07-Action Potentials

poopoopeepee

What are resting neurons?

-Neurons that are not tranmitting a nerve impulse

What is the charge of a resting neuron?

polarized: positive outside, negative inside

What makes a resting neuron polarized?

-Sodium Potassium Pumps pump 3 Na+ ions: 2K+ ions

-Na+ cannot easily come back to the cell, K+ can

-more Na on outside, less K on inside: positive outside, negative inside

When is an action potential established?

-Once the resting potential voltage is changed/depolarized— creates electric current that can travel through neuron

How do signals transmit in the neuron?

Neuron is stimulated(if strong enough to reach threshold)→ alters the shape of the proteins in the membrane→ Na+ are flooded into the cell→ makes the inside more relatively more positive than the outside: neuron is depolarized/action potential spike→ channels close so no more Na+ can enter→ K+ channels open→ K+ enters to reestablish original voltage(refractory period)

What is the refractory period?

When the Na+ is pumped out and K+ is pumped in to reestablish original polarity

-membrane be depolarized during this period

voltage of …

resting neuron? stimulus threshold? action potential spike?

• -70mV

• -55mV

• +30mV

How can we tell the difference between a light touch and slap?

• frequency of action potentials triggered

• action potentials always have the same peak voltage ∴ ∴1 action potentials cannot convey the magnitude of the stimulus

What is saltatory conduction?

Impulses jump from node to node, not across the axon

-depolarization only occurs at the nodes, the myalin sheath blocks this.