Neurotransmitters Flashcards
Define neurotransmitter
Chemical messengers released at a synapse by a pre-synaptic neuron, responsible for transferring information to the post-synaptic cell. They are regulated by modulators (other neurotransmitters) that will either amplify or damp synaptic activity. One neuro transmitter can bind to several receptors, therefore the effect of the active synapse is determined by the receptor itself rather than the neurotransmitter.
What are the 5 criteria of a neurotransmitter
1) it is synthesized by a neuron
2) it is present in the vesicles of the pre-synaptic neuron and can be released in a sufficient amount to exert an action on the target
3) if provided artificially, it can mimic the action of the body substance perfectly
4) it subsides a specific mechanisms to regulate its action, removing it from the synaptic cleft if necessary
5)it is able to bind with post synaptic receptors
Describe acethylcholine
- cholinergic transmitter
- cholin precursor required
- can be found everywhere in the brain and spinal cord
- also found in the PNS : controls the muscle contraction in gastrointestinal muscles and cardiac muscle
What are the acethylcholine receptors ?
- muscarinic : excitatory and inhibitory response in the encephalon
- nicotinic : excitatory response on neuromuscular junctions
Main roles :
Muscles contraction
Memory consolidation
Define glutamate
Most common excitatory neurotransmitter found in the CNS
Involved in cognition, memory consolidation and learning process
What are the main receptors of glutamate ?
NMDA
AMPAR
Define GABA
Directly synthesized from glutamate
Most important and most common inhibitory neurotransmitters in the CNS
Plays a role in control
Define melatonin
Produced in the hypophysis outside the blood brain barrier and in the epithalamus
Melatonin is responsible for regulating the sleep wake cycles also having an impact on immunological system
Describe the “melatonin cascade”
Tryptophan
5-hydroxy-tryptophan
Serotonin
N-acetylserotonin
Melatonin.
Define epinephrine
Produced in the adrenal glands as a stress response
Neurotransmitters : alpha and beta mainly excitatory
It is responsible for increasing the irrigation in certain muscles, increasing heart rate and blood sugar levels
Increases the diameter of pupils in stress situations
Define dopamine
Synthesized from amino acid tyrosine that develops into DOPA. After a quick process of decarboxylase, DOPA is transformed into dopamine.
Very unstable outside nervous system, usually desintegrated in a few seconds
Modulate the search for reward system
Regulates motor activity, mood, motivation and attention
Describe the catecholamine synthesis
L-tyrosine —> L-DOPA—> Dopamine —> noradrenaline—> Adrenaline
What are the dopaminergic pathways and their functions ?
1) mesocortical pathway
Goal directed behavior, attention and motivational responses
2) Mesolimbic pathway
Goal directed behavior, pleasure and emotional processes
3) nigrostriatal pathway
Movement coordination, attention and adaptation
What are the dopamin receptors ?
D1-cerebral cortex
D2-striatum
D3-limbic system
D4-PFC
D5-hippocampus
Define norepinephrin
Used by neurons in the locus coeruleus with action on sleep, wakefulness, feeding behavior and affecting attention and memory consolidation leading the CNS in a state of high alterness
What are the receptors of norepinephrin ?
NE alpha
NE beta
Both being primarily excitatory, playing a role in fear, flight-fight-freeze system
Define serotonin
Produced by brainstem nuclei with pathways leading to the hypothalamus and dorsal spinal cord Rexed laminae
What are the receptors for serotonin ?
1A
1B
1D
2A
2C
Ser3
Ser4
Ser5
Ser6
Ser7
What are the functions of serotonin ?
Ser modulates mood perception memory anger aggression fera appetite sexuality stress response and addiction
Ser also has an indirect influence on motor control cerebellar function circadian rhythm vascular tone in CNS respiratory drive and body temperature
Describe DA, NE and SE behavior
DA increase up to fear
NE increase up to distress
SE increase up to disgust
In zero they are in shame
Define oxytocin
Produced by the hypophysis under a positive feedback loop and released to the body under the hypophysis
What are the receptors for oxcytocin ?
OXTR
OTR
Can be found in the hippocampal formation, basal nuclei and brainstem
What are the effects of oxcytocin ?
- uterin contractions (facilitating birth)
- contraction around prostate during ejaculation
- associated to emotional dependency
Define endorphins
Produced by neurohypophysis they can also be synthetized by lymphocytes
The body can produced at least 20 different types of endorphins
Beta endorphin is the one with the most effects
Beta endorphins can bind to opioid receptors in the spinal cord ganglia and in the encephalon
