Neurophysio

Opening Remarks

• Good morning and introduction to today's session.

• Discussion about the cold weather in Michigan Tech and the amount of snow.

• Mention of a student who consistently wears shorts regardless of the chilly weather.

Class Announcements

• No new announcements, but a reminder about the homework assignment due this Friday.

• The assignment will differ in style and is expected to be submitted at the start of class.

• Urged students to access the website to help answer questions, as many answers are available directly through it.

Simulator Introduction

• Introduction of a simulator related to the day's topic: action potentials.

• Encouragement to explore the website and perform related experiments if interested.

• Mention of an upcoming test scheduled for the next Monday.

• Commitment to provide a cutoff point for the test and what learning objectives will be included.

Test Structure

• Test will be a Scantron format, with all used materials being closed notes and devices.

• Students can only keep the Scantron sheet after submission; actual questions will not be collected or graded immediately.

• Keys for the test will be posted at noon, allowing students to self-grade if they choose.

• Encouragement to review old exams as a study resource, emphasizing the class's multiple levels of difficulty.

• Final advice on preparation: understand jargon and core definitions, memorize essential concepts, and practice through tests.

Action Potentials: Core Topic

• The upcoming focus is on action potentials, fundamental to physiology and the nervous system.

• Action potentials represent rapid and reversible changes in membrane potentials of electrically excitable cells (e.g., neurons and muscle cells).

• Connection to the importance of action potentials in biological functions and understanding nervous system operations.

Understanding Action Potentials

• Definition:

  • An action potential is a rapid shift in membrane potential, usually characterized with references to changes from negative to positive voltages.

• Importance in physiology:

  • Serves as a crucial aspect of communication in biological systems, particularly within the nervous system.

Graphing Action Potentials

• Discussion about how to graphically represent action potentials, noting:

  • Resting membrane potential is typically around -70mV.

  • The spike of action potential typically rises to about +30mV within milliseconds.

• Emphasis on understanding how voltage changes over time can illustrate physiological processes.

Electrophysiological Basis of Action Potentials

• Action potentials are generated by the opening of voltage-gated sodium channels resulting in rapid depolarization as sodium ions (Na+) rush into the cell.

• Following depolarization, potassium channels open, leading to repolarization as potassium ions (K+) exit the cell.

Refractory Periods

• Explanation of two types of refractory periods that occur immediately after an action potential:

  • Absolute refractory period: No new action potential can be initiated regardless of stimulus strength.

  • Relative refractory period: A stronger-than-normal stimulus is necessary to initiate a new action potential due to the membrane's hyperpolarized state.

Communication Within the Nervous System

• Action potentials must travel efficiently across long distances within the body (e.g., from the brain to muscles).

• Introduction of the concept of conduction, which is essential for effective nervous system function.

• Next topic will include how conduction improves the speed of action potential propagation across neurons.