Introduction to Physiology Lecture 2

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Questions and Answers

What primarily contributes to the resting membrane potential (RMP)?

Increased Na+ permeability compared to K+

Sodium-potassium pump activity alone

Net diffusion of K+ out of the cell (correct)

High concentration of negatively charged proteins inside the cell

What does a greater membrane permeability to K+ indicate about the cell's resting state?

The cell has no influence from chloride ions

K+ ions move into the cell more easily than Na+

K+ ions will diffuse out more readily than Na+ ions can enter (correct)

K+ ions tend to stay within the cell

What equilibrium is achieved when the concentration of K+ is balanced by electrical forces?

Equilibrium potential (correct)

Resting potential only

Action potential

Threshold potential

Which factor does NOT play a role in the generation of the resting membrane potential?

The presence of ATP in the cell Signup and view all the answers

How is the resting membrane potential generated?

By opposing forces of concentration and electrical gradients Signup and view all the answers

What is the resting membrane potential (RMP) primarily determined by?

Distribution of ions across the membrane Signup and view all the answers

Which ion has a greater permeability that contributes to the formation of RMP?

K+ Signup and view all the answers

How does the Na+/K+ pump contribute to the resting membrane potential?

It moves more K+ in than Na+ out. Signup and view all the answers

What role do large indiffusible anions play in the resting membrane potential?

They help maintain a negative charge inside the cell. Signup and view all the answers

Why is the nerve resting membrane potential typically around -70mV?

Because K+ ions tend to leave the cell more readily. Signup and view all the answers

What is bioelectricity primarily associated with?

Electrical charges found in muscle and nerve cells Signup and view all the answers

Luigi Galvani's experiments highlighted the relationship between which two types of electricity?

Natural electricity and neural electricity Signup and view all the answers

What can excessive potassium levels in the body lead to?

Cardiac arrest Signup and view all the answers

What does the Nernst equation calculate in the context of neuronal activity?

Equilibrium potential for ions Signup and view all the answers

Which of the following ions primarily determines the resting membrane potential (RMP)?

Potassium (K+) Signup and view all the answers

What does the sodium-potassium pump contribute to the resting membrane potential?

It contributes approximately 6-8 mV towards the negative potential. Signup and view all the answers

Why does the resting membrane potential (Vm) not equal the equilibrium potential for K+ (EK) of -93 mV?

The resting membrane potential is influenced by the permeability to multiple ions. Signup and view all the answers

What does the GHK equation account for when predicting resting membrane potential?

The movement of all ions and their permeabilities. Signup and view all the answers

What characteristic of the neuronal membrane significantly affects resting membrane potential?

It has higher permeability to K+ than to Na+. Signup and view all the answers

How many sodium ions are pumped out and potassium ions are pumped in by the Na+/K+ pump?

3 Na+ out and 2 K+ in Signup and view all the answers

What primarily drives the resting membrane potential despite the sodium-potassium pump's activity?

Passive diffusion of K+ Signup and view all the answers

Study Notes

Course Information

Course: MD137
Course title: Introduction to Physiology
Lecturer: Leo Quinlan
Email: [email protected]
Academic year: 2024-2025
Subject: Physiology
School: School of Medicine
University: University of Galway

Lecture 2: Resting Membrane Potential (RMP)

Resting Membrane Potential (RMP): The electrical potential difference across the cell membrane when the cell is at rest.
Bioelectricity: Electrical charges found in cells, primarily nerves and muscle cells.
Biopotentials: Transmembrane potentials, which are the voltage difference across the cell membrane.

Glial Cells in CNS

Microglial cells are similar to macrophages in the peripheral nervous system (PNS), serving an immune function in the central nervous system (CNS).
Oligodendrocytes in the CNS myelinate central neuronal axons, similar to Schwann cells in the PNS.
Astrocytes support neurons and contribute to the blood-brain barrier.
Ependymal cells contribute to the blood-cerebrospinal fluid (CSF) barrier.

Learning Outcomes

Understand the concept of resting membrane potential (RMP).
Identify the main components involved in RMP formation.
Explain the formation of nerve RMP.
Explain why nerve RMP is approximately -70mV.
Understand the potential danger of potassium imbalances.

Measuring RMP

A voltmeter measures the voltage difference across the membrane.
A microelectrode is inserted into the cell to measure the inside potential.
A ground electrode measures the outside potential.
RMP is typically around -70mV.

RMP Formation - Key Factors

Ion concentration differences: Unequal distribution of ions across the cell membrane. Key ions are potassium (K+), sodium (Na+), and chloride (Cl−).
Membrane permeability: The cell membrane is selectively permeable to different ions. It is more permeable to K+ than Na+.
Sodium-potassium pump (Na+/K+ pump): Actively maintains the ion concentration gradients. This pump moves 3 sodium ions out of the cell for every 2 potassium ions it moves in. This pump creates an electrogenic difference.

Equilibrium Potential

Diffusion potential: the imbalance of charges inside and outside the cell membrane.
Equilibrium potential: the membrane voltage where the concentration gradient is balanced by the electrical gradient.
The equilibrium potential for potassium (Ek) is approximately -90mV.

Why is Vm close to EK + not equal to EK?

RMP is primarily a diffusion potential (not from the pump itself).
The membrane is relatively but not perfectly permeable to sodium (Na⁺).

GHK Equation

The Goldmann-Hodgkin-Katz (GHK) equation describes membrane potential considering all ion permeabilities
It accounts for the permeability of multiple ions and more accurately models membrane potential.

Additional Questions

What is the net driving force on K+ ions?
What is the net driving force on Na+ ions?
Which way do the ions diffuse?
What effect does increasing Na+ or K+ permeability have on Vm?

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Description

This quiz covers key concepts from Lecture 2 on Resting Membrane Potential (RMP) and the role of glial cells in the central nervous system. Understand the electrical properties of cell membranes and the various types of glial cells and their functions. Test your knowledge on bioelectricity and biopotentials in physiological contexts.