The Neurophysiology of Nerve Impulses

The Neurophysiology of nerve impulses

Abstract:

This report will discuss the effects of various substances used on a neuron creating ion conductance and ion channel behavior in the resting membrane, first for transmission signals and second using an electrical simulator creating stimulus on an Axon triggering action potentials.  In these experiments; first a neuron is place in a Petri dish, it is submerged into three different substances; a control, high potassium and low sodium. Using a microelectrode tip that is inserted into the neuron membrane to get transmission signals from a resting membrane, demonstrating that when different ions are present either out side or inside of a membrane, a nerve cell can be polarize. Next an Axon is used in a nerve chamber by using an electrical stimulator electrical current is applied to the axon at different voltages and frequencies to create action potentials.  An oscilloscope records the differenced in ions charge and voltage whether a neuron or an axon membrane is stimulated chemically or electrically, this stimulation creates a line traced on the oscilloscope screen and results are recorded. Base on the knowledge that nerves and muscles cells are “excitable” that is, they are capable of generating rapidly changing electrochemical impulses at their membranes (Guyton & Hall, 52) we can anticipate that the diffusion of ions like potassium, sodium or electrical activity (voltage) will allow diffusion into the channels of a membrane creating activity responsible for signal transmissions in nerves “action potentials”  

Introduction:

Signals are carried by sensory neurons from the peripheral nervous system; these are impulses that eventually reach the Central nervous system which control many cell functions. All this due to the membrane of neurons which conducts electrical signals when is stimulated. These experiments will introduce different concentration of ions and electrical currents to change the permeability of the neuron membrane through these changes it may allow a change on concentration of ions inside the nerve that may create a depolarization or in simple terms and action potential.

Methods

These experiments were conducted in a computerized lab. In the first lab activity 9.1 the chemical simulation lab, we used three different gradient solutions; a control, high potassium and a low sodium. Adding first the control solution with a concentration of 5nK+ and 15mMNa+ which it is similar to the extra fluid found in the nerve. The micromanipulators introduce the tip to the out side of the cell body of a neuron observing a 0 mV and inside a -70 mV noticing an impulse. Neuron then was clean and a new solution was introduced a high potassium 25Mk+ and 130mMNa+, using manipulator’s tip touching the inside of an axon we observed a change of -70mV and by adding more potassium a decrease in voltage -40mV intracellular were the axon in the extracellular part decreased to -0mV. The micromanipulator tip touches the cell body part extracellular and no voltage was notice -0mV, were in the cell body intracellular an action potential was observed at -40mV. Neuron was clean againg and a low chemical solution of sodium 5mMK+, 30mMNa+ and 170mMtmA+ was introduced. Using the micromanipulator once again, the tip touch the cell body extracellular given; a -0mV, touching the axon in the extracellular part resulting in -0mV and touching the axon in the intracellular part given an impulse on -72mV. All data was recorded in the same micromanipulator table.  The electrical stimulation lab used for activity 9.5 was conducted by applying different charges on stimulus voltages from 0mV up to a final 60mV and electrical intervals of stimuli by millisecond to an axon from 250(msce) down to 3.75(msce). First starting at 0mV voltage a stimulus was applied no action potential was generated, an increase to 20mV and a stimulus was applied not action potential was generated too, consequently voltage was increase and stimulus per millisecond reduce every time applying at the same time an electrical stimuli until  there was a impulse generated and an action potential was observed.

Materials:

Stimulator

Oscilloscope

 Nerve chamber

Neuron (invitro)

Three extracellular solution (control, High potassium and low sodium),

Microelectrode manipulator controller

 Microelectrode amplifier

Experiment Data:

Extracellular Fluid (ECF)           Microelectrode Position                         Voltage (mV)

Control                                       Cell body extracellular                                                  0

Control                                       Cell body intracellular                                                -70