The peripheral nervous system

However, all is not doom and gloom. There are some clues and hints to be had. The ancient herbal remedies of the past partially open the curtain to some of the body s jealously guarded secrets. Even the toxins of snakes, spiders, and plants can give important clues to the workings of the body and provide lead compounds to possible cures. 

To illustrate this, we are going to concentrate on one particular field—cholinergic and anticholinergic drugs. These are drugs which act on the peripheral nervous system, and so it is important to have some idea of how that system works before we proceed. 

The peripheral nervous system (Fig. 11.1) is, as the name indicates, that part of the nervous system which is outside of the central nervous system (CNS—the brain and spinal column). 

There are many divisions and subdivisions of the peripheral system which can lead to confusion. The first distinction we can make is between the following  

We need only concern ourselves with the latter—the motor nerves. 

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CCK is found in the digestive tract and the central and peripheral nervous systems. In the brain, CCK coexists with DA. In the peripheral nervous system, the two principal physiological actions of CCK are stimulation of gaU. bladder contraction and pancreatic enzyme secretion. CCK also stimulates glucose and amino acid transport, protein and DNA synthesis, and pancreatic hormone secretion. In the CNS, CCK induces hypothermia, analgesia, hyperglycemia, stimulation of pituitary hormone release, and a decrease in exploratory behavior. The CCK family of neuropeptides has been impHcated in anxiety and panic disorders, psychoses, satiety, and gastric acid and pancreatic enzyme secretions. 

There is a second family of small lipid-binding proteins, the P2 family, which include among others cellular retinol- and fatty acid-binding proteins as well as a protein, P2, from myelin in the peripheral nervous system. However, members of this second family have ten antiparallel p strands in their barrels compared with the eight strands found in the barrels of the RBP superfamily. Members of the P2 family show no amino acid sequence homology to members of the RBP superfamily. Nevertheless, their three-dimensional structures have similar architecture and topology, being up-and-down P barrels. 

Page et al. (28) studied the activation threshold of pyrethrins for certain insects. This threshold point of toxicant in the insect occurred when the natural activity was replaced by forced activity caused by the action of the pyrethrins on the peripheral nervous system. 

Acetylcholine (Ach) is an ester of acetic acid and choline with the chemical formula CH3COOCH2CH2N+ (CH3)3. ACh functions as a chemical transmitter in both the peripheral nervous system (PNS) and central nervous system (CNS) in a wide range of organisms, humans included. Neurotransmitter involved in behavioral state control, postural tone, cognition and memory, and autonomous parasympathetic (and preganglionic sympathetic) nervous system. 

The adrenergic system is an essential regulator that increases cardiovascular and metabolic capacity during situations ofstress, exercise, and disease. Nerve cells in the central and peripheral nervous system synthesize and secrete the neurotransmitters noradrenaline and adrenaline. In the peripheral nervous system, noradrenaline and adrenaline are released from two different sites noradrenaline is the principal neurotransmitter of sympathetic neurons that innervate many organs and tissues. In contrast, adrenaline, and to a lesser degree noradrenaline, is produced and secreted from the adrenal gland into the circulation (Fig. 1). Thus, the actions of noradrenaline are mostly restricted to the sites of release from sympathetic nerves, whereas adrenaline acts as a hormone to stimulate many different cells via the blood stream. 

The amide local anaesthetic lidocaine may also be used as an antianhythmic for ventricular tachycardia and exra-systoles after injection into the blood circulation. Drugs with high lipid solubility such as bupivacaine cannot be used for these purposes because their prolonged binding to the channel may induce dysrhythmias or asystolic heart failure [3]. Systemically applied lidocaine has also been used successfully in some cases of neuropathic pain syndromes [4]. Here, electrical activity in the peripheral nervous system is reduced by used-dependent but incomplete sodium channel blockade. 

NPY is primarily (but not exclusively) synthesised and released by neurons, which in the peripheral nervous system are predominantly sympathetic neurons [1]. In most cases, NPY acts as a co-transmitter that is preferentially released upon high frequency nerve stimulation. NPY can be metabolised by the enzyme dipeptidylpeptidase IV (also known as CD26) to generate the biologically active fragment NPY3 36. 

Toda N, Okamura T (2003) The pharmacology of nitric oxide in the peripheral nervous system of blood vessels. Pharmacol Rev 55 271-324... 

High amounts of somatostatin are found in the CNS, the peripheral nervous system, the gut and the endocrine pancreas whereas the kidneys, adrenals, thyroid, submandibular glands, prostate and placenta produce rather low amounts. In particular, the hypothalamus, all limbic structures, the deeper layers of the cerebral cortex, the striatum, the periaqueductal central grey and all levels of the major sensoty pathway are brain areas that are especially rich in somatostatin. Eighty percent of the somatostatin immunoreactivity in the hypothalamus is found in cells of the anterior periventricular nucleus (Fig. 1, [1]). The gut 5 cells of the mucosa and neurons, which are intrinsic to the submucous and... 

Discuss the activity of the central nervous system and the peripheral nervous system. 

The nervous system is a complex part of the human body concerned with die regulation and coordination of body activities such as movement, digestion of food, sleep, and elimination of waste products. The nervous system has two main divisions the central nervous system (CNS) and the peripheral nervous system (PNS). Figure 22-1 illustrates the divisions of die nervous system. 

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 central nervous system (CNS) includes the brain and the spinal cord. The CNS processes information to and from the peripheral nervous system and is the center of coordination and control for the entire body. Many dru stimulate die CNS, but only a few are used therapeutically. This chapter discusses die drills diat stimulate the CNS and the nursing implications related to dieir administration. 

At the start of the HIV epidemic in the 1980s, the peripheral nervous system involvement in HIV infection was not widely appreciated. However, as the number of cases grew, it became obvious that not only were peripheral neuropathies common in HIV infection, but were also present in all stages of the disease, from seroconversion through end-stage immunodeficiency. The neuropathic complications occurred as a result of a variety of pathological processes in HIV infection (Verma 2001). 

FuUer GN (1992) Cytomegalovirus and the peripheral nervous system in AIDS. J Acquir Immune Defic Syndr 5(Suppl 1) S33-S36... 

In the peripheral nervous system (PNS), HIV-1 infection and its treatment using HAART are associated with the development of neuropathic pain syndromes characterized by severe lancinating pain as well as parathesias and burning pain in the extremities. Damage to peripheral nerves has been associated with these syndromes. HIV-1-associated polyneuropathy has become the most common neurological complication of HIV-1 infection (Pardo et al. 2001). More than half of individuals with... 

It is easy to speculate that in an active neuron with a rapid firing pattern, the continued release of a peptide may eventually lead to depletion of the peptide occurring. This has been shown in the peripheral nervous system. If this also happens in the CNS it would provide a mechanism whereby the release and resultant receptor effects of a transmitter no longer match the firing pattern and demands of the neuron and so could contribute to long-term adaptations of neurons by a reduction in the time over which a peptide is effective. 

Neuropathic pain is defined as spontaneous pain and hypersensitivity to pain associated with damage to or pathologic changes in the peripheral nervous system as in painful diabetic peripheral neuropathy (DPN), acquired immunodeficiency syndrome (AIDS), polyneuropathy, post-herpetic neuralgia (PHN) or pain originating in the central nervous system (CNS), that which occurs with spinal cord injury, multiple sclerosis, and stroke. Functional pain, a relatively newer concept, is pain sensitivity due to an abnormal processing or function of the central nervous system in response to normal stimuli. Several conditions considered to have this abnormal sensitivity or hyperresponsiveness include fibromyalgia and irritable bowel syndrome. 

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