patch clamp Flashcards
What are the electrical signals generated by neurons called?
Changes in Vm
Vm stands for membrane potential.
How do neurons generate electrical signals?
By rapid changes in permeabilities to specific ions through opening and closing of ion channels
Usually, these channels are voltage-gated.
What is required for neuronal signaling?
Establishment and maintenance of concentration gradients across the membrane via active transporters
This creates electrochemical gradients.
What is a Leakage Channel?
Ion channel that is always open
What initiates the opening of a Voltage Gated Channel?
Change in the membrane voltage (membrane potential)
What causes a Ligand-Gated Channel to open or close?
Specific extracellular neurotransmitter
What are External and Internal channels in terms of gating?
External: neurotransmitter gated; Internal: cyclic nucleotide-gated
These channels open or close in response to specific molecules.
What factors influence Mechanical-Gated and Temperature Gated channels?
Changes in conformation
What does Patch Clamp measure?
Current flowing through a single ion channel
What is the purpose of using a fine glass pipette in Patch Clamp?
To gently attach to the surface of a cell and measure electric currents
The pipette contains a special liquid that mimics the inside of a cell.
What is cell-attached recording in Patch Clamp?
Pipette sticks to the cell without breaking the membrane, recording ion flow from a single channel
What does whole cell recording involve?
Breaking open the membrane slightly to measure currents from all channels in the cell
In inside-out recording, what is exposed to the controlled environment?
The inner part of the channel
What happens in outside-out recording?
A membrane patch is pulled away so the outer part of the channel is exposed
What is the purpose of using a K+ blocker when studying Na+ currents?
To ensure that only Na+ currents are observed
This technique isolates the Na+ current by preventing K+ from affecting the measurements.
What characterizes the difference between microscopic and macroscopic currents?
Microscopic: 1 channel, macroscopic: >1 channel
What causes neurons to become electrically active?
Changes in ion conductance (e.g., Na+, K+) and in membrane potential (Vm)
When do voltage-gated Na+ and K+ channels open?
During depolarization
What happens to Na+ channels during prolonged depolarization?
They become inactivated, entering a non-conducting state that is voltage-INdependent
What is the role of the positively charged voltage sensor in voltage-gated channels?
It detects the potential across the membrane, causing the channel to open or close
How does the closure of ion channels occur?
Closure (de-activation) is voltage-DEpendent
What is the difference between inactivation and closure in ion channels?
Inactivation is voltage INdependent; closure is voltage DEpendent
What sequential changes lead to action potentials?
Changes in voltage-gated Na+ and K+ permeability
How do Na+ and K+ channels differ in their kinetics?
Na+ channels activate and inactivate quickly; K+ channels activate more slowly
What regulates the shape and duration of action potentials?
Inactivation of Na+ channels and K+ channels
What is the function of active transporters in neurons?
To create and maintain ion gradients
What type of energy do active transporters require?
They require energy to function
List the two types of active transporters.
- ATPase pumps
- Ion exchangers
What is the function of the Na+/K+ ATPase pump?
Maintains gradient for Na+ and K+ by hydrolysis (water is mostly used to break down the chemical bonds that exists between a particular substance)
What is the role of the Ca2+ ATPase pump?
Prevents [Ca2+]i from accumulating
Where is the PMCA pump found, and what does it do?
Found in plasma membrane; extrudes Ca2+ from the cell
Where is the SERCA pump located, and what is its function?
Found in ER membrane; extrudes Ca2+ from the cytoplasm to store in ER
What does the Na+ pump maintain?
Gradient for Na+ and K+
It uses the hydrolysis of ATP.
How many Na+ ions are moved out and K+ ions moved in by the Na+ pump?
3 Na+ out/ 2 K+ in
This process is electrogenic and essential for electrical charge differences in nerve and muscle activity.
What is the significance of the conformational changes in the Na+ pump?
Associated with binding and hydrolysis of ATP
The pump changes shape as it binds Na⁺, uses ATP, and releases Na⁺ outside before pulling K⁺ inside.
What are ion exchangers?
Types of secondary active transporters
They move ions or molecules across a membrane by using the energy from another ion’s movement.
What do antiporters do?
Move two different ions/molecules in opposite directions
Example: Na⁺/Ca²⁺ exchanger moves Na⁺ in while pushing Ca²⁺ out.
What is the function of the Na⁺/Ca²⁺ exchanger?
Helps keep intracellular calcium levels low
It moves 3 Na+ in and Ca²+ out, with conformational changes driven by ion binding.
What do co-transporters do?
Move two different ions/molecules in the same direction
Example: Na⁺/Glucose cotransporter (SGLT) moves Na⁺ and glucose into the cell together.
What is the role of the Na⁺/Glucose cotransporter (SGLT)?
Helps absorb glucose in the intestines and kidneys
It moves Na⁺ and glucose into the cell simultaneously.
Fill in the blank: The transmembrane movement of ions by the Na+/Ca2+ exchanger helps keep [Ca2+] _______.
[Ca2+] low
What stimulates the release of neurotransmitters in the context of the Na+/Ca2+ exchanger?
Conformational changes driven by ion binding
This process occurs when 3 Na+ are moved in and Ca²+ is moved out.
K+ blocker for patch clamp
cesium
Na+ blocker for patch clamp
tetradotoxin
