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In a voltage gated channel, what happens when the threshold (-55mV) is reached?
Na gates open and Na starts to enter
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What happens when the Na channels are closing?
K channels are opening and K is leaving the cell
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Will the gates respond at -25mV?
yes (depolarization) The gates will open
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In the fourth stage of voltage gated channels, what is the slight overshoot?
hyperpolarization
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The period of a lack of activity occurs for how long? What is the length traveled?
1-2 minutes; 1 mm of axon length
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What is the absolute refractory period?
- The period from the opening of Na channels until they begin to reset to original state.
- Na is open and Na is entering.
- Follows stimulation during which no additional action potential can be evoked.
- Absolutely nothing can happen!
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What is the relative refractory period?
- Follows absolute refractory period.
- Interval when a threshold for action potential stimulation is elevated.
- Na has returned to resting state, some K is still open (and K is still leaving), repolarization is occurring.
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What are the 2 refractory periods (in order)?
absolute & relative
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What are the factors that affect conduction velocity? How so?
- Size (the bigger the axon, the more conductive)
- Myelination (the more myelinated, the more conductive)
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What are the 2 methods of conduction?
continuous conduction & saltatory conduction
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What is continuous conduction? Is it for myelinated or unmyelinated fibers?
- Unmyelinated.
- Threshold voltage in trigger zone begins impulse.
- Chain reaction (walking slowly and deliberately) of opening of Na channels...adjacent to adjacent to adjacent.
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How fast does continuous (impulse) conduction occur?
2 m/s
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What is saltatory conduction? Is it for myelinated or unmyelinated fibers?
- Myelinated.
- Skipping parts to go faster (walking normally).
- Skipping from node to node (excessive channels at nodes of ranvier).
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How fast does saltatory conduction occur?
120 m/s
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Is pain transmission happens down a myelinated or unmyelinated axon?
unmyelinated (takes a while for the pain to register)
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Why do large fibers have a higher velocity of nerve signal?
More surface area for signals.
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Small, unmyelinated fibers travel at what speed?
0.5 - 2 m/s
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Small, myelinated fibers travel at what speed?
3 - 15 m/s
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Large, myelinated fibers travel at what speed?
up to 120 m/s
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You pull your hand away from a hot stove even before the pain sets in. This is an example of...
myelinated fibers
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A junction that mediates information transfer between neurons or between a neuron and an effector cell.
Synapse
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What is toward (before) the synapse?
Presynaptic
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What is away from (after) the synapse?
Postsynaptic
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What have neurons that are electrically coupled via protein channels and allow direct exchange of ions from cell to cell (e.g from one muscle cell to another)?
Electrical synapses
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Specialized for release and reception of chemical neurotransmitters
chemical synapses
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What are the 3 ways in which neurotransmitter effects are terminated?
- degradation
- reuptake
- diffusion
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Prozac is an example of _____ (terminated neurotransmitter effect)
reuptake
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______ is the termination of neurotransmitters by enzymes; postsynaptic cell or within the synaptic cleft
degradation
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______ is the termination of neurotransmitters by astrocytes or the presynaptic cell
reuptake
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______ is the termination of neurotransmitters away from the synapse
diffusion
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What are the 3 synaptic regions?
- axosomatic (axon-body)
- axodendritic (avon-dendrite)
- axoaxonic (axon-axon)
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____ junctions are important for electrical synapses.
gap
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These 2 muscle types are involved in electrical synapse.
smooth & cardiac
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What mediate, modulate, and alter graded potentials on the postsynaptic cell? They can be ______ or _____.
neurotransmitters; excitatory or inhibitory
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What are the two types of summation be the postsynaptic neuron?
temporal and spatial
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Which summation is the response to successive releases of NT?
temporal sumamtion
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Which summation is the postsynaptic cell stimulated at the same time by multiple terminals?
spatial summation
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When a presynaptic cell is stimulated repeatedly or continuously, enhancing the release of NT.
synaptic potentiation
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Another neuron inhibits the release of excitatory neurotransmitter from a presynaptic cell.
presynaptic inhibition
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presynaptic inhibition causes postsynapse to _____.
hyperpolarize
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a NT acts via slow changes in target cell metabolism or when chemicals other than NT modify neuronal activity
neuromodulation
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bringing RMP closer to polarization is _____
excitatory
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moving RMP farther from threshold (hyperpolarization) is ______
inhibitory
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_____ is when it didn't make it threshold, goes back to RMP (no summation occurs)
subthreshold
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In summation, the synapse is stimualtd a second time shortly after the first, adding them together to pass the threshold.
temporal summation
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In summation, the synapses are simultaneously stimulated, adding them together allows them to pass threshold (E1 + E2)
spatial summation
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Hyperpolarization occurs, inhibition causes it to become more negative; no consequential
spatial summation of EPSP and IPSP
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In inhibition, ___ leaks in causing it to become more negative (hyperpolarization)
Cl-
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Negative ions flowing in is (inhibitory or excitatory)
inhibitory
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Positive ions flowing in is (inhibitory or excitatory)
excitatory
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What are some examples of chemical classes of NTs?
- ACh
- Biogenic Amines
- Amino Acids
- Peptides
- Novel messengers
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What are the functional classes of NTs?
- excitatory or inhibitory effects
- direct or indirect effects
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What decides excitatory vs inhibitory---the receptor or the NT?
receptor
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What are some types of NTs?
- ACh
- GABA
- Glycine
- Aspartic Acid
- Glutamate
- Monoamines
- substance P
- CCK
- beta-endorphine
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What are the 2 main types of NT receptors?
- channel-linked
- G protein-linked
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Classical receptors mediate direct transmitter action and result in brief, localized changes
channel-linked
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second messenger receptors mediate indirect transmitter action resulting in slower, more persistent, and often diffuse changes...they alter intermetabolism of the cell
g protein-linked
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What is the time from arrival of nerve signal at synapse to start of action potential in postsynaptic cell? How long is it?
synaptic delay; 0.5 msec
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The ____ synapses, the longer it takes.
more
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What are 3 kinds and examples of synapses with different modes of action?
- excitatory cholinergic synapse = ACh (think msucles!)
- inhibitory GABA-ergic synapse = GABA (keeps us from doing crazy things)
- excitatory adrenergic synapse = NE (can also be inhibitory)
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In excitatory cholinergic synapse, ___ floods in. Triggers release of ___ which crosses the synapse.
calcium; ACh
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The excitatory adrenergic synapse acts through ______ systems.
2nd messenger (cAMP)
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What are the 3 effects of cAMP?
- 1. binds to ion gate inside of membrane
- 2. activates cytoplasmic enzymes
- 3. induces genetic transcription & production of new enzymes
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____ receptors trigger opening to allow Cl- in
GABA
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Excitatory adrenergic synapse is responsible for enzymatic ______.
amplification
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Functional groups of neurons that integrate incoming information from receptors and relay the information to other areas
neuronal pools
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What are the are the 2 different zones of neuronal pools?
- facilitated zone
- discharge zone
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What are the 4 types of circuits?
- Diverging
- Converging
- Reverberating, oscillating
- Parallel after-discharge
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Which 2 circuits are common in sensory and motor pathways?
Diverging & converging
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What type of circuit is this?
parallel after-discharge
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What type of circuit is this?
converging (sources)
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What type of circuit is this?
diverging (pathways)
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What type of circuit is this?
reverberating, or oscillating
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Which circuit keeps the impulse going on and on and involves a sense of time (prediction)?
reverberating
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Which circuit has a more synaptic delay and mutple summations (strengthening the arrangement)?
parallel after-discharge
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What is exemplified by spinal reflexes--sequential stimulation of the neurons in a circuit.
serial processing (one before the next, before the next, before the next)
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What are the 2 patterns of neural processing?
serial and parallel
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What results in inputs stimulating many pathways simultaneously and is vital to higher level mental functioning?
parallel processing (going on at the same time)
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If you bother the cell body enough, it will _____.
die
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Axons will grow back where they were _____.
innervated
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What is chemically guided?
chemotaxis
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The strongest "sprout" is the one that ______.
survives
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What are the 6 steps of regeneration of pns fibers?
- 1. normal nerve fiber
- 2. injured fiber
- 3. degeneration of severed fibers
- 4. early regeneration
- 5. late regeneration
- 6. regenerated fiber
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The regeneration of PNS fibers is guided by what?
chemotaxis
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Memory and behavior have a ____ basis.
physical
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What happens while we are sleeping? It involves making more synapses, better synapses, and getting rid of old synapses.
synaptic potentiation
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What are the 3 types of memory?
- Immediate
- short-term
- long-term
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What are the 3 ways of getting from short term memory to long term memory?
- arousal
- repetition
- association
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Which memory involves what is going on right now (putting a noun and verb together).
immediate memory
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Which memory involves a minute to an hour ago (what you had for breakfast).
short-term memory
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Which memory involves remembering a year, month, etc ago?
Long-term memory
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