Nervous system sensory function

Various models demonstrated declines in test scores (executive abilities, manual dexterity, neuropsychiatric, peripheral nervous system sensory function) with historical tibia lead, longitudinal BLLs, cross-sectional (short-term)... 

To assess the effects of the test substance on the central Anon.27 nervous system, peripheral nervous system, sensory organs, respiratory and cardiovascular systems, smooth muscles including uterus, peripheral organs, renal function, and adverse effects observed in clinical studies... 

The nervous system is divided into two parts the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists of all afferent (sensory) neurons, which carry nerve impulses into the CNS from sensory end organs in peripheral tissues, and all efferent (motor) neurons, which carry nerve impulses from the CNS to effector cells in peripheral tissues. The peripheral efferent system is further divided into the somatic nervous system and the autonomic nervous system. The effector cells innervated by the somatic nervous system are skeletal muscle cells. The autonomic nervous system innervates three types of effector cells (1) smooth muscle, (2) cardiac muscle, and (3) exocrine glands. While the somatic nervous system can function on a reflex basis, voluntary control of skeletal muscle is of primary importance. In contrast, in the autonomic nervous system voluntary control can be exerted, but reflex control is paramount. 

Observational studies Comparative studies Drug-combination studies Placebo-controlled studies Systematic reviews Organs and systems Cardiovascular Respiratory Ear, nose, throat Nervous system Neuromuscular function Sensory systems Psychological Psychiatric Endocrine Metabolism Nutrition... 

Somatic versus autonomic. The somatic nervous system comprises functions that are conscious - conscious sensations such as touch, temperature, pain etc., and voluntary movements. Conversely, the autonomic nervous system deals with unconscious sensory input such as blood pressure, blood oxygen and carbon dioxide lev-els and the likewise unconscious regulatory responses to it. 

Secretoneurin (SN), a 33-peptide derived from secretogranin II (chromogranin C, chromogranins). SN is widely distributed throughout the central and peripheral nervous systems. Known functions of SN include chemotaxis of monocytes and endothelial cells, and inhibition of endothelial cell proliferation. In addition, SN is a potent chemoattractant for human eosinophils. Since it can be co-released with substance P and calcitonin gene-related peptide from sensory afferent c-fibers by capsaicin, it might represent another member of the group of inflammatory neuropeptides [R. Kirchmair et al., Neuroscience 1993, 53, 359 S. Dunzendorfer et al., Blood 1998, 91, 1527 C. J. Wiedermann, Peptides 2000, 21, 1289]. 

CGRP is widely distributed throughout the peripheral and central nervous systems and is found ia sensory neurons and ia the autonomic and enteric nervous systems. In many iastances CGRP is co-localized with other neuroregulators, eg, ACh ia motor neurons, substance P, somatostatin, vasoactive intestinal polypeptide (VIP), and galanin ia sensory neurons. It is also present ia the CNS, with ACh ia the parabigeminal nucleus and with cholecystokinin (CCK) ia the dorsal parabrachial area. CGRP functions as a neuromodulator or co-transmitter. 

Air-poUutant effects on neural and sensory functions in humans vary widely. Odorous pollutants cause only minor annoyance yet, if persistent, they can lead to irritation, emotional upset, anorexia, and mental depression. Carbon monoxide can cause death secondary to the depression of the respiratory centers of the central nervous system. Short of death, repeated and prolonged exposure to carbon monoxide can alter sensory protection, temporal perception, and higher mental functions. Lipid-soluble aerosols can enter the body and be absorbed in the lipids of the central nervous system. Once there, their effects may persist long after the initial contact has been removed. Examples of agents of long-term chronic effects are organic phosphate pesticides and aerosols carrying the metals lead, mercury, and cadmium. 

Peripheral nervous system Nerve tissues lying outside the brain and spinal cord, functions include the transmittal of sensory information such as touch, heat, cold, and pain, and the motor impulses for limb movement. 

Because of its motor, i.e., activating effect on vascular smooth muscle and its inhibitory effect on intestinal smooth muscle, the sympathetic nervous system has been cast into the role of the component of the nervous system that executes control of visceral function in times of physical emergency for the organism. The phrase fight or flight has been often used to describe the circumstances in which the adrenergic transmitters of the sympathetic system are dominant over the cholinergic parasympathetic system. This concept is perhaps oversimplified but it has the utility of a first approximation of how the two components of the ANS interact in the periphery. Sensory inputs which lead to increased blood pressure, for example, activate the sympathetic pathways. 

Animal behavior has been dehned by Odnm (1971) as the overt action an organism takes to adjnst to its environment so as to ensure its survival. A simpler definition is the dynamic interaction of an animal with its enviromnent (D Mello 1992). Another, more elaborate, one is, the outward expression of the net interaction between the sensory, motor arousal, and integrative components of the central and peripheral nervons systems (Norton 1977). The last dehnition spells out the important point that behavior represents the integrated function of the nervous system. Accordingly, disruption of the nervous system by neurotoxic chemicals may be expected to cause changes in behavior (see Klaasen 1996, pp. 466-467). 

Many tests have been devised to provide quantitative measures of behavioral disturbances caused by neurotoxic chemicals. Tests have been devised that assess the effects of chemicals on four behavioral functions (D Mello 1992). These are sensory, cognitive, motor, and affective functions. However, because the entire nervous system tends to work in an integrated way, these functions are not easily separable from one another. For example, the outcome of tests focused on sensory perception by rats may be influenced by effects of the test chemical on motor function. 

Neurotransmitter receptors have evolved as one of the key components in the ability of the central nervous system to coordinate the behaviour of the whole animal, to process and respond to sensory input, and to adapt to change in the environment. These same receptors are therefore ideal targets for drug action because of their central role in the activity of the nervous system. A rational approach to the development of new therapeutic strategies involving the action of drugs at receptors in the nervous system is based on knowledge of receptor structure, distribution and function. 

Henkin RI. 1976. Effects of vapor phase pollutants on nervous system and sensory function. In Finkel AJ, Duel WC, eds. Clinical implications of air pollution research. Acton, MA Publishing Sciences Group, 193-216. 

One of the most sensitive systems affected by lead exposure is the nervous system. Encephalopathy is characterized by symptoms such as coma, seizures, ataxia, apathy, bizarre behavior, and incoordination (CDC 1985). Children are more sensitive to neurological changes. In children, encephalopathy has been associated with PbB levels as low as 70 pg/dL (CDC 1985). The most sensitive peripheral index of neurotoxicity of lead is reported to be slowed conduction in small motor libers of the ulnar nerve in workers with 30-40 pg/dL lead in blood (Landrigan 1989). Other potential biomarkers of lead suggested for neurotoxicity in workers are neurological and behavioral tests, as well as cognitive and visual sensory function tests (Williamson and Teo 1986). However, these tests are not specific to elevated lead exposure... 

Figure 1.1 Functional components of the nervous system. The sensory division of the peripheral nervous system is sensitive to changes in the internal and external environment. The information gathered by this component is transmitted to the CNS where it is processed, integrated, and interpreted. The CNS then determines the appropriate response to this input. This response is carried out by the transmission of nerve impulses in the motor division of the peripheral nervous system to the effector tissues.

The brain is the integrative portion of the nervous system that serves to receive, process, and store sensory information and then plan and orchestrate the appropriate motor response. It is divided into several anatomically and functionally distinct regions (see Table 6.2). The forebrain consists of the cerebrum, basal ganglia, thalamus, and hypothalamus. The midbrain, along with the pons and the medulla of the hindbrain, composes the functional region referred to as the brainstem. The cerebellum is also considered a component of the hindbrain but is functionally distinct from the brainstem. 

Sensations interpreted as pain, including burning, aching, stinging, and soreness, are the most distinctive forms of sensory input to the central nervous system. Pain serves an important protective function because it causes awareness of actual or potential tissue damage. Furthermore, it stimulates an individual to react to remove or withdraw from the source of the pain. Unlike other forms of sensory input, such as vision, hearing, and smell, pain... 

Histamine in the nervous system may participate in a variety of brain functions. Several of the suspected physiological roles for histamine are related to its ability to increase the neuronal excitability [1, 2,15]. For example, mutant mice lacking the H, receptor show defective locomotor and exploratory behaviors [57], Neuronal histamine may increase attention and/or arousal by many mechanisms, including by enhancing sensory input [58], All available evidence from several species shows that histaminergic neurons, when activated, increase wakefulness... 

Although histamine is not stored in neurons outside of the central nervous system, mast-cell-derived histamine can modify peripheral sensory nerve function. Both acute and chronic pain states can result from inflammation or peripheral nerve cell injury, and there is substantial evidence that mast cell histamine participates in these disorders. 

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