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179 Cards in this Set

  • Front
  • Back
The nervous system is divided into
central nervous system (CNS)
peripheral nervous system (PNS)
The CNS consists of
brain and spinal cord
the PNS consist of
a network of nerves ans ganglia carryng signals into and out of the CNS;
cranial and spinal nerves
The NS consists of 2 kind of cells
neurons
supporting cells (glial cells)
_ are functional units of NS
neurons
_ maintain homeostasis
supporting cells
supporting cells are _ more common than _
x5
neurons
Neurons have a cell body that contains
nucleus
dendrites
axon
Neurons gather and transmit information by
-responding to stimuli
-sending and receiving electrochemical impulses
-releasing and receiving chemical messages
_ enlarged portion of neuron
cell body
cell body makes
macromolecules
Groups of cell bodies in CNS are called _
nuclei
Groups of cell bodies in PNS are called
ganglia
_= branched processes extending from the cell body's cytoplasm
dendrites
_ receieve information and convey it to cell body
dendrites
_= longest process
axons
_ conduct impulses away from cell body
axons
axon lenght = _
1 micon-1m
types of axon transport system
axoplasmic flow
axonal transport
_
moves compounds toward nerve endings via rhytmic contractions of axon
_
moves large and insoluble compounds bi-directionally
axonal transport moves along
microtubules
very fast
_ and _ enter CNS through axonal transport
viruses (herpes and rabies)
toxins (tetanus)
_ neurons conduct impulses into CNS
sensory/ afferent
_ neurons carry impulses out of CNS
motor/ efferent
motor/efferent consists of
somatic motor neurons
autonomic motor neurons
_ is responsible for reflexive and voluntary muscle control
somatic motor neurons
_ is responsible for smooth and cardiac muscle control and glands
autonomic motor neurons
_ integrate NS activity
association/interneurons
_ located entirely inside CNS
association/interneurons
PNS has _ and _ cells
schwann
satellite cells
_ myelinate PNS axons
schwann cells
CNS has _, _, _, _
obligodendrocytes
microglia (phagocytes)
astrocytes (enviorenmental regulators)
ependymal cells
Ependymal cells are
neural stem cells
_ are involved in NS maintenance
other glial cells
In PNS, each Schwann cell myelinates _ by wrapping round axon
1mm of 1 axon
_= electrically insulates axon
sheath of Schwann
Axons < 2 micrometers in diametes are usually _
unmylenated
In CNS each _ myelinates several CNS axons causing axons of CNS to appear _=
obligodendrocyte
white
white matter
_ = high concentrations of cell bodies and dendrocyes without myelin sheaths in CNS
gray matter
Uninsalted gap between adjacent Schwann cells is called _
node of Ranvier
Nerve regeneration occurs much more readily in _ than _ because _ produce proteins that inhibit regrowth and glial scars in CNS
PNS
CNS
oligodendrocytes
When axon in PNS is severed, distal part of axon _ and surviving _ form regeneration tube
degenerates
schwann cellls
Regeneration tube releases chemicals that attract _ and guides regrowing axon to _
growing axon
synaptic site
_= chemicals that promote fetal nerve growth
neurotrophins
_ are required for survival of many adult neurons and are important in regeneration
neurotrophins
_ are the most common glial cell
astrocytes
Astrocytes have numerous _ that terminate in end feet which surround _
cytoplasmic processes
capillaries
Astrocytes are involved in inducing capillaries to form _
blood-brain barrier
Astrocytes are involved in
-buffering K+ levels
-recycling NT
-regulating adult neurogenesis
-taking up of glucose from blood
-synapse formation
_ allows certain compounds to enter brain
blood brain barrier
BBB is formed by capillary _ in brain that are not as leaky as those in _
specializations
body
BBB do not have _ between adjacent cells; closed by _
gap
tight junctions
At rest, all cells have a _ internal charge and unequal distribution of _
negative
ions
Resting membrane potential is
the negative internal charge of cells
unequal distribution of ions results from-
-large anions being trapped inside cell
-Na+/K+ pump
-limited permeability keeps Na+ high outside cell
-K+ is very permeable and high inside cell because it is attracted by negative charges inside
Neurons have a RMP of
-70mV
_ can discharge (alter) their RMP quickly
excitable cells
Excitable cells allow permeability of ions through the _
rapid changes
Excitability resulting in the _ of ions down their _ gradient through ion channels
diffusion
electrochemical
_ and _ do this to generate and conduct impulses
-neurons
-muscles
Changes in the potential difference across the membrane can be measured by placing _ inside cell and _
1 electrode
1 electrode
_ occurs when membrance potential becomes more positive
depolarization
_ excites nerve impulses
excitatory
_ MP becomes more negative than RMP
hyperporlarization
_ inhibits berve impulses
inhibitory
hyperpolarization caused by _ charges leaving the cell or _ charges entering the cell
positive
negative
_ MP returns to RMP
repolarization
MP changes occur by ion flow through _
membrane channels
membrane channels include some that are:
-normally open (leak channel_
-normally closed until opened
-closed channels have molecular gates that can be opened
Some closed channels have molecular gates that can be opened include
-voltage gated channels
-1 type of K+ channel is always open
-other types are VG and is closed in resting cell
-some Na+ channels are VG;closed in resting cells
_ but sometimes flicker open randomly allowing leaks
Some Na+ channels are VG; closed in resting cells
When ion channels are closed, the plasma membrane is _ permeable
closed
Ion channels are specific for _
a particular ion
_ is a wave of MP change that sweeps along the axon from soma to synapse
Action potential
Wave is formed by _ of the membrane by _; followed by _ by _ efflux
rapid depolarization
Na+ influx
rapid repolarization
K+
Mechanism of Action Potential
Depolarization
Repolarization
Depolarization
-at threshold, VG Na+ channels open
-Na+ driven inward by its electrochemical gradient
-This adds to depolarization, opens more channels; positive feedback loop
-causes a rapid change in MP from -70 to +30 mV
Repolarization includes:
-VG Na+ channels close;VG K+ channels open
-electrochemical gradient drives K+ outward
-repolarizes axon back to RMP
Depolarization and repolarization occue via
diffusion
Depolarization and repolarization:
-Do not require active transport
-after an AP, Na+/K+ pump extrudes Na+, recovers K+
When MP reaches threshold, an AP is _
irreversibly fired
AP is irreversibly fired-
-because positive feedback opens more & more Na+ channels
-shortly after opening, Na+ channels close & become inactivated until repolarization
How stimulus intensisty is coded by
-increased stimulus intensisty causes more APs to be fired
-size of APs remains constant
Refractory periods include
-absolute refractory period
-relative refractory period
_ membrane cannot produce another AP because Na+ channels are inactivated
absolute refractory period
_ occurs when VG K+ channels are open, making it harder to depolarize to threshold
Relative refractory period
_ membrane cannot produce another AP because Na+ channels are inactivated
absolute refractory period
_ occurs when VG K+ channels are open, making it harder to depolarize to threshold
Relative refractory period
_ refers to the ability of axon to conduct current
axonal conduction
Axon cable properties are poor because
-cytoplasm has high resistance
-current leaks out through ion channels
Resitance _ as axon diameter _
decreases
increases
After axon hillock reaches threshold and fires AP, its _ depolarizes adjacent regions to threshold generating a new _
Na+
AP
In conduction in unmyelinated axon, process repeats all along _ to AP amplitude is _
axon
always the same
in unmyelinated axon, conduction is _
slow
in myelinated axons, _ can no flow across _, thus no _ occur under _ and no current leaks
ions
myelinated membrane
APs
myelin
Gaps in myelin are called _
nodes of ranvier
APs occur only in _
nodes
Current from AP at 1 node can _ next node to _
depolarize
threshold
Fast because APs skip from node to node called _
saltatory conduction
_ a functional connection between a neuron (presynaptic) and another cell (postsynaptic)
synapse
there are _ and _ synapses
chemical
electrical
Synaptic transmission in chemicals is via _
neurotransmitters (NT)
_ are rare in NS
electricals
Depolarization flows from _ into _ cells through channels called _
presynaptic
postsynaptic
gap functions
_ are formed by connexin proteins
gap proteins
gap functions are found in _ and _ muscles, _, and _ cells
smooth and cardiac
brain
glial
Synaptic cleft seperates _ of presynaptic from postsynaptic cell
terminal bouton
NTs are in _ in presynaptic cell
synaptic vesicles
Vesicles fuse with _
bouton membrane
chemical synapse release NT by _
exocytosis
amount of NT released depends upon _
frequency of APs
In synaptic transmission
-APs travel down axon to depolarize bouton
-opens VG Ca2+ channels in bouton
-Ca2+ driven inby electrochemcial agent
-trigeers exocytosis of vesicles; relese of NTs
Neurotransmitter release is rapid because vesicles are _ before APs arrive
already docked at release sites on bouton
docked vesicles are part of _
fusion complex
_ triggers exocytosis of vesicles
Ca2+
_ diffuses across cleft
NT (ligand)
NT binds to _
receptor proteins on postsynaptic membrane
chemically regulated ion channels open
-depolarizing channels cause EPSPs -hyperpolarizing channels cause ISPS
-these affect VG channels in postsynaptic cells
EPSPs stands
excitatory postsynaptic potentials
IPSPs
inhibitory postsynaptic potentials
EPSP and IPSPs _ and if MP in postsynaptic cell reaches thereshold, a new _ is generated
summate
AP
_ are the most widely used NT
acetylcholine (ACh)
Acetylcholine are located in all _, used in _
neuromuscular junctions
brain
ACh in _ where it can be _ or _ depending on receptor subtype _ or _
ANS
excitatory
inhibitory
nicotinic
muscarinic
In ligand-operated channels, Ion channel runs through _, opens when _ binds
receptor
lingand (NT)
nicotinic ACh channels are formed by _
5 polypeptide subunits
Nicotitic ACh channels:
-2 subunits contain ACh binding sites
-opens when 2 AChs bind
-permits diffusion of Na+ into K+ out of postsynaptic cell
-inward flow of Na+ dominates
-produces ESPS
In G protein operated channels, receptor is not part of the _
ion channel
G protein receptor is a 1 subunit membrane _ that _ channel indirectly through G protein
polypeptide
activates
Binding of 1 ACh activates _
G protein cascade
In muscarinic ACh channel, different subunit activation causes _
different results
In muscarinic ACh Channel,
-opens some K+ channels, causing hyperpolarization
-closes some K+ channels in other organs, causing depolarization
_ inactivates ACh, terminating its action
Acetylcholinesterase
Acetylcholinesterase located in _
cleft
_= synapse between somatic motor neuron and skeleptal muscle cells
neutrotransmitters-neuromuscular junction (NMJ)
NMJ uses _ as NT
acetylcholine
Large synapses on skeletal muscle are termed _ or _
end plates
neuromuscular junctions
NMJ produce large EPSPs called _
end plate potentials
End plate potentials open VG channels _ end plate causing _
beneath
muscle contraction
_ blocks ACh action at NMJ
curare
Monoamine NTs include
serotonin
norepinephrine
dopamine
Receptors activate _ to affect ion channels
G protein cascade
Serotonin is derived from _
tryptophan
Norepi and dopamine are derived from _
tyrosine
Norepi and dopamine are derived from tyrosine called _
catecholamines
After release, monoamine NTs are mostly inactived by _
presynaptic reuptake
After release, monoamine NTs are mostly inactived by presynaptic reuptake and breakdown by _
monoamine oxidase (MAO)
MAO inhibitors are _
antidepressants
_ involved in regulation of mood, behavior, appetite and cerebral circulation
Serotonin
LSD is structurally similar to _
serotonin
SSRIs are
serotonin specific reuptake inhibitors
SSRIs include
antidepressants
-prozac
-zolof
-paxil
-luvox
Luvox block reuptake of _ prolingnig its action
serotonin
_ involved in motor control and emotional reward
Dopamine
degeneration of dopamine motor system neurons causes _
parkinson's disease
_ is involved in addiction
reward system
_ treated y anti-dopamine drugs
schizophrenia
_ used in PNS and CNS
norepinephrine (NE)
In PNS, norepinephrine is a _
sympathetic NT
In CNS, norepinephrine affects _
general level of arousal
_ stimulates NE pathways
amphetamines
_ and _ are major CNS excitatory NTs
glumatic acid
aspartic acid
_ is an inhibitory NT
glycine
glycine:
-opens CI- channels which hyperpolarize
-strychnine blocks glycine receptors
GABA is
gamma aminobutyric acid
_ most common NT in brain
GABA
GABA is an _ , opens _ channels
inhibitory
Cl-
synaptic integration- EPSPs:
-graded in magnitude
-have no threshold
-cause depolarization
-summate have no refractory period
_ takes place when EPSPs from different synapses occur in postsynaptic cell at same time
spatial summation
_ cause EPSPs to fade quickly over time and distance
cable properties
_ occurs because EPSPs that occur closely in time can sum before they fade
temporal summation
in synaptic plasticity, _ of synapse can increase its ease of transmission
repeated use
_= high frequency stimulation oftern causes enhanced excitability
long term potentiation
_ believe to underlie learning
long term potentiation
Synaptic plasticity:
=synaptic facility
- high frequency stimulation often caused enhanced excitability (long term potentiation)
repeated use of a synapse can also _ its ease of transmission =
synaptic depression
In postsynaptic inhibition,
-GABA and glycine produce IPSPs
-IPSPs dampen EPSPs
-making it harder to reach threshold
_ occurs when one neuron synapses onto axon or bouton of another neuron, inhibiting release of its NT
presynaptic inhibition