Lecture 3 + 4 - Basics of Neurophysiology Flashcards
What is an electrolyte?
A fluid with a high concentration of ions
Where is potassium highly concentrated?
Inside the cell
Where is sodium highly concentrated?
outside the cell
Where is chloride highly concentrated?
outside the cell
Where is calcium highly concentrated?
outside the cell
What is electric current?
the rate of flow of electric charge past a point or region. it exists when there is a net flow of electric charge
How is electric current carried (in the body)?
Carried by ions in an electrolyte
In terms of neurons, when do we see a current?
When ions flow through specialized pore in the cellular membrane
What is voltage?
a electrical potential difference between 2 points
How do neurons create a electrical potential difference (voltage)?
by controlling ion concentrations on either side of the membrane (intra vs extracellular)
What are the different states of the Na voltage gated ion channel?
Open, Closed, inactivated
What are the different states of the potassium voltage gated ion channels?
Open, closed
What does “gate” mean in terms of trans-membrane protein channels?
refers to what causes the ion channel to change states
How do ligand-gated ion channels work?
they open when they come in contact with a ligand or “a key” which can be another ion or a compound
Where are thermally and mechanically gated ion channels found?
primarily in sensory neurons
What are the 2 forces need for electrochemical equilibrium?
- Electrostatic force
- Molecular diffusion force
What are the 2 key concepts of electrostatic force (coulombs law)?
- Opposites attract, like repels
- greater the distance, weaker the the attractive force (closer the distance, stronger the attractive force)
What occurs at electrochemical equilibrium?
electro-static force is equal and opposite to the force of chemical diffusion
Which ligand allows Na to rush in?
Glutamate, acetylcholin
What ligand allows Cl to rush in?
GABA
What is the difference between Na+ and K+ voltage gated ion channels?
Na+ has 3 states, K+ has 2 states
True/false: leak channels are always open?
true
What are leak channels critical for?
establishing baseline resting voltage of the neuron
Which ion has the most leak channels?
K+
What does the Nerst equation calculate?
Voltage at equilibrium
What is the equilibrium potential for potassium?
-84mV
What is the equilibrium potential for sodium?
67mV
What is the equilibrium potential for chloride?
-67mV
What is the equilibrium potential for Calcium?
116mV
What is the resting potential of a neuron?
-65mV
What 2 factors determine the resting potential of a neuron?
- Permeability (neuron primarily permeable to K+ via leak channels)
- Intra vs extracellular concentration (K+ more concentrated inside)
Rank the following ions MOST to LEAST permeable at rest: Na, Cl, K
- K (1) - most
- Cl (0.45)
- Na (0.04) - least
Explain the process of a action potential:
- All voltage gated channels closed (K+ leak channels open)
- Na+ enters the neuron, making the the membrane potential more +, causing more voltage gated Na+ channels to open
- Na+ channels inactivate while the K+ channels slowly open
- K+ is still entering the cell making the voltage more - than at rest
