University:
Binghamton University
Course:
BIOL 313 | Cellular Neurobiology
Academic year:

2024
Views:

283

Pages:

2
Author:

CrystalMintah

Electrical Synaptic Transmissions vs Chemical Synaptic Transmission Electrical features of electrical synapses : a. Features include I. current from one neuron flows through gap junctions directly into the next cell II. Physical feature: 2 neurons come very close together, connected by connexons - Connexon: protein mace channels with 6 subunits arranged in a circle around a pore down the center (image on her iPad lol) - Connexons made of the protein connexin b. Electrical features of electrical synapses ● Transmission is fast ● Transmission is reliable - will work over and over again ● Transmission can go either direct (though there are one-way electrical synapses ) ● Though there are one-way electrical synapses 1. Cell A - Cell B and vice versa Transmission does not need an action potential to work 2. Can be small Vm changes Transmission can even be of a hyperpolarizing current - Are useful in cases where you need 1. Fast and reliable transmission ex. Escape reactions 2. You need a synchronized firing of a group of neurons It can be modified in some circumstances and in some cases can close a connexons on both cells - So modify connectivity - Some only transmit in one direction Given 2 neurons, that are synaptcially coupled What are ways to determine whether that synapse is electrical 1. One way is to look at it, visible connexons, proximity between the two cells 2. Check timing 3. Can pass sub-threshold stimuli between the cells - don't need it on cation potential 4. Pass current from A to B or B to A (not always true) 5. Pass hyperpolarizations between the cells Chemical Synaptic transmission 1. Visually: there is a gap between the two neurons called the synaptic cleft : there are also vesicles of neurotransmitters 2. The signal typically goes one ONLY way across the synapse (presynaptic to postsynaptic) 3. Presynapyci signal may fire an action potential while postsynaptic cell hyperpolarizes ( different signs across the synapse) 4. The pre-synaptic cell must fire an action potential for the postsynaptic cell to get the signal 5. Presynapse will not function without extracellular calcium. The pre-synaptic cell needs calcium to release its neurotransmitter. 6. The pre-synaptic to post-synaptic cell signal can be amplified in the postsynaptic cell. Ex: Chemical Synapses 1.) Presynaptic cell fires an action potential 2.) Calcium is required for the presynaptic cell to….. 3.) Release vesicles of neurotransmitters into the synaptic cleft 4.) The neurotransmitters diffuse across the cleft 5.) Then it binds at receptors on the postsynaptic cell 6.) This results in the opening of ion channels The postsynaptic response to neurotransmitters depends on the receptor the postsynaptic cell has - What does it open a channel to - Whether it causes a channel to open or close After chemical synapses have transmitted a signal The neurotransmitters must be destroyed or removed from the synaptic cleft (1) Synapse uses ACh as a neurotransmitter (2) Presynaptic cell fires an action potential and releases ACh which crosses the synaptic cleft (3) Ach binds a receptor on a postsynaptic cell and opens an ion channel to generate depolarization in the postsynaptic cell (4) If that depolarization crosses the threshold for this postsynaptic cell ….. (5) An action potential will be fired