Electrochemical Impulse Aka An Action Potential By Rita

Electrochemical Impulse Aka: An Action Potential By: Rita Kumar

Discovery of electrochemical impulses Luigi Galvani (1737 – 1798) Luigi Galvani Julius Bernstein (18391917) K. S. Cole and H. J. Curtis • experimented with frogs at University of Bologna in a solution of saltwater • Proposed the membrane hypothesis (1902) Cole and Curtis decided to test this theory • accidentally touched two different metals together • Neurons have selectively permeable cell membranes. These membranes allow for the transport of K+ and Na+ ions Extracted neuron from a squid • results indicated electrical stimulation • At rest, the neuron has a potential difference across its membrane tested with an electrode spanning the cell membrane • K+ flow out of the cell, resulting in a decrease of potential difference They proved Bernstein’s hypothesis K. S. Cole

Sodium Potassium Pump

Steps in an Electrotonic Potential � There are voltage gated ion channels for sodium and channels for potassium ions. � A stimulus forces a Na+ channel open. � Sodium ions flow into the cell � The voltage across the membrane will increase � When the voltage reaches its threshold potential, other voltage gated ion channels are stimulated, and they open as well � Electrotonic potentials faster than action potentials. � The effect of electrotonic potential decrements the further down the cell you go.

Steps in an Action Potential

Saltatory Conduction � Saltatory conduction is facilitated by the myelin sheath. � Rather than having an action potential travel all the way down the axon, it “jumps” from node to node. � Much faster than action potential across an unmyelinated nerve. � Factors affecting saltatory conduction: ◦ Neuron size: Bigger neuron, faster conduction

Function of Intracellular Structures in Saltatory Conduction Intracellular Structure Role in Nerve Impulse Dendrites Receive a stimulus Soma Collects stimuli from the dendrites Cell Nucleus N/A Axon Hillock Determines whether the strength of an impulse is enough to fire action potential Nodes of Ranvier Allow for an action potential to travel down the axon Myelin Sheath Integral part of saltatory conduction Schwann Cell Form the myelin sheath around the axon Synaptic Terminal Send the impulse to another neuron or a muscle cell

What Does It Do For the Body? � The purpose of electrochemical impulse is to pass a stimulus-generated impulse down the neural axon to a receptor, be it another neuron or a muscle. � The passing of electrochemical impulses allows for organisms to recall, feel, think, emote, hear, see, etc. � Without proper nerve conduction, diseases such as multiple sclerosis may occur.

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