8.1.4 - Transmission Of Nerve Impulses

Question 1

Describe The Resting Potential
(4 Points)

Answer 1

~ Outside of the membrane is positively charged, the inside is negatively charged.

~ There are more positive ions outside than inside the membrane, so the membrane is polarised.

~ Voltage across the membrane at rest is -70mv.

~ Resting potential is created and maintained by sodium-potassium pumps and potassium ion channels, in the membrane.

Question 2

Describe The Sodium-Potassium Pump Of The Resting Potential
(4 Points)

Answer 2

~ Carrier proteins, they use ATP to actively transport sodium ions out of the neurone and potassium ions into the neurone.

~ Membrane isn’t permeable to sodium ions, they can’t diffuse back in.

~ Creating a concentration gradient, as there are more positive sodium ions on the outside, then inside, generating a negative charge inside the neurone.

~ Membrane is permeable to the potassium ions, so they can diffuse back out via the potassium ion channels.

Question 3

Describe The Potassium Ion Channels

Answer 3

Allow facilitated diffusion of potassium ions out the neurone, through facilitated diffusion.

Question 4

Describe How An Action Potential Is Generated & What Is The Process
(4 Points)

Answer 4

~ Neurone is stimulated, sodium ion channels open, and move down the concentration gradient.

~ Reducing the potential difference across the neurone membrane, as the inside becomes less negative.

~ If it reaches -55mv, voltage gated sodium ion channels open.

~ Action potential is initiated then depolarisation, repolarisation, hyperpolarisation occurs.

Question 5

Describe Depolarisation Of The Action Potential
(2 Points)

Answer 5

~ When the charge has been reversed from -70mv to +30mv.

~ Voltage gated sodium ion channels open, greater influx of sodium ions into the membrane.

Question 6

Describe Repolarisation Of The Action Potential
(3 Points)

Answer 6

~ At -30mv the voltage gated sodium channels close, and the voltage gated potassium channels open.

~ Allowing the diffusion of potassium ions out of the neurone, down their concentration gradient.

~ Causes the inside of the neurone to become negatively charged again.

Question 7

Describe Hyperpolarisation Of The Action Potential
(2 Points)

Answer 7

~ Voltage gated potassium channels are slow to close, causing an overshoot of potassium ions.

~ Causing the potential difference to fall below -70mv.

Question 8

Describe The Refractory Period Of The Action Potential
(2 Points)

Answer 8

~ A new action potential cannot be generated.

~ As ion channels are recovering.

Question 9

Describe Resting Potential Of The Action Potential
(2 Points)

Answer 9

~ Ion channels are closed.

~ Sodium-potassium pump, returns the membrane to its resting potential and maintains it until the membrane is excited by another stimulus.

Question 10

Describe The Wave Of Depolarisation
(3 Points)

Answer 10

~ Some sodium ions diffuse sideways.

~ Causing sodium ion channels to open in the next region of the neurone.

~ Causing a wave of depolarisation.

Question 11

Describe The All-Or-Nothing Principle
(2 Points)

Answer 11

~ The threshold potential of -55mv, isn’t reached.

~ No action potential would be initiated.

Question 12

Describe How Action Potentials Go Faster In Myelinated Neurones
(2 Points)

Answer 12

~ Action potentials occur at the node of ranvier, through local currents.

~ Action potential, jumps from one node to the next, known as saltatory conduction.

Question 13

How Can Impulse Transmission Be Prevented?
(3 Points)

Answer 13

~ Painkillers and anaesthetics.

~ Which bind to sodium ion channels, preventing them from opening.

~ Preventing membrane depolarisation.