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Functions of the NS. (5)
muscle contraction, sensory, metabolic, immune, integrative/cognitive
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Terminally differentiated neuroepithelial derivative.
neuron
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Means of electrochemically transmitting information.
axon
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_____________ of ions across ____________ create a membrane potential.
Concentration differences; selectively permeable membranes
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Neurons have a high intracellular conc of _____.
K+
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Neuronal plasma membranes are selectively permeable to _______, allowing it to move out of the cell down its conc gradient and creating a net _______ within the cell.
K+; negative
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Membrane potential is established because _____ diffuses down its conc gradient out of the cell, but the ______ charge that builds within the cell attracts diffusing ______ against their conc gradient and back into the cell.
K+; negative; K+
-
Permeability of the membrane to _______ is low and constant; therefore, membrane potential is mainly controlled by __(2)__.
Cl-; Na+ and K+
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Membrane potential is ______ (charge).
negative
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At rest, extracellular concs of __(2)__ are high relative to inside the cell.
Na+ and Cl-
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Everywhere except _____________, the negative and positive charges are ____________.
adjacent to the surfaces of the cell membrane; exactly equal (electrical neutrality)
-
The _____________ establishes the high intracellular K+ conc and low intracellular _____ conc.
Na+K+ATPase pump; Na+
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________________ is the primary basis for the -90mV membrane potential.
K+ diffusion down its conc gradient out of the cell
-
In the resting stage, the membrane is _________.
polarized
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During membrane depolarization, the membrane suddenly becomes ____________, resulting in a massive influx; this leads to ______________.
more permeable to Na+; elimination of membrane potential
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The influx of Na+ that leads to membrane depolarization is mediated by activation of ____________, which occurs through ____________ that caused a conformational change.
voltage-gated Na+ channels; reduction of the membrane potential (from -90 to -50)
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The reduction in membrane potential necessary for activation of voltage-gated Na+ channels must be sufficient to _______________ and induce a ____________.
surpass threshold of activation; positive-feedback loop of voltage-gated Na+ channel acitvation
-
Depolarization will spread in __________ where ____________.
all directions; resting/polarized membranes are encountered
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Repolarization is achieved due to the slow conformational change in a ___________. allowing ___________.
voltage-gated K+ channel; efflux of K+
-
Diffusion of ________ to the __________ re-establishes resting membrane potential.
K+; exterior
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Na+/K+ concs are re-established by the ___________.
Na+K+ATPase pump
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__________ is the most efficient way to generate ATP; therefore, the brain does not utilize __________; the implication of this is...
Aerobic glycolysis; anaerobic metabolism; oxygen and/or glucose deficiency impair neuron conduction within 5-10 seconds
-
Neurons utilize _________ almost exclusively for their energy demands.
blood glucose
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Modulation of initiation/propagation of action potentials is driven by... (3)
increased extracellular K+ (decreasing K+ leak channel), decreased extracellular Ca2+ (required to stabilize Na+ channel), inhibition of voltage-gated Na+ channels (ie. local anesthetics, toxins)
-
Diminished K+ diffusion potential interferes with ___________.
membrane repolarization
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______ binds the extracellular domain of the voltage-gated Na+ channel, stabilizing the channel.
Ca2+
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Reducing extracellular Ca2+ reduces the voltage at which __________; this results in __________.
Na+ channels become activated; hyperexcitable neurons
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Depolarization proceeds along the length of the axon, reaching the __________, where stimulatory or inhibitory signals are transmitted downstream through the __________.
presynaptic terminal (axon terminus); synaptic cleft
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Neurotransmitters are synthesized in the __________ or the _________ and are packaged in ___________.
presynaptic terminal; neuron cell body; synaptic vesicles
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Depolarization of the presynaptic terminal activates ____________, allowing a(n) ___________.
voltage-gated Ca2+ channels; influx of Ca2+ and Na+
-
A rise in intracellular Ca2+ causes fusion of __________ with the _________, releasing ___________ into the __________.
synaptic vesicles; plasma membrane; neurotransmitters; synaptic cleft
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What are the receptors types on postsynaptic neurons for neurotransmitters? (2)
ion channels (binding results in opening channels to alter membrane permeability), enzyme receptors (cause internal metabolic change to alter reactivity of the neuron)
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Excitation of ion channel receptors results in opening __________; inhibition of ion channel receptors results in opening __________.
Na+ channels; K+ channels
-
Small molecule neurotransmitters are ________ acting and primarily affect __________.
rapidly; conduction through ion channels
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Neuropeptide neurotransmitters are _________ acting and primarily affect ___________.
slowly; enzyme receptors
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The junction b/w an axon terminus and muscle.
motor end plate
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Motor end plates utilize ___________ neurotransmitters.
small molecule, rapidly acting
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The 3 functional units of the nervous system.
sensory, motor, processing/integratory
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The pattern of dendritic development is a reflection of ____________.
neuronal function
-
Maintains the functional integrity of the cellular processes; has great metabolic burden.
neuron cell body
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The size of the cell body reflects ___________.
the length of the axon it must support
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Extensive roughER in neurons is required for synthesis of __________, which is proteins and glycoproteins utilized in the maintenance of axonal and dendritic structure and function.
nissl substance
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Communication b/w cellbody and axon is through ____________, which can be... (3)
axoplasmic transport; fast antegrade (secretory vesicles, mitochondria), slow antegrade (cytoskeleton), retrograde
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____________ and ___________ makes the neuron particularly susceptible to injury.
High metabolic rate; specialization
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If integrative function of one neuron is lost, the function of the __________ is altered.
entire circuit
-
Depolarization events jump b/w _____________.
Nodes of Ranvier (unmyelinated areas of axon)
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Schwann cells are in the _________; oligodendroglia are in the _________.
PNS; CNS
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Neuroglia are... (5)
oligodendroglia, astrocytes, ependymal cells, choroid plexus epithelia, microglia
-
Palm-like cytoplasmic extensions progressively wrap around axonal processes, excluding cytoplasmic content.
myelin
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_____________ a predominant membrane lipid constituting myeline that is an excellent insulator.
Sphingomyelin
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In the CNS, ___________ stabilizes the multilamellar structure of myeline.
myeline basic protein
-
In the CNS, ____________ plays a role in induction of myelination.
myelin-associated glycoprotein
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With __________, action potentials are restricted to exposed portions of the axon, or Nodes of Ranvier.
saltatory conduction
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With saltatory conduction, currents lower the membrane potential and activate ____________ at the next __________, leading to ____________.
voltage-gated Na+ channels; Node of Ranvier; depolarization of each node
-
What are the advantages of saltatory conduction? (2)
increased velocity of nerve impulse, conserves energy for neuron
-
Functions of schwann cells. (3)
myelination of nerve fibers, structural support for nerve fibers, support axonal metabolism
-
Schwann cells produce __________ and _________, effectively creating...
basement membrane; collagen; a tube through which the axon courses, the neurilemmal tract.
-
The schwann cell:axon ratio in myelinated fibers is _____, which is important for ___________.
1:1; reinnervation in the PNS
-
Regeneration of an axon (reinnervation) is only successful if there is...
a neurilemmal tract guiding the axon sprout to its destination.
-
Schwann cells in the PNS are the functional equivalent of _________ in the CNS.
astrocytes
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Myelination occurs late in fetal life and early into the post-natal period, thus...
protracts the NS develop and increases the opportunity for developmental defects.
-
Myelin can be replaced because __(2)__ retain the ability to proliferate.
oligodendroglia and schwann cells
-
Neuroectodermal derivative which retains the ability to replicate in the CNS.
astrocytes
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__________ provide structural support to nervous tissue parenchyma via their extensive ___________.
Astrocytes; cytoplasmic processes
-
__________ may fill in or delineate tissue defects in the CNS, forming scar tissue.
Astrocytes
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Functions of astrocytes. (4)
structural support to CNS parenchyma, basic metabolic support to neurons and oligodendroglia, directly support neuronal signal transduction, form the BBB
-
Astrocytes form a syncytium with other astrocytes via _________ in their cytoplasmic processes; thus, they are able to have...
gap junctions; continuous communication for nutrition and waste removal.
-
Astrocytes directly support neuronal signal transduction by... (3)
terminate neurotransmitter stimulation, neurotransmitter recycling, reverses extracellular electrolyte imbalances that result from membrane repolarization
-
__(2)__ form the blood brain barrier.
Astrocyte processes and endothelial cells
-
Resident macrophages of the brain and are unique amongst glial elements in that they are derived from mesenchyme.
microglia
-
Microglia have a key role as _________.
antigen-presenting cells
-
Cellular components of the grey matter of the CNS. (4)
neuron cell bodies, astrocytes, oligodendrocytes, microglia
-
Cellular components of the white matter of the CNS. (4)
axonal processes, oligodendroglia an myelin, astrocytes, microglia
-
Components of the PNS. (2)
ganglia/plexus, nerve fibers
-
Ganglia/plexus of the PNS are composed of... (2)
neuron cell bodies, sustenacular cells
-
Nerve fibers of the PNS are composed of... (3)
axonal processes, schwann cells, fibrous connective tissue
-
_____________ occurs as ingrowth during embryogenesis and is necessary for nutrition and waste removal.
Vascularization
-
Doe grey or what matter have more vascularization and metabolic activity?
grey matter
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The BBB is permeable to... (2)
lipid soluble compounds, (slightly) electrolytes.
-
The BBB is impermeable to... (2)
plasma proteins, large (water soluble) organic compounds.
-
What is the anatomic basis for the BBB?
non-fenestrated capillary endothelial cells with tight junctions b/w cells
-
The basal lamina upon which the endothelium of the BBB rest is surrounded by ____________.
astrocytic foot processes
-
Functions of CSF. (3)
waste removal supply of metabolites, protective cushion for nervous tissue
-
The __________ is responsible for CSF production.
choroid plexus
-
The choroid plexus is composed of specialized structures in the...
lateral ventricles and roof of the third and fourth ventricles.
-
Choroidal epithelia are specialized ___________ responsible for CSF production.
ependymal cells
-
Capillaries of the choroid plexus have __________ endothelium, with __________ of the choroidal epithelium, creating the blood-CSF barrier.
fenestrated; tight junctions
-
For CSF production, _______ is actively transported into the ventricular system by the ___________, carrying __(2)__ along with it; __(2)__ are actively transported out of CSF.
Na+; Cl- and water; K+ and bicarb
-
What are the functions of CSF? (3)
waste removal, metabolite supply, protective function
-
The _______ of the brain and the ________ of the spinal cord contain CSF.
ventricular system; duct system
-
CSF is resorbed in the _________.
subarachnoid space
-
Describe the flow of CSF from where it is produced to the spinal cord.
lateral ventricles--> interventricular foramen--> third ventricle--> mesencephalic aqueduct--> fourth ventricle--> lateral apertures to the subarachnoid space--> spinal cord central canal
-
The subarachnoid space is created by the _________.
meninges
-
The tough fibrous connective tissue covering that protects the brain and spinal cord from penetrating injury and forms the periosteum of the interior surface of the cranial vault.
dura mater/ pachymeninges
-
The deicate collagen and reticular fibers that send supportive trabeculae to the pia mater.
arachnoid membrane/ leptomeninges
-
What are the 2 components of the leptomeninges?
arachnoid membane and pia mater
-
Layer of the meninges that is intimately associated with the surface of the brain and spinal cord.
pia mater/leptomeninges
-
The subarachnoid space is b/w the _________ and _________ and is filled with _________.
arachnoid membrane; pia mater; CSF
-
Glial cells of neuroectodermal origin that have apical cilia that cause the continuous movement of CSF into the subarachnoid space.
ependymal cells
-
_________ lined by ependymal cells extend into the dorsal sagittal sinus, permitting the resorption of CSF.
Arachnoid granulations
-
The perivascular space is where ____________ occurs.
modification of CSF composition
-
The CNS corollary to lymphatics of other organ systems.
perivascular space
-
The perivascular space is potential space b/w the _________ and the __________.
endothelial basement membrane; basement membrane of the pia mater
-
Why does the CNS lack a classical lymphatic draining system, and how does it overcome this?
due to the presence of the BBB; when fluid escapes, it accumulates in the perivascular space and then passes through the subarachnoid space to the arachnoid vili to be resorbed
-
Due to the BBB, vascular leakage in the CNS occurs only in association with...
inflammation or other pathologic processes that increase vascular permeability.
-
Finger-like extensions of the arachnoid membrane that project into large venous sinuses; cells contain valve-like pores to permit unidirectional flow of material from the subarachnoid space into venous circulation.
arachnoid villi
-
_________________ is the primary determinant of CSF pressure.
Rate of absorption into arachnoid villi
-
Clusters of arachnoid villi.
arachnoid granulations
-
CSF passing along cranial nerves and spinal nerve roots, going into lymphatics does not play a major role in CSF pressure; it does, however, play a major role in...
initiating adaptive immune responses for processes that begin in the CNS.
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