Synapses and the role of Neurotransmitters Flashcards
What makes up the CNS?
Brain and spinal cord
What makes up the PNS?
Sensory neurones
Motor neurones
Autonomic nervous system (ANS)
What makes up the ANS?
Sympathetic
Parasympathetic
Enteric
What are some neuronal specialisations?
Dendrites
Axons
Axon terminals
Synaptic bouton
What do dendrites do?
Receive input from other neurones
What do Axons do?
Carry out impulse conduction
What is the purpose of the axon terminal?
Release of neurotransmitter
How are neurones classified?
Based on morphological criteria:
Number of processes - uni/bi/multi/pseudo
Dendrites - shape/presence or absence of spines
Connectors - motor/interneurones
Axon length - golgi type 1 / 2
Neurotransmitter
What is a unipolar nerve cell?
a single axonal process
What is a multipolar nerve cell?
nerve cell with multiple axonal processes
What is a bipolar cell?
2 axonal processes
What’s the fastest electrical synapse?
the gap junction
What are some features of the gap junction?
direct transfer of ionic current (also small molecules)
-bi-directional
Where are gap junctions found?
between neurones in the CNS
What type of neurones takes information to the brain
Afferent
What type of neurone takes information away from the brain?
Efferent
What is a chemical synapse?
Unidirectional
Close association between presynaptic axon terminal and post synaptic membrane.
Release of neurotransmitters
How does synaptic transmission work?
- action potential invades the nerve terminal
- depolarisation triggers Ca2+ channel opening causing Ca2+
- Neurotransmitter released by exocytosis
- Neurotransmitter diffuses across the synapse and binds to a receptor
- post synaptic effect
- rapid termination of signal
How is the signal terminated?
- re-upatake of neurotransmitter
- enzymatic breakdown
What is the major excitatory neurotransmitter?
glutamate
What is the major inhibitory neurotransmitter?
GABA
How do neurotransmitter receptors work?
They are membrane spanning proteins that have a structural change when neurotransmitter binds.
- each receptor is specific for a neurotransmitter
- one neurotransmitter can have several receptor subtypes
What can act as neurotransmitters?
- amino acids
- monoamines
- acetylcholine
- neuroactive peptides
What are the two types of receptor signalling mechanisms?
Ionotropic (receptor operated/ligand gated channels)
Metabotropic (G protein coupled)
How does the ionotropic receptor signalling mechanism work?
-trasmitter binding causes a conformational change which causes a channel to open, allowing ion movement
How does the metabotrophic receptor signalling mechanism work?
-transmitter binding causes a conformational change which activates a G protein which activates effector systems which has indirect effects of opening or closing ion channels, this stimulates or inhibits enzymes/secondary messenger systems
What are some excitatory ionotropic receptors?
Glutamatergic receptors (AMPA/NMDA/Kainate)
Ach (nicotinic)
GABAb
What are some inhibitory ionotropic receptors?
GABAa
Glycine
