Quiz 2 - The Nervous System Flashcards
Peripheral nervous system
all of the nervous tissue located outside of the CNS – primarily nerves that function as communication links between the body and CNS
2 types of peripheral nerves
cranial nerves and spinal nerves
Ganglia
collections of neuronal cell bodies that exist outside of the CNS.
In the fully developed spinal cord what two distinct areas are visible in the cross-sectional view?
The gray matter and the white matter
Gray matter of spinal cord
The gray matter resembles the shape of a butterfly and primarily contains neuronal cell bodies. The “wings” of the butterfly are called ventral (anterior) and dorsal (posterior) horns. Some regions of the spinal cord (thoracic, sacral) also have a lateral horn of gray matter that contains neurons associated with the autonomic (visceral) nervous system.
Gray matter consists of neuronal cell bodies
White matter
surrounds the gray matter and primarily contains axons that are organized into tracts.
Where is the spinal cord contained?
within the vertebral canal, a channel through the vertebral column.
Spinal cord enlargements
Swellings that reflect the large number of neurons (cell bodies) in that area (more gray matter)
There’s the cervical enlargement and the lumbar enlargement
Cervical enlargement
found in the C5-T1 regions of the spinal cord; neurons provide innervation to the upper extremity.
Lumbar enlargement
found in the L1-S3 regions of the spinal cord; neurons provide innervation to the lower extremity
The vertebral column consists of ___ vertebrae divided into 5 sections
33
5 subdivisions of the vertebral column
cervical (w/enlargement), thoracic, lumbar (w/enlargement), sacral, and coccygeal
Why are the sacral and coccygeal regions dubbed the “sacrum” and the “coccyx”?
Because the vertebrae in those regions are fused
How many vertebrae are in each section?
Cervical (7), thoracic (12), lumbar (5), sacral (5), coccygeal (4)
Vertebrae in which regions are separated by intervertebral discs?
Vertebrae in the cervical, thoracic and lumbar regions are separated by intervertebral discs
On the lateral aspect of the column there are ________.
Intervertebral foramina (holes)
What is the function of the intervertebral foramina?
they permit the passage of vessels and nerves into or out of the vertebral canal
Does the spinal cord extend the entire length of the vertebral canal? Why?
No, because of unequal growth rates of the vertebral column and spinal cord
To where does the vertebral column extend in adults and in infants?
In adults it extends from the foramen magnum of the skull to the upper lumbar region (L1- L2) of the vertebral column
In infants it may extend as far as L3
Conus medullaris
The terminal portion of the spinal cord (found at L1-L2 vertebral levels in adults)
Meninges
3 connective tissue layers that surround the spinal cord and the brain
What is the thick, outermost layer of the meninges?
The dura mater
What is the middle layer of the meninges, which resembles a spider web?
The arachnoid mater
It is closely associated with the dura mater and lines the dural sac (note – it is not attached to the dura!)
What is the innermost layer of the meninges? (The one closest to the spinal cord)
The pia mater
Epidural (extradural) space
- The area between the dura mater and the vertebral canal.
- Filled with fat and contains the internal vertebral venous plexus.
- Begins at the foramen magnum and ends inferiorly at the sacral hiatus. -Local anesthesia is often injected into the epidural space (epidural block) to anesthetize the nerve roots (e.g. for childbirth).
The dura matter around the spinal cord forms a tube known as the ___.
Dural (thecal) sac (ends at S1-S2)
- Begins at the foramen magnum where it is continuous with the dura mater around the brain.
- Extends approximately to the S2 vertebral level (varies between S1-S3), where it is continuous with the outer part of the external filum terminale (coccygeal ligament) that is anchored to the coccyx.
- Has sleeve-like projections that surround the spinal nerve roots as they exit the vertebral canal.
The subdural space
- Exists between the dura and arachnoid mater
- Is a potential space (i.e. it does not normally contain anything, but could expand if something such as blood leaked into it)
Subarachnoid space
- located between the arachnoid mater and pia mater
- contains cerebrospinal fluid (CSF)
- extends inferiorly as far as the dural sac (S2); therefore, fluid may be sampled from the subarachnoid space without fear of puncturing the spinal cord (access via lumbar puncture)
- is continuous with the subarachnoid space of the brain.
Can the pia mater be separated from the spinal cord?
No
At the conus medullaris, what happens to a thin strand of the pia mater?
At the conus medullaris, a thin strand of pia mater continues inferiorly as the internal filum terminale, which becomes invested by dura mater at the inferior limit of the dural sac (the pia + dura is called the external filum terminale)