As the nerve impulse enters the ______ ____ of the axon terminal it opens voltage gated channels in the _________________ membrane that allows _____to enter.
The Ca++
promotes synaptic _____________ containing a neurotransmitter to fuse with the axon membrane and release the ___________________ into the ___________ cleft.
The ________________ crosses the synapse and joins with the chemically gated protein _______________ in the __________________ neuron
membrane which allows _____ to enter the cell causing the resting membrane to be __________________.
b. action potential of postsynaptic neuron becomes less likely
Cl - or K+ channels are opened
Does the Cl - ions go into the cell or out? K+
into or out?
Does the internal cell become more or less negative?
This is called _______________________________.
Will current be likely to flow in the cell?
ON TO THE AXON HILLOCK (trigger zone)
This depolarization causes a current to flow. The charge flows along an electrical concentration __________ to the more - areas of the cell membrane toward the______________ of the
cell body.
This is a ___________ (local) potential meaning if it is not strong enough it will dissipate before it reaches the axon hillock. Graded
potentials occur at the synapse in ________ and ___ ______.
A threshold EPSP and threshold IPSP stimulates a neuron simultaneously. Would an action potential result?
A neuron sending repeated stimuli (temporal summation) at subthreshold to another neuron in rapid succession, may sum up to an
__________________ potential
If the synaptic (local
graded) potentials add up to _____________ they will reach the _____ ______. The nerve impluse than continues down the axon as an _________
__________
Only the _____________ can generate an action potential.
All-or-nothing
The action potential is generated
along the axon membrane by opening voltage gated ________channels and Na+ diffuses in and the membrane is _____________
Soon after voltage
sensitive ________ channels open and K+ diffuses out, and the membrane is _________________,
This depolarization and repolarization occurs all the way down the axon
with out diminishing in strength which is characterized as _______ ____ ___________
In myelinated axons the action potential jumps from ________ to _______ this type of conduction is called _____________ and is much faster then in
________________axons.
Meanwhile back at the synapse.......REPOLARIZATION
Another nerve impulse may not be received by a postsynaptic neuron, until it goes back to the ________________ state.
Absolute refractory period
Relative refractory period
Neurotransmitter bound to a postsynaptic neuron producing a continuous postsynaptic effect must be removed from its receptor
Blocks reception of additional "messages"
Removal of neurotransmitters occurs when they:
Are degraded by enzymes
Are reabsorbed by astrocytes or the presynaptic terminals
Diffuse from the synaptic cleft
Example - __________________ swiftly removes ACh from the receptors thus cutting off the influx of Na+ and eflux of ____.
The ______ pump
is activated to reestablish the ionic conditions. The membrane than returns to its __________ __________ potential of ________ mV.
Thus the membrane is _____________ to polarized.
Interfers with deactivation of
the neurotransmitter. - MAOI's inhibit the
action of the enzyme Monoamine oxidase (reduces levels of dopamine and norepinephrine)