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Lecture 10

BIOB32H3 Lecture Notes - Lecture 10: Gap Junction, Saltatory Conduction, Electrical Synapse

Biological Sciences
Course Code
Kenneth Welch

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BIOB32- Lecture 10
- The neurons or the axon of the neuron determines how fast the signal is propagated- depends
on how well the sodium channel is imported into the axon,
- The potassium that is coming out is the offsetting of depolarization
- If you have a bigger tube, it will easily permit the flow of charge along the inside of the axon
- The axons of the squid can be about 1 mm wide and this is long enough to stick something into
the axon, we don’t need some fancy equipment and microscope for that
- This is not the case of all animals because not all of the have the space
- We have insulating cells that hope to prevent the nuclear charge across the membrane , in
peripheral nervous system the Schwann cell does the same thing
- Myelin cells reduces the, we are increasing the resistance to flow through. we are also reducing
membrane capacitors  tendency of them to line up along the membrane inside and outside
- The inside is relative negative compared to the outside
- The distance along the electrical organisation increases
Saltatory conduction
- The action potential wave is not a continuous wave that continues along
- Instead there is the jumping of action potential from one side to the other
- The greater potential is great enough to allow depolarization to that threshold value to the next
node of ranvier – action potential initiates there and so on and so forth
(excitable) cell-to- cell communication
- This involves the understanding of synaptic function
- With relatively small amount of them we can begin to develop relatively relative amount of the
circuit, circuits that can turn other circuits on or off
Electrical synapse
- The simplest form of synapses
- We have the membrane of two different cells that are very very closely aligned with each other
and they are connected with the gap junction
- 1 connexion molecules open 6 connectin molecules
- When they are open they can allow relatively small molecules to pass in and out
- This is the fastest type of synapse because we do not have an additional step
- We would see a high intensity of gap junction , this can connect other neurons as well
- We want all the muscles cells to contract at the same time
- The rapid conduction of the rapid cell among themselves plays a function there
Electrical synapse function
- There is a distance from where I injected the current and from where I absorb the greater
potential here
- The signal of depolarization could be a hyperpolariation, cell B looks like the one in cell 1,
because the charge is directly flown we can’t have a depolarization here and a hyperpolatization
- The synapse can transfer action potential by having a greater action potential to pass across the
electrical synapse
- These gap functions are not necessarily open all the time, in the cell in the situation, ,there are
some that are close until the signal comes by
- Only one of the connexion molecules can open to a certain stimulus
- We can have the transmission of signals that can occur in one direction but will not occur in the
other direction
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