Potentials Flashcards

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1
Q

Explain how the resting potential of –70 mV is maintained in the sensory neurone
when no pressure is applied.

A
  1. Membrane more permeable to potassium ions
    and less permeable to sodium ions;
  2. Sodium ions actively transported/pumped out
    and potassium ions in;
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2
Q

Explain how applying pressure to the Pacinian corpuscle produces the changes in
membrane potential recorded by microelectrode P.

A
  1. (Pressure causes) membrane/lamellae to
    become deformed/stretched;
  2. Sodium ion channels in membrane open and
    sodium ions move in;
  3. Greater pressure more channels open/sodium
    ions enter;
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3
Q

The membrane potential at Q was the same whether medium or heavy pressure
was applied to the finger tip. Explain why

A
  1. Threshold has been reached;
  2. (Threshold or above) causes a maximal response
    / all or nothing principle;
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4
Q

Multiple sclerosis is a disease in which parts of the myelin sheaths surrounding
neurones are destroyed. Explain how this results in slower responses to stimuli.

A
  1. Less/no saltatory conduction / action
    potential/impulse unable to ‘jump’ from node to
    node;
  2. More depolarisation over length/area of
    membranes;
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5
Q

Define nerve impulse

A

self-propagating wave of electrical energy that travels down axon membrane

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6
Q

Name the resting potential in humans

A

-65mV

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7
Q

Describe how the resting potential is established

A

S/K pump actively transports Na+ out at a greater rate of P+ in. 3 Na+ for 2K+
Electrochemical gradient due to move Na+ outside than inside axon. Vice versa with K+

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8
Q

Describe how the action potential is established

A

Stimulus detection causes a temporary reversal of charges above the threshold
Na+ voltage-gated channel open so Na+ enter the axon down their con. gradient
This causes a positive feedback mechanism along the axon
The axon becomes depolarise and the membrane potential reverses
Na+ channels close and K+ channels open
K+ leaves via electrochemical gradient
Hyperpolarization occurs
Na/K pump restores resting potential hence repolarisation

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9
Q

Name the action potential in humans

A

40 mV

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10
Q

Describe what an action potential is

A

A travelling wave of depolarisation

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11
Q

How does the impulse travel down a myelinated neurone?

A

salvatory conduction ( faster)

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