How nerves work 2

Question 1

Satellite cells

Answer 1

work in PNS

they surround and support neuron cell bodies

Question 2

what is the action potential

Answer 2

transmit signals over long distances

Question 3

what is the graded potential

Answer 3

determine when an action potential should be fired- if graded potential reaches threshold then an a.p is fired

Question 4

what is the resting potential

Answer 4

keeps the cell ready to respond

all cells need to have r.p so that they are ready to fire other ones

Question 5

amitotic define

Answer 5

no ability to divide- neurons can’t replicate, they are irreplaceable

Question 6

what is the normal resting membrane potential inside a neuron and outside?

Answer 6

inside = -70 mV
outside= 0 mV
at rest there are more potassium ions inside the neuron and more sodium outside

Question 7

what causes change in the resting membrane potential?

Answer 7

leaky potassium channels opening. Potassium moves out of the cell down its conc gradient making the inside of the cell more -ve

Question 8

what is the equilibrium potential?

Answer 8

as K+ moves out of the cell an electrical gradient forms (different in electrical charge across membrane) and eventually…
so the eq. potential is when the electrical gradient pulling K+ back in = the conc gradient pushing k+ out

Question 9

what is the relationship between conc gradient and electrical gradient?

Answer 9

the bigger the conc gradient the bigger the electrical gradient

Question 10

what happens if you increase K+ conc in ECF so outside the cell?

Answer 10

it depolarises the cell and brings it slightly closer to 0

this causes action potentials to be fired

Question 11

what is the blood brain barrier?

Answer 11

a semi-permeable membrane that protects the brain from changes in plasma K+ conc
- capillaries of the brain have tight junctions (in between epithelial cells) so stop the K+ leaking out and astrocytes help regulate it too

Question 12

does the heart have any protection from depolarisation caused by changes in plasma K+ conc?

Answer 12

no, depolarisation causes spontaneous contractions and so there is no protection from K+ changes

Question 13

which organ works to remove K+ and regulate the conc of it?

Answer 13

kidney

Question 14

what other leaky channels are there other than K+?

Answer 14

Cl- and Na+ these have a smaller effect on the resting potential however
at rest there is a higher conc of both ions outside the cell
if you have leaky Na+ channels then it will move into the cell making it more +ve
if you have leaky Cl- channels then it will move into the cell making it more -ve

Question 15

Hyperpolarisation

Answer 15

change in a cell’s membrane potential that makes it more negative

Question 16

define overshoot

Answer 16

going above 0 +ve

Question 17

define repolarising

Answer 17

coming down towards 0 from +ve

Question 18

calcium movement

Answer 18

calcium moves into the cell and when it does a massive influx occurs as there is an even greater electrical gradient due to 2+ charge

Question 19

Na+/K+ pump

Answer 19

Sodium potassium ATPase- protein enzyme pump.
Pumps 2 K+ into cell, 3 Na+ outside of cell- no resting membrane potential still though as still equal charge even when pump has been working. But if you then add leaky K+ channels then some of the K+ moves out of the cell

Question 20

what does the equilibrium potential depend on in the first place?

Answer 20

the concentration gradient

Question 21

give some examples of graded potentials?

Answer 21

generator potentials- at sensory receptors
postsynaptic potentials- at synapses
endplate potentials- at NMJ
pacemaker potentials- in pace maker tissues