Integrated Physiology: Action Potential & ANS

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Questions and Answers

What primarily generates the resting membrane potential in neurons?

Selective K+ permeability (correct)

Calcium channels

Chloride ion concentration

Sodium permeability

Which ion channel is responsible for the depolarization phase of the action potential?

Ca2+ channels

Cl- channels

K+ channels

Na+ channels (correct)

During which phase of the action potential do Na+ channels become inactivated?

Refractory period

Resting potential

Repolarization (correct)

Threshold potential

What is the value of the typical resting membrane potential for neurons?

-70mV Signup and view all the answers

What does the Nernst equation predict?

The equilibrium potential for a single ion species Signup and view all the answers

What occurs during the absolute refractory period?

Na+ channels cannot be stimulated Signup and view all the answers

Which ion has the highest permeability during the repolarization phase?

K+ Signup and view all the answers

What is the role of the myelin sheath in axonal conduction?

Facilitating faster action potential generation Signup and view all the answers

What is a compound action potential?

The sum of multiple axon action potentials measured together Signup and view all the answers

Which part of the neuron receives incoming signals?

Dendrite Signup and view all the answers

Which fiber type transmits information about pain and temperature?

Aδ Signup and view all the answers

Which fiber type is responsible for motor control to muscle spindles?

Aγ Signup and view all the answers

Which of the following is NOT a benefit of myelination?

Increases membrane permeability Signup and view all the answers

In demyelination, which of the following occurs?

Increased membrane capacitance Signup and view all the answers

What is the primary reason for the increased conduction velocity in myelinated axons?

Both A and B Signup and view all the answers

Which of the following is TRUE about the nodes of Ranvier?

Both A and B Signup and view all the answers

What is 'saltatory conduction'?

The jumping of action potentials from one node of Ranvier to the next Signup and view all the answers

What is the main function of the B fibers?

Preganglionic autonomic Signup and view all the answers

What is the primary function of the inactivation gate in a Na+ channel?

To ensure that the action potential only travels in one direction by preventing the opening of Na+ channels in the direction from which the action potential has already traveled. Signup and view all the answers

What is the main characteristic that distinguishes the relative refractory period from the absolute refractory period?

The relative refractory period is a period of reduced excitability but still allows for the generation of action potentials with a strong enough stimulus. Signup and view all the answers

Why is the 'all-or-none' principle important for action potential propagation?

It allows the nervous system to encode stimulus intensity by altering the frequency of action potentials rather than the amplitude. Signup and view all the answers

Based on the analogy of a toilet flushing, what would correspond to the 'absolute refractory period'?

The period when the bowl is full and the cistern is empty. Signup and view all the answers

Which of the following is NOT a property of action potentials?

They are graded potentials, meaning their amplitude can vary with stimulus strength. Signup and view all the answers

Which of the following factors contributes to the faster conduction velocity of action potentials?

Both A and B. Signup and view all the answers

What is the primary role of the sodium-potassium pump in the context of action potentials?

To establish the electrochemical gradient that drives the movement of ions during action potentials. Signup and view all the answers

What is the significance of the "undershoot" phase during an action potential?

It is the phase where the neuron is hyperpolarized and less likely to fire another action potential. Signup and view all the answers

Study Notes

Course Information

Course title: Integrated Physiology
Course code: PH2130
Instructor: Stuart Cruickshank

Presentation Topics

Action Potential
Neurotransmitters
Autonomic Nervous System

Why Emphasize the ANS?

Vasovagal syncope is an example
[YouTube Video Link]

Neuron Structure

Cell body (soma)
Dendrites
Axon hillock (initial segment)
Axon
Axon collaterals
Myelin sheath
Nodes of Ranvier
Terminal branches/axon terminals (synaptic knobs)
Presynaptic terminals

Axonal Conduction

Resting membrane potential
Ion channels generating action potential
Speeding up action potentials
Compound action potentials

Resting Membrane Potential

Generated by selective potassium (K+) permeability of the membrane
Ion distribution across the membrane (diagrammed)

Nernst Equation

Predicts equilibrium potential for a single ion species
Formula and variables (R, T, z, F) are defined

Electrophysiology Summary

Short description of electrophysiology, with relevant ions(Na+, Ca2+, Cl-) and membrane potential(-70mV)

Action Potential Permeability Changes

Graph showing permeability changes of Na+, K+ during an Action Potential

Action Potential Summary

Depolarization phase
Repolarization phase
Resting membrane potential
Threshold potential
Diagrams showing ion movement during different phases of the Action Potential

Refractory Periods

Absolute Refractory Period
- Na+ channels cannot be stimulated again until inactivation gate resets
Relative Refractory Period
- Requires a stronger-than-usual stimulus to create another AP

Self-propagation of Action Potentials

Diagram showing sequential activation of Na+ channels along an axon, leading to propagation down the axon

Properties of Action Potentials

Voltage-gated channels mediate action potentials
All-or-none response to stimulus
Signalled through frequency changes, not amplitude
Refractory periods prevent overlapping action potentials
Self-propagating for long-distance signaling
Conduction velocity improved by large axons or myelination

Nerve Fiber Types

Classification based on myelination and conduction velocity
Different classes of nerve fibers and their associated functions

Myelination

Speeds up action potential transmission
Diagram demonstrating myelinated vs. unmyelinated axons
Saltatory conduction
Increased membrane resistance during myelination

Demyelination

Opposite effect to myelination
Diagram showing effect of demyelination, which slows conduction significantly

Key Concepts

Important concepts related to resting/action potentials, affecting velocity, myelination and de-myelination, refractory periods.

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Description

This quiz covers key topics in Integrated Physiology, focusing on the Action Potential and the Autonomic Nervous System. Delve into concepts like resting membrane potential, ion channels, and neuron structure. Enhance your understanding of essential electrophysiological principles and their applications.