physiology: electrical signaling

Question 1

What is the three compnents in signaling

Answer 1

Ions, membranes & channels

Question 2

What is the resting membrane potential

Answer 2

Difference in ions & charge between two spaces

Question 3

When is a signal conducted

Answer 3

When resting membrane potential is altered

Question 4

What is the purpose of the ion channels

Answer 4

Allow for exchange of ions between extra- & intra-cellular space

Question 5

What is the two process by which ions moves across the membrane

Answer 5

1. Diffusion
2. Electrostatic force

Question 6

What is diffusion

Answer 6

Ions move down their concentration gradient

Question 7

What law explains diffusion

Answer 7

Fick’s law of diffusion

Question 8

What is electrostatic force

Answer 8

Ions are attracted to opposite charge & repelled by same charge

Question 9

What law explains electrostatic force

Answer 9

Ohm’s Law

Question 10

What is the two rules in equilibrium potential/reversal potential

Answer 10

1. Equilibrium potential for attracting ions back into cell balance the concentration gradient pushing ions out of cell
2. Ion will move towards equilibrium potential

Question 11

What is the Nernst equation purpose

Answer 11

Determine equilibrium potential

Question 12

What is the driving force

Answer 12

Ions move at a rate proportional to difference between membrane- & equilibrium potential

Question 13

What ions are high in concentration inside the cell

Answer 13

Potassium

Question 14

What ions are low in concentration inside the cell

Answer 14

Calcium, sodium & chloride

Question 15

How does the Na-K ATPase pump work

Answer 15

Uses ATP to move 2K+ into cell & 3Na+ out of cell

Question 16

How is potassium pushed out via leaky channels

Answer 16

Concentration gradient establish electrostatic gradients

Question 17

What does the difference in ion inside & outside the cell form

Answer 17

Concentration gradient

Question 18

What is an action potential

Answer 18

Electric signals sent down axons generated by rapid rising & falling membrane potentials

Question 19

Explain the process of generating an action potential

Answer 19

1. Ion channels open causing depolarization of neuron resulting in net influx of + charge
2. Depolarization to -55mV causing voltage gated sodium channels to open at axon hillock & sodium rush into cells
3. Sodium channels become inactivated and potassium channels open causing repolarisation
4. Hyperpolarization occur due to Na/K pump

Question 20

What is the absolute refractory period

Answer 20

Sodium channel inactivated & voltage gated potassium channels open & flows into cell

Question 21

What is the relative refractory period

Answer 21

Sodium channels remain closed but can be activated with stronger stimulus

Question 22

What is the four component of a voltage gated channel

Answer 22

1. Vestibule: entrance to pore is charted & attracts ions around pore mouth
2. Voltage sensor: located on membrane spanning domain & senses a stimulus & signals gate to open/close
3. Gate: regulates flow of ions & modified by mechanical, electrical or chemical actions
4. Selectively filter: region of channel which pore is very narrow & distinguish which ions enter

Question 23

When is the voltage gated sodium channel more likely to open & at what rate

Answer 23

Increased voltage & fast rate

Question 24

When is the voltage gated sodium channel more likely to close & at what rate

Answer 24

Increased voltage & slower rate

Question 25

What is the resting state of the voltage gated sodium channel

Answer 25

Inactivation gate is open & activation gate is closed resulting in movement of no ions

Question 26

What is the activated state of the voltage gated sodium channel

Answer 26

Voltage change opens activation gate resulting in movement of ions leading to generation of action potential

Question 27

What is the inactivated state of the voltage gated sodium channel

Answer 27

inactivation gate is closed & activation gate is open resulting in movement of no ions

Question 28

When is the voltage gated sodium channel more likely to open & at what rate

Answer 28

Increased voltage at slower rate

Question 29

What is the resting state of the voltage gated potassium channel

Answer 29

Channels are closed resulting in no movement of ions

Question 30

What is the activated state of the voltage gated potassium channel

Answer 30

Channels are open resulting in movement of ions down concentration gradient

Question 31

What is active conduction

Answer 31

Use of sodium & potassium challenges to mitigate decay of action potential

Question 32

What is length constant

Answer 32

Measure of how fare the voltage travels down the axon before decays to 0

Question 33

What does increase in axons thickness mean for length constant

Answer 33

Lower internal resistance

Question 34

What is time constant

Answer 34

If voltage change is applied inside a neuron the time it takes for neuron to be fully charged to a stable voltage

Question 35

What is the three effects of myelin

Answer 35

1. Reduces membrane capacitance 2. Increased membrane resistance 3. Saltatory conduction

Question 36

How does myelin reduce membrane capacitance

Answer 36

Due to less charged along surfaces causing speed up action potential propagation

Question 37

How does myelin increase membrane resistance

Answer 37

Lower transmembrane current resulting in speed up action potential propagation

Question 38

How does myelin cause saltatory conduction

Answer 38

Increases speed of signal conduction down axon due to jumping between nodes

Question 39

What three factors speeds up action potential propagation

Answer 39

1. Larger axon diameter 2. Increased membrane resistance 3. Increased peak voltage gated sodium channel conductance

Question 40

What two factors slows down action potential propagation

Answer 40

1. Increased membrane capacitance 2. Increased axial resistance