Neural Control Mechanisms

April 21, 2006

Nerve cells called neurons generate electric signals that pass from one end of the cell to another and release chemical messengers called neurotransmitters to communicate with other cells

Action potentials are large, rapid alterations in the membrane potential. Membranes capable of producing action potentials are called excitable membranes. Examples are membranes in nerve and muscle cells. During an action potential, voltage gated Na+ channels open and allow a large influx of Na+ ions into the cell, making inside of the cell less negative and this is called depolarization. The membrane starts returning rapidly to the resting membrane potential because Na+ channels close, voltage gated K+ channels open, K+ moves out and this is called repolarization.
The potential at which a membrane is depolarized to generate an action potential is called the threshold potential and stimulus that is strong enough to depolarize the membrane is called threshold stimulus.

Nervous System

April 21, 2006

The central nervous system(CNS) is made of the brain and the spine

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CNS.html

The peripheral nervous system is made of sensory neurons(running from stimulus receptors to the CNS – receptors) and the motor neurons(running from the CNS to the muscles and the glands – effectors)

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/PNS.html

Arrhythmias

April 21, 2006

Arrhythmias (or dysrhythmias) are problems that affect the electrical system of the heart muscle, producing abnormal heart rhythms. They can cause the heart to pump less effectively

A number of factors can contribute to arrhythmias. They include coronary artery disease, high blood pressure, diabetes, smoking, excessive use of alcohol or caffeine, drug abuse and stress.

A heart rate of less than 60 beats per minute is called bradycardia. Physically active people often have a resting heart rate slower than 60 beats per minute. For them, this isn't abnormally slow.

Rapid heart beating, called tachycardia or tachyarrhythmia, can produce palpitations, rapid heart action, chest pain, dizziness, lightheadedness, fainting or near fainting if the heart beats too fast to circulate blood effectively.

http://www.americanheart.org/presenter.jhtml?identifier=4469

Fibrillation

April 21, 2006

 During atrial fibrillation, the heart's two small upper chambers (the atria) quiver instead of beating effectively. Blood isn't pumped completely out of them, so it may pool and clot.

http://www.americanheart.org/presenter.jhtml?identifier=4451

Ventricular fibrillation (ven-TRIK'u-ler fib"rih-LA'shun) ("V fib") is a condition in which the heart's electrical activity becomes disordered. When this happens, the heart's lower (pumping) chambers contract in a rapid, unsynchronized way. (The ventricles "flutter" rather than beat.) The heart pumps little or no blood.

http://www.americanheart.org/presenter.jhtml?identifier=4784

 Atrial fibrillation, according to WebMD.com, is "the most common form of irregular heartbeat (arrhythmia).

A common method to prevent atrial fibrillation, according to WebMD.com, is to have a person take antiarrhythmic medications. "These drugs work mostly by stabilizing the heart muscle tissue or slowing the heart rate."

If prevention doesn’t work, the current procedure to interrupt an episode of atrial fibrillation, Au-Yeung said, is called electrical cardioversion, during which an electric shock is administered to a person’s heart, attempting to resynchronize it and restore its natural rhythm.

Tachycardia

April 21, 2006

Tachycardia is a fast heart rate (usually over 100 beats per minute) caused by disease or injury. It can also be part of a normal response to increased activity or oxygen demands. The average heart beats between 60 and 100 times per minute. When the tachycardia is due to disease or injury, it usually requires treatment

http://www.sjm.com/conditions/condition.aspx?name=Ventricular+Tachycardia+(VT)

http://www.studentbmj.com/back_issues/1101/education/410.html

More info on

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1. bioelectric phenomena, biomaterials, biomechanics, rehabilitation and human performance.

2. overview of physiology, anatomy and physiological modeling

3. neuroengineering

4. biomedical instumentation

5. clinical engineering

6. Biosensors

7. Biomedical Materials and Artificial Organs

8. Cardiovascular Engineering

9. Life Support Engineering