Nerve fibers adrenergic

A pathologic disturbance in the CNS, autonomic nerve fibers, adrenergic receptors, or baroreceptors ... 

The purpose of these neuronal mechanisms is to regulate BP and maintain homeostasis. Pathologic disturbances in any of the four major components (autonomic nerve fibers, adrenergic receptors, barore-ceptors, or central nervous system) conceivably could lead to chronically elevated BP. These systems are physiologically interrelated. A defect in one component may alter normal function in another, and such cumulative abnormalities then may explain the development of essential hypertension. 

N euro transmitters are chemical substances called neurohormones. These are released at Hie nerve ending that facilitate the transmission of nerve impulses. The two neurohormones (neurotransmitters) of the sympathetic nervous system are epinephrine and norepinephrine Epinephrine is secreted by the adrenal medulla Norepinephrine is secreted mainly at nerve ending of sympathetic (also called adrenergic) nerve fibers (Pig. 22-2). 

Antiadrenergic drugs—drug that block adrenergic nerve fibers. These dm i block the adrenergic nerve fibers within the central nervous system (CNS) or within the peripheral nervous system. 

The adrenergic pathways that use epinephrine as a neurotransmitter, which have been explored only recently. One of these systems is also tegmental and is mixed with noradrenergic cells. The other is thalamic-hypothalamic, involved with the vagus nerve. Some adrenergic fibers are also found in the fourth ventricle and the spinal cord. 

It has been known for many years that autonomic effector tissues (eg, gut, airways, bladder) contain nerve fibers that do not show the histochemical characteristics of either cholinergic or adrenergic fibers. Both motor and sensory NANC fibers are present. Although peptides are the most common transmitter substances found in these nerve endings, other substances, eg, nitric oxide synthase and purines, are also present in many nerve terminals (Table 6-1). Capsaicin, a neurotoxin derived from chili peppers, can cause the release of transmitter (especially substance P) from such neurons and, if given in high doses, destruction of the neuron. 

The sympathetic nervous system innervates the major lymphoid organs such as the spleen with nerve fibers reaching both the vasculature and the parenchyma where lymphocytes, primarily T cells (T helper type 1-2, T l, T j2), reside (Friedman and Irwin, 1997). T cells possess receptors for both norepinephrine and neuropeptide Y that are released in response to sympathetic nerve stimulation. The adrenergic receptors are primarily the subtype, which is consistent with data demonstrating that (32 agonists can markedly influence the immune system (Kohm and Sanders, 2001). For example, stimulation of T cell receptors results in increased cyclic AMP formation, which can modulate cytokine expression, i.e., decreasing... 

E. Nonadrenergic, Noncholinergic (NANC) Transmission Some nerve fibers in autonomic effector tissues do not show the histochemical characteristics of either cholinergic or adrenergic fibers. Some of these are motor fibers that cause the release of ATP and possibly other purines related to it. Purine-evoked responses have been identified in the bronchi, gastrointestinal tract, and urinary tract. Other motor fibers are peptidergic, ie, they release peptides as the primary transmitters (see list above under Cotransmitters). 

Von Euler, U. S., 1947, A specific sympathomimetic ergone in adrenergic nerve fibers (sympathin) and its relations to adrenaline and noradrenaline, Acta Physiol. Scand. 12 73-97. 

Kalia M, Fuxe K, Goldstein M. Rat medulla oblongata. II. Dopaminergic, noradrenergic (Al and A2) and adrenergic neurons, nerve fibers, and presumptive terminal processes. J Comp Neurol 1985 233 308-332. 

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