Neurobiology 3 Flashcards
Synaptic transmission
What are the key features of synapses and impulse transmission?
-Neurotransmitter
-Receptors
-Pump
-Degrading enzyme
-Degraded NT
Where are neurotransmitters stored?
In vesicles and released into synaptic cleft.
What causes the release of vesicles?
They fuse with plasma membrane of presynaptic terminal.
What is a synapse?
Junction where information is passed from one neurone to another or a muscle.
Point of communication between neurones/ target tissue (e.g. skeletal muscle)
Describe neurotransmitter release.
The release is phasic. Occurs in bursts in response to AP invading presynaptic terminals.
Neurotransmitters interact with post-synaptic receptors, which recognise chemical receptors. Activation of receptors cause influence on electrical / chemical properties of cell.
How is neurotransmitter release phasic?
High conc of neurotransmitter and is cleared away. Maintained by mechanisms (e.g. enzymes in synaptic cleft that degrade the neurotransmitters).
Who does the term ‘synpase’ originate from?
Michael Foster
Charles Sherrington
How is energy made in postsynaptic dendritic spine? Why?
Energy source is made locally.
Few have mitochondria.
What is a chemical synapse?
Chemical release from presynaptic neurone to modulate postsynaptic neurone (or muscle).
What is the difference between electrical and chemical synapse?
Electrical:
-no delay (rapid)
-can be two-way
-little plasticity, ability to change properties / strength of communication at synapse
Chemical:
-delay (at least 0.5ms), have to release neurotransmitter, diffuse across the cleft and then activate post-synaptic receptors
-one-way, unidirectional (pre to post)
-plastic (history dependent), strength of transmission can be modulated
What is retrograde transmission?
Molecules made in the post-synaptic cell can be released and influence pre-synaptic terminal.
E.g. endocannabinoids
What makes up an electrical synapse?
2 adjacent cells are brought together (a few nm apart). Both cells have channels, which come together to form an Fe2+ permeable ion channel between the two cells.
Electical synapses
What are examples of chemical neurotransmitters?
Amino acids- GABA (inhibitory) and glutamate (major excitatory neurotransmitter in the NS)
Amines- noradrenaline, dopamine and 5-HT
Neuroactive peptides (slow)- orexin, substance P, VIP neurotensin, enkephalins, CCK
Others- acetylcholine, nitric acid, ATP
Where do synapses occur?
Synapses have plasticity- can change appearance, number and properties.
Axodendritic synapse, axosomatic synapse and axoaxonic synapse
What can affect the presence of synapse?
PSD95- post synpatic density protein 95 kDa
Major constituent of the postsynaptic density and marker of synapses
Cal = calbindin, Ca2+ binding protein found in some neurones
