Session 3 Flashcards
(16 cards)
What allows membrane potentials to be set up?
The membrane is selectively permeable to different ions
How are membrane potentials measured?
Using a fine micro electrode that penetrates the cell membrane
When is a resting membrane potential reached?
When the membrane potential and outward movement of K+ ions comes to an equilibrium
Why is the resting membrane slightly less negative than Ek?
The membrane is not perfectly selective to K+, so other channels are open
What accounts for the very negative resting membrane of skeletal muscle?
Membrane is permeable to K+ and CL- so the resting membrane potential lies close to both Ecl and Ek (-90mV)
Give the values of Ek, Ena, Ecl and Eca
Ek: -95mV
Ena: +70mV
Eca: +122mV
Ecl: -96mv
What happens to the membrane potential when the membrane permeability to an ion is increased?
It moves towards the equilibrium potential for that ion
What is the equilibrium potential for an ion?
The membrane potential at which there is no net movement of the ion across a perfectly selectively permeable membrane
What is fast and slow synaptic transmission?
Fast - receptor protein is an ion channel
Slow - receptor protein and ion channel are separate - they are linked either by G proteins or intracellular messengers
Explain how excitatory transmitters work
They open ligand gated channels that cause depolarisation (Na+, Ca2+, anions in general). The resulting change in potential is called an excitatory post-synaptic potential. They have a longer time course than an AP (~20ms) and are graded with the amount of transmitter. Transmitters include ACh and glutamate.
Explain how inhibitory transmitters work
They open ligand gated channels that cause hyperpolarisation (K+, CL-), leading to an inhibitory post synaptic potential. Transmitters include glycine and GABA.
What happens to the membrane potential when the membrane permeability to an ion is increased?
It moves towards the equilibrium potential for that ion
What is the equilibrium potential for an ion?
The membrane potential at which there is no net movement of the ion across a perfectly selectively permeable membrane
What is fast and slow synaptic transmission?
Fast - receptor protein is an ion channel
Slow - receptor protein and ion channel are separate - they are linked either by G proteins or intracellular messengers
Explain how excitatory transmitters work
They open ligand gated channels that cause depolarisation (Na+, Ca2+, anions in general). The resulting change in potential is called an excitatory post-synaptic potential. They have a longer time course than an AP (~20ms) and are graded with the amount of transmitter. Transmitters include ACh and glutamate.
Explain how inhibitory transmitters work
They open ligand gated channels that cause hyperpolarisation (K+, CL-), leading to an inhibitory post synaptic potential. Transmitters include glycine and GABA.
