Electro chemical impulses

Question 1

How are the electrical chemical impulses (messages) sent and what are the ions

Answer 1

Neurons send messages electrochemically, these ions are Na+ cl- k+ and ca2+

Question 2

how is a voltage difference produced (easy)

Answer 2

having seperate positive and negative charges

Question 3

what are voltage differences a result of

Answer 3

the pumping of sodium ions out of the cell and potassium ions into the cell through the Na+ and k+ pump

Question 4

what is different about the pumping of sodium and potassium in and out

Answer 4

when potassium ions are pumped in they are ready to diffuse back out as the membrane is permeable for them

but when sodium is pumped out, they cant come back in as the membrane is not permeable for them.

Question 5

Nerve impulse 2 points

Answer 5

Nerve membrane contains Na+ and K+ voltage gated channels, they can open or close

-opening and closing of gated channels affects the movement of ions which affects the charge and concentration across the membrane

Question 6

what is the resting potential of a neuron

Answer 6

The resting potential of neurons is about -70 mV. At resting potential concentration of ions is kept constant through Na+/K+ pumps. When the threshold is reached, the Na+ gated channel are opened.

Question 7

what is another way of saying action potential

Answer 7

nerve impulse

Question 8

what causes the action potential and what initiates it

Answer 8

positive ions moving in and then out of the neuron at certain spots along the neuron

Initiated by a stimulus ex prick

Question 9

what is the action potential initiated by

Answer 9

a stimulus ex pin, prick, ight, heat or sound above a certain threshold

Question 10

why are Na+ and K+ channels called voltage gates

Answer 10

because they act only when the surrounding area reaches a certain voltage

Question 11

what is the threshold

Answer 11

-55mv

Question 12

what happens when k+ ions pour outside neuron

Answer 12

hyperpolarization -90mv

Question 13

how long does the refractory period last

Answer 13

1-2 msec

Question 14

briefly explain the all or none law

Answer 14

it basically states that the axons fire metaphorically like a gun.

if they do fire the size, speed etc is always the same

and therefore stronger stimulus have a higher intensity by having a higher frequency (firing more frequently) ex # of action potentials per second

Question 15

channel
inactivation

Answer 15

following depolarization the sodium channels begin to close, called channel
inactivation