinal cord here
What are Lateral horns?
Lateral horns
* Visceral motor neurons (ANS)
* Only found in thoracic and upper lumbar regions of spinal cord
What are Dorsal horns?
Dorsal horns
* Sensory neurons enter spinal cord here
Organization of Gray Matter in Spinal Cord
Four classes of neurons in PNS travel to/from specific regions of
spinal cord
*Somatic sensory and visceral sensory
*Somatic motor
*Visceral motor
Somatic sensory and visceral sensory neurons
Somatic sensory and visceral sensory
* Sensory cell bodies are located in dorsal root ganglia
* Dorsal root to dorsal horns
What are Somatic motor neurons?
Somatic motor
* Cell bodies are in ventral horns
* Axons exit via ventral root
what are Visceral motor neurons?
Visceral motor
* Cell bodies from lateral horns exit through ventral root
Types of Spinal Roots?
*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)
What are examples of Ascending Pathways?
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
What are Descending Pathways?
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)
What is the Reflex Arc?
*An automatic and rapid motor response
*Doesn’t require input from brain
Types of Reflex Arcs?
*Monosynaptic reflex
*Polysynaptic reflex
What are Monosynaptic reflex?
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
What are Polysynaptic reflex?
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)
