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Questions and Answers
What is the resting membrane potential?
What is the resting membrane potential?
The constant membrane potential present in the cells of nonexcitable tissues and those of excitable tissues when they are at rest.
Which ions are primarily responsible for the generation of the resting membrane potential?
Which ions are primarily responsible for the generation of the resting membrane potential?
- Calcium (Ca+)
- Potassium (K+) (correct)
- Anions (A-) (correct)
- Sodium (Na+) (correct)
Calcium ions significantly contribute to the resting membrane potential in most cells.
Calcium ions significantly contribute to the resting membrane potential in most cells.
False (B)
The membrane is more permeable to K+ than to Na+ at rest.
The membrane is more permeable to K+ than to Na+ at rest.
The potential that would exist when K+ movement is balanced is known as the ______ potential.
The potential that would exist when K+ movement is balanced is known as the ______ potential.
What is the equilibrium potential for K+ ($E_{K+}$)?
What is the equilibrium potential for K+ ($E_{K+}$)?
What is the Nernst equation used to calculate?
What is the Nernst equation used to calculate?
What is the equilibrium potential for Na+ ($E_{Na+}$)?
What is the equilibrium potential for Na+ ($E_{Na+}$)?
What is the primary direction of the concentration gradient for K+ ions?
What is the primary direction of the concentration gradient for K+ ions?
The electrical gradient for K+ ions moves toward the negatively charged side of the membrane.
The electrical gradient for K+ ions moves toward the negatively charged side of the membrane.
What is the voltage of the membrane potential at equilibrium for K+?
What is the voltage of the membrane potential at equilibrium for K+?
When both K+ and Na+ effects are taking place concurrently, their interactions create a ______ in the membrane potential.
When both K+ and Na+ effects are taking place concurrently, their interactions create a ______ in the membrane potential.
What two forces act on K+ ions when they are moving across the membrane?
What two forces act on K+ ions when they are moving across the membrane?
The Na+-K+ pump maintains higher concentrations of Na+ inside the cell compared to outside.
The Na+-K+ pump maintains higher concentrations of Na+ inside the cell compared to outside.
What ultimately happens when the opposing electrical and concentration gradients for K+ ions reach equilibrium?
What ultimately happens when the opposing electrical and concentration gradients for K+ ions reach equilibrium?
The balance point where the net movement of K+ ions ceases is known as the K+ _____ potential.
The balance point where the net movement of K+ ions ceases is known as the K+ _____ potential.
What is the main effect of K+ leaving the cell on the membrane potential?
What is the main effect of K+ leaving the cell on the membrane potential?
Match the ions with their respective concentration gradients in relation to the cell.
Match the ions with their respective concentration gradients in relation to the cell.
What does the resting membrane potential refer to?
What does the resting membrane potential refer to?
Sodium ions (Na+) have a higher concentration inside the cell than outside at rest.
Sodium ions (Na+) have a higher concentration inside the cell than outside at rest.
What is the role of the Na+-K+ pump?
What is the role of the Na+-K+ pump?
The large negatively charged intracellular proteins are referred to as ______.
The large negatively charged intracellular proteins are referred to as ______.
Match the ion to its primary location in relation to resting membrane potential:
Match the ion to its primary location in relation to resting membrane potential:
When the membrane is at resting potential, how much more permeable is it to K+ than to Na+?
When the membrane is at resting potential, how much more permeable is it to K+ than to Na+?
Calcium ions contribute significantly to the resting membrane potential in most cells.
Calcium ions contribute significantly to the resting membrane potential in most cells.
Why are anions unable to pass through the plasma membrane?
Why are anions unable to pass through the plasma membrane?
The selective movement of ions through the plasma membrane contributes to the ______ properties of the membrane.
The selective movement of ions through the plasma membrane contributes to the ______ properties of the membrane.
Which ion is present in a higher concentration inside the cell compared to outside?
Which ion is present in a higher concentration inside the cell compared to outside?
What does a membrane potential of -90 mV indicate?
What does a membrane potential of -90 mV indicate?
The Nernst equation can be used to calculate the equilibrium potential for any ion based solely on its concentration inside the cell.
The Nernst equation can be used to calculate the equilibrium potential for any ion based solely on its concentration inside the cell.
What happens when the concentration gradient for Na+ moves this ion into the cell?
What happens when the concentration gradient for Na+ moves this ion into the cell?
The constant in the Nernst equation that incorporates several factors is ____.
The constant in the Nernst equation that incorporates several factors is ____.
Match the following terms with their definitions:
Match the following terms with their definitions:
What does a greater concentration gradient for an ion indicate about its equilibrium potential?
What does a greater concentration gradient for an ion indicate about its equilibrium potential?
A high concentration of K+ outside the cell will increase the equilibrium potential for K+ to a positive value.
A high concentration of K+ outside the cell will increase the equilibrium potential for K+ to a positive value.
What is the impact of Na+ movement across the membrane on membrane potential?
What is the impact of Na+ movement across the membrane on membrane potential?
The formula used to calculate the equilibrium potential for K+ is $E_{K+} = 61 log rac{C_o}{C_i}$, where C_o is the concentration of the ion ____ the cell.
The formula used to calculate the equilibrium potential for K+ is $E_{K+} = 61 log rac{C_o}{C_i}$, where C_o is the concentration of the ion ____ the cell.
If the equilibrium potential for K+ is -90 mV, which of the following concentrations is accurate?
If the equilibrium potential for K+ is -90 mV, which of the following concentrations is accurate?
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Study Notes
Resting Membrane Potential
- The resting membrane potential (RMP) is the constant membrane potential present in non-excitable cells and excitable cells at rest.
- Excitable tissues (nerve and muscle cells) produce rapid, transient changes in their membrane potential when excited, serving as electrical signals.
- The unequal distribution of key ions between the intracellular fluid (ICF) and extracellular fluid (ECF), and their selective movement through the plasma membrane contribute to the electrical properties of the membrane.
- The ions primarily responsible for RMP are sodium (Na+), potassium (K+), and intracellular anions (A-; large, negatively charged proteins).
Ion Concentrations and Permeabilities
- Na+ concentration is higher in the ECF, while K+ concentration is higher in the ICF.
- The Na+-K+ pump actively maintains this concentration difference using energy (ATP).
- The plasma membrane is virtually impermeable to A-, these proteins remain trapped inside the cell.
- The membrane is more permeable to K+ than Na+ at rest due to the presence of more open channels for K+ movement.
- K+ and Na+ can passively cross the membrane through specific protein channels.
- The relative concentrations and permeabilities of ions are crucial for understanding forces acting across the plasma membrane.
Potassium (K+) Equilibrium Potential (Ek+)
- The concentration gradient for K+ favours its movement out of the cell.
- As K+ leaves the cell, the inside becomes more negative relative to the outside, establishing a membrane potential.
- The negative membrane potential draws K+ back into the cell, counterbalancing the outward concentration gradient.
- Equilibrium is reached when the opposing forces (concentration and electrical gradients) balance, resulting in no net K+ movement.
- The membrane potential at this equilibrium is called the potassium equilibrium potential (Ek+) which is -90 mV.
- The Nernst equation can be used to calculate the equilibrium potential for an ion:
E=61logCoCiE = 61 log \frac{C_o}{C_i}E=61logCi​Co​​ where:- E = equilibrium potential in mV
- Co = concentration of the ion outside the cell (mM)
- Ci = concentration of the ion inside the cell (mM)
Sodium (Na+) Equilibrium Potential (ENa+)
- The concentration gradient for Na+ favours its movement into the cell.
- As Na+ enters the cell, the inside becomes more positive relative to the outside, building a membrane potential.
- This positive potential repels further inward movement of Na+ until equilibrium is reached, where the opposing forces (electrical and concentration gradients) balance.
- The equilibrium potential for Na+ (ENa+) is +60 mV.
- The magnitude of ENa+ is smaller than Ek+ because the concentration gradient for Na+ is smaller than that of K+.
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