Neuro Foundation: Module 1.0 - 1.4 Flashcards
Who completed the orignal work for Patch clamp Electrophysiology?
Erwin Neher, Bert Sakmann, and Neher
What year did Erwin Neher and Bert Sakmann win the Nobel prize for their work on the patch clamp technique?
1991
What are 4 types of Ion channel gating?
- Ligand Gated
- Phosphorylation/ Dephosphorylation
- Voltage Activated
- Stretch/ Pressure Activated
What are 3 instances of inactivation for voltage-gated ion channels?
- Refractory Period
- Internal Incease of Ca2+
- Internal Increase of Ca2+ may cause dephosphorylation of the channel
Describe Purkinje Neuron morphology and where in the brain they are found.
- A vere large highly branched dentritic tree.
- Single Long Axon
- Found highly in the cerebellum.
Describe Cortical Neuron morphology and where in the brain they are found.
- Encompasses Pyrmadical neurons and Interneurons
- Most Abundant Class of neuron in the Cerebral Cortex
Describe Pyramidal Neuron morphology and where they are found in the brain.
- Most abundant type of Cortical Neuron
- Has a Pyramidal shaped cell body
- Highly Abdundant in Cortex yet also found highly in the Hippocampus
What are 3 different types of spiking patterns in neurons?
- Single AP
- Bursting
- Rythmically Bursting (Important in Locomotion and Respiration)
What is the term given to phospholipids to reference their hydrophobic and hydrophilic properties?
Amphipathic
At low concentrations in water what do phospholipids form?
Lipid Monolayer
At high concentrations in water what do phospholipids form?
Micelles and eventually lipid bilayers
What is the difference in permeability between a phospholipid bilayer and the plasma membrane?
-Phospholipid Bilayer - Impermeable barrier to Ions
-Plasma Membrane: Semipermeable to do protein transporters.
What are features of Lipid Rafts?
- Packed tightly with Sphingolipids
- Packed with cholesterol
- Raft does not disaccociate
- Has many Receptors and Proteins
- Need to move around membrane
What are 2 features that affect membrane fluidity?
- Saturated vs Unsaturated Fatty Acids
- Cholesterol Concentration
What is the equation that describes the simplest form of Diffusion?
Fick’s Law
Flux of Solute X (Jx) will depend on the Permeability of X (Px) multiplied by the difference in concentrations.
**Only works for Uncharged Particles **
What is the driving force?
Determines passive transport of solute against a membrane. Encompasses electochemical gradient and potential energy difference between the compartments and voltage difference if applicable.
What is the state of solute X when no net driving force is acting on it?
At Equilibrium
No Net Transport
What are the 4 modes of Transport across a membrane?
- Simple Diffusion
- Facilitated Diffusion
- Primary Active Transport
- Secondary Active Transport
What are 3 protein complexes that substances can use to cross membrane in facilitated diffusion?
- Pores: Channels that are always open
- Channels: Can be opened or closed by the action of specific mechanisms; Pores with gating mechanism
- Carriers: facilitate passive transport thrugh membranes; can be used in Active Transport
What are 4 examples of pores?
- Porins: Found in outer membrans of gram negative bacteria and mitochondria
- Perforin: Cytotoxic T lymphcytes use these glycoproteins to form pores on target cells to allow cytoplasm to leak out. Allow passage of all material killing target cell.
- Nuclear Pore Complex: Regulates traffic in and out of the nucleus
- Aquaporin: Pores that allow the passage of water
Pores are aqueous transmembrane conduits that are always open.
What are the 4 functional components of a channel?
- Gate: Conformation change determines whether channel is opened or closed
- Sensors: Can respond to signals (ligands, voltage, second messengers)
- Selectivity Filter: Determines the particular ions or classes of ion that have access to the channel.
- Open Channel Pore: Ions can flow passively through it until channel closes.
Channels are gated pores
Explain the transportation process of carriers.
What is the difference between the rate of transport (flux) between simple and facilitated diffusion?
Simple diffusion transport rate increases linearly with concentration and has no maximum.
Facilitated Diffusion has a limited number of proteins with set speed and will eventually reach a transport maximum.
What is an example of Primary Active Transport?
Sodium Potassium Pump
Why do we call the Na/K pump electrogenic?
Generates a -1 Charge intracellulary each cycle.
Explain the Enzymatic Cycle of the Na-K Pump.
Make sure to know the effect of Oubain on this pump
What are 2 different types of transporters used in Seconary Active transport?
- Symporters
- Antiporters
What is one example of a Symporter?
Na/Glucose CoTransporter (SGLT)
Explain how the effect of Na Gradient on Glucose Transport was studied.
Studied in membrane vesicles of kidney epithelia.
What type of gradient do most Symporters use?
The Na Gradient
What is an example of an Antiporter?
Na - Ca Exchanger (NCX)
Free concentration of Ca is toxic to cell, needs to be removed or bound to certain proteins and taken to mitochondria. Virtually 0 Free concentration of Ca in the cell.
Where does the seperation of charges occur that cause resting membrane potential?
Right at the membrane.
What does the Plasma Membrane act as?
Capacitor
2 Conductive Material - Polar Heads; 1 Insulative - Hydrophobic Interior
What type of electrical composition is the cytosol and ECF?
Electroneutral
Difference in charges occurs at the membrane.
What is the distance of the plasma membrane that allows seperation of charges but still can feel the magentism of the other side?
5nm
Where is there high concentration of Na+ and Cl-?
Extracellulary
Where is there. high concentration of K+ and Organic Anions (Amino Acids and Proteins)?
Intracellulary
Organic anions are non permeable anions that help keep K inside the cell
What is the Equilibrium Potential?
The electrical and chemical driving forces are equal and opposite. No net change of ion movement.
What is the Nernst Equation and what does it describe?
Describes the equilibrium potential for any ion species, which is the potential necessary to balance an ionic concentration gradient across a mebrance so that the net flux of the ion is zero.
If calculating anIon - flip concentration ratio and remove valence sign
What is the most negative membrane potential physiologically possible?
Ek
What is the slope of the following plot based on the Nernst Equation?
58 mV
What determines the direction and rate ions flow?
The Driving Force
Given that equilibrium potential has no net flux of that ion
What determines the driving force of that ion?
The difference between the Equilibrium Potential and the Membrane Potential
What describes the current passing through channels?
Ohm’s Law
Given a cell with equal concentrations of ion inside and out
What is the membrane potential and what is the driving force dependant on?
Membrane Potential = 0
Driving force is only dependant on voltage.
What does a negative and positive driving force mean for cations?
- -DF : Movement into the cell
+ +DF: Movement out of the cell
Opposite for anions.
What 2 ions contribute to the resting membrane potential and why?
Na+ and K+ becaue their background leak channels are open at resting potentials.
What is the steady state condition?
Neither Na or K is at their equilibrium potential but the net flex of charge is null.
More K+ leak channels keep resting membrane potential closer to EK
What would happen to the gradient if the steady state is allowed to continue?
The steady state gradients would disipate.
What prevents the disipation of ionic gradients in the steady state?
The Na-K Pump
What is the effect of using Ouabain?
Blocks Na/K Pump
Loss of Ion Gradients
Induction of Seizures
What is the equation used to calculate membrance potential with multiple different types of ion channels?
The Goldman Equation
What is the permeability of K in the Goldman equation?
Permeability of K is 1
All other ion permeabilities calculated in comparison to K
What is the resting potential of a cell?
-64 mV
What is the simplified Goldman equation?
What is a potential difference (E) measured in?
Volts
What does current refer to?
Is the net flow of charge from one point to the other and is measured in amperes (A).
What does Resistance (R) refer to?
Is measured in ohms and refers to the resistance to the movement of current.
What are the limitations of the goldman equation?
Cannot determine how fast membrane potential changes to changes in permeability.
Cannont determine direction or magnitude of individual currents.
What can be used to solve the limitations of the Goldman equation?
Use an Equivalent circuit
What are the circuit equivalents in a cell?
Plasma membrane - Capacitor
Channels - Resistors/Conductors
Na/K Pump - Generator
Channels have limited speed - control rate of entry
What does capacitance refer to?
The ability of a sytem to store an electric charge.
What equation represents the electrical potential difference (voltage) across a capacitor.
V = Q/C
What is Ohm’s Law?
V = I x R
Can also be expressed in terms of conductance
Can be used for unitary current(1 channel aswell)
What is Ohm’s Law for a cell with a membrane potential and a concentration gradient?
What is Ex also called on an IV plot?
Reversal Potential
Who proposed the equivalent circuit?
Hodgkin and Huxley (1952)
Example of an equivalent circuit.
