Nervous system parasympathetic

Responses to activation of the parasympathetic system. Parasympathetic nerves regulate processes connected with energy assimilation (food intake, digestion, absorption) and storage. These processes operate when the body is at rest, allowing a decreased tidal volume (increased bronchomo-tor tone) and decreased cardiac activity. Secretion of saliva and intestinal fluids promotes the digestion of food stuffs transport of intestinal contents is speeded up because of enhanced peristaltic activity and lowered tone of sphincteric muscles. To empty the urinary bladder (micturition), wall tension is increased by detrusor activation with a concurrent relaxation of sphincter tonus. 

Activation of ocular parasympathetic fibers (see below) results in narrowing of the pupil and increased curvature of the lens, enabling near objects to be brought into focus (accommodation). 

The cell bodies of parasympathetic preganglionic neurons are located in the brainstem and the sacral spinal cord. Parasympathetic outflow is channeled from the brainstem (1) through the third cranial nerve (oculomotor n.) via the ciliary ganglion to the eye (2) through the seventh cranial nerve (facial n.) via the pterygopalatine and submaxillary 

Localization of Receptors Agonist Antagonist Receptor Type 

Target tissues of 2 nd parasympathetic neurons e.g., smooth muscle, glands ACh Muscarine Atropine Muscarinic (M) cholino-ceptor G-protein-coupled receptor protein with 7 transmembrane domains 

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The sympathetic or adrenergic nervous system operates in juxtaposition to the parasympathetic nervous system to maintain homeostasis in response to physical activity and physical or psychological stress. Sympathomimetic neurotransmission is generally mediated by norepinephrine [51-41 -2] (1), CgH NO, released from presynaptic storage granules upon stimulation. A second endogenous sympathomimetic agent, epinephrine [51-43-4] (2),... 

Moreover organophosphoric acid esters have found application as insecticides (e.g. Parathion). Some derivatives are highly toxic to man (e.g. Sarin, Soman). The organophosphonates act as inhibitors of the enzyme cholinesterase by phosphorylating it. This enzyme is involved in the proper function of the parasympathetic nervous system. A concentration of 5 x 10 g/L in the air can already cause strong toxic effects to man. 

The simplification of the local anesthetic phaimacophore of cocaine to an aryl substituted ester of ethanolamine has been described previously. Atropine (S2) is a structurally closely related natural product whose main biologic action depends on inhibition of the parasympathetic nervous system. Among its many other actions, the compound exerts useful spasmolytic effects. 

Parasympathetic nervous system. That portion of the autonomic nervous system that utilizes acetylcholine as the neurotransmitter at the neuro-effector junctions. 

The part of the vertebrate nervous system that regulates involuntary action, such as the intestines, heart and glands it is divided into the sympathetic nervous system and the parasympathetic nervous system. 

Parasympathetic Nervous System Parasympatholytics Parasympathomimetics Parathyroid Hormone Paraventricular Nucleus Parkin... 

Discuss important aspects of the parasympathetic nervous system. 

Giolinergic drugs mimic the activity of the parasympathetic nervous system (PNS). They also are called parasympathomimetic drugs. An understanding of the PNS is useful in understanding the cholinergic dni. ... 

The PNS has two neurohormones (neurotransmitters) acetylcholine (ACh) and acetylcholinesterase (ACliE). ACh is a neurotransmitter responsible for die transmission of nerve impulses to effector cells of die parasympathetic nervous system. ACh plays an important role in die transmission of nerve impulses at synapses and myoneural junctions. ACh is quickly... 

The parasympathetic nervous system is capable of maintaining gastrointestinal motility, etc., even when connections to the central nervous system have been... 

Ocular Effects. One study reported that seven children exposed to methyl parathion by inhalation, oral, and possibly dermal routes exhibited pinpoint pupils (miosis) (Dean et al. 1984). This effect is a consequence of the effects on the parasympathetic nervous system. No other studies were located regarding ocular effects in humans after oral exposure to methyl parathion. 

Clinical signs and symptoms of toxicity are related to the overstimulation of muscarinic, nicotinic, and central nervous system receptors in the nervous system. Muscarinic receptors are those activated by the alkaloid drug muscarine. These receptors are under the control of the parasympathetic nervous system, and their hyperactivity results in respiratory and gastrointestinal dysfunction, incontinence, salivation, bradycardia, miosis, and sweating. Nicotinic receptors are those activated by nicotine. Hyperactivity of these receptors results in muscle fasciculations even greater stimulation results in blockade and muscle paralysis (Lefkowitz et al. 1996 Tafliri and Roberts 1987). Hyperactivity of central nervous system receptors results in the frank neurological signs of confusion, ataxia, dizziness, incoordination, and slurred speech, which are manifestations of acute intoxication. Muscarine and nicotine are not... 

Automaticity of cardiac fibers is controlled in part by activity of the sympathetic and parasympathetic nervous systems. Enhanced activity of the sympathetic nervous system may result in increased automaticity of the SA node or other automatic cardiac fibers. Enhanced activity of the parasympathetic nervous system tends to suppress automaticity conversely, inhibition of activity of the parasympathetic nervous system increases automaticity. Other factors may lead to abnormal increases in automaticity of extra-SA nodal tissues, including hypoxia, atrial or ventricular stretch [as might occur following long-standing hypertension or after the development of heart failure (HF)], and electrolyte abnormalities such as hypokalemia or hypomagnesemia. 

Sinusitis symptoms typically last 7 to 1 0 days after a viral infection and are caused by activation of the immune system and parasympathetic nervous system. 

Vagal maneuvers Maneuvers that stimulate the activity of the parasympathetic nervous system and thereby inhibit atrioventricular nodal conduction. Examples of vagal maneuvers include cough, carotid sinus massage, and Valsalva maneuver. 

PAM chloride - 2-pralidoxime chloride. See oxime, parasympathetic nervous system -the part of the autonomic nervous system that decreases pupil size, heart rate, and blood pressure and increases functions, such as secretion of saliva, tears, and perspiration. 

Figure 15.4 Effects of the autonomic nervous system on mean arterial pressure. The baroreceptors, chemoreceptors, and low-pressure receptors provide neural input to the vasomotor center in the brainstem. The vasomotor center integrates this input and determines the degree of discharge by the sympathetic and parasympathetic nervous systems to the cardiovascular system. Cardiac output and total peripheral resistance are adjusted so as to maintain mean arterial pressure within the normal range.

Figure 15.5 Effects of sympathetic and parasympathetic nervous activity on mean arterial pressure. The parasympathetic nervous system innervates the heart and therefore influences heart rate and cardiac output. The sympathetic nervous system innervates the heart and veins and thus influences cardiac output. This system also innervates the arterioles and therefore influences total peripheral resistance. The resulting changes in cardiac output and total peripheral resistance regulate mean arterial pressure.

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