Neurophysiology Flashcards
Glial cells general function
Support cells of the nervous system
Two subdivisions of glial cells
Macroglia and microglia
Types of microglia (1)
Macrophages (garbage collectors of the nervous system)
Types of macroglia (3)
Astrocytes, oligodendrocytes, Schwann cells
Most abundant macroglia in the brain
Astrocytes
Two major functions of astrocytes
- Support neurons (nutritive - provide growth factors and nutrients to neurons and physical - physically contact the neurons and hold them in place)
- Fundamental component of the blood brain barrier (filter blood vessel content and the brain tissue itself)
Oligodendrocyte structure
Cell body in middle, projections wrap around the axons of neurons many times
Oligodendrocyte function
Creates myelin sheath in the CNS to assist in conduction.
Schwann cell structure
Cell body of the Schwann cell is contained within the myelin sheath, instead of being in the middle like oligodendrocytes
- 1 Schwann cell can only contact one axon
Schwann cell function
Creates myelin sheath in the PNS to assist in conduction
True or false: dendrites are the only region of input in the neuron
False, a neuron can also get input from the cell body or axon
Soma/cell body function
Integration
- Takes vast input and converges the input in the cell body. The cell body then “decides” whether or not the info gets passed down the neuron.
Most ions will be surrounded with a _____
Hydration shell
What properties contribute to the membrane potential?
Properties of the membrane and hydration shells
What is potential (voltage) in general terms?
Separation of electric charges
Resting membrane potential is approximately what value?
-65 mV
There is more Na+ on the (inside/outside) of the neuron
Outside
There is more K+ on the (inside/outside) of the neuron
Inside
What causes there to be so much Na+ on the outside of the cell and lots of K+ inside the cell?
The Na+/K+ ATPase
How is the resting membrane potential negative if there’s so much K+ on the inside of the cell?
K+ leak channels in membrane allow K+ to diffuse down concentration gradient
Neurons are more permeable to (Na+/K+) because…
Neurons are more permeable to potassium due to leak channels.
If a neuron is less permeable to K+, what happens to resting potential?
Resting membrane potential becomes more positive (more K+ remains in the neuron, so less flows out)
What is driving force?
The force generated from concentration differences.
What’s the driving force for Na+?
The driving force is into the cell.
What’s the driving force for K+?
The driving force is out of the cell.
What is electromotive force based on?
Coulomb’s law
What’s the electromotive force for Na+ at resting membrane potential?
Into the cell because Na+ is attracted to the negativity inside the cell.
What’s the electromotive force for Na+ when the inside of the membrane is positive?
Out of the cell
What’s the electromotive force for K+ at resting membrane potential?
Into the cell because K+ is attracted to the negativity inside the cell.
What’s the electromotive force for Cl- at resting membrane potential?
Out of the cell because Cl- is repelled by the negativity inside the cell.
Describe the movement of K+ across the membrane if this ion could free flow
As potassium moves down its concentration gradient (out of the neurron), the inside of the neuron gets more negative so the emf of K+ into the cell increases. K+ would then move out until the driving force and the emf are equal and opposite -> results in “equilibrium” aka “equilibrium potential” (net movement is 0).
Describe the movement of Na+ across the membrane if this ion could free flow
As sodium moves down its concentration gradient (into the neuron), the inside of the neuron gets more positive so the the emf of Na+ out of the cell increases. Na+ would then move in until the driving force and the emf are equal and opposite -> results in “equilibrium” aka “equilibrium potential” (net movement is 0).
What’s the only thing that can change equilibrium potentials of ions?
Changing the ion concentrations
If there’s more Na+ on the outside of a cell, the cell membrane potential would…
Increase, because of an increased driving force (some Na+ would inevitably get in)
If you add more K+ to the outside of the cell, the cell membrane potential would become…
More positive, because less ions flow out (smaller driving force).
What does the Nernst equation show?
The relation between the concentration difference of a permeating ion across a membrane, and the membrane potential at equilibrium
- Only looking at one ion by itself
- The ion needs to be able to move across the membrane
Nernst equation shortcut at 18 degrees
E(mV)= 58log(Cout/Cin)
Nernst equation shortcut at 37 degrees
E(mV)=61log(Cout/Cin)
Nernst equation shortcut at 18 degrees with Ca2+
E(mV)=29log(Cout/Cin)
- just 58/2
Nernst equation shortcut at 37 degrees with Ca2+
E(mV)=30.5log(Cout/Cin)
- just 61/2
Nernst equation for Cl-
E=Rt/zF ln (Cin/Cout)
- Cin and Cout is flipped
What can the Goldman equation be used to find?
The overall cell membrane potential
- Includes all ions, and considers permeability
Which ion has the greatest effect on overall cell membrane potential?
Potassium, because it has the greatest permeability
- Why resting potential is -65 mV and equilibrium potential of K+ is -75 mV
What is the synaptic bouton?
Synapse
More Cl- on the (inside/outside) of the cell
Outside
Equilibrium potential is also known as what other two things?
- Nernst potential
- Reversal potential
