Synapses Flashcards
What is a synapse?
Communication between neurons
What is the sending neuron called?
Pre-synaptic neuron
What is the receiving neuron called?
Post-synpatic neuron
What are the two types of synapses?
Chemical - slower but more prices, more common
Electrical - fast transmission
Where is the pre-synpatic membrane found?
Membrane of terminal button
Where is the postsynaptic membrane?
Membrane of receiving neuron
What is the synaptic cleft?
The gap of extracellular fluid between the sending and receiving neuron
What are synaptic vesicles?
These are spherical inside the terminal button and contain neurotransmitters
Is communication between neurons chemical or electrical?
Chemical
It goes across the synaptic cleft to produce a postsynaptic potential - a brief change in polarisation and this may trigger an action potential in the receiving neuron
What is an axodendritic synapse?
Most common - Axon (terminal buttons) to dendrites (from sending axon to dendrites of receiving neuron)
What is an axosomatic synpase?
Axon terminal buttons to soma (from sending axon to soma of receiving neuron)
What is an dendrodentritic synapse?
Dendrite to dendrite transmission
What is an axoaxonic synpase?
when neuron A synpases on the terminal button of neuron B. This increases/decreases the effects of neuron B on another neuron C. and is called pre-synaptic facilitation/inhibition.
The advantage of presynaptic facilitation and inhibition is that they selectively influence single synapses rather than the entire neuron.
What substances are released and allow communication between neurons?
- neurotransmitters
- neuromodulators (proteins)
- Hormones
What are neurotransmitters?
Released by terminal buttons across the synapse to receptors (travel short distance)
What are neuromodulators?
Peptides released by terminal buttons to receptors
Released in large amount and travel further
What are Hormones?
Travel in blood to TARGET cells
Produced and released by endocrine glands
Once synthesized in the terminal button, what do neurotransmitters travel in when they are in the terminal button?
Packaged vesicles called quanta
Neuromodultaros (large peptides) and assembled in the cell body, packaged in vesicles and transported to the axon terminal. What is axoplasmic transport?
The active process by which vesicles and transported from the soma to terminal buttons along microtubule
What is a fusion pore?
The first stage of release of transmitter substance
When some synaptic vesicles ‘dock’ against the presynaptic membrane, groups of protein molecules in the vesivle attached to protein molecules in the membrane, forming a FUSION PORE.
What is exocytosis?
The membrane of the vesicle fuses with the membrane of the pre-synaptic membrane and the contents of the vesicle move into the synpatic cleft. This is called exocytosis
What happens after exocytosis?
Transmitters diffuse across synaptic cleft to postsynaptic membrane, and look for specific receptors to interact with.
During exocystosis, what stimulates transmitter release from the vesicles?
When the action potentital reaches the terminal button, it depolarises the votage dependant membrane, causing the Calcium channels to open
Calcium ions (Ca2+) are higher OUTSIDE the cell, so they flood INTO the cell, by diffusion and electrostatic pressure
Ca2+ bind to proteins on the surface of the vesicles and activate these proteins. These proteins docks with other proteins on the surface of the presynatpic membrane. This creates the fusion pore and changes the shape of the protein, making the pore open.
What does Calcium allow?
- Produce movement of the vesicles
- Docking of vesicles
- Opening of the vesicles when the vesicle and membrane fuse together