Sympathetic division

Originates in thoracic and lumbar regions of the spinal cord (T j-L2) 

Activity often involves mass discharge of entire system Predominates during emergency fight-or-flight reactions and exercise 

Originates in brainstem (cranial nerves III, VII, IX, and X) and sacral region of spinal cord (S2-S4) 

Terminal ganglia located near or embedded within target tissue 

Long cholinergic preganglionic fibers short cholinergic postganglionic fibers 

---

Muscarinic receptors are responsible for postganglionic parasympathetic neurotransmission and thus for control of a wide range of smooth muscle, cardiac muscle and secretory responses. Some responses originating in the sympathetic division of the autonomic nervous system, such as sweating and piloerection, also are mediated through muscarinic receptors. 

Noise can strongly arouse the sympathetic division and hence can be physiologically wearing. As such, it is a significant detractor from health and happiness. 

Erection involves a coordinated action of the autonomic nervous system, and certain drugs may interfere with either the sympathetic division (e.g., aj- receptors) or the parasympathetic division (e.g., noncholinergic neurotransmitters). 

The answer is d. (Hardman, pp 192-193.) Nicotine is a depolarizing ganglionic blocking agent that initially stimulates and then blocks nicotinic muscular (NM) (skeletal muscle) and nicotinic neural (NN) (parasympathetic ganglia) cholinergic receptors. Blockade of the sympathetic division of the autonomic nervous system (ANS) results in arteriolar vasodilation, bradycardia, and hypotension. Blockade at the neuromuscu-... 

As in the sympathetic division, parasympathetic preganglionic neurons synapse in the periphery with a postganglionic fiber. This synapse usually takes place in a terminal ganglion that is located directly in the organ or tissue supplied by the postganglionic neuron. Consequently, the parasympathetic ganglia are usually embedded directly in the innervated organ or tissue. 

Except for skeletal muscle, virtually all tissues in the body are innervated in some way by the ANS.9 Table 18-1 summarizes the innervation and effects of the sympathetic and parasympathetic divisions on some of the major organs and tissues in the body. As indicated in Table 18-1, some organs, such as the heart, are innervated by both sympathetic and parasympathetic neurons. Other tissues, however, may only be supplied by the sympathetic division. The peripheral arterioles, for instance, are innervated by the sympathetic division but receive no parasympathetic innervation. 

Finally, activation of the sympathetic division tends to result in a more massive and diffuse reaction than does parasympathetic activation. Parasympathetic reactions tend to be fairly discrete and to affect only one organ or tissue. For instance, the parasympathetic fibers to the myocardium can be activated to slow down the heart without a concomitant emptying of the bowel through an excitatory effect on the lower gas-... 

Consequently, the adrenal medulla serves to augment the sympathetic division of the ANS. In situations where a sudden increase in sympathetic function is required (i.e., the fight-or-flight scenario), the adrenal medulla works with the sympathetics to produce a more extensive and lasting response. 

Sympatholytics Various sites within the sympathetic division of the autonomic nervous system Decrease sympathetic influence on the heart and/or peripheral vasculature... 

The release of epinephrine and norepinephrine from the adrenal medulla is controlled by the sympathetic division of the autonomic nervous system. As discussed in Chapter 18, sympathetic cholinergic preganglionic neurons directly innervate this gland. An increase in sympathetic activity causes increased firing in these neurons, which in turn stimulates the release of epinephrine and norepinephrine from the adrenal medulla. 

Though continually active to some degree (for example, in maintaining the tone of vascular beds), the sympathetic division has the property of adjusting in response to stressful situations, such as trauma, fear, hypoglycemia, cold, or exercise. 

Effects of stimulation of the sympathetic division The effect of sympathetic output is to increase heart rate and blood pressure, to mobilize energy stores of the body, and to increase blood flow to skeletal muscles and heart while diverting flow from the skin and internal organs. Sympathetic stimulation also results in dilation of the pupils and the bronchioles (Figure 3.3). 

The parasympathetic division maintains essential bodily functions, such as digestive processes and elimination of wastes, and is required for life (see Figure 3.3). It usually acts to oppose or balance the actions of the sympathetic division and is generally dominant over the sympathetic system in "rest and digest" situations (see Figure 3.4). The parasympathetic system is not a functional entity as such and never discharges as a complete system. If it did, it would produce massive, undesirable, and unpleasant symptoms. Instead, discrete parasympathetic fibers are activated separately, and the system functions to affect specific organs, such as the stomach or eye. 

B. The sympathetic division is activated in response to stressful situations. 

Correct answer = C. The parasympathetic system maintains essential bodily functions, such as vision, movement of food, and urination. It uses acetylcholine, not norepinephrine, as a neurotransmitter, and discharges as discrete fibers that are activated separately. The postganglionic fibers of the parasympathetic system are short compared to the sympathetic division. The adrenal medulla is under control of the sympathetic system. 

Sweating is stimulated by direct action of the increased endogenous acetylcholine on muscarinic receptors of sweat glands in the skin these glands are innervated by the sympathetic division of the autonomic nervous system. Agitation is produced by a central excitatory effect on cholinergic neurones in the brain, but in large doses anticholinesterases can cause depression of the respiratory centre in the medulla. 

Sympathetic division ganglia a minority of postganglionic endings, e.g. sweat glands... 

Sympathetic division. The ganglia only are stimulated, also the cholinergic nerves to the adrenal medulla. These effects are overshadowed by effects on the parasympathetic system and are commonly evident only if atropine has been given to block the latter, when tachycardia, vasoconstriction and hypertension occur. 

The sympathetic division (adrenergic component of the autonomic nervous system), when stimulated, has the following effects on the heart (receptor effects) ... 

The family of adrenergic receptors (ARs the ar, a2-, and P-ARs) are key regulators of the sympathetic division of the autonomic nervous system, involved in both central and peripheral cardiovascular function. Here, we review our current understanding of the cellular localization and trafficking properties of the ar, a2-, and P-ARs. We then examine recent evidence indicating that the cellular localization of these receptors and their excursion into intracellular compartments play an underappreciated role in the activation of both G protein and novel non-G protein-dependent cellular signaling. 

SYMPATHOMIMETIC AGENTS mimic the actions of the sympathetic division of the autonomic nervous system. The effects of this system on the tissues and organs are mediated by adrenaline and noradrenaline - which act predominantly as hormone or neurotransmitter, respectively. These catecholamines act at one of two receptor types, a-adrenoceptor and P-adrenoceptor, to exert the actions of the system. Sympathomimetics are of two types. 

Figure 6-1. Schematic diagram comparing some features of the parasympathetic and sympathetic divisions of the autonomic nervous system with the somatic motor system. Parasympathetic ganglia are not shown as discrete structures because most of them are diffusely distributed in the walls of the organs innervated. ACh, acetylcholine Epi, epinephrine NE, norepinephrine, D, dopamine N, nicotinic M, muscarinic a, p, alpha and beta adrenoceptors D, dopamine, receptors. (Reproduced, with permission, from Katzung BG [editor] Basic Clinical Pharmacology, 8th ed. McGraw-Hill, 2001.)...

---