Neuro Lectures

-Time delay across the synapse -Transmission is unidirectional while electrical is in both directions -Transmission may be influenced by previous activity (potentiation/depression/muscle fatigue -Temporal and spatial summation of transmission -Transmission excitatory or inhibitory (depending on neurotransmitter)

They are only on the ending of the neuron and not the membrane.

Depolarization of post-synaptic cell (muscle) called end-plate potential and always big enough to generate an action potential.

-Small fluctuations in resting potential of postsynaptic cell b/c of baseline release of neurotransmitter w/o stimulation -Supports quantum theory of neurotransmitter release (see PPT 6-7) -With 2 or 3 or 4 synaptic vesicles releasing neurotransmitter, will be graded 5 times or more.

-Change in membrane potential by action of multiple MEPP (see PPT 6-8) -Latency b/c of conduction time plus chemical synaptic transmission -Under normal circumstances, EPP is supra-threshold and muscle AP and contraction follows inevitably. -Can be graded so increase summation and frequency b/c of higher levels of neurotransmitter

-Magnitude of EPP not as much as action potential -When AP generated, voltage becomes + and goes to 35-40. -For EPP, response is never past 0. Not as positive as action potential. -Curare: prevent an action potential (paralytic toxin). Blocks generation of EPP or AP and stops contraction of muscle. Muscle relaxant.

-Membrane potential at which chemical/electrical driving force equal and opposite, no net flow of ions across the membrane -Increasing current or flow of outward current means any stimulation causes increase flow of ions, inside or outside

I EPSP = g EPSP x (Vm - E EPSP) I EPSP is the current, g EPSP is teh permeability for that ion, Vm is the resting membrane potential, and E EPSP is the potential generated through stimulus. -if Vm > E EPSP than current is positive and you have hyperpolarization -if VM < E EPSP then current is negative and you have depolarization

-For Na/K+ channel, halfway between equilibrium potentials -At reversal potential, NEITHER ion is in equilibrium, but current is zero b/c influx of Na+ balances efflux of K+.

-See PPT 6-11. Membrane potential of -65 mV and reversal potential 0 for the stimulus. -As you increase from -65 to more positive but less than 0, still have depolarization but effect is reduced. -Above 0, you have hyperpolarization and as become more positive then the effect of hyperpolarization will increase.

Hyperpolarization Outward or positive

Depolarization Inside or negative

When you are only referring to a single ion

When you go more - to resting membrane potential, depolarization affect greater. Synaptic potential is positive, and inward current is negative. As you climb up to 0, this effect becomes less and less. Then, as you become more positive, the synaptic potential becomes more negative and current becomes more positive.

-Affects neuromuscular junctions and causes muscle weakness -Antibodies block Ach receptor, blocking stimulatory effect of Ach -ACh receptor is destroyed, ACh cannot bind to post-synaptic neuron so no AP