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Saltatory conduction is defined as an action potential moving in discrete jumps down a myelinated axon. This process is outlined as the charge passively spreading to the next node of Ranvier to depolarize it to threshold which will then trigger an action potential in this region which will then passively spread to the next node and so on.
Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N 9-glycosidic bond.
The circus movement can occur around an anatomical or functional core. Either type may occur alone, or together. [citation needed] Anatomically defined re-entry has a fixed anatomic pathway. Anomalous conduction via accessory pathways (APs) creates the re-entry circuit (which are also called bypass tracts), that exists between the atria and ...
The A 1, together with A 2A receptors of endogenous adenosine play a role in regulating myocardial oxygen consumption and coronary blood flow. Stimulation of the A 1 receptor has a myocardial depressant effect by decreasing the conduction of electrical impulses and suppressing pacemaker cell function, resulting in a decrease in heart rate.
If the patient is stable, adenosine may be used for restoration of sinus rhythm in patients with macro-reentrant supraventricular tachycardias. It causes a short-lived cessation of conduction through the atrio-ventricular node breaking the circus movement through the node and the macro-reentrant pathway restoring sinus rhythm.
There are two types of active transport: primary active transport that uses adenosine triphosphate (ATP), and secondary active transport that uses an electrochemical gradient. This process is in contrast to passive transport , which allows molecules or ions to move down their concentration gradient, from an area of high concentration to an area ...
This makes adenosine a useful medication for treating and diagnosing tachyarrhythmias, or excessively fast heart rates. This effect on the A 1 receptor also explains why there is a brief moment of cardiac standstill when adenosine is administered as a rapid IV push during cardiac resuscitation.
C fibers have slow conduction velocities of less than 1.3 m/s because they do not have a myelin sheath at all. C fibers account for 60-70% of primary afferent neurons that innervate the skin. C fibers are activated by both mechanical and thermal stimuli, and also respond to algesic chemicals, such as capsaicin. Some C fibers respond only to ...