5 Membrane Potential Flashcards
Anki:
receive, process, and transmit information to other cells.
Neurons
What are the three (3) main parts/functional units of a neuron?
- Soma (metabolic maintenance)
- dendrites (receive signals)
- axons or nerve fibers (transmit signals)
A part/functional unit of a neuron that is responsible for the metabolic maintenance of the neuron.
Soma
A part/functional unit of a neuron that acts as the receptive surface, bringing signals from other neurons toward the cell body.
Dendrites
What are the three (3) types of neurons?
- Sensory (afferent)
- motor (efferent)
- interneurons.
A type/functional unit of a neuron that conducts signals away from the cell body and carries information for long distances with high fidelity and without loss.
Axon
Where are the motor-neuron dendrites and soma innervated?
On the surface membrane
What initiates an action potential (nerve impulse) in a neuron?
Soma
Where is the action potential carried from in a neuron?
from the spike-initiating zone near the axon hillock to the axon terminal.
Where does the action potential travel to in motor neurons?
skeletal muscle cells or glands.
- It is the electrical potential difference across the cell membrane.
- difference in electric potential between the interior and the exterior of a biological cell.
- the result of an excess of negative charges on one side of the plasma membrane and positive charges on the other side.
- a source of potential energy to move molecules across membranes.
Membrane potential (Vm)
What causes the membrane potential in a neuron?
different concentrations of K+, Na+, and Cl- ions on each side of the cell membrane.
What is the typical range of membrane potential in neurons?
between -60 mV and -80 mV
It is a source of potential energy to move molecules across membranes.
membrane potential
Does every cell have a membrane potential (or voltage)?
Yes
It is a localized electrical gradient, with anions concentrated inside the cell and cations concentrated in the extracellular fluid.
membrane potential
What are the two factors that influence potential difference? (2)
- concentration gradient for an ion
- membrane’s permeability to that ion.
How is membrane potential measured?
microelectrode connected to a reference electrode via a voltmeter.
What is the typical resting potential of an unstimulated cell?
Approximately -70mV.
In which direction does K+ move?
K+ moves outward.
In which direction does Na+ move?
Na+ moves inward.
Does Cl- have a gradient for movement?
No, Cl- has no gradient for movement.
It means there are equal numbers of anions and cations.
Electroneutral
What balances the outward concentration gradient?
The inward electrical gradient.
What happens when potassium ions move out of the cell?
- more negative inside the cell
- more positive outside the cell
What is the effect of excess negative charge inside the cell?
It draws positive charges into the cell.
What happens as more potassium leaves the cell?
The electrical force increases until it balances the driving force from the potassium concentration gradient.
The membrane potential at which the electrical force and concentration gradient for a specific ion balance each other.
Equilibrium potential (Eion)
How many ions can move across the membrane to achieve equilibrium?
Eion (equilibrium potential) = Vm (membrane potential)
- Only a single ion can move across the membrane.
It calculates the potentials of two different elements and then calculate the difference between these elements to predict the potential across a cell.
Nernst equation
It calculates the membrane potential considering the permeability and concentration of all relevant ions.
Goldman-Hodgkin-Katz equation
What is the principal intracellular cation?
K+ (Potassium)
What is the principal extracellular cation?
Na+ (Sodium)
What are the principal intracellular anions? (4)
- Proteins
- amino acids
- sulfate
- phosphate
What is the principal extracellular anion?
Cl– (Chloride ion)
At resting potential, where is the concentration of K+ greater? Where is the concentration of Na+ greater?
- Concentration of K+ is greater inside the cell
- Concentration of Na+ is greater outside the cell
What do sodium-potassium pumps use to maintain K+ and Na+ gradients?
energy of ATP
What does the opening of ion channels in the plasma membrane convert?
Chemical potential to electrical potential
What type of channels are more open at resting potential in a neuron?
K+ channels
What happens to K+ at resting potential in a neuron?
K+ diffuses out of the cell
What contributes to the negative charge within a neuron at resting potential?
Anions trapped inside the cell
A gate that allows ions to diffuse across the plasma membrane; they are always open.
non-gated ion channels
How do excitable cells generate large changes in their membrane potential?
By opening or closing gated ion channels in response to stimuli.
What happens when ion channels open or close?
The membrane’s permeability to particular ions changes, altering the membrane potential.
What are the two (2) types of gated ions?
- Chemically-gated ion channel
- Voltage-gated ion channel
An ion channel that opens or closes in response to a chemical stimulus (ligand-gated).
chemically-gated ion channel
An ion channel that opens or closes in response to a change in membrane potential.
voltage-gated ion channel
What do changes in membrane potential of a neuron give rise to?
Nerve impulses.
Changes in membrane potential where the magnitude of change varies with the strength of the stimulus.
Graded Potential
What are the two (2) types of Graded Potential?
- Hyperpolarization
- Depolarization
What type of graded potential? Gated K+ channels open, K+ diffuses out of the cell, and the membrane potential becomes more negative.
hyperpolarization
What type of graded potential? Gated Na+ channels open, Na+ diffuses into the cell, and the membrane potential becomes less negative.
Depolarization
- It is an “all or nothing” response triggered when the threshold potential is reached.
- Depolarization that results in graded potentials summing to approximately -55mV, achieving the threshold potential.
Action potential
What are the two (2) voltage-gated Na+ channels? (What is their function)
- closed activation gates open rapidly in response to depolarization
- open inactivation gates close slowly in response to depolarization
What is this period?
* A temporary inactivation of the Na+ channels.
* After an action potential, a second action potential cannot be initiated.
Refractory period
