Direct Synaptic Transmission Flashcards
What are the two major types of direct synaptic trasmission
Electrical synapse and chemical synapse
What is electrical synapse?
It the direct transmission of ions and other small molecules through gap junctions.
What is chemical synapse?
It is the conversion of the electrical signal into a chemical one through the release of neurotransmitter.
What did Otto Lowei do?
He was the first to demonstrate chemical transmission in neurons
What are properties of electrical synapses
- Small molecules move through pores directly form cell to the other
- Direct electrical coupling
- Fast
- Bidirectional
What was the experiment Otto Lowei carried out?
He removed the heart of a frog but it kept it connected to the vagus nerve. He transferred fluids between inhibited hearts.
What makes up a gap junction?
Pair of connexon; one in each membrane
What makes up a connexon?
6 connexins (polypeptide subunit)
What is the pore size of a connexon?
1.5 nm
Why would a gap junction close?
lowering of cytoplasmic pH or elevation in Ca (both signs of damaged cell)
If you inject a current into cell A with gap junctions to cell B, what would you observe.
You would observe an outward current in cell A and B
What animal has a giant synapse that makes it easy to do experiments?
The crayfish; stimulation causes tail flip
How large is the synaptic cleft?
50 nm
What causes acetylcholine to be released?
Depolarization of presynaptic terminal causes voltage-gated Ca channels to be opened. This causes formation of vesicles and neurotransmitter release.
direct synaptic transmission
neurotransmitters bind ionotropic channel (nAChR)
