15.2 the nerve impulse

Question 1

how is a electrochemical gradient created by the Na+-K+ pump?

Answer 1

1- higher [K+] inside & higher [Na+] outside
2- membrane is more permeable to K+ ions (more open K+ channels)
3- ATP used to active transport 2 K+ in & 3 Na+ ions out

Question 2

how does open-gated K+ channels establish the resting potential?

Answer 2

K+ ions could freely move down concentration gradient (out of phospholipid bilayer)

Question 3

how is an action potential generated? (6)

Answer 3

1- energy of stimulus causes Na+ voltage-gated channels to open
-> influx of Na+ ions diffuse into axon membrane down electrochemical gradient
2- depolarisation of the axon membrane causes more Na+ voltage-gated channels to open until action potential is established
3- Na+ voltage-gated channels close
-> further Na+ influs stopped & K+ voltage-gated channels open
4- K+ ions diffuse out of membrane & repolarises the axon
5- outward diffusion of K+ ions causes hyperpolarisation & k+ voltage-gated channels close
6- Na+ - K+ pump re-establishes resting potential

Question 4

what is the voltage of an action potential?

Answer 4

40 mV