Nervous System: Transmission of Neural Impulses (HY)

Question 1

What is the name of the enzyme that transports sodium and potassium across the axon membrane? How many sodium ions are transported out and how may potassium are transported in?

Answer 1

sodium potassium ATPase

3 sodium out; 2 potassium in

Question 2

what is resting membrane potential?

Answer 2

-70mV

Question 3

when the axon hillock receives a enough excitatory signal, what happens?

Answer 3

depolarization –> if it passes threshold value, then action potential is triggered

Question 4

when the axon hillock receives a enough inhibitory signal, what happens?

Answer 4

hyperpolarization –> less likely to trigger action potential

Question 5

what is temporal summation?

Answer 5

integrating multiple signals over a short time period

one pre-synaptic neuron

Question 6

what is spatial summation?

Answer 6

integrate multiple signals based on number and location of incoming signals; some signals are given more weight than others

multiple pre-synaptic neurons

Question 7

what are the three states of sodium ion channels and when do these three states occur?

Answer 7

1. closed: before reaching threshold voltage
2. open: from threshold voltage to ~+35mV
3. inactive: from +35mV to resting potential
   1 again: closed: once it reaches resting potential

Question 8

what is absolute refractory period and relative refractory period?

Answer 8

absolute refractory period: no amount of stimulation can cause another action potential
relative refractory period: a greater than normal amount of stimulation is required to cause another action potential

Question 9

what are the steps of an action potential

Answer 9

1. depolarization until threshold
2. more depolarization with Na+ influx
3. repolarization with K+ efflux
4. hyperpolarization
5. sodium potassium ATPase restores resting potential

Question 10

what is saltatory conduction?

Answer 10

signal “hopping” between nodes of Ranvier since the myelin sheath prevents ion movement

Question 11

How does increased length and increase cross-sectional area affect conduction speed?

Answer 11

increased length –> increased resistance –> slower

increased cross section –> lower resistance –> faster

Question 12

when a neuron signals to a gland/muscle (not another neuron) what is the postsynaptic cell called?

Answer 12

an effector

Question 13

what are the twp types of neurotransmitter receptors?

Answer 13

1. ligand gated ion channels

2. g protein coupled receptors

Question 14

what are the three mechanisms to remove neurotransmitters from the synaptic cleft?

Answer 14

1. breakdown of neurotransmitters by enzymes (ex. acetylcholine)
2. reuptake carriers that take neurotransmitters back into presynaptic neuron (serotonin, dopamine, norepinephrine)
3. neurotransmitter diffusion out of synaptic cleft (ex. nitric oxide)