8. Changing Membrane Potentials Flashcards
When are they used?
Action potentials in nerve and muscle cells
Triggering and control of muscle contraction
Control of secretion of hormones and neurotransmitters
Transduction of sensory information into electrical activity by receptors
Postsynaptic actions of fast synaptic transmitters
Depolarisation definition
Decrease in size of membrane potential from its normal value
Cell interior becomes less negative
Hyperpolarisation definition
Increase in size of membrane potential from normal value
Cell interior becomes more negative
How do membrane potentials arise?
As a result of selective ionic permeability, changing selectivity between ions will change membrane potential
What happens if you increase membrane permeability to a particular ion?
It moves the membrane potential towards the equilibrium potential for that ion
What does opening K+ or Cl- channels cause?
Hyperpolarisation
What does opening Na+ or Ca2+ channels cause?
Depolarisation
Nicotinic acetylcholine receptors
At neuromuscular junction Have intrinsic ion channel Opened by binding of acetylcholine Channel lets Na+ and K+ through Moves membrane potential towards 0mV, between Ena and Ek
Ligand gating
Channel opens or closes in response to binding of chemical ligand
Channels that respond to extracellular or intracellular transmitters
Voltage gating
Channel opens or closes ion response to changes in membrane potential
Channels involved in action potentials
Mechanical gating
Channel opens or closes in response to membrane deformation
Where do synaptic connections occur?
Nerve cell - nerve cell
Nerve cell - muscle cell
Nerve cell - gland cell
Sensory cell - nerve cell
Fast synaptic transmission
Receptor protein is also an ion channel
E.g. ACh
Transmitter binding causes channel to open
Excitatory synapses
Transmitters open ligand gated channels, cause membrane depolarisation
Can be permeable to Na+, Ca2+
Causes excitatory post-synaptic potential (EPSP)
Longer tie course than AP
E.g. acetylcholine, glutamate
Inhibitory synapses
Transmitters open ligand-gated channels, cause hyperpolarisation
Permeable to K+ or Cl-
E.g. glycine, GABA
