Questions and Answers
The difference in charge across the membrane induces a voltage difference and is called _______________
Nernst equilibrium potential
Neurons can produce a spike of electrical activity called _______________
action potential
The electrical burst in a neuron travels along the neuron’s ___________ to its ___________ where it passes the signals to other neurons.
axon, axon terminal
What is the primary principle that causes ions to flow across the neuron's membrane?
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What is the pump that pumps three sodium ions out of the neuron for every two potassium ions pumped in?
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What is the electrical gradient that occurs when more potassium ions diffuse out, making the outside of the cell more positive and the inside more negative?
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At what potential does the Equilibrium position occur for potassium ions if the cell is permeable to potassium ions?
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What is the model that is based on the nonlinear interaction between membrane potential and the opening and closing of sodium and potassium ion channels?
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Study Notes
Cell Resting State
- A cell at rest has a higher concentration of potassium ions (K+) inside the cell and a higher concentration of sodium ions (Na+) outside the cell.
- This concentration gradient creates a negative net charge within the cell, maintained by a voltage gradient.
Depolarization and Repolarization
- When a cell becomes depolarized, sodium ions (Na+) enter the cell, making the charge within the cell more positive.
- When a cell repolarizes, potassium ions (K+) leave the cell, and the charge within the cell returns to a negative state.
Ion Flow and Resting Potential
- Even when the cell is at rest, potassium ions (K+) still flow out of the cell, causing a slight undershoot or hyperpolarization of the resting potential.
- The sodium-potassium pump and leakage channels compensate for this undershoot, re-establishing the initial resting potential.
Ions and Electric Charge
- An ion is an atom or group of atoms with an electric charge, which occurs when the number of electrons does not match the number of protons.
- Positive ions are called cations, while negative ions are called anions.
- Common ions in the body include sodium, potassium, calcium, chloride, and bicarbonate.
Neuron Electrical Activity
- The difference in charge across the membrane induces a voltage difference, known as the Nernst equilibrium potential.
- Neurons can produce a spike of electrical activity called an action potential.
- The electrical burst in a neuron travels along the axon to the terminal, where it passes signals to other neurons.
Nernst Equilibrium Potential
- The Nernst equation can estimate the resting potential of a neuron based on the concentration gradients of different ions.
- For example, if a cell has only potassium channels, the concentration gradient favors potassium ions to exit the cell, making the outside more positive and the inside more negative.
Diffusion Potential
- As potassium ions diffuse out of the cell, they carry a positive charge with them, making the outside of the cell more positive and the inside more negative.
- This electrical gradient, known as the diffusion potential, blocks the further exit of potassium ions despite the existing concentration gradient.
Hodgkin and Huxley Model
- The Hodgkin-Huxley Model describes the interaction between membrane potential (voltage) and the opening and closing of sodium (Na+) and potassium (K+) ion channels.
- Both Na+ and K+ ion channels are voltage-dependent, and their opening and closing changes with the membrane potential.
- The model acknowledges the role of ionic sodium and potassium currents, as well as leak currents, through the use of conductance terms (gating variables).
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Description
Understand the ionic movements and charge changes within a cell during depolarization and repolarization. Learn how sodium and potassium ions affect the cell's net charge and voltage gradient.
