3.6.2.1 nerve impulses Flashcards Preview

SHHS - Science - NEW AQA A-Level Biology (Year 2) > 3.6.2.1 nerve impulses > Flashcards

Flashcards in 3.6.2.1 nerve impulses Deck (13)
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1

What is the voltage across the membrane at resting potential?

-70mV

2

How is resting potential maintained?

Sodium potassium pumps transports 3 sodium ions out of the neurone for every 2 potassium ions that are transported in. The membrane is impermeable to sodium and permeable to potassium.

3

What happen in response to the stimulus to make the inside of the neurone less negative?

Sodium channels open. Sodium diffuses into the neurone down the electrochemical gradient. 

4

What happens if the threshold (around -55mV) is reached?

Depolarisation occurs. More sodium channels open, sodium diffuses rapidly into the neurone. 

5

At what potential difference do sodium channels close?

+30mV

6

After depolarisation, how does the neurone return to resting potential?

Sodium channels close and potassium channels open. Potassium diffuses out of the neurone. 

7

Why does hyperpolarisation occur?

The potassium ion channels are slow to close so there's a slight overshoot where too many potassium ions diffuse out of the neurone. 

8

What is the refractory period?

The period of time after an action potential when the neurone can't be excited. 

9

How does the nuerone respond to a bigger stimulus?

Action potentials will occur more frequently. 

10

During an action potential, the membrane potential rises to +40 mV and then falls. Use information from the graph to explain the fall in membrane potential.

 

Potassium channels open;

Potassium out;

Sodium channels close;

11

 

Sodium and potassium ions can only cross the axon membrane through proteins.

Explain why.


can not pass through phospholipid bilayer;
because water soluble / not lipid soluble / charged / hydrophilic /
hydrated;

12


Explain the importance of reflex actions.


1. automatic (adjustments to changes in environment) / involuntary;
2. reducing / avoiding damage to tissues / prevents injury / named injury
    e.g. burning;
3. role in homeostasis / example;
4. posture / balance;
5. finding / obtaining food / mate / suitable conditions;
6. escape from predators;

13


Give two differences between a cholinergic synapse and a neuromuscular junction.


neurone to neurone and neurone to muscle;
action potential in neurone and no action potential in muscle /
sarcolemma;
no summation in muscle;
muscle response always excitatory (never inhibitory);
some neuromuscular junctions have different neurotransmitters;