Electrochemical Impulses and Synapse

Question 1

Electrochemical Impulses

Answer 1

Wave of depolarization sent along the axon primarily involving the movement of sodium and potassium ions across the cell membrane

Question 2

Resting Neuron

Answer 2

Neuron not conducting signals that has potential energy due to the charge difference inside and outside the cell - cell is polarized at -70 mV

Question 3

Resting Neuron: Why Polarized?

Answer 3

1. Large negatively charged molecules inside the cell (proteins, phosphates, and sulfates)
2. K+ channel is slightly open, allowing K+ ions to freely flow out of cell

Question 4

Action Potential

Answer 4

When the axon is sufficiently stimulated (threshold is reached), Na+ channels open and K+ channels close, letting in Na+ ions; cell is depolarized = +40 mV

Question 5

Transfer of Action Potential

Answer 5

Na+ ions attracted to negatively charged molecules further down axon, so they move along axon; triggers further sodium channels to open and initiates more action potentials

Question 6

Repolarization

Answer 6

Na+ channels close and K+ channels open to let out K+ ions to restore negative internal charge - cell is hyperpolarized = -90 mV

Question 7

Resting Balance

Answer 7

Resting potential is restored through the sodium-potassium pump, which transports 2 K+ ions in for every 3 Na+ ions it transports out; cell is back at -70 mV; refractory period = time it takes for neuron to reset back to resting before next action potential

Question 8

Synapse

Answer 8

Gap between presynaptic neuron (neuron sending signal), and postsynaptic neuron (neuron receiving signal)

Question 9

Transmitting Message Between Neurons

Answer 9

When stimulus reaches end of axon, calcium channels open to let in C2+ ions which cause vesicles at end of axon to release neurotransmitters (like acetylcholine) into synapse through exocytosis; neurotransmitters bind to sodium receptors on dendrites of postsynaptic neuron, causing nearby sodium channel to open, letting in Na+ ions, triggering wave of depolarization in that neuron - cholinesterase also in synapse to break down acetylcholine to prevent message from constantly being sent and from neuron being in constant state of depolarization