chapter 12: EPSP/IPSP, summation types, neural coding, and neuronal pools

what does EPSP stand for?

excitatory postsynaptic potentials

what does IPSP stand for?

inhibitory postsynaptic potentials

EPSP/IPSP are at

subthreshold, local membrane potential changes

being at subthreshold means that it either makes it

easier or more difficult to generate an action potential

a single EPSP does not change the membrane enough

to initialize action potential

since EPSP’s cannot initialize an action potential, they can be summed in what two ways?

temporal summation and spatial summation

the presynaptic neuron fires rapidly vs slowly

temporal summation

multiple presynaptic neurons stimulate one postsynaptic neuron

spatial summation

the sum effect of all signals at the trigger zone

determines if the signal is sent on

neural coding is the

integration of signals

all action potentials coming from the same neuron

are exactly the same magnitude (all or none)

the purpose of the signal is

qualitative information

the intensity of the signal is

quantitative information

for qualitative information what type of neural coding is used?

labeled line code

for quantitative information what neural coding is used?

**recruitment** (spatial summation) and **frequency** (temporal summation)of action potentials

in labeled line code, each nerve fibers leads to a

receptor that recognizes a specific stimulus

in labeled line code, the brain associates any signal from those nerve fibers

with that kind of stimulus

example of labeled line code is

the optic nerve and light

what coding is also possible under labeled line code?

combinational coding

in spatial summation, weak stimuli recruit

few neurons with LOW thresholds

in spatial summation, stronger stimuli recruit

many neurons with HIGHER thresholds

stimulus strength in spatial summation is interpreted by

the number and type of neurons fired

in temporal summation,

higher frequency action potentials are interpreted as more intense

neurons are arranged in

neuronal pools ---- i.e. **circuits**

what is a diverging circuit?

neurons arranged in a branching pattern (one stimulates many)

a diverging circuit allows one stimulated neuron

to have a large effect

what is a converging circuit?

input from many different nerve fibers that can be funneled to one neuron

a converging circuit integrates information

from multiple sources

examples of a converging circuit

regulation of breathing ---- integrates info from the blood, lungs, and organs

what is a reverberating circuit?

loop of neurons that stimulate one another

a reverberating circuit will continue until

inhibited

what type of memory is the reverberating circuit?

short term/immediate memory

what is a parallel after-discharge circuit?

input neuron diverges to stimulate chains of neurons that converge on a single neuron

when does the signal reach the final neuron on a parallel after-discharge circuit?

at different times creating a prolonged signal

what is an example of parallel after-discharge circuit?

reflexes - one input results in a short term but continuous muscle contraction

stopping the neural impulse appropriately is as important as

starting it correctly

what is the first step is stopping the neural impulse?

the presynaptic neuron is no longer stimulated and stops releasing the neurotransmitter

after the presynaptic neuron is no longer stimulated and stops releasing neurotransmitter, the remaining neurotransmitter may leave the synaptic cleft by…..

diffusion, reuptake, or degradation

diffusion in cessation of the signal

i.e. - LEAVING THE SYNAPSE

astrocytes in the CNS will gather the neurotransmitters and put them back in the neurons

reuptake in cessation of the signal

neurotransmitters re-absorbed by the neuron (SR!!!!)

degradation in cessation of the signal

i.e. - in the synaptic cleft

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e.g. ACh is degraded by acetylcholinesterase