Excitable cells Flashcards
(36 cards)
ion channels
can be gated by ligands, force, temperature or voltage
or they can be active over the full physiological range= leakage channels
example of ligand-gating
ACh receptor
composed of 5 subunits
once of which alpha contains binding site for ACh
binding causes conformational shift that is transferred to transmembrane domain
opening channel
physical gating
both temperature and pressure act in a way to subtly change the conformation
allowing ion transport
voltage gating
changes in the potential difference in charge across membrane
causes cationic amino acid side chains to initiate conformational change
leak channels
active over full physiological range of voltage
responsible for resting potential
electrochemical gradient of K+ via K2p channels
intracellularly which ion channel maintains
Na+/K+
ATPase that works to distribute cations such that the resting potential is maintained
graded potentials
result of stimulation from a focal stimulus of a receptor either by the world or by upstream neuron
transient and diminish
can change the membrane potential and if they depolarise to the threshold they can generate an AP
action potentials
all or nothing principle
result of two different currents/channel openings, fast Na+ channels followed by slow K+ channels
action potential process
depolarisation reaches the threshold level
na+ channels open
Na+ influx
Na+ channels close and K+ channels open
K+ move out
K+ channels close
Na+/K+ pump resets the membrane potential
action potential propagation
oligodendrocytes in the CNS and Schwann cells in the PNS electrically insulate axons
significantly increasing the speed of conduction through saltatory conduction
where are voltage gated Na+ and K+ channels concentrated
at the nodes of Ranvier
electrical synapses vs chemical
electrical are in the minority
much simpler
can’t encode complex information unlike chemical synapses
what are electrical synapses facilitated by
transmembrane proteins called connexons
synchronise activity of groups of neurons
chemical synapses
action potential arrival triggers the opening of voltage gated Ca2+ channels and Ca2+ influx
drives exocytosis of vesicles
what can neurotransmitters be
small molecules (including amino acids) or peptides
most prominent neurotransmitters
glutamate
gamma aminobutyric, GABA
what type of neurotransmitter is glutamate
excitatory
what type of neurotransmitter is gamma aminobutyric
inhibitory
what is in the image
inotropic
what is in the image
metabotropic NT receptors
where are AChR expressed
throughout the brain and spinal cord
also in skeletal and smooth muscles
what is in the image
ACh recpetor
what is in the image
GABAa receptor
what is in the image
metabotropic receptor
mGluRs
binding of the glutamate induces a conformational change that activates G-proteins which either directly or indirectly open ion channels
