neurons, like skeletal muscle cells, have threshold levels, therefor the operate in what?
an "all or none principle"
what does the all or none principle mean for neurons?
the neuron transmits a nerve impulse or it does not transmit a nerve impulse
a) no such thing as 1/4 or 1/2 strength
what are the 3 types of stimuli?
a) threshold stimulus or liminal stimulus
b)subthreshold stimulus or subliminal stimulus
c)summation of inadequate stimuli
what is the most common stimuli for neurons?
summation of inadequate stimuli
what is a threshold stimulus or liminal stimulus?
a single stimulus that is strong enough to initiate a nerve impulse in the post-synaptic neuron
what is a subthreshold stimulus or subliminal stimulus?
a single stimulus that is too weak to initiate a nerve impulse in the post-synaptic neuron
what is a summation of inadequate stimuli?
a series of stimuli that are too weak to initiate a nerve impulse b themselves->collectively add together and initiate a nerve impulse in post-synaptic neuron
any one _____-synaptic neuron may be connected to thousands of _____-synaptic neurons. hundreds of them may be active at one time
a)post
b)pre
whether the post-synaptic neuron initiates a nerve impulse is determined by what?
comulative effect of all active pre-synaptic neurons
where is cumulative effect expressed at?
the "axon hillock"
what are the 2 types of stimulation by pre-synaptic neurons?
1.excitatory post-synaptic potential (EPSP)
2. inhibitory post-synaptic potential(IPSP)
what is excitatory post-synaptic postential (EPSP)?
neurotransmitter that moves the post-synaptic closer to threshold level->more likely to initiate a nerve impulse
what is inhibitory post-synaptic potential(IPSP)?
neurotransmitter that moves the post synaptic neuron farther from threshold level (hyperpolarizes)-> less likely to initiate a nerve impulse
1EPSP=1 IPSP
neuron X has a threshold level= 100 EPSP's, if neuron x recieves 100 EPSP's + 20 IPSP's at same time-> will it initiate a nerve impulse?
no
1EPSP=1 IPSP
neuron X has a threshold level= 100 EPSP's, if neuron x recieves 150 EPSP's + 49 IPSP's at same time-> will it initiate a nerve impulse?