How Nerves Work 3 Flashcards

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1
Q

When is an AP sent?

A

When the RMP depolarises to threshold at around -55mV

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2
Q

What causes the depolarisation of the RMP?

A

External stimuli acting on specific sets of ion channels to create graded potential where the size of potential is related to the size of the stimulus

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3
Q

What is a synapse?

A

A junction between 2 neurones where AP releases transmitter molecules that activate receptor on the second cell which open ion channels creating another graded potential

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4
Q

What happens at an NMJ?

A

Motor neurone depolarises the muscle to threshold by evoking a graded potential known as the endplate potential

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5
Q

What are examples of graded potential?

A
  • Generator potentials at sensory receptors
  • Postsynaptic potentials at synapses
  • Endplate potentials at NMJ (skeletal muscle)
  • Pacemaker potential in pace maker tissues
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6
Q

What are properties of graded potentials?

A
  • Electrotonic potentials
  • Decremental potentials
  • Non-propagated potentials
  • Local potentials
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7
Q

Why are graded potentials decremental and non-propagated?

A

As you further away from the site of stimulus, more current leaks out along the membrane and as a result the membrane potential gets smaller and smaller

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8
Q

Where can graded potential signal stimulus intensity?

A

In their amplitude

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9
Q

What is meant by graded potentials being graded?

A

A stronger stimulus would open more channels, creating a bigger current flow and therefore a bigger potential

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10
Q

Why can graded potentials be depolarising or hyperpolarising?

A
  • Firing an AP depends on reaching a firing threshold.

- Graded potentials can therefore excite or inhibit a cell

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11
Q

What do EPSPs or IPSPs depends on?

A

Which ion channels are opened

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12
Q

Opening which ion channels would cause hyperpolarisation?

A

Potassium and chlorine

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13
Q

What would opening potassium and chlorine channels do?

A
  • Causes hyperpolarisation
  • Takes them away from threshold
  • IPSP
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14
Q

What would opening Na and Cl channels do?

A
  • Causes depolarisation
  • Takes then towards threshold
  • EPSP
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15
Q

What are ligand-gated ion channels?

A

Postsynaptic potentials are produced by a neurotransmitter opening or closing ion channels

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16
Q

What are voltage-gated ion channels?

A

Action potentials are produced by depolarisation of the membrane potential opening ion channels

17
Q

Why are graded potentials important in synaptic integration?

A

Graded potentials can summate

18
Q

What is temporal summation?

A

One stimulus that is stimulated again quickly and the second EPSP adds on.

19
Q

What is spatial summation?

A

When 2 separate stimuli add together

20
Q

What is integration?

A

Looking at all of the inputs and deciding whether or not to send one of those long distance signals (AP)

21
Q

What is synaptic integration?

A

The process of summing all those inputs in space and time to determine whether or not the initial segment reaches threshold

22
Q

What do IPSPs tend to do?

A

Stop the cell reaching threshold