MD137 Lecture 2: Resting Membrane Potential

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Questions and Answers

What is the primary ion that contributes to the resting membrane potential due to its greater permeability?

Cl-

Ca2+

K+ (correct)

Na+

The concentration gradients for K+ and Na+ across the cell membrane create which type of potential?

Diffusion potential (correct)

Chemical potential

Thermal potential

Hydrostatic potential

What occurs at equilibrium concerning ion movement across the membrane?

Concentration forces are neutralized by electrical forces (correct)

No ions move across the membrane

Electrical forces exceed concentration forces

Ions move in only one direction

What factor pulls K+ ions into the cell despite their net diffusion outwards?

Electrochemical gradient Signup and view all the answers

Which of the following best describes the resting membrane potential?

The voltage when ion movement is at electrochemical equilibrium Signup and view all the answers

What does the Nernst equation primarily calculate?

Equilibrium potential for an ion Signup and view all the answers

What is the equilibrium potential for potassium ion (K+) based on the content?

-93 mV Signup and view all the answers

Which ion is primarily responsible for establishing the resting membrane potential (RMP)?

K+ Signup and view all the answers

What is the total contribution of the Na+/K+ pump to the resting membrane potential (RMP)?

6-8 mV Signup and view all the answers

What factor does the GHK equation take into account that the Nernst equation does not?

Permeability of multiple ions Signup and view all the answers

How does the mobility of Na+ affect the resting membrane potential?

It slightly affects RMP as it is relatively impermeable. Signup and view all the answers

What is the major role of the Na+/K+ pump in maintaining the cellular environment?

To maintain ionic gradients Signup and view all the answers

What primarily affects the resting membrane potential (RMP) of a neuron?

The unequal distribution of ions across the cell membrane Signup and view all the answers

Why does the resting membrane potential not equal the equilibrium potential for K+?

Because the membrane has a significant permeability to Na+. Signup and view all the answers

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

The presence of large negatively charged proteins inside the cell Signup and view all the answers

Which ion has a greater permeability that contributes to resting membrane potential?

K+ Signup and view all the answers

What role does the Na+/K+ electrogenic pump play in resting membrane potential?

It maintains the unequal distribution of ions necessary for RMP Signup and view all the answers

What concept relates to the voltage difference across a cell membrane?

Bioelectricity Signup and view all the answers

Luigi Galvani's experiments demonstrated a relationship between which two types of electricity?

Biological electricity and artificial electricity Signup and view all the answers

Which factors are NOT involved in the formation of the resting membrane potential?

Equal ion concentration on both sides of the membrane Signup and view all the answers

What can be a dangerous effect of potassium in a patient's bloodstream?

Inhibition of Na+/K+ pump function Signup and view all the answers

Study Notes

Course Information

Course: MD137
Course description: Introduction to Physiology
Lecturer: Leo Quinlan
Lecturer email: [email protected]
Academic year: 2024-2025

Lecture 2: Resting Membrane Potential (RMP)

Topic: Resting Membrane Potential (RMP)
Content:
- RMP is the electrical potential difference across the cell membrane of a neuron when it is at rest.
- RMP is typically around -70mV.
- Key factors that contribute to the formation of RMP:
  - Unequal distribution of ions across the membrane
  - Greater membrane permeability to potassium (K+) ions than sodium (Na+) ions
  - Large negatively charged, impermeable anions inside the cell
  - Sodium-potassium pump (Na+/K+ pump)
- The Na+/K+ pump actively maintains the ion gradients across the membrane.

Glial cell types in the CNS

Microglial cells - immune function
Oligodendrocytes - myelin sheath production
Astrocytes - neuronal support, blood-brain barrier
Ependymal cells - blood-CSF barrier

Learning Outcomes

Define resting membrane potential (RMP)
Describe the components that form RMP
Explain the formation of the nerve's RMP
Explain the reason for RMP being near -70mV
Explain how potassium can be lethal

Exitable Central Neurons

Central neurons exhibit various wave patterns
Specific frequencies are denoted as alpha, beta, theta, and delta waves.

Exitable Peripheral Neurons

Graphs show characteristic oscillations of excitability in peripheral neurons.

Bioelectricity

Electrical charges exist in cells, especially nerve and muscle cells.
Biopotentials are transmembrane potentials, resulting from voltage differences across cell membranes.
Luigi Galvani's experiments demonstrated the electrical nature of nerve impulses in frogs.

Measuring RMP

Measuring RMP
Using a voltmeter and microelectrodes
Measuring the voltage diffrence between the outside of the cell and inside the cell.

Membrane Potential Changes

Depolarization - membrane potential becomes less negative
Repolarization - membrane potential returns to resting level
Hyperpolarization - membrane potential becomes more negative

Bioelectricity - Equilibrium

Equal distribution of charges across a cellular membrane.

What contributes to RMP Generation

Unequal ion distribution across cell membranes
Higher membrane permeability to K+ ions than Na+ ions
Presence of large, impermeable anions inside the cell
Sodium-potassium pump (Na+/K+ pump)

Typical ion concentrations in neurons

Table detailing typical ion concentrations inside and outside a neuron's axon

Membrane Permeability (K+ vs. Na+)

Explain the relative differences in permeability of the membrane to K⁺ vs Na⁺ ions.
K⁺ is more permeable.

Equilibrium Potential of K+ (EK)

Derive EK using the Nernst equation.
Use data to confirm.

Importance of the Na+/K+ Pump

Maintain ion concentration gradients.
Contribute about 6-8mV to the overall RMP

Potentials in real neurons

Passive K⁺ distribution is not the entire cause of membrane potential
Membranes are relatively, not absolutely, impermeable to Na⁺
Na+/K+ pump plays as major contributor

GHK Equation

More comprehensive model for calculating membrane potential (Em)
Considers all ion permeabilities

Questions

Net driving force on K⁺ ions
Net driving force on Na⁺ ions
Ion diffusion direction
Impact of altered extracellular ion concentrations on membrane potential (Vm).

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Description

This quiz covers the resting membrane potential (RMP) as discussed in Lecture 2 of the MD137 Introduction to Physiology course. It explores the electrical potential difference across the cell membrane of neurons at rest, key factors contributing to RMP, and the role of the Na+/K+ pump. Additionally, it touches on glial cell types in the CNS.