Synaptic Transmission Flashcards
What are the two main types of synaptic transmissions?
Direct Transmission can occur at either electrical synapses or at chemical synapses with inotropic receptors. Indirect transmission occurs at chemical synapses with metabotropic receptors.
Direct Transmission Electric Synapses
Looking at Direct Transmission, are electrical synapses more or less common in the vertebrate brain?
Direct Transmission Electric Synapses
Electrical synapses are much less common in the vertebrate brain than are chemical synapses.
Direct Transmission Electric Synapses
Anatomically, Electrical synapses ______________ seen by electron microscopy. (add image)
Lack of synaptic vesicles
Direct Transmission Electric Synapses
How do electrical synapses function?
The presynaptic and postsynaptic cells are connected to each by the gap junction.
Direct Transmission Electric Synapses
What is the connection of electrical synapse mediated by?
Connexons
Direct Transmission Electric Synapses
How many subunits are in the connexons? Also, what is the function?
There are 6 subunits, which are called connexins, the surround the pore of the gap junction. Connexons in the presynaptic membrane line up with the connexons in the postsynaptic membrane –> forming the pore between the two cells. This allow the ions to flow across both membranes.
Direct Transmission Electric Synapses
True or False: Electrical synapses have a synaptic delay.
False; Due to the direct connection between cells, the electrical transmission is very fast.
Direct Transmission Electric Synapses
True or False: Chemical transmission generally has a synaptic delay of a few milliseconds.
True; due primarily to the amount of time it takes for vesicles to fuse and release NTs.
Direct Transmission Electric Synapses
In the chick ciliary ganglion cell experiment, when the postsynaptic cells are hyperpolarized, what does the electrical synapse do to the cell membrane during depolarization?
The electrical synapse no longer drives the cell to an action potential, instead if create a subthreshold. The chemical synapse will occur at the subthreshold.
Direct Transmission Electric Synapses
Again looking at the chick ciliary ganglion cell experiment, if the postsynaptic cell is further hyperpolarized, will an action potential occur?
No, neither the chemical or electrical synapse drives the cell to the threshold. However, a fast, short PSP occurs –> electrical synapse then a delayed, longer-lasting chemical postsynaptic potential occurs. This experiment illustrates that the electrical synapse do not have a synaptic delay.
Direct Transmission Electric Synapses
Choose the correct terminology. Electrical synapses are (more/less reliable) than chemical synapses.
More reliable
Direct Transmission Electric Synapses
Why do chemical synapses fail on being reliable?
Due to synaptic depression or due to the presence of neurotoxins.
Direct Transmission Electric Synapses
Where can you find electrical synapses? In what pathways?
Neuronal pathways underlying escape reflexes
direct synaptic chemical synapses
What is the best example to study direct synaptic excitation?
Neuromuscular junctions
direct synaptic chemical synapses
When the muscle membrane potential was clamped at -40mv, what did the nerve produced?
An inward current of Na ions due to the Na driving force. There is a small efflux of K+ ions but for right now, not that noticeable.
direct synaptic chemical synapses
What happened to the nerve stimulation when the membrane potential was more negative?
The endplate current increases in amplitude.
direct synaptic chemical synapses
When the membrane was depolarized what happen to the endplate current?
The endplate current decreased in amplitude, and even reversed direction?
direct synaptic chemical synapses
What is a reversal potential?
In general, the currents reversed from inward to outward after there is no net flow. An example, When the voltage clamp at -75mv, the nACh will let a large influx of Na+ ions, the inward current, and small reflux of K+ ions, the outward current. When the voltage clamp was at 10mv there is a large influx of K+ ions, there is small reflux of Na+ ions.