Nervous System Flashcards
What is the CNS encased in?
The CNS (brain and spinal cord) is encased in connective tissue layers, the meninges, but CNS tissue contains very little collagen, making it soft and easily damaged by injuries.
What does white matter contain?
White matter includes myelinated axons, often grouped together as tracts, and the myelin-producing oligodendrocytes.
What does gray matter contain?
Gray matter contains abundant neuronal cell bodies, dendrites, astrocytes, and microglial cells, and is where most synapses occur.
The major structures of the CNS
The major structures
comprising the CNS are the cerebrum, cerebellum, spinal cord, and brain stem
Nerve cell bodies of the CNS
Nucleus (mostly brain)
Nerve cell bodies of the PNS
Ganglion
Nerve cell fibers of the CNS
Tract (mostly spinal cord)
Nerve cell fibers of the PNS
Nerve
The major structures of the PNS
Cranial nerves, spinal nerves, and ganglia
Cauda Equina
The long bundle of nerves that extend to form lumbar, coccygeal, and sacral spinal nerves.
Clinically important because of lumbar punctures (spinal tap) used to access subarachnoid space
The two anterior projections (horns) of gray matter in the spinal cord
Contain cell bodies of motor neurons whose axons make up the ventral roots of spinal nerves.
The two posterior projections (horns) of gray matter in the spinal cord
Contain interneurons which receive sensory fibers from neurons in the spinal
(dorsal root) ganglia.
What does the central canal develop from?
Near the middle of the cord the gray matter surrounds a
small central canal, which develops from the lumen of
the neural tube, is continuous with the ventricles of the brain, is lined by ependymal cells, and contains CSF
The dorsal root of spinal
cord contains what fibers?
The dorsal root of spinal
cord has only sensory
fibers.
The ventral root of spinal
cord contains what fibers?
The ventral root has only
motor fibers.
What do the fibers of the dorsal and ventral roots become?
The fibers of the dorsal and ventral roots mix together, and then divide distally into the posterior (dorsal) ramus and anterior (ventral) ramus. Each ramus has a mixture of sensory and motor fibers.
Meningeal layers
Dura mater (most external), Arachnoid, Pia mater (most internal)
What is in the subarachnoid space?
CSF
Extradural or Epidural Hermatoma
Blood from torn branches of a middle meningeal
artery collects between the external periosteal layer of the dura and the skull bones, usually after a blow to the head.
Dural border or Subdural Hematoma
Classically is called a subdural hematoma; however, this term is a misnomer because there is no naturally occurring space at the dura-arachnoid junction. The “space” is called a potential space. The blood creates a
space at the dura-arachnoid junction.
Subarachnoid hemorrhage
An extravasation (escape) of blood, usually arterial, into the subarachnoid space, where CSF is found.
Blood-brain Barrier (BBB)
Allows very tight control of the passage of substances from blood into the CSF of the CNS. It is extremely important clinically because it blocks or slows down the transport of many types of
drugs, such as those that might be used to treat Alzheimer’s, Parkinson’s
Disease and brain cancer, into the brain.
Choroid Plexus
Removes water from blood and releases it as the CSF (cerebrospinal fluid); in this sense, it “produces” CSF.
Choroid Plexus location and composition
The choroid plexus consists of folds of highly vascular tissue, projecting into the large ventricles of the brain. Ependyma and vascularized pia mater
It is found in the roofs of the third and fourth ventricles and in
parts of the two lateral ventricular walls.