Lecture 8 - Spinal Cord, Spinal Nerves, and Cranial Nerves Flashcards
How does the organization of grey and white matter differ in the brain and spinal cord?
Brain: grey matter on the outside
Spinal cord: white matter on the outside
What are the ventral and dorsal horns of the spinal cord?
Butterfly like structure that exists in the center of the spinal cord and contains grey matter
What is another name for the spinal cord dorsal horns?
Sensory horns
What is another name for the spinal cord ventral horns?
Motor horns
What is another name for sensory neurons?
Ascending neurons
What is another name for motor neurons?
Descending neurons
How to recognize ventral and dorsal horns?
Ventral horns are larger
Where is the ascending white matter located in the spinal cord?
Dorsal column
Where is the descending white matter located in the spinal cord?
Lateral and anterior columns
What are the 2 major enlargements of the spinal cord? Purpose?
- Cervical
- Lumbar
Control over limb and sensory functions resulting from the abundance of cell bodies in the cervical and lumbar vertebrae
What is the main function of the thoracic spinal cord? What does this mean for the composition of this part?
Posture
Less cell bodies
List the 4 parts of the spinal cord from top to bottom.
- Cervical
- Thoracic
- Lumbar
- Sacral
Describe the input and output of information in the spinal cord.
- Dorsal root has afferent sensory fibers with cell bodies in dorsal root ganglia (semiunipolar neurons)
- Ventral root has efferent motor fibers with cell bodies situated in the ventral horn
Describe the nature of spinal nerves.
Mixed: carry both sensory and motor information
How many pairs of spinal nerves?
31
List the 31 pairs of spinal nerves and their abbreviations. Note?
- Cervical nerves: C1-8
- Thoracic nerves: T1-12
- Lumbar nerves: L1-5
- Sacral nerves: S1-5
- Coccygeal nerve: Co
Note: numbered from top to bottom on spinal cord
Where do the C1-C7 nerves exit?
Superior to the namesake vertebra
How many cervical vertebra are there?
7
Where does the C8 nerve exit?
Inferior to C7 vertebrae
Where do spinal nerves inferior to C8 exit?
Inferior to namesake vertebra
What are the 2 ways of classifying the neurons of the spinal cord?
- Sensory or motor
2. Somatic or visceral
What are nerves?
Bundles of neurons
What types of neurons does the dorsal root of the spinal cord contain?
- Somatic sensory
2. Visceral sensory
What types of neurons does the ventral root of the spinal cord contain?
- Somatic motor
2. Visceral motor
What cell bodies are included in the dorsal horns of the spinal cord?
Cell bodies of interneurons
Where are the visceral neurons located compared to the somatic ones?
More central to the spinal cord canal
How does each spinal nerve attach to the spinal cord?
Via dorsal and ventral roots
Where do the dorsal roots of the spinal cord synapse? Onto what?
In the dorsal horn onto second order sensory neurons
Where do the ventral roots of the spinal cord synapse? Onto what?
Project into body to directly or indirectly control muscle
Where are the sympathetic chain ganglia located? How many of them?
Parallel to the spinal cord
2: one on each side
What is the role of the sympathetic chain ganglia? How?
Control autonomic functions by interacting with the spinal nerves or their anterior rami
What does histology of the human spinal cord show? What are these called?
Layers of neurons (Rexed lamina) in both the ventral and dorsal horns:
Dorsal: horizontal layers
Ventral: columns
Describe the connective tissue compartmentalization of the PNS nerves.
Endoneurium surrounds individual axon fibers
Perineurium surrounds fascicles = bundles of axon fibers
Epineurium surrounds nerves (which are composed of many fascicles) and the vasculature
What are spinal cord nerve rootlets?
Several of them form a dorsal or ventral root
What is a spinal nerve root?
Where the dorsal and ventral roots come together
What do the spinal nerve roots divide in?
Rami (branches)
What do the anterior rami supply?
Limbs and ventral portion of the body
What do the posterior rami supply?
Back muscles and skin covering them
What do the nerves become after the rami? 3 options
- Anterior rami => plexuses formed by the combination of rami from neighboring anterior rami
- Anterior rami of the thoracic nerves => intercostal nerves
- Posterior rami: directly innervate deep muscles and skin of the back
What are the 4 basic plexuses?
- Cervical
- Brachial
- Lumbar
- Sacral
Can nerves get to the body from all levels of plexuses?
YUP
Where is the cervical plexus located?
Neck
From what anterior rami is the cervical plexus formed?
Anterior rami of C1-C5
What 3 parts of the body does the cervical plexus innervate?
- Back of head
- Neck
- Diaphragm
Which specific nerves innervates the diaphragm? What 3 cervical nerves does it come from?
2 phrenic nerves (right and left)
Come from C3, C4, C5
What happens if you severe one of the 2 phrenic nerves?
Partial diaphragmatic paralysis