#10: Nerve Signals

Question 1

Electrochemical Impulse

Answer 1

transmission of an electrical impulse down a neuron is generated by the movement of Na+ (and K+) ions

Question 2

Resting neuron

Answer 2

net positive charge on the outside and a net negative charge on the inside
the potential difference across the membrane is –70 mV
(referred to as resting potential)

Question 3

Resting potential

Answer 3

results from the accumulation of Na+ ions on the outside of the membrane

Question 4

Depolarization

Answer 4

upon excitation, Na+ channels in the membrane open and Na+ rushes into the cell via diffusion
the rush of Na+ into the cell causes a reversal in charge
potential difference across the membrane changes to between +30 and +40 mV
(calledaction potential)

Question 5

Action potential

Answer 5

moves down the neuron in a wave-like fashion by triggering the opening of adjacent Na+ channels
after the action potential has moved through an area, sodium-potassium pumps use ATP to move Na+ ions out of the cell and K+ ions into the cell

Question 6

Repolarization

Answer 6

pump moves the ions in a 3 : 2 ratio (Na+ : K+)

as a result, the resting potential is re-established (net positive charge on the outside, -70 mV)

Question 7

Refractory period

Answer 7

nerve cell cannot fire again until the resting potential has been re-established
the time needed to do so is called the refractory period

Myelinated cell’s transmit impulses faster b/c action potential jumps between nodes

Question 8

Threshold level

Answer 8

minimum level of a stimulus required to produce an impulse down a neuron

Question 9

Stimuli below the threshold level…

Answer 9

will not generate an impulse

Question 10

Stimuli above the threshold level…

Answer 10

will generate an impulse

Question 11

Synapses

Answer 11

small spaces between neurons or effectors (muscles/glands)

Question 12

Neurotransmitters (NT)

Answer 12

used to transmit impulses across a synapse

the axon terminal of the presynaptic neuron contains vessels that hold NT
upon stimulation, the vessels release the NT
the NT diffuse across the synapse and initiate an impulse in the postsynaptic neuron(s)

Question 13

1. Excitatory (type of NT)

Answer 13

increase likelihood that impulse fires

Question 14

2. Inhibitory (type of NT)

Answer 14

decrease likelihood that nerve impulses fire

Question 15

Electric Synapses

Answer 15

Very rare
Presynaptic and postsynaptic cells are in direct contact
Allows current to flow through instantly

Question 16

Chemical Synapses

Answer 16

Make up the majority of synapses
Delays transmission as neurotransmitter is released, diffusion, and binding of neurotransmitter across synapse
Allows neurons to receive input from hundreds to thousands at the same time

Question 17

Method -chemical synapses

Answer 17

Action Potential reaches axon terminal
Ca2+ gates open and flow into the cytosol
Triggers protein in synaptic vesicles to fuse with cell membrane
Neurotransmitter is released through exocytosis
Neurotransmitter binds to postsynaptic receptor, opening ion channels for AP to continue