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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.
