Lecture Notes on Neuronal Action Potentials and Basic Electricity in Physiology

Summary of the Class

In today's class, the professor discussed how our neurons communicate using electrical impulses through a process called action potentials. The discussion included an introductory explanation of basic electrical principles within our body and how these principles facilitate communication within the nervous system.

Key Points from the Lecture

Neuronal Communication

Neurons send impulses of one uniform strength and speed.
Variation occurs in the frequency or number of pulses.
Our brain interprets these signals, organizing them by factors such as location, sensation, magnitude, and importance.

Concept of Action Potentials

An action potential is an electrical impulse occurring when a neuron is sufficiently stimulated.
This is a fundamental aspect of neurophysiology and involves the transmission from one neuron to another.

Basics of Electricity in the Body

The body is analogous to a battery, electrically neutral overall but with areas of positive and negative charge.
Membranes separate these charges to build potential energy, which can be used when charges are allowed to unite.

Membrane and Cellular Function

Voltage: the measure of potential energy generated by separated charges, measured in millivolts within the body.
Current: the flow of electricity from one point to another, influenced by voltage and resistance.
Resistance: the obstruction to the flow of current, varying between insulators and conductors.

Neuron as an Electrical System

Resting Membrane Potential: When inactive, a neuron has more negative charges inside compared to outside, sitting around -70 millivolts.
Sodium-Potassium Pump: Key component managing ion concentration and charge differences across the neuron membrane.

Ion Channels and Gates

Voltage-Gated Channels: Open at specific membrane potentials.
Ligand-Gated Channels: Open in response to specific neurotransmitters.
Mechanically Gated Channels: Triggered by physical stimulation like stretch.

Action Potential Dynamics

Initiated when a neuron reaches a threshold of about -55 mV after being stimulated.
Involves a sudden influx of sodium ions through voltage-gated channels, causing depolarization.
Followed by the opening of potassium channels leading to repolarization and possibly a brief hyperpolarization.
Action potentials are unidirectional due to the refractory period, preventing the backward flow of the impulse.

Signal Variability

The strength of the action potential does not vary; rather, the frequency and speed of action potentials change based on the stimulus.
Frequency: Varies with the intensity of the stimulus; important for determining the response intensity.
Speed: Influenced by the myelin sheath on axons; myelinated axons transmit impulses faster due to saltatory conduction.

Upcoming Sessions

The transference of action potentials between neurons and the role of neurotransmitters will be discussed in future lectures.

These lecture notes serve to encapsulate the critical aspects discussed today on how electrical principles are foundational to neuronal functions and communication, establishing a basis for understanding more complex neural mechanisms in upcoming classes.

"Understanding Neuronal Action Potentials and Electricity"