Neurophysiology - Neurotransmitters Flashcards
Neurotransmitters (8) - Definition and Regulation
Chemical messengers, released at a synapse by a pre-synaptic neuron, responsible for transferring info to a post-synaptic cell (target).
Regulated by other transmitters acting on the pre-synaptic neuron (modulators), either increase or decrease synaptic activity.
- Acetylcholine
- Glutamate
- Gamma amino butyric acid
- Melatonin
- Epinephrine
- Norepinephrine
- Dopamine
- Seratonin
What makes a Neurotransmitter? (5)
Synthetized by a neuron.
Present in a vesicle of a pre-synaptic neuron and released in a sufficient amount.
If provided artificially: mimics action of body substance perfectly.
Decreases a specific mechanism to regulate its action, removing it from the synaptic cleft if necessary.
Able to bind to a post-synaptic receptor.
Acetylcholine (ACh)
Excitatory and inhibitory, depending on the post-synaptic receptor.
Can be found everywhere in the brain and spinal cord. Also present in PNS, activating muscle contraction in gastrointestinal system, and in ANS -> cardiac muscle.
Acetylcholine Receptors (2)
Nicotinic: excitatory response in neuromuscular junctions.
Muscarinic: Excitatory and inhibitory response in encephalon.
Important role in muscle contraction (peripheral) and processes involving memory consolidation (central).
Glutamate (Glu) - Function and Receptors
Most common excitatory NT in the CNS. Involved in cognition, memory consolidation and learning.
Most cells can produce enough Glu to produce excitatory effects in some systems. NMDA and AMPAR post-synaptic receptors.
Gamma Amino Butyric Acid (GABA) - Synthesis and Function
Synthetized directly from Glu.
Most abundant, important inhibitory NT in CNS. Plays a role in control, avoiding over-excitation of neurons.
Almost all neurons produce GABA, and have receptors for it.
Lack of GABA can lead to epilepsy, panic disorders and movement disorders.
GABAergic Drugs
Affect the whole brain, body!
Sedative, patients will have fatigue, reduced memory span and attention span.
Brain adapts to the drugs, destroying GABA receptors and reducing production which becomes a big problem when patient stops taking the drugs.
Melatonin (MEL) - Production and Function
Produced in hypophysis and epithalamus.
Responsible for regulating sleep-wake cycles, also having an impact on immunological system.
We need serotonin to produce melatonin.
Epinephrine (EPI) - Function and Production
Produced in adrenal glands.
Stress response. Increasing focus, muscle activity, heart rate, blood sugar levels, diameter of pupils in stressful situations.
Burns reserves you might need later.
Dopamine (DA) - Synthesis and Function
Synthesis: amino acid tyrosine -> DOPA -> Dopamine.
Modulate search for reward system, regulating motor activity, mood, motivation and attention.
Goal-Directed behavior (motivation), not released when the outcome is known.
Increases release of BDFN & GNF.
↑ DA: Better movement, faster automatic response, ↑ attention, ↑ motivation.
Dopaminergic Pathways (3)
- Mesocortical
- Mesolimbic
- Nigrostriatal
Regulation of movement
Regulation of automatic reaction
Regulation of attention
Motivation
Dopaminergic Pathways - Mesocortical Pathway
Associated with goal-directed behavior. attention and motivational responses.
From ventral tegmental area (VTA) to the PFC and aCC.
Dopaminergic Pathways - Mesolimbic Pathway
Associated with goal-directed behavior, pleasure and emotional processes.
From ventral tegmental area (VTA) to AM.
Dopaminergic Pathways - Nigrostriatal Pathway
Associated with movement coordination, attention and adaptation.
Substantia Nigra(SN) to dorsal striatum.
DA Receptors
D1-D6.
D2 opens channels that permit reuptake of DA from synapse to pre-synaptic neuron.
Nicotine, caffein and cocaine bind to D2 receptors, closing the channels, inhibiting the reuptake of DA -> ↑DA.
Norepinephrine (NE) - Production, Function and Receptors
Produced in Locus Coeruleus (LC).
Action on sleep, wakefulness, feeding behavior and affecting attention and memory consolidation, leading CNS to a state of high alert.
NE alpha and beta receptors, primarily excitatory, play a role in fear-fight-flight-freeze system.
Norepinephrine - Network
AM and LC are in a excitatory loop, activate each other. LC has a inhibitory affect on EPT (melatonin), affecting sleep. AM and aCC are in a inhibitory loop, stopping the excitatory cycle (LC-AM).
AM -> HPT -> HYP -> SRG -> ↑Cortisol -> ↓BDFN, GNF -> aCC. AM can inhibit aCC in this way aswell.
Serotonin (SE) - Production and Function
Produced in the Raphe nuclei.
Released when we engage in a situation that gave us pleasure (can be a threat being destroyed).
Ser, serotonin receptors have:
Behavioral effects: modulates mood, perception, memory, anger, aggression, fear, appetite, sexuality, stress response, addiction.
Influences: motor control, cerebellar function, circadian rhythm, vascular tone in CNS, respiratory drive and body temp.
Oxytocin (Ox) - Production, Function and Receptors
Produced in HPT under a positive feedback loop, released over HYP.
Receptors found on in hippocampal formation, BN and brainstem.
Effects of Ox on AM: emotional attachment.
Endorphins (END) - Production, Function and Concentration(high&low)
Produced in the HYP. Makes us less aware of perception of pain (emotional and physical).
Low concentration: Sensation of anxiety and increased awareness of pain.
High concentration: Sense of euphoria and pleasure, with suppression of physical and emotional pain.
DA and Addiction
Pathway involved nigrostriatal and VTA-AM projections. Caffeine, cocaine, nicotine and amphetamine inhibit reuptake of DA, Increasing the DA levels in synaptic bouton.
Histamine - What is it and its function
Chemical messenger. Something between a neurotransmitter and hormone. Mediating cellular responses to allergens, inflammatory processes and gastric acid secretion.
How does Histamine reach the brain and what affect does it have?
Histamine does not cross the blood brain barrier. Histamine releasing neurons are re located in the hypothalamus and project to practically all brain regions. Bring histamine into brain and release it.
Hyperactive reaction of fear, anxiety so you run away from the threat.
Adverse Effects of Histamine Release (7)
Itching sensation
Hypotension
Tachycardia
Bronchospasm
Angioedema
Disruption of cardiac rhythm
Increased secretion of gastric acid that can lead to ulcers.
