Module 2.2, 2.3: The Spinal Cord and Cranial Nerves Flashcards
Describe the spinal cord and its extension.
The spinal cord extends from the brain stem to the first lumbar vertebra where it officially terminates as the conus medullaris. The extension of the cord beyond L1 is a collection of nerve roots called the cauda equina which runs to its end at the coccyx.
What is the function of the spinal cord? How many pairs of spinal nerves?
The spinal cord (and its extension) is how all impulses travel between the brain and the rest of the body by 31 pairs of spinal nerves.
List the 3 protections for the spinal cord.
Like the brain, the spinal cord is protected by the bony vertebral column, meninges and cerebrospinal fluid.
Describe the 3 spinal cord meninges and their associated tissues and fluids.
The spinal dura mater is a single layer sheath, the arachnoid mater is loose connective tissue, and the pia mater is a microscopic layer covering the spinal cord and continues as the filum terminale which anchors the spinal cord from the conus medullaris to the coccyx. The epidural space of adipose tissue is between the vertebral column and the dura mater, and the CSF is between the arachnoid and pia mater.
Why is a spinal tap performed in the subarachnoid space inferior to L1?
Because the cord ends at L1, the subarachnoid space inferior to this point is the location chosen to perform a spinal tap because there is less risk of damage to the spinal cord.
What are the 2 grooves of the spinal cord?
The anterior median fissure (deep) and the posterior median sulcus.
Describe the composition of the gray matter of the spinal cord.
The gray matter of the cord is composed of multipolar neurons and supporting cells.
Describe the composition of the white matter of the spinal cord.
The white matter of the cord is composed of myelinated and un-myelinated nerve fibers (axons).
Describe the function of the white matter of the spinal cord.
The white matter fibers of the spinal cord are composed of ascending tracts that proceed up to the brain carrying sensory inputs and descending tracts that proceed down to (or within) the cord carrying motor outputs.
Describe the central canal.
An opening that runs the length of the spinal cord and is filled with CSF.
What are the different horns of gray matter?
2 smaller ventral horns, 2 dorsal horns, and 2 lateral horns.
What is the gray commissure?
A cross-bar that connects the anterior horns.
What are the ventral horns?
Contain somatic motor neurons whose axons serve as efferent pathways to skeletal muscles by way of the ventral roots of the spinal cord.
What are the dorsal horns?
Serve as one of the afferent pathways from receptors by way of the dorsal roots of the spinal cord.
CN 1 - list name, type and what it controls.
1st - Olfactory - Sensory - Sense of smell.
CN 2 - list name, type and what it controls.
2nd - Optic - Sensory - Sense of sight.
CN 3 - list name, type and what it controls.
3rd - Oculomotor - Motor (Somatic and visceral) - Eye movement, Visceral motor = pupil dilation.
CN 4 - list name, type and what it controls.
4th - Trochlear – Somatic motor - Eye movement.
CN 5 - list name, type and what it controls.
5th - Trigeminal - Motor and sensory - Chewing and sensation of face, nose, and mouth.
CN 6 - list name, type and what it controls.
6th - Abducens - Motor - Eye movement.
CN 7 - list name, type and what it controls.
7th - Facial – Somatic and Visceral Motor and sensory - Facial expressions and sensation of tongue.
CN 8 - list name, type and what it controls.
8th - Vestibulocochlear - Sensory - Hearing and balance.
CN 9 - list name, type and what it controls.
9th - Glossopharyngeal - Motor and sensory - Swallowing and taste.
CN 10 - list name, type and what it controls.
10th - Vagus - Motor and sensory - Digestion, regulation of heart rate.
CN 11 - list name, type and what it controls.
11th – Accessory - Motor - Rotation of the head and movement of upper shoulders.
CN 12 - list name, type and what it controls.
12th - Hypoglossal - Motor - Tongue movements.
What are the special senses?
Sight, smell, hearing, taste and balance.
What does visceral motor mean? What division of the nervous system contains visceral motor nerves?
The nerves in the autonomic system are called visceral motor when they control smooth muscles or involuntary functions.
How many pairs of cranial nerves do humans have and what do most of them (except for one) control?
Humans have twelve pairs of cranial nerves most of which control the head, neck, and face (except the vagus nerve).
What is a characteristic of sensory nerves?
Long dendrites.
What is a characteristic of motor nerves?
Long axons.
What is the optic chiasm?
Where the optic nerves cross before they synapse with the thalamus.
Lateral horns
Located primarily at the thoracic level of the spinal cord. The lateral horns contain autonomic sympathetic motor neurons whose axons serve as efferent pathways to visceral organs.
