L7: Neurons & Neuron Communication I Flashcards
How are electrical potentials measured?
1) Extracellular Recording
2) Intracellular Recording
3) Patch Clamping
1) Electrode outside cell
2) Electrode inside cell
3) Electrode sealed to cell surface
At rest, is the inside of the membrane more negative/postive than the outside?
More negatively charged (hyperpolarised)
3 ways how the electrochemical gradient across a membrane is established
1) Ion pumps
2) Selective Permeability
3) Charge Separationn
How does ion pumps establish electrochemical gradient?
Move ions AGAINST their conc grads using ATP
How does selective permeability establish electrochemical gradient?
Membrane is impermeable, allowing ion movement only through specialised channels
How does charge separation establish electrochemical gradient?
Membrane acts as barrier that stores & mainntains charge difference between inside & outside
Key Components of the membrane
Key Components of the membrane
Na+/ K+ ATPase Pump
Na+ channels
K+ channels
How is the resting membrane potential usually determined by?
Na+ & K+ ion distribution
What is the equilibrium potential (E) of an ion?
The voltage required to prevent its movement down its gradient
Effect of Na+ & K+ if inside the cell is negative/positive
Negative: K+ prevented from leaving
Positive: Na+ prevented froom entering
Why is Vm closer to Ek than Ena?
Membrane is 50x more permeable to K+ than Na+
Equation for conc grad for +ve ions
(C) out / (C) in
Equation for conc grad for -ve ions
(C) in / (C) out
Nernst Equation
E = 58 (mV) x log (C) out / (C) in
What mV do cells need to be to stop K+ leaving & stop Na+ leaving ?
K+ : -90mV
Na+ : +50mV
Action of Na+ into the cell
Resulting in depolarisation (more +)
Action of K+ out of the cell
Resulting in repolarisation (more -)
Two forces ions are under
1) Electrostatic force (dependent on charge)
2) Force of diffusion (dependent on concentration)
3 functional states of ion channels
1) Closed (resting)
2) Open (active)
3) Inactive (refractory
2 refractory periods
1) Absolute
2) Relative
Define absolute refractory period
No AP possible (Na+ channels inactivated)
Define relative refractory period
Stronger stimulus required (due to repolarisation)
How are nerve impulses conducted down a myelinated neuron?
Jump from node to node
How are nerve impulses conducted down a non-myelinated axono?
Continuous conduction: slow signal transmission
Use of blue & yellow light in Optogenetics
Blue: Open cation channels
Yellow: Open Cl- channels
Functional states of ion channels
1) Closed (resting)
2) Open (active)
3) Inactive (refractory)
Functional states of ion channels in V-gated Na channels & K channels
Na has all 3 states
K has 2 BUT inactive state
