3.6.2.1 nerve impulses Flashcards

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1
Q

What is the voltage across the membrane at resting potential?

A

-70mV

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2
Q

How is resting potential maintained?

A

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.

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3
Q

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

A

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

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4
Q

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

A

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

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5
Q

At what potential difference do sodium channels close?

A

+30mV

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6
Q

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

A

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

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7
Q

Why does hyperpolarisation occur?

A

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

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8
Q

What is the refractory period?

A

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

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9
Q

How does the nuerone respond to a bigger stimulus?

A

Action potentials will occur more frequently.

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10
Q

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.

A

Potassium channels open;

Potassium out;

Sodium channels close;

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11
Q

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

Explain why.

A

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

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12
Q

Explain the importance of reflex actions.

A

  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;
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13
Q

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

A

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;

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