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Neurotransmission and Ion Channels: An Overview, Quizzes of Physiology

Definitions and information on various terms related to neurotransmission and ion channels, including autacoids, neurotransmitters, ionic currents, voltage-gated channels, and chemically gated channels. It also covers concepts such as synaptic integration, axonal transport, and synaptic plasticity.

Typology: Quizzes

2014/2015

Uploaded on 10/10/2015

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TERM 1
autociods
DEFINITION 1
autacoids or "autocoids" are biological factors which act like
local hormones, have a brief duration, and act near the site of
synthesis.
TERM 2
modulator?
DEFINITION 2
neuromodulators control ligand gated channels.
TERM 3
hormone communication?
DEFINITION 3
Communication in seconds, minutes, or hours Time needed
to reverse or modify effects Dependent on nervous system
TERM 4
neurotransmitter?
DEFINITION 4
neurotransmitters control ligand gated channels.
TERM 5
excitability is?
DEFINITION 5
depolarization in cell. stimulation increases excitability. hyper
polarization decreases excitability of a cell.
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autociods

autacoids or " autocoids " are biological factors which act like local hormones, have a brief duration, and act near the site of synthesis. TERM 2

modulator?

DEFINITION 2 neuromodulators control ligand gated channels. TERM 3

hormone communication?

DEFINITION 3 Communication in seconds, minutes, or hours Time needed to reverse or modify effects Dependent on nervous system TERM 4

neurotransmitter?

DEFINITION 4 neurotransmitters control ligand gated channels. TERM 5

excitability is?

DEFINITION 5 depolarization in cell. stimulation increases excitability. hyper polarization decreases excitability of a cell.

what is potential difference?

The difference in charge (created by different concentrations of ions) between the ICF and the ECF TERM 7

how is potential difference measured?

DEFINITION 7 Can be measured by oscilloscope Note that the electrodes must be placed in the ECF and the ICF Measured in voltage (usually mV) TERM 8

what are ionic currents?

DEFINITION 8 A current is a flow of charged particles. That definition holds no matter where the current is found, but the particles that make up the current across the PM are different from those in a wire TERM 9

an increased permeability in PM

causes?

DEFINITION 9 An increase in PM permeability for a specific ion causes an ionic current to flow at a limited portion of the membrane Occurs only at specific ion channels in membrane Ionic current is the result of diffusion Causes differences in potential across the PM TERM 10

Voltage Gated Channels

(VGC)

DEFINITION 10 Primarily in axons Open in response to depolarization Mechanism for the action potential (among other things)

IPSP

is the last part of the postsynaptic responses it =Inhibitory hyperpolarization.An inhibitory postsynaptic potential is a kind of synaptic potential that makes a postsynaptic neuron less likely to generate an action potential. TERM 17

synaptic integration

DEFINITION 17 Neurons integrate excitatory and inhibitory signals at the postsynaptic membrane Summation of these signals is the determining factor for action potential in the postsynaptic neuron TERM 18

afferent

DEFINITION 18 Sensory (Afferent) Input from receptors To CNSsee slide 13 from powerpoint TERM 19

efferent

DEFINITION 19 Motor (Efferent) Output To effectors TERM 20

structure of

neurons?

DEFINITION 20 Parts of neurons Dendrites (receive information) Body (a.k.a. soma, makes neurotransmitters) Axon (a.k.a. nerve, send information)

function of categories of neurons

see page 241 figure 8.2 from book TERM 22

neuronal anatomy

DEFINITION 22 see page 241 figure 8. TERM 23

what are the two mechanisms of axon

transport?

DEFINITION 23 Axoplasmic flow Axonal transport TERM 24

Axoplasmic flow does?

DEFINITION 24 transport rate comparatively slow. molecules transported only from cell body. bulk movement of proteins in axoplasm, including microfilaments and tubules. transport accomplished by peristatic waves of axion membrane TERM 25

Axonal transport does?

DEFINITION 25 transport rate comparatively fast. molecules transported from cell body to axon endings and in reverse direction. transport of specific proteins, mainly of membrane proteins and acetylcholineesterase.transport dependent on cage like microtubules structure within axon and on actin and Ca+

What is an action potential?

all or nothing, goes above threshold.see page 252 table 8. and page 256 figure 8. TERM 32

what is a leak channel?

DEFINITION 32 the membrane of the neuron cell body has open leak channels that allow positive charge to leak out into the extracellular fluid. some positive ions leak out the cell across the membrane as the depolarization wave moves through the cytoplasm TERM 33

what ions do leak channels carry?

DEFINITION 33 k+ TERM 34

how are leak channels used by

neurons?

DEFINITION 34 see page 252 table 8. TERM 35

Where are voltages gated ion channels

located?

DEFINITION 35 Primarily in axons

What do voltages gated ion channels do? how

are they controlled?

Open in response to depolarization Mechanism for the action potential (among other things) TERM 37

Where are chemically gated ion channels

located?

DEFINITION 37 Post-synaptic membrane TERM 38

What do chemically gated ion channels do?

how are they controlled?

DEFINITION 38 Open in response to neurotransmitters Effects vary TERM 39

Depolarization

DEFINITION 39 is membranes response to voltage gated ion channels. Stimulation, increases excitability of the cell Positive charges flow into cell through ion channels TERM 40

Example of depolarization

DEFINITION 40 first graded potential reaches the trigger zone. its depolarization opens voltage gated Na+ channels Na+ enters the axon and the initial segment of the axon depolarizes. positive charge from the depolarized trigger zone spreads by local current flow.

all or none law

Action potentials occur maximally or not at all In other words, either the threshold is reached and an action potential takes place or it isnt reached and there is no action potential. All action potentials look essentially the same. TERM 47

what is the refractory

period?

DEFINITION 47 is the time potentialsee page 260 TERM 48

Absolute Refractory

Period

DEFINITION 48 During an action potential, a second stimulus will not produce a second no matter how strong it is Corresponds to the period when the Na + channels are being inactivated ( msec) TERM 49

Relative Refactory

Period

DEFINITION 49 Another action potential can be produced, but only if the stimulus is greater than the threshold stimulus Corresponds to the time when the K+ channels are open (several msec)the nerve cell membrane becomes progressively more 'sensitive' (easier to stimulate) as the relative refractory period proceeds. TERM 50

what determines speed of conduction?

DEFINITION 50 Myelin increases conduction velocity by lowering membrane

capacitance

capacitance Capacitance = ability to store electrical chargesee page 282 TERM 52

three elements of synapse

structure?

DEFINITION 52 Axons split into endings tipped by axonal bulbspresynaptic membrane is here Vesicles with neurotransmitter fuse with PM Neurotransmitter in synaptic cleft Postsynaptic membrane can be a dendrite, a soma, or another axon Neurotransmitter binds with receptors Chemically gated channels respond TERM 53

what happens at the postsynaptic

membrane?

DEFINITION 53 Neurons integrate excitatory and inhibitory signals at the postsynaptic membrane TERM 54

what is the sum of these

signals?

DEFINITION 54 Summation of these signals is the determining factor for action potential in the postsynaptic neuron TERM 55

how does nervous system code the intensity

of the stimulus?

DEFINITION 55 The trick that the nervous system uses is that the strength of the stimulus is coded into the frequency of the action potentials that are generated. Thus, the stronger the stimulus, the higher the frequency at which action potentials are generated

Presynaptic modulation allows?

presynaptic modulation of an axon terminal allows selective modulation of collateral and their targets. postsynaptic modulation occurs when a modulatory neuron synapses on a postsynaptic cell body dendrites. TERM 62

What causes EPSP in postsynaptic neuron

DEFINITION 62 Neurotransmitters create rapid short acting fast synaptic potentials. ion channels open, more Na+ in =EPSPor Neurotransmitters create rapid short acting fast synaptic potentials.Which alters open state of ion channels. ion channels close less K+ out =EPSP TERM 63

what causes IPSP in postsynaptic neuron

DEFINITION 63 Neurotransmitters create rapid short acting fast synaptic potentials. Ion channels open, more K+ our or Cl- in = IPSP. or Neurotransmitters create rapid short acting fast synaptic potentials. which alters open state of ion channels. ion channels close. less Na+ in =IPSP TERM 64

action potential vs. EPSP

DEFINITION 64 EPSP= A postsynaptic potential becomes excitatory when the neuron is triggered to release an action potential.action potential =Action potential is a momentary event wherein the cells electrical membrane potential instantly rises and falls. TERM 65

EPSP occurs

when

DEFINITION 65 Excitatory postsynaptic potential occurs when there is a flow of positively charged ions towards the postsynaptic cell, a momentary depolarization of postsynaptic membrane potential is created.

spatial summation occurs?

spatial summation occurs when the currents from nearly simultaneous graded potentials combine. summation of several subthreshold signals results in an action potential. see figure 8.24 page 278 TERM 67

temporal summation

DEFINITION 67 if the interval of time between action potentials is shortened the muscle fiber does not have time to relax completely between two stimuli resulting in a more forceful contraction. takes place in neurons. TERM 68

temporal summation in the neurons means?

DEFINITION 68 that the strength of a graded potential of the neuron increases when two depolarizing stimuli occur close together in time. TERM 69

summation in muscle fibers means that

DEFINITION 69 tension of the fiber increases with repeated action potentials. TERM 70

most important NT in CNS

DEFINITION 70 glutamate (excitatory) and GABA (inhibitory)

NT are removed from the synaptic cleft by

diffusion into the extracellular space, reuptake by the presynaptic cell, or degradation by enzymes TERM 77

Monamine neurotransmitters?

DEFINITION 77 neurotransmitters and neuromodulators that contain one amino group that is connected to an aromatic ring by a two- carbon chain TERM 78

catecholamines?

DEFINITION 78 any of a class of aromatic amines that includes a number of neurotransmitters such as epinephrine and dopamine. TERM 79

MAO is?

DEFINITION 79 mono amine oxidase found in mitochondira. Once back in the axon terminal, norepinephrine is either transported back into vesicles broken down by intracellular enzymes MAO. TERM 80

what is COMT?

DEFINITION 80 is one of several enzymes that degrade catecholamines such as dopamine, epinephrine, and norepinephrine. In humans, catechol-O-methyltransferase protein is encoded by the COMT gene.

What compound is used to turn off

ACh?

Remember that you must be able to turn a signal off for physiological control ACh has low affinity for its receptors - Stays in synaptic cleft -Will restimulate PSM receptors until removed TERM 82

memorize table

DEFINITION 82 page 268 TERM 83

Synaptic plasticity

DEFINITION 83 the ability of the nervous system to change activity at synapse is called synaptic plasticity. TERM 84

presynaptic inhibition and postsynaptic

inhibition

DEFINITION 84 see figure 8.26 on page 279 TERM 85

what is longer-term potentiation?

DEFINITION 85 is a persistent increase in synaptic strength following high- frequency stimulation of a chemical synapse. Studies of LTP are often carried out in slices of the hippocampus, an important organ for learning and memory.