neural signaling

what do neurons do?

they control the communication of nerve impulses, which are electrical signals.

which direction do nerve impulses travel?

dendrites to axon terminals (left to right)

why is the myelin sheath critical for neural processing?

this layer of phospholipids allows signal transmission to be far more efficient by allowing neural impulses jump through the nodes of Ranvier instead of traveling the whole axon. it also acts as an insulator, which prevents ions from leaking out of the membrane.

what is synaptic transmission/saltatory conduction?

the action of nerve impulses jumping through the nodes of ranvier.

what physical features of an axon help with transmission efficiency?

myelination and a wide axon diameter

what ions are responsible for nerve impulses?

Na⁺ and K⁺ - a concentration difference of these two ions across the membrane creates an electrical charge difference.

organize ions by charge and location.

Chloride/large organic ions	Potassium	Sodium
Negative charge	Positive charge	Positive charge
Remain inside the cell	more on the inside to start	more on the outside to start

what is the voltage at resting potential?

-70mV (polarized)

how is resting potential established?

1. the sodium/potassium pump (ATP) pumps 3 Na⁺ out of the neuron for every 2 K⁺ into the neuron > salty banana.

2. the membrane is 50x more permeable to K⁺ than Na⁺, so some K⁺ ions leak out.

3. the proteins that are too large remain inside of the cell, maintaining a negative charge.

define action potential.

the movement of a signal down the axon, which is associated with a change in charge difference when the neuron is stimulated to a sufficient amount.

define threshold potential.

the minimal input necessary for an action potential; voltage = -50-55 mV inside the neuron.

what is occurs during depolarization?

1. the Na⁺ channels open so that more ions can flow INTO the cell.

2. as a result, the membrane potential climbs to around +30 mV.

what happens after the nerve impulse/action potential occurs?

repolarization- Na⁺ channels close while K⁺ channels open so that K⁺ ions can flow out of the cell. consequently, the membrane potential returns to negative.

what happens during the undershoot phase?

the K⁺ channels close slower than than those of Na⁺, resulting in a negative charge greater than resting potential. to adjust, the Na⁺/K⁺ pump will restore the membrane potential back to -70 mV.