Transmission Within A Neuron Flashcards
Information processing in a neuron…
Neurotransmitter input - electrochemical
Action potential in neuron - electrical
Synaptic transmission; neurotransmitter output - chemical
Neuron vs a transistor
Neuron - transistor
10,000’s of inputs - 2 inputs
Integration of inputs highly complex - integration of inputs follows a simple rule
Integration depends on chemical circumstances - integration is constant
1 output - 1 output
Inside a neuron…
Organic anions-
k+
Water
The cell membrane…
Made of lipid (fat) and proteins
The barrier between intracellular and extracellular space
Outside neuron…
Cl-
NA+
Water
At resting potential…
More negative anions inside
More positive cations outside
Electrical potential - resting potential is -70mV
Ion concentrations …
Ions passively move down chemical and electrical gradients. Sodium moves in and potassium moves out which reduces the resting potential to 0mV
Outside - inside a neuron is a massive electrical gradient which exceeds the fields strength of heavy lightning
Inside - outside of a neuron…
Chemical or osmotic gradient
Intracellular K+ wants out
Extracellular said Na+ wants in
In order to maintain the resting potential…
An active sodium-potassium pump needs to maintain resting potential by moving 3 NA+ outside and 2 K+ inside. This uses a lot of energy
The structure of a neuron…
Input - processing - output - transmission to next neuron
The action potential…
Is a very rapid, strong change of membrane voltage
It is set in its shape, it does not change amplitude for a stronger neuron
It is guided by voltage sensitive ion channels and massive electrical or chemical gradients
An ion channel…
Is macro molecule/protein
Normally blocks ion flow
Changes structure when electrical field changes
Triggered by EPSP from dendrite
Depolarisation in action potentials is…
When the membrane reaches a threshold of -55mV and the voltage gated sodium channels open and sodium rushes into the neuron
The potential is +40 mV
Re polarisation in action potential is…
When the membrane reaches +40mV sodium channels close and voltage gated potassium channels open. Potassium rushes out. The potential is -80mV
Recovery in action potential…
Is when the membrane hyper polarises. Potential is at -80mV
All the channels close and the sodium-potassium pump works to restore the normal ion balance. Potential returns to -70mV
The puffer fish is lethal because,..
Tetrodotoxin blocks sodium channels and prevents action potentials.
70 micrograms can kill you in 30 minutes
Actual information processing of signals in neurons…
Occurs in dendrites and soma, inputs interact with each other here and a complex biophysical process decides whether an input is forwarded.
The speed of an action potential …
About 2 metres per second in a regular neuron
In myelin and salutatorian conduction the speed is 17 metres per second
What is myelin?
A fatty layer of insulation which is generated by Schwann cells and digodendrocytes
There is a loss of myelin in MS
Most axons are myelinated
Salutatorian conduction is..
When myelin covers an axon with gaps and action potentials can jump from one node to another which is fast and efficient transmission
