Flashcards in Neurophysiology Deck (30)
Communication depends on what two things?
1) voltage difference across the membrane
2) differential permeability
What is differential permeability?
Permeability is ease with which something can cross. These changes in differential permeability are going to change over time concerning what can cross the membrane at different time periods.
What level of mV is a Resting Membrane Potential?
-70 mV from inside to outside of cell
What is a potassium leak?
Potassium going through a non-gated channel
What contributes to the level of mV, -70 mV, at Resting Membrane Potential?
1) The Sodium-Potassium Pump: uses ATP that goes against the concentration gradient of the Neuron. 3 Na+ come out, 2 K+ come in.
2) The Potassium Leak: Potassium will move from a higher concentration to a lower concentration via a non-gated potassium channel, which is always open.
3) Large negatively proteins that are contained in the inside of the cell
What happens when, when generating an action potential, the local potential is brought to the level of threshold?
Voltage-Gated Sodium Channels open.
What level of mV is threshold at?
How many mV are needed to bring the local potential, at the Resting Membrane Potential, up to the level of threshold?
What happens when Voltage-Gated Sodium Channels open?
Sodium will pour in using the concentration gradient and depolarizing.
What closes at +20 mV during an action potential?
Voltage-Gated Sodium Channels close and deactivate.
What opens at +20 mV during an action potential?
Voltage-Gated Potassium Channels open.
How is repolarization caused?
By potassium leaving via the Voltage-Gated Potassium Channels being open.
Besides Voltage-Gated Potassium Channels being opened during repolarization, what else occurs, causing the potential to decrease to -90mV?
The Potassium Leak via the non-gated potassium channel, which is always open.
During an action potential, what happens during repolarization when the potential gets back down to -70mV?
Voltage-Gated Potassium Channels are unlocked.
Information travels along the axon via:
How do you get another action potential to happen?
With a refractory period, which is a time period in which no action potential will occur
2 kinds of Refractory Periods:
1) Absolute refractory period: no new action potential will happen no matter what
2) Relative refractory period: no new action potential will be generated UNLESS a greater than normal stimulus is present
How many mV is a normal stimulus?
If you are at a potential of -85 mV, which refractory period are you in and how much of a stimulus would be necessary in order to bring it back to threshold to start another action potential?
The Relative Refractory Period and a greater than normal stimulus of +30 mV is needed to get to threshold.
What is Continuous conduction?
Every point along the axon is undergoing depolarization in series.
What is saltatory conduction?
Depolarization only occurs at the Nodes of Ranvier, due to the presence of myelin (wrapping of the neurolymmocyte). It is quicker than continuous conduction.
True or False: Because of Na+ pouring in during depolarization at one area of an axon, the next area will also receive some of the Na+, causing it to reach threshold and generate its own new action potential.
Na+ pouring in during depolarization at one area of an axon, the next area will also receive some of the Na+, causing it to reach threshold and generate its own new action potential, but will not cause the previous axon to receive another action potential because of what?
Because the previous axon would be in the Absolute Refractory Period, during which no new action potential will happen no matter what.
Are there gates below the myelin sheath? What disease effects the myelin sheath?
There are no gates below the myelin sheath. Multiple sclerosis effects the myelin sheath.
What are three ways that you could increase conduction velocity?
1) Increase temperature
2) Increase myelination
3) Increase diameter
2 kinds of synpases:
What are chemical synapses?
1) An action potential reaches the axon terminal
2) Voltage-Gated Ca2+ Channels open and calcium comes in
3) Causes the synaptic vescicles, containing neurotransmitters, to fuse with the presynaptic terminal
4) Neurotransmitters travel across the synaptic cleft
5) To the Ligand-Gated Sodium Channels of the postsynaptic cell, causing them to open
6) Sodium will come in due to the concentration gradient and act as another stimulus
2 kinds of Postsynaptic Potentials:
What is an excitatory postsynaptic potential?
A positive movement in the membrane potential, bringing it closer to threshold. Easier to get an action potential.