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Cell Physiology And Pharmacology > Changing Membrane Potentials > Flashcards

Changing Membrane Potentials Flashcards

1
Q

What is the main purpose of changes in membrane potential?

A

It underlies many forms of signalling between and within cells

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2
Q

Give 3 examples of signalling involving changes in membrane potential

A
  • Action potentials is nerve and muscle cells
  • Triggering and control of muscle cells
  • Control of hormone and neurotransmitter secretion
  • Transduction of sensory information
  • Postsynaptic actions of fast synaptic transmitters
  • Regulation of smooth muscle tone
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3
Q

What is depolarisation and what is its effect?

A
  • Decrease in the size of the membrane potential from its normal value
  • Cell interior becomes less negative
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4
Q

What is hyperpolarisation and what is its effect?

A
  • Increase in the size of the membrane potential from its normal value
  • Cell interior becomes more negative
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5
Q

How are membrane potentials created?

A

Result of selective ionic permeability

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6
Q

What is an equilibrium potential in terms of ions and membranes?

A

Membrane potential of an ion when there is no net movement of ions

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7
Q

What is the effect of increasing membrane permeability on equilibrium potential?

A

Moves the membrane potential towards the ion’s equilibrium potential

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8
Q

Which channels open during hyperpolarisation?

A

K+ and Cl- Channels

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9
Q

Which ion channels open during depolarisation?

A

Na+ or Ca2+

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10
Q

What does the GHK equation represent?

A
  • Contribution of each ion to the membrane potential

- Depends on membrane permeability to the ion

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11
Q

Give an example of a membrane potential channel that is less selective

A
  • Nicotinic Acetylcholine Receptors

- Ion channels for Na+ and K+ open

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12
Q

What 3 types of gated ion channels contribute to membrane potential?

A
  • Ligand gating
  • Voltage gating
  • Mechanical gating
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13
Q

What is the mechanism of an ion ligand gated channel? Give an example

A
  • Channel that opens or closes in response to a chemical ligand binding
  • Synapse channel responding to extracellular transmitters
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14
Q

What is the mechanism of an ion voltage gated channel? Give an example

A
  • Charged gates that sense depolarisation
  • Channels open or close in response to membrane potential changes
  • Channels involved in action potentials
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15
Q

What is the mechanism of an ion mechanical gated channel? Give an example

A
  • Channel opens or closes in response to membrane deformation (stretch/shrink)
  • Mechanoreceptors in hair cells/carotid sinus stretch receptors
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16
Q

Name 3 cell to cell synaptic connections

A

nerve cell > nerve cell
nerve cell > muscle cell
nerve cell > gland cell
sensory cell > nerve cell

17
Q

What is fast synaptic transmission?

A
  • Receptor protein is also an ion channel

- Transmitter binding causes the channel to open

18
Q

What is an excitatory synapse?

A

A synapse where transmitters open ligand-gated channels that cause membrane depolarisation

19
Q

What is an excitatory post-synaptic potential (EPSP)?

A

A change in membrane potential

20
Q

What is a characteristic and a transmitter involved in excitatory synapses?

A
  • Longer time course than an action potential
  • Graded with amount of transmitter
    Transmitters - Acetylcholine, Glutamate
21
Q

What is the mechanism of an inhibitory synapse?

A

Transmitters open ligand-gated channels that cause hyperpolarisation

22
Q

What ions are involved in inhibitory synapses and what is the effect?

A
  • Permeable to K+ or Cl-

- Moves membrane away from the activity threshold

23
Q

Give an example of a transmitter involved in an inhibitory synapse

A
  • Glycine

- GABA

24
Q

What is slow synaptic transmission?

A

The receptor and channel are separate proteins

25
Q

What are the 2 mechanisms involved in slow synaptic transmission?

A
  • Direct G-Protein gating

- Gating via an intracellular messenger

26
Q

What are the steps involved in slow synaptic transmission using intracellular messengers?

A

Receptor > G-Protein > Enzyme > Signalling Cascade > Intracellular Messenger > Channel

27
Q

Which 2 factors influence membrane potential?

A
  • Changes in Ion concentration

- Electrogenic pumps

28
Q

What is the effect of extreme ion concentration changes on membrane potential?

A

Can alter membrane excitability in vital organs such as the heart

29
Q

Give an example of an electrogenic pump and its mechanism

A
  • Na+/K+ ATPase
  • 3 Na+ out for every 2 K+ in
  • Makes membrane potential slightly more negative
30
Q

What is responsible for the entire membrane potential and what does it set up?

A
  • Active transport of ions

- Sets up and maintains the ionic gradient

Cell Physiology And Pharmacology (17 decks)

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