Compound Action Potentials
Yentl Smith
BIOL 3810-504
Compound Action Potentials
Date Performed: 15FEB2011
Date Due: 01MAR2011
Introduction
Neurons are the cells that receive and transmit electrical signals (University of North Texas, 2010). The ability of the neuron to conduct these impulses is because of an electrochemical voltage across the plasma membrane of that neuron. An action potential is an all or nothing response to a stimulus along a single axon. A compound action potential is a graded response that results from the stimulation of more than one axon.
Action potentials can be broken down into five different phases: resting potential, threshold, rising, falling, and recovery. The inside of a cell is negatively charged and the potential difference across the plasma membrane is between 50 and 90 mV. In a resting cell, the membrane is more permeable to potassium than sodium. When synaptic activity makes the cell less negative, the sodium channels open. If the cell voltage goes past a certain level, an action potential is produced. Action potentials, changes in the membrane potential that happen when a nerve cell membrane is stimulated (Ritchison), happen within milliseconds. After the voltage has reached the threshold potential, more voltage-gated sodium channels open and the voltage of the membrane reaches its most positive value. The voltage-gated sodium channels close soon after opening, and with that, the potassium channels open. Now potassium is rushing back into the cell, repolarizing the cell back to its resting level. Now, because there are many more potassium gates are open than there were when the cell was resting, the cell hyperpolarizes. Finally, the extra potassium gates that were open, close and the sodium channels are ready to open again. There is no such thing as a weak or a partial action potential because action potentials are all-or-none (Randall, French, & Burggren, 2002). Either the threshold is reached, causing an action potential, or it’s not
BIOL 3810-504
Compound Action Potentials
Date Performed: 15FEB2011
Date Due: 01MAR2011
Introduction
Neurons are the cells that receive and transmit electrical signals (University of North Texas, 2010). The ability of the neuron to conduct these impulses is because of an electrochemical voltage across the plasma membrane of that neuron. An action potential is an all or nothing response to a stimulus along a single axon. A compound action potential is a graded response that results from the stimulation of more than one axon.
Action potentials can be broken down into five different phases: resting potential, threshold, rising, falling, and recovery. The inside of a cell is negatively charged and the potential difference across the plasma membrane is between 50 and 90 mV. In a resting cell, the membrane is more permeable to potassium than sodium. When synaptic activity makes the cell less negative, the sodium channels open. If the cell voltage goes past a certain level, an action potential is produced. Action potentials, changes in the membrane potential that happen when a nerve cell membrane is stimulated (Ritchison), happen within milliseconds. After the voltage has reached the threshold potential, more voltage-gated sodium channels open and the voltage of the membrane reaches its most positive value. The voltage-gated sodium channels close soon after opening, and with that, the potassium channels open. Now potassium is rushing back into the cell, repolarizing the cell back to its resting level. Now, because there are many more potassium gates are open than there were when the cell was resting, the cell hyperpolarizes. Finally, the extra potassium gates that were open, close and the sodium channels are ready to open again. There is no such thing as a weak or a partial action potential because action potentials are all-or-none (Randall, French, & Burggren, 2002). Either the threshold is reached, causing an action potential, or it’s not
Cited: Randall, D., French, K., & Burggren, W. (2002). Eckert Animal Physiology Mechanisms and Adaptations. New York, New York: W. H. Freeman and Company. Ritchison, G. (n.d.). Neurons & the Nervous System. Retrieved 02 24, 2011, from Neurons & the Nervous System: http://people.eku.edu/ritchisong/301notes2.htm Sasaki, T., Matsuki, N., & Ikegaya, Y. (n.d.). PubMed. Retrieved 02 25, 2011, from Action Potential modulation during axonal conduction: http://www.ncbi.nlm.nih.gov/pubmed/21292979 University of North Texas. (2010). Animal Physiology Lab. Denton, TX: University of North Texas.