Autonomic nervous system parasympathetic branch

Atropine, an alkaloid from Atropa belladonna, is the classical parasympatholytic compound. It competes with acetylcholine for the binding at the muscarinic receptor. Its affinity towards nicotinic receptors is very low, so that it does not interfere with the ganglionic transmission or the neuromotor transmission, at least in therapeutic dosages. However, in the central nervous system muscarinic receptor do play an important role and while atropine can penetrate the blood-brain barrier it exerts pronounced central effects. Atropine, like all other antagonists of the muscarinic acetylcholine receptor inhibit the stimulatory influence of the parasympathetic branch of the autonomous nervous system. All excretory glands (tear, sweat, salivary, gasto-intestinal, bronchi) are... 

The somatic nervous system is composed of sensory afferents and motor efferents and serves to perceive external states and to modulate appropriate body responses. The autonomic nervous system (ANS), together with the endocrine system, controls the milieu interieur. It adjusts internal organ functions to the changing needs of the organism. The ANS operates largely autonomously, beyond voluntary control, at the subconscious level. Its central components reside in the hypothalamus, brain stem, and spinal cord. The ANS has sympathetic and parasympathetic branches. Both are made up of afferent, mainly in the vagus nerve, and efferent fibers. 

A low level of tonic activity of the sympathetic nerves to vascular smooth muscle adrenergic receptors exists so that withdrawal of sympathetic vasomotor tone results in vasodilatation and reduced pressure. Conversely, enhancement of sympathetic vasomotor tone augments the level of vasoconstriction leading to elevated pressure. While the parasympathetic branch of the autonomic nervous system innervates some blood vessels, it does not generally play a role in regulating peripheral resistance. 

The afferent neurons of the autonomic nervous system are important in the reflex regulation, for example, by sensing pressure in the carotid sinus and aortic arch and signaling the CNS to influence the efferent branch of the system to respond. Conditions such as trauma, fear, hypoglycemia, cold, or exercise activate the sympathetic neurons. Both sympathetic and parasympathetic neurons emerge from the brain stem or spinal cord. Blood pressure is regulated largely by sympathetic control of vascular tone. 

A neurotransmitter linked with memory processes that is found both in the brain and In the parasympathetic branch of the autonomic nervous system. 

The other branch of the autonomic nervous system is the parasympathetic branch, which in general balances the actions of the sympathetic branch by exerting opposite effects. Parasympathetic activity reduces heart rate, bkxxl pressure, and so on. In contrast to sympathetic neurons, parasympathetic synapses arc primarily cholinergic. 

The autonomic nervous system is divided into two branches. The sympathetic branch produces the physiological effects that accompany emotional arousal, and the parasympathetic branch controls the body when at rest. 

Autonomic nervous system (ANS) Part of the PNS has two branches sympathetic and parasympathetic (Chapter 3). 

In the peripheral nervous system, norepinephrine is an important neurotransmitter in the sympathetic branch of the autonomic system. Sympathetic nerve transmission operates below the level of consciousness in controlling physiological function of many organs and tissues of the body. The sympathetic system plays a particularly important role in regulating cardiovascular function in response to postural, exertional, thermal, and mental stress. With sympathetic activation, the heart rate is increased, peripheral arterioles are constricted, skeletal arterioles are dilated, and the blood pressure is elevated. In addition, sympathetic nerve stimulation dilates pupils inhibits smooth muscles of the intestines, bronchi, and bladder and closes the sphincters. Sympathetic signals work in balance with the parasympathetic portion of the autonomic nervous system to maintain a stable internal environment. 

Stimulation of the parasympathetic and sympathetic branches in the autonomic nervous system results in a wide array of symptoms, depending on which system is more stimulated (Table 4-2). The chemical, route of exposure, and dose determine the symptoms. 

Previously in this chapter you learned that the autonomic nervous system has two branches. These are the sympathetic branch and parasympathetic branch. Both branches act on the same organ cells but in an opposite way. The sympathetic branch stimulates a response and the parasympathetic branch depresses a response by the organ cell. Together, they keep the organ in balance (homeostasis). 

Papilloma—branching or lobulated benign tumor derived from epithelial tissue Parasympathetic—craniosacral portion of the autonomic nervous system Parenteral—introduced other than by way of the intestines, (e.g., subcutaneous, intramuscular, intravenous)... 

Meditation is a simple way to safely balance a person s physical, emotional, and mental states. It has been shown to reduce activity in the nervous system. This is the function of the parasympathetic branch of the autonomic or involuntary nervous system. More and more doctors are prescribing meditation as a way to relax from the everyday stresses of life (Figure 6.3). 

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