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