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.
Node of Ranvier (or nodal gap)
The gap between two
Schwann cells.
These regions are uninsulated and but rich in ion channels, allowing them
to regenerate the action
potential.
Endoneurium
Surround axons and Schwan cells
Perineurium
Surrounds fascicles or bundles of nerve fibers
Epineurium
Surrounds multiple fascicles of nerve fibers.
Ascending Tracts (Afferent/Sensory)
Conscious tracts – The dorsal column-medial lemniscal pathway and the anterolateral system,
for touch and some types of proprioception.
Unconscious tracts – The spinocerebellar tracts, for muscle proprioception.
Dorsal column–medial lemniscus pathway (DCML)
Conveys sensations of fine touch, vibration, two-point discrimination, and proprioception (position) from the skin and joints.
Spinothalamic tract (part of the anterolateral system)
The spinothalamic tract consists of two pathways: anterior and lateral. The anterior spinothalamic tract
carries information about crude touch. The lateral spinothalamic tract conveys pain and temperature.
Spinocerebellar tracts
Carry unconscious proprioceptive information from the muscles to the
cerebellum. We cannot mentally acknowledge these signals, but they help the brain coordinate and refine motor actions.
Somatosensory Cortex of the brain
Postcentral Gyrus
Somatomotor Cortex of the brain
Precentral Gyrus
Descending Tracts (Efferent/Motor)
Pyramidal tracts and Extrapyramidal tracts
Pyramidal tracts
Originate in the cerebral cortex, carrying motor fibers to the spinal cord
and brain stem. They are responsible for the voluntary control of the musculature of the
body and face.
Extrapyramidal tracts
Originate in the brain stem, carrying motor fibers to the spinal cord. They are responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and movement.
Autonomic Nervous System (ANS)
It is structurally a division of the peripheral nervous
system that supplies smooth muscle and glands,
and influences the function of internal organs.
It is functionally a system that acts unconsciously
to regulate “visceral” bodily functions.
Two divisions of ANS
Sympathetic and Parasympathetic
Parasympathetic Nervous System
A division of the ANS used for “rest-and-digest” or “feed-and-breed.”
Structure: The parasympathetic division has craniosacral “outflow,” meaning that the neurons begin at the cranial nerves (ie, the oculomotor nerve, facial nerve, glossopharyngeal nerve
and vagus nerve) and sacral (S2-S4) spinal cord.
Sympathetic Nervous System
A division of the ANS used for “fight-or-flight-or-freeze.”
Structure: The sympathetic division has thoracolumbar
“outflow,” emerging from the spinal cord in the thoracic and lumbar areas, terminating around L2-L3
Which of these general effects is associated with the sympathetic division of the ANS?
Quick response
The pia mater is closely applied to the entire surface of the CNS tissue. What is its function?
It forms a physical barrier separating CNS tissue from CSF in the subarachnoid space.
Which type of glial cells are associated with ganglia?
Satellite cells
The central canal of the spinal cord and the ventricles of the brain are formed from the embryonic ____________
Neural tube
The Nodes of Ranvier contribute to saltatory conduction. Which is true?
In saltatory conduction the action potential is faster than that in unmyelinated fibers.
Ganglia are clusters of neuron cell bodies in the PNS. In the CNS, clusters of neuron cell bodies are called
Cerebral nuclei
Where in the brain is the somatosensory cortex located?
Postcentral gyrus
Where is the choroid plexus found?
In the roofs of the 3rd and 4th brain ventricles
What are the components of the choroid plexus?
Ependyma and pia mater with blood vessels.
The choroid plexus consists of ependyma and vascularized pia mater. It functions as a type of barrier between
Blood and the CSF
What is the clinical advantage of knowing the location of the various dermatomes?
This knowledge can help diagnose which spinal nerves may be damaged.
Which meningeal layer lies between the CSF and the tissue of the CNS
Pia mater
The dura mater is
One of the meninges of the CNS
Around the spinal cord, the dura mater is separated from the periosteum of the vertebrae by the
Epidural space
The epineurium
Wraps the entire nerve in a layer of connective tissue
In a ___________________, blood from the middle meningeal artery accumulates between the skull bones and the dura mater.
Extradural hemorrhage
Where in the nervous system do most synapses occur?
Gray matter
What happens at the tissue level in Multiple Sclerosis?
White blood cells penetrate the blood-brain barrier and attach the myelin sheath.
Myelin is composed of
Lipids and proteins
In the PNS, bundles of myelinated axons are called
Nerves
Where do the cell bodies of the post synaptic neurons lie?
The cell bodies of the postsynaptic neurons of the sympathetic system lie in the sympathetic chains (paravertebral) and in prevertebral ganglia.
The arachnoid has two parts:
A layer of connective tissue adjacent to the dura mater, and a network of collagen and fibroblasts, connected to the pia mater.
The anterior horns of the spinal cord contain mainly cell bodies of ___________________
Motor neurons
Which of these characteristics is associated with the sympathetic division?
Thoracolumbar outflow
What is the caudal equina?
It is the collection of the spinal nerves searching the lumbar, coccygeal, and sacral regions.
Typically, a spinal nerve has
Both sensory and motor fibers
Which tract conveys information about pain and temperature?
Lateral Spinothalamic tract
Which of these tracts carry “unconscious” information about body position?
Spinocerebellar tract
Sensory nerve fibers are
Afferent
The autonomic nervous system regulates or manages
Homeostasis
A subarachnoid hemorrhage may result from a
Saccular aneurysm
What is filled with CSF and cushions and protects the CNS?
Subarachnoid space
What releases excess CSF into the blood?
Arachnoid villi
What protects neurons and glia from bacterial toxins, infectious agents, etc., and maintains the composition and balance of ions in the interstitial fluid?
Blood-Brain barrier
One of the functions of the sub-arachnoid space is to
Cushion the CNS from damage
In general, the descending pathways of the central nervous system are composed of what type of nerve fibers?
Motor
How many pairs of thoracic nerves are there in humans?
12
Ganglia are clusters of nerve cell bodies that are found…
Only in the peripheral nervous system
The blood-brain barrier is made up of three parts: a capillary endothelium in which the cells are tightly connected and allow almost no passage of substances, a basement membrane that envelopes the capillaries, and
A layer of perivascular astrocytic “feet”
In the CNS, bundles of myelinated axons are called
Tracts
The autonomic nervous system differs anatomically from somatic nerve pathways in that
The ANS has a two-neuron efferent pathway
White matter is white because of
The lipid content of the cell membrane sheaths
Reversed prompt
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 is the CNS encased in?
Reversed prompt
White matter includes myelinated axons, often grouped together as tracts, and the myelin-producing oligodendrocytes.
What does white matter contain?
Reversed prompt
Gray matter contains abundant neuronal cell bodies, dendrites, astrocytes, and microglial cells, and is where most synapses occur.
What does gray matter contain?
Reversed prompt
The major structures
comprising the CNS are the cerebrum, cerebellum, spinal cord, and brain stem
The major structures of the CNS
Reversed prompt
Nucleus (mostly brain)
Nerve cell bodies of the CNS
Reversed prompt
Ganglion
Nerve cell bodies of the PNS
Reversed prompt
Tract (mostly spinal cord)
Nerve cell fibers of the CNS
Reversed prompt
Nerve
Nerve cell fibers of the PNS
Reversed prompt
Cranial nerves, spinal nerves, and ganglia
The major structures of the PNS
Reversed prompt
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
Cauda Equina
Reversed prompt
Contain cell bodies of motor neurons whose axons make up the ventral roots of spinal nerves.
The two anterior projections (horns) of gray matter in the spinal cord
Reversed prompt
Contain interneurons which receive sensory fibers from neurons in the spinal
(dorsal root) ganglia.
The two posterior projections (horns) of gray matter in the spinal cord
Reversed prompt
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
What does the central canal develop from?
Reversed prompt
The dorsal root of spinal
cord has only sensory
fibers.
The dorsal root of spinal
cord contains what fibers?
Reversed prompt
The ventral root has only
motor fibers.
The ventral root of spinal
cord contains what fibers?
Reversed prompt
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.
What do the fibers of the dorsal and ventral roots become?
Reversed prompt
Dura mater (most external), Arachnoid, Pia mater (most internal)
Meningeal layers
Reversed prompt
CSF
What is in the subarachnoid space?
Reversed prompt
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.
Extradural or Epidural Hermatoma
Reversed prompt
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.
Dural border or Subdural Hematoma
Reversed prompt
An extravasation (escape) of blood, usually arterial, into the subarachnoid space, where CSF is found.
Subarachnoid hemorrhage
Reversed prompt
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.
Blood-brain Barrier (BBB)
Reversed prompt
Removes water from blood and releases it as the CSF (cerebrospinal fluid); in this sense, it “produces” CSF.
Choroid Plexus
Reversed prompt
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.
Choroid Plexus location and composition
Reversed prompt
The gap between two
Schwann cells.
These regions are uninsulated and but rich in ion channels, allowing them
to regenerate the action
potential.
Node of Ranvier (or nodal gap)
Reversed prompt
Surround axons and Schwan cells
Endoneurium
Reversed prompt
Surrounds fascicles or bundles of nerve fibers
Perineurium
Reversed prompt
Surrounds multiple fascicles of nerve fibers.
Epineurium
Reversed prompt
Conscious tracts – The dorsal column-medial lemniscal pathway and the anterolateral system,
for touch and some types of proprioception.
Unconscious tracts – The spinocerebellar tracts, for muscle proprioception.
Ascending Tracts (Afferent/Sensory)
Reversed prompt
Conveys sensations of fine touch, vibration, two-point discrimination, and proprioception (position) from the skin and joints.
Dorsal column–medial lemniscus pathway (DCML)
Reversed prompt
The spinothalamic tract consists of two pathways: anterior and lateral. The anterior spinothalamic tract
carries information about crude touch. The lateral spinothalamic tract conveys pain and temperature.
Spinothalamic tract (part of the anterolateral system)
Reversed prompt
Carry unconscious proprioceptive information from the muscles to the
cerebellum. We cannot mentally acknowledge these signals, but they help the brain coordinate and refine motor actions.
Spinocerebellar tracts
Reversed prompt
Postcentral Gyrus
Somatosensory Cortex of the brain
Reversed prompt
Precentral Gyrus
Somatomotor Cortex of the brain
Reversed prompt
Pyramidal tracts and Extrapyramidal tracts
Descending Tracts (Efferent/Motor)
Reversed prompt
Originate in the cerebral cortex, carrying motor fibers to the spinal cord
and brain stem. They are responsible for the voluntary control of the musculature of the
body and face.
Pyramidal tracts
Reversed prompt
Originate in the brain stem, carrying motor fibers to the spinal cord. They are responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and movement.
Extrapyramidal tracts
Reversed prompt
It is structurally a division of the peripheral nervous
system that supplies smooth muscle and glands,
and influences the function of internal organs.
It is functionally a system that acts unconsciously
to regulate “visceral” bodily functions.
Autonomic Nervous System (ANS)
Reversed prompt
Sympathetic and Parasympathetic
Two divisions of ANS
Reversed prompt
A division of the ANS used for “rest-and-digest” or “feed-and-breed.”
Structure: The parasympathetic division has craniosacral “outflow,” meaning that the neurons begin at the cranial nerves (ie, the oculomotor nerve, facial nerve, glossopharyngeal nerve
and vagus nerve) and sacral (S2-S4) spinal cord.
Parasympathetic Nervous System
Reversed prompt
A division of the ANS used for “fight-or-flight-or-freeze.”
Structure: The sympathetic division has thoracolumbar
“outflow,” emerging from the spinal cord in the thoracic and lumbar areas, terminating around L2-L3
Sympathetic Nervous System
