Neurotransmitters Flashcards
name the parts of the neuron
dendrites, soma, axon, synaptic terminal
why does a dendrite have spines?
increase surface area
what happens in the dendrites?
information reception
what happens in the soma?
integration of signals
what happens in the axon?
rapid information transfer (action potential)
how many ms does an action potential take to pass through one neuron to the next?
2
how big is the synapse?
20-100nm
which type of impulse does the dendrite usually receive?
excitatory
which type of impulse does the soma usually receive?
inhibitory
what happens in the presynaptic terminal?
biosynthesis, packaging and release of the neurotransmitter
what happens when the neurotransmitter binds to the receptor?
activation
what happens after receptor activation?
inactivation
what are the three main types of neurotransmitter?
amino acids, amines and neuropeptides
give an example of an amino acid neurotransmitter
glutamate, gamma amino butyric acid, glycine
give an example of an amine neurotransmitter
noradrenaline, dopamine
give an example of a neuropeptide neurotransmitter
opioid peptides
Is glutamate excitatory or inhibitory?
excitatory
Is GABA excitatory or inhibitory?
inhibitory
where is glycine important as a neurotransmitter?
spinal cord
where is noradrenaline an important neurotransmitter?
sympathetic nervous system
does the parasympathetic nervous system slow or increase heart rate?
slows
does the sympathetic nervous system slow or increase heart rate?
increases
what is the variance of concentration of neurotransmitters in the CNS
nM to mM
What is the range of speed of responses a neurotransmitter can produce?
microseconds to milliseconds (rapid) or seconds (slow)
what does the action potential cause at the presynaptic terminal?
voltage gated calcium channels open, calcium influx into cell causing synaptic vesicle exocytosis
what happens when an excitatory neurotransmitter binds to a receptor on the post synaptic membrane?
Na+ flows into cell, causing depolarisation and transmission of an action potential
what happens when a reuptake protein on the presynaptic membrane takes in a neurotransmitter?
reloaded into vesicles
what happens after the neurotransmitter is removed from the cleft?
sodium potassium pumps return membrane potential to resting
what size increase in intracellular calcium concentration does transmitter release require?
less than 1micromolar to 200 micromolar
how many molecules of transmitter in each pre-synaptic vesicle?
4,000-10,000
how fast is influx of Ca2+ ions
ms down to 200microseconds
what happens during the process of electromechanical transduction?
membrane depolarisation, Ca2+ channels open, Ca2+ influx, vesicle fusion, vesicle exocytosis, transmitter release
how do the neurotransmitters get into the vesicles?
protein pumps
what allows the docking of vesicles?
vesicle proteins
what does alpha latrotoxin do and where is it found?
stimulates transmitter release to depletion and produced by black widow spider
what do zinc dependent endopeptidases do and give two examples and what they cause
inhibit transmitter release, tetanus toxin - causes paralysis,
botulinum toxin C causes flaccid paralysis
Is vesicle docking and exocytosis an active or passive process and what does it require?
active, ATP
How are vesicles replenished?
vesicle recycling - protein pumps fill them up
what are the two main classes of neurotransmitter receptor? Relative speed of responses?
ion channel receptor - fast, g-protein coupled receptor -slow
what are the main effectors of the G protein coupled receptor?
enzymes or channels
glutamate and gamma amino butyric acid use which kind of receptor in the CNS?
ion channel
ACh at the neuromuscular junction binding nicotinic receptors uses which kind of receptor?
ion channel
G-protein coupled receptor is used for which neurotransmitters and where?
In the CNS and peripheral nervous system,
ACh at muscarinic receptors in heart tissue, dopamine, noradrenaline, serotonin and neuropeptides
what is the advantage of multiple subunit combinations (5 types of subunit) in an ion channel?
distinct functional properties
Depolarisation or hyperpolarisation?
Glutamate
GABA
Glycine
Depolarisation (Na+)
Hyperpolarisation (Cl-)
Hyperpolarisation (Cl-)
What are the two main types of glutamate receptors?
AMPA and NMDA
AMPA receptors are what kind?
rapid excitatory
NMDA receptors are what kind?
slow component of excitatory transmission
Which ion(s) do AMPA receptors allow influx of and what is the rate of onset, offset and desensitisation?
Na+, rapid
Which ion(s) do NMDA receptors allow influx of? What is their role in the body?
Ca2+ and Na+
Serve as coincidence receptors which underly learning mechanisms
what is a coincidence receptor?
It relies on pre-depolarisation of the post-synaptic membrane to work
how is glutamate reuptaken?
into pre-synaptic bulb and into glial cells
how is glutamate modified in the glial cells?
glutamine synthetase modifies glutamate to glutamine
what happens if there is excess glutamate in the brain?
GABA neurons are stimulated
What happens if excess glutamate levels are not decreased or GABA is not released?
abnormal cell firing leading to seizures
as the glutamate level comes down, what happens to glutamine levels?
they increase slowly as glutamate is broken down
how many people worldwide are affected by epilepsy?
50 million
how many epilepsy seizures are refractory to treatment?
25-30%
How is GABA formed?
decarboxylation of glutamate by glutamic acid decarboxylase (GAD)
which enzyme in the glial cells breaks down GABA?
GABA transaminase
How many subunits make up a GABA a receptor?
5
which 4 types of drugs facilitate GABA transmission?
antiepileptic
anxiolytic
sedative
muscle relaxant
