week 4: neurobiology: action potential and autonomic nervous system

Question 1

neurones at rest

Answer 1

transmembrane potential
outisde:
Na+ =150mM
K+ = 4mM

inside:
Na+= 15mM
K+= 140mM

Question 2

difference in inside and outside neurone concentrations at rest due to the

Answer 2

sodium potassium pump

Question 3

Sodium/ potassium ATP pump

Answer 3

uses energy from ATP
ATP>ADP
uses energy to pump Na ut and K in

Question 4

why can sodium and K not cross membrane unless transported

Answer 4

charged ions

Question 5

inside of cell has very …. charge compared to outside

Answer 5

negative

Question 6

how can we measure potential difference between outside and inside of cell

Answer 6

using electrodes
can be inserted inside neurons

Question 7

resting potential of cell

Answer 7

-65mV

Question 8

electrochemical force

Answer 8

electrical driving force and chemical driving force combines

Question 9

electrical driving force of a neurone ???

Answer 9

inside of a cell is - and attracts +
+ > - ?????

Question 10

chemical driving force of a neurone

Answer 10

conc gradient
high conc Na+ outside, low conc inside

Question 11

equilibrium potential

Answer 11

membrane potential where electrical force is equal and opposite to the clinical force

can be worked out for any ion

Question 12

equilibrium potential

Answer 12

membrane potential of cell in which there is no movement of ions

eg
electrical force (driving in) = chemical force (driving out)

Question 13

Nernst equation Ex=

Answer 13

(RT/zF) x (ln[X]o/[X]i)

R=gas constant
(8.314472 JK-1mol-1)
T= absolute temp
z= charge of ion
F= faradays constant
(9.6485309 X10^4 Cmol-1)
[X]o= conc of ion outside cell
[X]i = conc of ion inside cell

Question 14

simplified Nernst equation
Ex=

Answer 14

58 x log ([X]O/[X]i)

Question 15

when does the simplified Nernst equation work

Answer 15

monocovalent cations at room temp

Question 16

at equilibrium potential, electrical gradient =

Answer 16

same magnitude but in opposite direction to chemical gradient

Question 17

ligand gated ion channels

Answer 17

on post synaptic membrane
neurotransmitter binds to receptor
conformational change to receptor
ion channel opens
inside of cell becomes less negative

Question 18

are channels directional

Answer 18

no
electrochemical force of ion sets direction of travel

Question 19

acetylcholine binds to receptor on post synaptic membrane

Answer 19

channel opens
lots of Na+ enters
small amount of K+ leaves
depolarisation occurs ‘inside of cell becomes more +

Question 20

how are neurotransmitters released at a synaptic terminal

Answer 20

exocytosis

Question 21

AP 1 - neurotransmitters bind to cell

Answer 21

membrane depolarised

Question 22

AP 2- membrane depolarisation reaches threshold potential

Answer 22

voltage-gated Na+ open
large influx of Na+
overshoot: membrane potential becomes +

Question 23

AP 3- Na+ channels become deactivated…

Answer 23

voltage gated K+ channels open
K+ moves out of cell
repolarisation occurs

Question 24

AP 4- afterhyperpolarisation/ undershoot

Answer 24

resets using sodium-potassium ATP pump

Question 25

absolute refractory period

Answer 25

time where cant inject more current and get a second AP
sodium channels inactivated
no ions can flow through even when they are open

Question 26

relative refractory period

Answer 26

still possible to get a second AP
larger stimulus can result in AP
membrane potential is more negative than resting potential

Question 27

what does the absolute refractory period ensure

Answer 27

action potential propagation is unidirectional

Question 28

why does AP only propagate in one direction

Answer 28

sodium channels become inactivated after a while
cant maintain depolarisation
when inactivation is lost, membrane is repolarised so channel is no longer open

Question 29

where are sodium and potassium channels present in myelinated neurones

Answer 29

at nodes of Ranvier

Question 30

saltory conduction

Answer 30

action potentials jump from node to node

Question 31

electrical synapses

Answer 31

no neurotransmitter release
protein channels- gap junction channels
couple cytoplasm of two cells
allows ions and small molecules to flow through
change in pre-synaptic neurone fed immediately through to post-synaptic neurone
direct and quick signal trasmission

Question 32

chemical synapses

Answer 32

use neurotransmitters
most of synapses in brain