Intro Mind and Brain (Psych 251) Topic 1 - Foundation- Neurons

Inhibitory Post synaptic potentials
--> hyperpolerizations
-returns to its steady state membrane potential

Excitatory postsynaptic potentials
--> Depolarization
-up to a point it will just return to its resting membrain potential, but if you depolarize it past threshold, and action potential will fire

-rapid depolarization and repolarization
-occurs at threshold potential (55mV)-All or none --> constant amplitude (100mV above resting), -->Constant timecourse (1ms)-Refractory period (5 ms)

Voltage gated Na+ Channel
-Voltage gated K+ channel
--> normally closed untill a certain voltage causese them to open

Voltage gated Na+ channels open, and positive Na+ ions flow into cell

Even more voltage gated Na+ channels open, increasing depolarization

Voltage gated K+ channels open and K+ ions flow out of cell (so membrane potential starts to decline)

VoltagColtage gated Na+ start to close, while voltage gated K+ channels still open
-another action potential cannot be generated (absolute refractory period)

Harder than usual to generate an action potential but not impossible
-Voltage gated K+ channels close when membrane is hyperpolarized (below resting potential) and membrane potential returns to steady state at the resting potential

A mathematical model of action potentials
awarded 1963 Nobel Prize

-passive
-relatively fast-expoentially attenuating
-Travel only short distances (dies off)

-Relatively slower
-can travel longer distances (doesn't dissapate because all or none response and
- self regenerating propogation down length of axon.

Relatively fast, self regenerating, long distances
-myelinated sections of electronic conduction (reduced leakiness of membrane, few ion channels so doesn't dissipate) with
Nodes of Ranvier where action potentials fire
-(combines benefits of both action potential firing with electrotonic conduction)

-As slow as <1m/s (3.6 km/h)
-As fast as >120 m/s (432 km/h)

-Axon diameter
-Myelination
-Temperature