Synapses Flashcards
Contains protein molecules that transmit chemical messages
Presynaptic membrane
What NTs are commonly reuptaken by astrocytes and why?
Glutamate and GABA because they are very excitatory and inhibitory (respectively)
Not typical at axon terminals. Synapses are not usually this type
Electrical synapse “gap junction”
A method of NT deactivation that requires certain molecules to find and break down specific NTs
Breakdown by enzymes
This postsynaptic receptor opens channels directly, provides immediate rxns required for muscle activity and sensory processing, has a fast activation, has a brief duration and is the classic model of ligand-gated receptors
Ionotropic receptors
What method of NT inactivation did the first attempts to prevent depression use
Breakdown of enzymes. MAOs
Type of synapse in which the axon terminal secretes directly into the bloodstream
Axosecretory
What are the 4 ways of inactivating a NT?
Diffusion, breakdown by enzyme, uptake into glial cells, reuptake into presynaptic terminal via transporter
NT is released toward a single postsynaptic neuron in this type of synapse
Directed synapse
What is it called when a different neuron is involved with facilitation or inhibition of another neuron presynaptically? It is affecting another neurons decision
Neuromodulation
Small space separating presynaptic terminal and postsynaptic dendritic spine
Synaptic cleft
Type of synapse in which an axon terminal ends on soma
Axosomatic
How can blocking and supercharging reuptake receptors have an effect on us?
They can have many different medical applications
These are activated by a NT (first messenger)
g-proteins
How are NTs stored
Vesicles which are membrane-bound organelles in the axon terminal
Direct AP propagation, nearly instantaneous, only excitatory
Electrical synapse “gap junction”
Site to which a NT molecule bonds
Postsynaptic receptor
What are the six steps for triggered release of a NT
- ) Arrival of AP at axon terminal
- ) VG Ca channels open; calcium enters and SNARE proteins activate
- ) Vesicles move to and dock on presynaptic membrane
- ) Vesicles fuse with presynaptic membrane and release NT into synaptic cleft (exocytosis)
- ) NT binds with receptors on pre or postsynaptic membrane
- ) NT is inactivated or removed from synaptic cleft
What are the two types of pre-synaptic receptors?
Heteroreceptors and autoreceptors
When a vesicle fuses with the presynaptic membrane and releases NTs into the synaptic cleft
Exocytosis
The gap is small at around 20 nm. The junction where neurotransmitters are releases
Chemical synapse
Bi-directional. Message can travel both ways
Electrical synapse “gap junction”
Typical at axon terminals. This is the most common synapse we see
Chemical synapse
These postsynaptic receptors open channels indirectly, are versatile, use second messengers (g-proteins), have a slow activation, and have a long lasting duration of effects
Metabotropic receptors
The gap is very small at about 3.5 nm. The presynaptic and postsynaptic membrane are fused at the connexon. Shared cytoplasm
Electrical synapse “gap junction”
Type of synapse that is inhibitory, typically located on cell body, flat vesicles, sparse material on membranes, narrow cleft, and small active zone
Type II synapse
What are the four requirements to be a NT
Synthesis in cell, triggered release (AP), effect on receptors (a biological effect), and a mechanism for inactivation
Large compartment that holds synaptic vesicles
Storage granule
Organelle that provides the cell with energy
Mitochondrion
How is a NT synthesized in the axon terminal
Ingredients from food pumped into cell via transporters
A protein that acts as an assistant to bring the vesicles containing NTs to the presynaptic membrane to fuse
SNARE proteins
Type of synapse that is excitatory, typically located on dendrites, round vesicles, dense material on membranes, wide cleft, and a large active zone with lots of receptors on postsynaptic membrane
Type I synapse
The least common method of NT inactivation that occurs when the NT floats away from high concentration to low concentration
Diffusion
Proteins in membrane that respond to chemical messages; contain recognition molecules
Receptors
Round granule that contains NTs
Synaptic vesicle
Seen in areas like the heart to help it contract
Electrical synapse “gap junction”
What common treatment works by stopping the SNARE protein from pulling the vesicle to the presynaptic membrane and releasing NTs?
Botox
Presynaptic receptor that is involved with feedback, regulation, and reuptake. “Self”
Autoreceptors
A chemical that carries a message to initiate a biochemical process that isn’t a NT
second messengers (g-proteins)
EPSPs, IPSPs, and initiation of other chemical rxns and biological processes are involved with these types of receptors
Postsynaptic receptors
How can we increase or decrease NTs?
Blocking/supercharging reuptake receptors, not allowing astrocytes to uptake NTs, increasing or decreasing certain amounts of enzymes, adding or taking away astrocytes to encourage diffusion or encourage uptake
The classic model of ligand-gated receptors
Ionotropic receptors
Excites or inhibits other neurons. Allows more signaling flexibility
Chemical synapse
A method of NT inactivation that occurs when presynaptic auto receptors take up the NT with a transport protein to be repackaged and used again
Reuptake
How is a NT synthesized in the cell body
DNA to RNA proteins, transported on microtubules to axon terminal, bigger molecules called neuropeptides are more likely to be formed here as opposed to axon terminal
When axoaxonic synapses between an axon terminal and another axon fiber have an effect on the release of neurotransmitters by the target axon through presynaptic facilitation or presynaptic inhibition
Neuromodulation
The released NT diffuse over a wide area to effect many neurons in this type of synapse. Has a bit of a bigger gap
Non-direct synapse (volume transmission)
Type of synapse in which the axon terminal end on a dendrite spine (the type we see most often)
Axodendritic
Type of synapse in which the axon terminal secretes into a another axon
Axoaxonic
Some receptors use two different messengers. What are they?
The first are NTs and the second are g-proteins (guanine)
A method of NT inactivation that occurs when an astrocyte takes a NT in, deactivates it, and sends it back into the postsynaptic terminal
Uptake into glial cells
What are the two types of postsynaptic receptors?
Ionotropic and metabotropic
What can g-proteins do?
alter rate of ion flow in a membrane channel, formation of new ion channels, production of new proteins through DNA
What are the 6 parts of a synapse?
Presynaptic membrane, synaptic cleft, postsynaptic membrane, mitochondrion, synaptic vesicles, and receptors
Axo-axonic presynaptic receptors involved with neuromodulation
Heteroreceptors
Type of synapse in which an axon with no connection secretes into extracellular fluid
Axoextracellular
Type of axon terminal in which an axon terminal ends on another axon terminal
Axosynaptic
Contains protein receptor molecules that receive chemical messages
Postsynaptic membrane
