Neuroscience Chapter 3: Neuronal Membrane

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Questions and Answers

What is the primary function of the phospholipid bilayer in the neuronal membrane?

To form a barrier isolating the cytosol from extracellular fluid (correct)

To provide energy for action potentials

To synthesize proteins for neurotransmitter release

To facilitate the movement of ions into the cell

What type of charge do cations carry?

Net positive charge (correct)

Net negative charge

Variable charge depending on the ion

No charge

Which feature of water contributes to its function as a solvent in biological systems?

It has a high molecular weight

It has an uneven electrical charge (correct)

It is a non-polar substance

It can form covalent bonds

Which type of compound typically does not dissolve in water?

Hydrophobic compounds Signup and view all the answers

What is the resting membrane potential primarily dependent on?

The movement of ions across the membrane Signup and view all the answers

What is the primary reason for the resting membrane potential being negative?

Potassium ions diffuse out of the cell more than sodium ions diffuse in Signup and view all the answers

What role does the sodium-potassium pump (Na+/K+ ATPase) play in maintaining the resting membrane potential?

It stabilizes resting membrane potential by maintaining ion concentration gradients Signup and view all the answers

Which statement accurately describes membrane permeability at rest?

The membrane is more permeable to K+ than Na+ due to more leakage channels Signup and view all the answers

What factors contribute to the generation of resting membrane potential?

Differences in ion concentrations and permeability of the plasma membrane Signup and view all the answers

How does the resting membrane potential relate to ion channel distribution?

The relative ion permeabilities are determined by the number of channels for each type of ion Signup and view all the answers

What is resistance in the context of electrical charge movement?

The difficulty of charges to move Signup and view all the answers

According to Ohm's law, how is current related to voltage and resistance?

Current is equal to voltage divided by resistance Signup and view all the answers

What phenomenon is described by the need for tiny ion concentration changes to cause large changes in membrane potential (Vm)?

Sensitivity of the membrane Signup and view all the answers

What is the equilibrium potential (Eion) in the context of ion movement?

The balance point where ionic concentration gradient is equal to electrical potential difference Signup and view all the answers

What happens when there is no net current flow between two points?

The points have the same potential Signup and view all the answers

What primarily determines the rate of ion movement across a neuronal membrane?

Membrane potential and ion equilibrium potential Signup and view all the answers

Which ion is more concentrated on the inside of a typical neuronal cell?

K+ Signup and view all the answers

What defines a conductor in electrical terms?

A substance with low electrical resistance Signup and view all the answers

What is the primary function of the sodium-potassium pump?

Pump sodium ions out and potassium ions in Signup and view all the answers

What occurs when opposite charges are kept separated across a membrane?

They generate potential energy Signup and view all the answers

What is the resting membrane potential in neurons?

It is the voltage across the membrane at any moment Signup and view all the answers

What does the Nernst equation calculate?

Equilibrium potential for each ion Signup and view all the answers

What condition is NOT considered when calculating the equilibrium potential using the Nernst equation?

Ion size Signup and view all the answers

What is the role of membrane protein channels in neuronal function?

They allow ions to flow according to concentration gradients Signup and view all the answers

If there is no voltage across a membrane, what is the result concerning ionic movement?

No net movement of ions will occur Signup and view all the answers

How much ATP can the sodium-potassium pump consume in the brain?

70% Signup and view all the answers

How does the presence of K+ channels in the neuronal membrane affect membrane potential?

They cause a flow of K+ down the concentration gradient Signup and view all the answers

What has the highest concentration outside a typical neuronal cell?

Na+ Signup and view all the answers

What is the primary mechanism by which ions diffuse when gated channels are open?

Along chemical concentration gradients from higher concentration to lower Signup and view all the answers

What is significant about the potassium channels in relation to resting membrane potential?

Their selective permeability to K+ ions is a key determinant of resting membrane potential Signup and view all the answers

What discovery is associated with the Shaker potassium channel?

It was found in fruit flies and is part of a family of potassium channels Signup and view all the answers

Which structure within potassium channels is crucial for their selective permeability?

The pore loop area Signup and view all the answers

What effect does increased extracellular K+ concentration have on membrane potential?

It leads to a depolarization of the membrane Signup and view all the answers

What prestigious award did MacKinnon receive for his work on K+ channels?

The Nobel Prize in Physiology or Medicine Signup and view all the answers

Which statement accurately describes the number of subunits in potassium channels?

They consist of four subunits Signup and view all the answers

To what type of genetic disorders are mutations in specific K+ channels linked?

Inherited neurological disorders Signup and view all the answers

Study Notes

Neuronal Membrane Overview

Neuron communication relies on electrical signals known as action potentials, requiring a baseline resting membrane potential.
Resting membrane potential is the electrified state of neuronal cells, vital for action potentials to occur.

Key Components of Neuronal Membrane

Cytosol and extracellular fluid primarily consist of water, a polar solvent essential for dissolving ions.
Ions are charged atoms or molecules; cations have a positive charge, while anions have a negative charge.
The phospholipid bilayer forms a barrier that isolates neuronal cytosol from extracellular fluid, distinguishing hydrophilic (water-soluble) and hydrophobic (water-insoluble) substances.

Electrical Principles in Neuron Function

Ohm’s law explains the relationship between current (I), conductance (g), and potential (V): I = gV.
Voltage measures the potential energy generated by separated charges, with net charge differences leading to varying voltages.
Current signifies the flow of electric charge between two points, dependent on voltage and resistance.

Membrane Potential Dynamics

Neurons maintain a resting membrane potential that can change rapidly compared to other cell types.
The energy required to separate opposite charges across membranes contributes to potential energy.

Ionic Basis of Resting Membrane Potential

The equilibrium potential (Eion) depicts no net ion movement across membranes without channel proteins.
The presence of K+ channels leads to ionic flow down concentration gradients, altering charge/voltage across the membrane.
The Nernst equation calculates equilibrium potentials, accounting for ion charge, temperature, and concentration ratios.

Ion Distribution and Movement

Ion concentrations vary, with K+ primarily inside and Na+ along with Ca2+ predominantly outside the cell.
Sodium-potassium pumps (3 Na+ out, 2 K+ in) actively transport ions against their gradients, consuming up to 70% of brain ATP.

Membrane Permeability

Neuronal membranes are selectively permeable, with K+ permeability 25 times greater than Na+ due to more leakage channels.
More potassium diffuses out than sodium diffuses in, contributing to the negative internal charge and establishing resting membrane potential.

Role of Ion Channels

Membrane permeability relies on distinct ion concentrations, channel presence, and ion-specific conductance.
Gated channels allow ion diffusion along concentration and electrical gradients; potassium channels are central to resting membrane potential regulation.
Various types of K+ channels exist, such as the Shaker potassium channel, identified in fruit flies.

Potassium Channel Structure and Function

Potassium channels consist of four subunits, forming a selective filter for K+ ions through the pore loop area.
MacKinnon's research on K+ channels won the 2003 Nobel Prize, revealing that specific mutations lead to neurological disorders.

Importance of Extracellular K+ Concentration

The resting membrane potential closely aligns with EK due to high K+ permeability, making it sensitive to extracellular K+ changes.
Elevated extracellular K+ levels can cause membrane depolarization, significantly affecting neuronal activity.

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Description

This quiz explores the key components of the neuronal membrane, focusing on ion movements and the resting membrane potential. Understand the cellular electricity involved and the important ion channels that facilitate neuronal communication through action potentials.