Membrane potential and resting membrane potential. Changes in the membrane potential

Question 1

membrane potential definition

Answer 1

difference in electrical potential charge from inside and outside of cell membrane

Question 2

membrane potential cause 1

Answer 2

1 - unequal distribution of ions on either side of the membrane

Question 3

membrane potential cause 2

Answer 3

2- selective permeability of each ion

• at rest, membrane is more permeable to k+ than na+ due to k+ leak channels
• making inside more negative

Question 4

membrane potential - formation

Answer 4

presence of ion channels, ion pumps, ion exchangers

presence of sodium-potassium pump
- x3Na+ out/ x2K+ in
- development of concentration gradient

presence of equilibrium potential = the membrane potential where there is no flow of ions in/ out of membrane

Question 5

equilibrium potential of sodium

Answer 5

+60mV
more sodium ions outside cell

Question 6

equilibrium potential of potassium

Answer 6

-90mV
more potassium ions inside cell

Question 7

equilibrium potential of calcium

Answer 7

+120mV
more calcium outside cell

Question 8

membrane potential - factor 1

Answer 8

concentration gradient

greater differences in conc from area 1 and area 2 = greater conc. gradient = more MP

Question 9

membrane potential - factor 2

Answer 9

selective permeability

presence of:
- voltage gated ion channels
- ligand gated ion channel
- mechanical gated ion channel
- leak channels
- temperature gated channel

allow entry to specific ions only

Question 10

membrane potential - factor 3

Answer 10

changes in extracellular concentrations

• hyperkelemia = more k+ in extracellular concentration causing depolarisation
• hypokelema = less k+ in extracellular concentration causing hyperpolarisation

Question 11

membrane potential - factor 4

Answer 11

changes in intracellular concentrations

presence of negatively charged ions like cl- cause membrane to be more negative

Question 12

membrane potential - factor 5

Answer 12

ion channel modulators

presence of neurotransmitters can open/ close ion channels like GABA

presence of drugs like block ion channels like local anaesthetics blocking Na+

Question 13

membrane potential - factor 6

Answer 13

temperature

higher temp = more KE = more fluidity = more ion flow = changing MP

Question 14

membrane potential - factor 7

Answer 14

pH

amino acid residues of carrier proteins on cell membrane require optimal pH or it will denature = non functional membrane

Question 15

membrane potential - factor 8

Answer 15

mechanical forces

forces can open/ close/ deform channels

Question 16

resting membrane potential definition

Answer 16

differences in electrical potential across the membrane when the cell at rest
inside cell is more negative than outside -> appox. of cells = -40 to -90mV

Question 17

resting membrane potential - function 1

Answer 17

• provides baseline for action potential generation in muscle/ nerve cells

Question 18

resting membrane potential - function 2

Answer 18

cell signalling transduction pathways

Question 19

resting membrane potential - function 3

Answer 19

• maintain electrochemical balance of cells in homeostasis

Question 20

resting membrane potential - function 4

Answer 20

• influences transport mechanisms like SAT

Question 21

list the types of changes in membrane potential

Answer 21

1 - pacemaker potential
2 - action potential
3 - graded potential
4 - synaptic potential

Question 22

changes in membrane potential - pacemaker potential

Answer 22

• when cardiac pacemaker cells gradually + spontaneously depolarise leading to generation of AP
• AP needed for rhythmic contractions for regular heartbeat

Question 23

changes in membrane potential - action potential

Answer 23

• rapid + temporary changes of membrane potential as it moves along neurone down axon

phases
1 - depolarisation = membrane potential more positive than resting membrane potential - due to influx of Na+
2 - repolarisation = membrane potential more negative than resting potential due to influx of k+
3 - hyperpolarisation = overtime of k+ channels making membrane more negative

feautures
1 - all or nothing principle
- action potential must reach threshold for stimulus release
2 - refractory periods - absolute + relative
3 - AP remains same strength throughout

Question 24

changes in membrane potential - graded potentials

Answer 24

• localised changes in membrane potential
• depending on strength/ magnitude of stimulus it can generate an AP

types
receptor-graded
- generated by sensory receptors in response to external stimuli
synaptic graded
- generated by synapse in response to neurotransmitter

features
1 - strength decreases as it travels
2 - amplitude is proportional to stimulus
3 - can be summated due to multiple signals

Question 25

changes in membrane potential - synaptic potential

Answer 25

= changes in membrane potential of post-synaptic terminal when neurotransmitter released from pre-synaptic terminal binds to it

EPSP = depolarising change = more likely to reach threshold for excitation = AP produced

IPSP = hyperpolarising change = less likely to reach AP = AP not produced