Neurotransmitters Flashcards
What does action potential cause in presynaptic neuron?
Opening of voltage-gated Ca2+ channels
What does opening of voltage-gated Ca2+ cause?
Ca2+ influx
What does Ca2+ influx cause?
Neurotransmitter-filled vesicles to fuse with cell membrane
What happens after neurotransmitter-filled vesicles fuse with cell membrane?
Neurotransmitter is released into synaptic cleft and binds to receptors
What happens when neurotransmitter binds to receptors on post-synaptic neuron?
Causes ion channels to open and result in ion influx into postsynaptic neuron
Criteria for a substance to be a neurotransmitter:
Synthesised in pre-synaptic neuron
Stored presynaptically
Released on demand
Inactivated
What things can happen to the neurotransmitter in synaptic cleft?
Re-uptake
Enzymatic inactivation + degradation
Diffusion
What causes synthesis of neurotransmitter?
Uptake of precursors
What happens after neurotransmitter is synthesised?
Transport/uptake into vesicles
What happens to excess neurotransmitter?
Degradation
What happens after neurotransmitter interacts with postsynaptic receptors?
Inactivation
Reuptake of neuotransmitters:
Re-uptake by nerve terminal
Re-uptake and release by non-neuronal cells
Characteristics of receptors for neurotransmitters?
Specific
May be more than one types of receptor for neurotransmitter
What influence a receptor’s response to a neurotransmitter?
Patterns of expression and receptor type
Types of receptors:
Ionotropic
Metabotropic
What groups are neurotransmitters classified in?
Amino acids
Biogenic amines
Peptides
Examples of amino acid receptors:
Glutamate
GABA
Glycine
What is glutamate like?
Amino acid
Primary excitatory neurotransmitter in central nervous system
What’s Glutamate involved in?
Memory
Learning
Cell death
What does GABA stand for?
Gamma-aminobutyric acid
What is GABA like?
Amino acid
Principle inhibitory neurotransmitter in central nervous system
What does GABA act via?
Via chloride channels - so takes membrane potential away from threshold
What is Glycine like?
Amino acid
Second most common inhibitory neurotransmitter in central nervous system
Primary inhibitory neurotransmitter in spinal cord and brainstem
What is the post-synaptic action of glutamate mostly?
Via ionotropic receptors
Types of receptors for glutamate:
NMDA
Kainate
AMPA
NMDA receptors:
Calcium ions
Kainate receptors:
Sodium and potassium ions
AMPA receptors:
Permeable to cations (e.g. calcium, sodium and potassium)
Distribution of glutamate:
Neurons spanning hemispheres
Neurons descending to brain stem or spinal cord
(Dys)functions off glutamate:
Synaptic plasticity
Excitotoxicity
Migraine
Epilepsy
What is synaptic plasticity?
Synapses are strengthened or weakened by feedback mechanisms
What is involved in excitotoxicity?
Excessive stimulation of NMDA receptors cause large influx of Ca2 ions - can result in cell depth
How is glutamate associated with epilepsy?
Excessive excitation causes feedback loop
How can epilepsy begin as?
Partial seizures
What happens if epilepsy becomes more uncontrolled?
Grand Mal seizures
What can seizures be treated with?
Phenytoin
Benzodiazepines
What does Phenytoin do?
Increases refractory period esteem firings in voltage gated sodium channels
What do benzodiazepines do?
Increase action of GABA - as inhibitory
How do benzodiazepines work?
Act on separate receptor binding site on GABA - leads to channel opening more often
Where is GABA found?
Predominantly in interneurons of CNS
Striatum and globes pallidus
What does GABA act on?
Ligand gated chloride channels
What is GABA inactivated by?
Presynaptic reuptake
What does alcoholism do to GABA?
Changes GABA transmission
Leads to withdrawal results in convulsive movements and seizures
How can GABA effected by alcoholism be treated with?
Benzodiazepines and phenytoin
What’s tetanus caused by?
Toxin from clostridium tetani
What happens in tetanus?
Inhibits glycine release
Mild effects of tetanus:
Restricted to muscles innervated by cranial nerves
Serious effects of tetanus:
Epileptiform fits
What’s tetanus treated with?
Anti-toxin and benzodiazepines
Give examples of Biogenic Amines:
Catecholamines
Indolamines
Examples of catecholamines:
Dopamine
Noradrenaline
Adrenaline
What is dopamine involved with?
Neuromodulator
Pleasure, addiction and movement
What’s noradrenaline also known as?
Norepinephrine
What’s noradrenaline involved with?
Sympathetic nervous system
What’s a decrease of noradrenaline usually seen in?
Parkinson’s and ADHD
What is adrenaline involved with?
Sympathetic nervous system
Peripheral hormone from adrenal medulla
What’s adrenaline also known as?
Epinephrine
What are all catecholamines synthesised in?
Bouton
What are all catecholamines principally inactivated by?
Re-uptake
What are adrenoceptors?
G-protein linked metabotropic receptors
What’s the locus coeruleus associated with?
Sleep
Wakefulness
Alertness
Attention
What’s the medulla/hypothalamus associated with?
Feeding behaviour
Blood pressure regulation
What are dopaminergic receptors?
G-protein linked metabotropic receptors
What’s Nigrostriatal associated with?
Motor control
What’s Mesolithic and mesocortical associated with?
Behavioural effects
What’s tuberohypophyseal system associated with?
Endocrine control, via anterior pituitary
What structures are involved with noradrenaline pathways in brain?
Locus coeruleus
Medulla/hypothalamus
What receptors are found in noradrenaline pathways?
Adrenoceptors
What structures are involved with dopamine pathways in brain?
Nigrostriatal
Mesolimbic and mesocortical
Tuberohypophyseal system
What receptor is found in dopamine pathways?
Dopaminergic
Effects of dopamine:
Parkinson’s
Schizophrenia
Addiction
Examples of catecholamines:
Noradrenaline
Adrenaline
Dopamine
Examples of indolamines:
Serotonin
Receptors in serotonin pathways:
Large family of both excitatory and inhibitory receptors in CNS and PNS
What does serotonin modulate?
A range of neurotransmitters such as glutamate, GABA and dopamine
What structures are involved with serotonin pathways in the brain?
Locus coeruleus
Raphe nuclei
What’s locus coeruleus associated with?
Sensory signals
What’s raphe nuclei associated with?
Sleep
Wakefulness
Mood
Effects of serotonin:
Depression and OCD
Give examples of peptide based neurotransmitters:
Encephalin
Endorphin
Dynorphin
Where are peptides made?
In cell body and transported to bouton
What are peptide generally?
Neurotransmitters or neuromodulators
Effects of endorphins and encephalins:
Pain
Emotional perception
What causes pain?
Endorphins and encephalins act on opioid receptors as endogenous ligands
What do opioids do?
Cause downregulation of opioid receptors in CNS
Give an example of an ester based neurotransmitter:
Acetylcholine
Where’s acetylcholine found?
Peripheral and central nervous system
At neuromuscular junction
What are neurons like in CNS?
Project to hippocampus and cortex
What are hippocampus and cortex essential for?
Formation of new memories and learning
What’s Alzheimer’s disease associated with?
Dysfunction of ACh in CNS
What’s ACh?
Acetylcholine
What does nicotine do?
Acts on nicotonic ACh receptors
What do anticholinesterases do?
Prevent breakdown of ACh + prolong its activity
Can be therapeutic but also toxic
