Flashcards in M&R 3.1 - Resting Membrane Potential and Changing Membrane Potential Deck (25):
What is the resting potential range for animal cells?
-20mV to -90mV
What is the resting potential range for nerve cells?
-50mV to -75mV
What is the resting potential range for smooth muscle cells?
What is the resting potential range for cardiac and skeletal muscle cells?
-80mV to -90mV
At rest, which ion dominates permeability?
- More inside the cell than out so moves out of cell
How does the domination of K+ create a potential?
- Open K+ channels dominate membrane ionic permeability at rest
- No net movement of K+ but there is a negative membrane potential
- Creates an electrical gradient which draws K+ back in
What is the Nernst equation used for?
The application of the balance between electrical and chemical gradients to give the membrane potential at which the specific ion will be in equilibrium
How do voltage gated ion channels indirectly affect the membrane potential?
- Have spontaneous opening and closing
- Leakage of Na+ or K+ into the cell makes the membrane less negative
- Leakage of Cl- into the cell makes the membrane more negative
Why is the resting potential of nerve cells and cardiac muscle not exactly Ek?
It's slightly less negative due to the membrane not being perfectly selective for K+
Describe the selectivity of smooth muscle for K+
Lower due to higher contribution from other channels which results in a more positive resting potential
Why is the resting potential of skeletal muscle close to both Ek and Ecl?
Both Cl- and K+ channels are open
What does a change in permeability of a membrane do to the membrane potential?
Membrane potential moves closer to Ep for the specific ion
What is the definition of depolarisation?
The DECREASE in size of the membrane potential from its normal value therefore causing the inside of the cell to become LESS negative
What is the definition of hyperpolarisation?
The INCREASE in size of the membrane potential from its normal therefore causing the inside of the cell to become MORE negative
Give an example of a less selective ion channel. How does it work?
- Nicotinic acetylcholine receptor at the neuromuscular junction
- Ach binds which causes the channel to open
- Influx of Na+ and K+
- Moves membrane potential to around 0mV which is between Ena and Ek
Name the three types of gating
- Ligand e.g. Synapses
- Voltage (respond to a change in membrane potential)
- Mechanial e.g. Stretch receptors
What are the two types of synapse?
- Fast (excitatory and inhibitory)
Describe a fast synapse
The receptor proteins is also an ion channel
What is an excitatory post synaptic potential?
- A depolarisation of the membrane due to the positive Ep that increases the chance of generating an action potential on the PSM
- Longer and graded in size depending on the transmitter
- Fast and slow responses
What is an inhibitory post synaptic potential?
- A hyperpolarisation of the membrane due to a negative Ep
Describe a slow synapse
Receptor and channel are separate proteins
Describe how G proteins are used in slow synapses
- G protein is released upon binding of the ligand
- Binds to effector (usually the channel)
- Localised and quite rapid
Describe how intracellular messengers are used in slow synapses
- Bind to an enzyme
- Enzyme converts substrate into a signalling molecule
What are the other two influential factors of membrane potentials?
- Ion concentration
- Electrogenic pumps