Week 5: Neurotransmitters Flashcards
receptors can be found on?
soma/cell body & dendrites
What is a neurotransmitter
chemical messenger molecules that transmit signals from a neuron to a target cell across a synapse
Why do we need neurotransmitters?
action potentials cannot jump from one cell to another
What is the qualities that make a neurotransmitter?
It has to be synthesized, stored and released by the neuron
What is the point of neurotransmitters?
they exert excitatory or inhibitory effects on the neuron depending on specific neurotransmitter eg. GABA inhibitory, glutamate excitatory
how does glutamate exert an excitatory effect
when glutamate binds to receptors, sodium channels open up, making the inside of the postsynaptic neuron less negative. there is an influx of positive ions into the cell. hence, the membrane potential becomes closer to the threshold (-55 mV) and increases the likelihood of an AP occuring.
How does GABA exert an inhibitory effect
the inhibitory neurotransmitter binds to the post-synaptic receptor, causing chloride channels to open, influx of negative ions into the cell, causing the membrane potential to be further away from threshold, and ceasing the message being passed by preventing initiation of AP occurring
What effect can acetylcholine have on AP?
Inhibitory and Excitatory
What happens to neurotransmitters once they have an effect on AP
- destroyed by specific enzymes
- reabsorbed by presynaptic terminal
- absorbed and recycled by glial cells
why must neurotransmitters be removed?
prevent overstimulation of post synaptic cells
What is one way in which neurotransmitters transit their signal in the post-synaptic neuron
- Ionotropic neurotransmission eg. glutamate receptors open and close in response to NT binding
What is another way in which neurotransmitters transit their signal in the post-synaptic neuron
- metabotropic neurotransmission eg. senses ligang binding and activates secondary messengers like other effector proteins, which causes signalling cascades within the cell
What are the major neurotransmitters
- amino acids (amino acidergic)
- classical amine neurotransmitters
What is a characteristic of amino acids
fast neurotransmission
What is a characteristic of classical amine neurotransmitters
slower neurotransmission
What neurotransmitters fall under amino acids?
glutamate and GABA
What neurotransmitters fall under classical amine groups?
dopamine, norepinephrine, epinephrine (catecholaminergic), serotonin (serotonergic), acetylcholine (cholinergic)
What is the main precursor for classical amine nt
Tyrosine
Tyrosine hydroxylase rate-limiting enzyme
serotonin is synthesised from?
tryptophan
Where is serotonin produced
in the intestine
Serotonin effects?
appetite, mood, behavior, memory, learning
what are the two main receptor families involved with acetycholine?
nicotinic and muscarinic
Why care about neurotransmitters?
it can increase potential for many drug targets
what is a graded potential?
a localised change in membrane potential that acts as the stimulus for the neuron, to either bring a neuron to threshold and initiate AP (EPSP) or the opposite effect to prevent an AP (IPSP)
What is an EPSP
a local change in the membrane potential that makes a post synaptic neuron more likely to generate AP
EPSPS can summate for a larger net effect to make the post-synaptic neuron __ likely to produce an AP
more
what are the two types of summation?
spatial (enough synapses close together)
temporal (post-synaptic membrane is depolarised in rapid succession)
What is IPSP
local changes in the membrane potential that makes post-synaptic neuron less likely to generate an ap.
