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Questions and Answers
Which ion has the highest concentration gradient and membrane permeability at rest?
Which ion has the highest concentration gradient and membrane permeability at rest?
- Sodium ion (Na+)
- Potassium ion (K+) (correct)
- Chloride ion (Cl-)
- Calcium ion (Ca2+)
Sodium ions have a higher concentration inside the cell compared to outside.
Sodium ions have a higher concentration inside the cell compared to outside.
False (B)
What is the resting membrane potential (RMP) of a typical nerve cell?
What is the resting membrane potential (RMP) of a typical nerve cell?
-70 mV
The diffusion of chloride ions into the cell is prevented by the attraction force between chloride and __________ ions outside the membrane.
The diffusion of chloride ions into the cell is prevented by the attraction force between chloride and __________ ions outside the membrane.
Match the following ions with their concentration gradient direction at rest:
Match the following ions with their concentration gradient direction at rest:
What type of channels allows for the movement of sodium ions across the resting membrane?
What type of channels allows for the movement of sodium ions across the resting membrane?
What is the typical value of resting membrane potential (RMP) in millivolts?
What is the typical value of resting membrane potential (RMP) in millivolts?
The potassium leak channels are more effective than sodium leak channels at rest.
The potassium leak channels are more effective than sodium leak channels at rest.
What is one factor that contributes to the negative charge inside a cell?
What is one factor that contributes to the negative charge inside a cell?
The sodium-potassium pump exchanges 3 Na+ for _____ K+.
The sodium-potassium pump exchanges 3 Na+ for _____ K+.
Match the following factors with their contributions to the resting membrane potential:
Match the following factors with their contributions to the resting membrane potential:
What happens to the resting membrane potential when extracellular K+ ions increase?
What happens to the resting membrane potential when extracellular K+ ions increase?
The net loss of positive ions from the cell interior makes the inner side of the membrane positive.
The net loss of positive ions from the cell interior makes the inner side of the membrane positive.
What is the value of the potential difference when both electrodes are in extracellular fluid?
What is the value of the potential difference when both electrodes are in extracellular fluid?
The term RMP stands for _____ membrane potential.
The term RMP stands for _____ membrane potential.
Which of the following explains why the inside of the cell is more negative?
Which of the following explains why the inside of the cell is more negative?
What is the primary reason that excitable tissues are called 'excitable'?
What is the primary reason that excitable tissues are called 'excitable'?
Resting membrane potential (RMP) is defined as the potential difference between the inside and outside of the membrane when the cell is active.
Resting membrane potential (RMP) is defined as the potential difference between the inside and outside of the membrane when the cell is active.
What is the typical value of the resting membrane potential (RMP)?
What is the typical value of the resting membrane potential (RMP)?
The ___ equation calculates the equilibrium potential for an ion based on its concentration gradient.
The ___ equation calculates the equilibrium potential for an ion based on its concentration gradient.
Match the following types of stimuli with their examples:
Match the following types of stimuli with their examples:
Which ion is predominantly found at a higher concentration inside the cell compared to outside?
Which ion is predominantly found at a higher concentration inside the cell compared to outside?
The sodium-potassium pump helps maintain the resting membrane potential by moving sodium ions out and potassium ions in.
The sodium-potassium pump helps maintain the resting membrane potential by moving sodium ions out and potassium ions in.
What is the effect of increasing extracellular potassium concentration on RMP?
What is the effect of increasing extracellular potassium concentration on RMP?
The membrane is more permeable to ___ ions than to sodium ions at rest.
The membrane is more permeable to ___ ions than to sodium ions at rest.
What characteristic of resting membrane potential allows it to behave like a capacitor?
What characteristic of resting membrane potential allows it to behave like a capacitor?
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Study Notes
Resting Membrane Potential (RMP)
- RMP is the potential difference between the inside and outside of a cell membrane when the cell is at rest.
- RMP is typically -70 mV, with the inside of the cell being negative relative to the outside.
- RMP is caused by an unequal distribution of ions across the cell membrane.
Factors Contributing to RMP
- Potassium leak channels: Potassium ions (K+) leak out of the cell more readily than sodium ions (Na+) leak in. This creates a net loss of positive charge from the inside of the cell, making it negative.
- Large intracellular anions: Proteins, sulfates, and phosphates are negatively charged and are concentrated inside the cell. These negatively charged molecules contribute to the negative charge inside the cell.
- Sodium-potassium pump: This actively transports 3 sodium ions out of the cell for every 2 potassium ions it pumps in. This creates a net loss of positive charge from the inside of the cell, further increasing the negative charge.
Measuring RMP
- RMP can be measured using microelectrodes inserted inside and outside the cell.
- The difference in voltage between the two electrodes is the RMP.
Changes in Extracellular Ion Concentrations
- Increased extracellular potassium: This can reduce the efflux of potassium ions from the cell and even cause potassium ions to flow into the cell, leading to depolarization (less negative).
- Changes in extracellular sodium: Changes in extracellular sodium concentration have a smaller effect on RMP compared to potassium concentration changes.
Importance of Intracellular Recording
- Intracellular recording allows for precise measurement of membrane potential changes, which is crucial for understanding how cells communicate and respond to stimuli.
- It is especially important for studying action potentials.
Types of Membrane Channels
- Leak channels: These channels are always open and allow ions to passively diffuse across the membrane.
- Active Channels (AKA gated channels): These channels can open and close in response to various stimuli, such as a change in voltage (voltage-gated channels), the binding of a ligand (ligand-gated channels), or mechanical stress (mechanically-gated channels).
Exciting Tissues
- Excitability is the ability of a cell or tissue to respond to a stimulus.
- Excitability is driven by the polarization of the cell membrane.
- The cell membrane behaves like a capacitor, storing electrical charge.
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