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ICPP > 6 - Resting Membrane Potential > Flashcards

6 - Resting Membrane Potential Flashcards

1
Q

What are the resting membrane potentials for:

- Cardiomyocytes

- Neurones

- Skeletal myocytes

- Smooth myocytes

A

-80 mv

-70 mv

-90 mv

-50 mv

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2
Q

How is the membrane potential measure?

A
  • 2 electrodes
  • Microelectrode (fine glass pipette) filled with conducting solution (KCl) that can penetrate cell membrane
  • Diamter of electrode 1 um
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3
Q

What is the resting potential?

A

The electrical charge across a membrane, expressed as the intracellular potential. (mV)

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4
Q

What is the range of resting potentials for animal cells and nerve cells and what cells have the largest resting potential?

A
  • -20 to -90 mv
  • Nerve -50 to - 75 mv
  • Cardiac (-80) and Skeletal muscle (-90)
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5
Q

What are the concentrations of Na, Cl, A, K intracellularly and extracellularly?

A
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6
Q

Why is there a concentration difference extracellulary and intracellularly in ions?

A

Membrane is selectively permeable due to different ion channels

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7
Q

How is the resting potential generated?

A
  • Membrane permeable to K+ as K+ channels open
  • K+ diffuses out of the cell down it’s concentration gradient
  • Anions cannot leave cell as membrane not permeable to them
  • Generates electrochemical gradient, K+ reaches equillibrium due to electrochemical gradient
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8
Q

How do you work out the membrane potential for a particular ion at equilibrum and why is it not always equal to the actual membrane potential?

A
  • Nernst equation (Ek)
  • Membrane not selectively permeable to the one ion alone
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9
Q

What is the resting potential compared to Ek like in:

  • Cardiac and Nerve cells
  • Smooth muscle cells
  • Skeletal muscle
A

ALL Ek -95mV

  1. Almost the same, membrane permeable to K+
  2. Lower, -50mV, membrane less permeable to K+
  3. In between Ek and Ecl as cells permeable to Cl too
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10
Q

What can changes in membrane potential do?

A
  • Trigger AP
  • Trigger and control muscle contraction
  • Control secretion of hormones and neurotransmitters
  • Post synaptic actions of fast synaptic transmitters
  • Transduce sensory information into electrical activity
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11
Q

What are the equilibrium potentials for all of the main ions?

A
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12
Q

What changes membrane potential and what are the causes of hyper and depolarisation?

A

CHANGING IONIC PERMEABILITY

Hyper: Opening Cl- or K+ channels

De: Opening Ca2+ or Na+

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13
Q

What is a more accurate way of working out the membrane potential?

A
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14
Q

What are the characteristics of the acetylcholine receptor?

A
  • Opened by acetylcholine
  • Allows cations through, mainly Na, but not fully selective
  • Moves membrane potential towards 0 as average of ENa and EK
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15
Q

How can membrane potential change?

A

Changing permeability of the membrane due to

  • Ligand gated channels
  • Mechanical gated channels
  • Voltage gated channels
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16
Q

What happens during fast synaptic transmission?

A
17
Q

What happens at a excitatory synapse?

A
  • Ligand opens depolarising channels, Na and Ca
  • Change in membrane potential is called EPSP (excitatory post synaptic potential)
  • Longer than AP
  • Graded by amount of neurotransmitter
  • Acetylcholine and glutamate
18
Q

What happens at an inhibitory synapse?

A
  • Transmitter opens hyperpolarising channels so membrane permeable to K+ and Cl-

- IPSP

Glycine and GABA

19
Q

What happens during slow synaptic transmission?

A

Receptor is not an ion channel, channel is signalled to open in other ways

20
Q

What other factors can affect membrane potential apart from ion permeability?

A
  1. Ion concentration changes extracellularly (e/g eating bananas)
  2. Electrogenic pumps (Na/K ATPase)
21
Q

What is bad about high potassium levels in the blood?

A

HYPERKALEMIA (above 4.5 mmol, 6 severe)

Leads to excitable cells as less K+ leaves cells as less of a concentration gradient so membrane potential less negative and closer to threshold

- Tachycardia

- Palpatations

- Muscle spasms

ICPP (12 decks)

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