transmission between neurons Flashcards
transmission between neurons, neural integration, drugs and neurotransmitters (32 cards)
how do neurons send messages?
via synaptic transmission
chemical process
messages sent across the synapse from one neuron to another (mainly chemical synapses)
what are neurotransmitters?
released from one neuron and attach to another neuron
chemical messengers
initiates reaction that ultimately results in postsynaptic potential
what are presynaptic neurons?
neuron that releases the neurotransmitter
what are postsynaptic neurons?
neuron that receives the neurotransmitter
what is a synapse?
junction between two neurons
terminal buttons and membrane (normally of dendrite)
what are synaptic vesicles?
some vesicles are made in the soma and transported to the button
other vesicles made by recycling from those that have already released neurotransmitters
how wide is the synaptic cleft?
20nm wide
what are astrocytes?
clear away any neurotransmitters
what is the process of synaptic transmission?
action potential arrives at terminal button
Ca channels open, Ca2+ enters (due to diffusion and electrostatic pressure)
vesicles fuse with membrane and Ca makes pore open and widen
release of neurotransmitters (exocytosis)
neurotransmitter diffuses across the cleft and binds to postsynaptic membrane
binding has an effect on the channels - opens or closes
open channels permit flow of ions, which channels polarisation of membrane and has excitatory or inhibitory effect
what is EPSP?
excitatory postsynaptic potential
what is IPSP?
inhibitory postsynaptic potential
what is binding?
neurotransmitter diffuses across the cleft and binds to binding site on postsynaptic membrane (altering the membrane potential - postsynaptic potential)
specific neurotransmitter binds to specific site
postsynaptic potential depends on which ion channel is opened
what happens when sodium channels opened?
sodium enters
depolarisation
excitatory postsynaptic potential
what happens when potassium channels opened?
potassium leaves
hyperpolarisation
inhibitory postsynaptic potential
what is an ionotropic receptor?
contains binding site and ion channel
opens when molecule attaches to binding site
direct way of opening ion channel
what is a metabotropic receptor?
contains binding site
initiates chain reaction that eventually opens ion channels
requires energy
postsynaptic potentials slower than those produced by ionotropic receptors
indirect ways of opening ion channel
what happens at termination?
reuptake
enzymatic deactiviation/degradation
what is reuptake?
transmitter is taken back by the presynaptic terminal via transporter molecules
what is enzymatic deactiviation/degradation?
transmitter broken down by an enzyme
what does excitatory mean?
increases likelihood of neuron firing
what does inhibitory mean?
decreases likelihood of neuron firing
what is integration?
summation of post synaptic potentials in control of neuron firing
does an inhibitory postsynaptic potential always inhibit behaviour?
no
inhibition of inhibitory neurons = more likelihood of behaviour
excitation of inhibitory neurons = less likelihood of behaviour
what is GABA?
gamma aminobutyric acid
most abundant inhibitory neurotransmitters in CNS
reduces chances of neuronal firing
