Nervous System 1 - Membrane Potential Flashcards
What is plasticity?
The changing of the connectivity and physiological strength of synapses
What are the 4 specialized sub regions for receiving/integrating inputs?
- Dendrites
- Cell body
- Axon
- Synaptic terminals
What is Hyperpolarization?
Moving to a more negative potential
What is Depolarization?
Going from resting potential to a more positive value
What is repolarization?
Returning to a resting potential
What is Vo?
Extracellular Voltage = 0 mV
What is Vi?
Intracellular voltage
What is Vm?
Membrane potential
What is Vrest?
Resting potential
What is Inward current?
Cations flowing into the cell or anions flowing out of the cell
What is Outward current?
Cations flowing out of the cell and anions flowing in
What is the sign of inward current?
Negative
What is the sign of outward current?
Positive
What is the charge of of cells at rest?
At rest the inside has a negative charge relative to the outside
What is the Resting charge of cells due to?
Difference in ion concentrations and permeabilities across the membrane
What cation is permeable to the cell at rest?
K+
How is K+ permeable to the cell at rest?
It has leakage channels that are open at resting potential allowing it to leak out
How are concentration gradients in a resting cell maintained?
By the active transport of K+ and Na+
How must ions pass through the lipid bilayer?
Through ion channels
What can gated channels open and close in response to?
Changes in the membrane voltage
What are electrical signalling a result of?
Ions moving through ion channels
What are the two ways channel activation can occur?
- Binding of a chemical ligand
* Changes in membrane potential (Vm)
What are the two ways a Ligand can open a channel?
It binds to the protein or a phosphate group binds to the channel opening it
How do voltage gated channels work?
When membrane potential becomes depolarized the channel can open and allow ions to cross the membrane
How can channel inactivation (closure) occur?
Prolonged depolarization can cause the membrane to close
What are the characteristics of Voltage dependant Na+ channels at rest?
The channels are closed because the activation gate within the channel is closed blocking sodium ions from entering the cell
What is the state of Voltage dependant Na+ channels when the membrane is depolarized?
The activation gate is opened allowing sodium ions to flow into the cell down its concentration gradient
When the cell is at rest where is the greater concentration of sodium ions?
Outside the cell
When the cell is at rest where is the greater concentration of potassium ions?
Inside the cell
What is the state of voltage dependant Na+ channels after 1 msec of depolarization?
The inactivation gate is closed preventing sodium from flowing into the cell
What are Channelopathies?
Diseases arising from mutation of genes encoding ion channel subunits
What could happen if a channel remains open for too long?
Cells become hyperexcitable
What is the concentration of calcium ions relative to the cell?
Ca2+ ions are kept in extremely low concentration inside the cell
What direction is the concentration gradient for Ca2+?
Ca2+ gets pushed into the cell
What direction is the concentration gradient for Cl-?
It tends to get pushed into the cell
What are the two driving forces on ions?
Chemical and Electrical driving forces
What is the magnitude of chemical driving forces on ions proportional to?
The concentration gradient
What is the electrical driving force on ions provided by?
Membrane potential
What is Conductance (g)?
The ease with which ions flow across the membrane
What is the equilibrium potential for ion x?
The membrane potential at which the current carried by ion x is 0
What is the formula for the driving force on an ion?
Membrane potential - Equilibrium potential of ion
What is the rule about membrane potential?
It will always move towards the equilibrium potential of the ion whose conductance increases
What is the equation for calculate the Equilibrium potential for an ion?
Ex= (58/x) log [(conc. outside the cell)/(conc. inside the cell)
Why is the resting membrane potential close to Ek?
Because the membrane is highly permeable to K+ and much less permeable to Na+
