Nervous system autonomic motor

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. 

Cholinergic neurotransmission ChEs terminate cholinergic transmission in the central nervous system (CNS), in NMJs and in the autonomic system (the parasympathetic system, somatic motor nerves and pre-ganglionic sympathetic nerves). A few sensory cells and the NMJ in nematodes also include ChEs. 

Local anaesthetics are drugs that reversibly interrupt impulse propagation in peripheral nerves thus leading to autonomic nervous system blockade, analgesia, anaesthesia and motor blockade in a desired area of the organism. 

Neurohumoral transmitters are chemicals that facilitate the transmission of nerve impulses across nerve synapses and neuroeffector junctions. Acetylcholine is a neurohumoral transmitter that is present in the peripheral autonomic nervous system, in the somatic motor nervous system, and in some portions of the central nervous system. 

Lefkowitz RJ, Hoffman BB, Taylor P. 1996. Neurotransmission The autonomic and somatic motor nervous systems. In Hardman JG, Limbird EE, eds. Goodman Gilman s the pharmacological basis of therapeutics. New York, NY McGraw-Hill, 105-139. 

Figure 1. A depiction of the several different ionic currents necessary for the acute function of neuromuscular transmission in the skeletal motor and the efferent autonomic nervous system. The boxed current designations are associated, by the arrows, with those cellular regions where their physiological role is most evident, although these currents often exist in other regions of the cell. = neurotransmitter-activated current ...

The afferent division carries sensory information toward the CNS and the efferent division carries motor information away from the CNS toward the effector tissues (muscles and glands). The efferent division is further divided into two components (1) the somatic nervous system, which consists of motor neurons that innervate skeletal muscle and (2) the autonomic nervous system that innervates cardiac muscle, smooth muscle, and glands. 

The cell bodies of visceral motor neurons are found in the lateral horn. The axons of these neurons form efferent nerve fibers of the autonomic nervous system (ANS). The ANS innervates cardiac muscle, smooth muscle and glands (see Chapter 9). The axons of these neurons exit the spinal cord by way of the ventral root. 

Release autonomic nervous system all postganglionic neurons of parasympathetic system some sympatheticpostganglionicneurons innervating sweat glands (alpha motor neurons innervating skeletal muscle)b adrenal medulla (20% of secretion) secretion)... 

Hoffman, B.B., Lefkowitz, R.J., and Taylor, P., Neurotransmission the autonomic and somatic motor nervous systems, in Goodman and Gilman s The Pharmacological Basis of Therapeutics, 9th ed., Hardman, J.G. and Limbird, L.E., Eds., McGraw-Hill, New York, 1996, chap. 6. 

Hoffman, B. B. and Taylor, P. Neurohumoral transmission the autonomic and somatic motor nervous systems. In J. G. Hardman and L. E. Limbird (eds.), Goodman Gilman s Pharmacological Basics of Therapeutics, 10th edn. New York Macmillan, pp. 115-154, 2001. 

HT may be involved in a wide variety of behaviors by setting the tone of brain activity in relationship to the state of behavioral arousal/activity. Serotonin has been implicated in practically every type of behavior, e.g. appetitive, emotional, motoric, cognitive, autonomic. However, from a physiologic perspective, it is not clear whether 5-HT affects such behaviors specifically, or more generally by coordinating the activity of the nervous system, particularly to set the tone of activity in conjunction with the organism s level of arousal. 

The autonomic nervous system is by definition that part of the nervous system that innervates smooth muscle, cardiac muscle and glands. It is thus a motor system. Perception arising from the viscera involves pathways similar to those arising from the body surface and skeletal muscle. Thus there are visceral afferent fibres that pass from the viscera to the central nervous system. Such impulses then ascend the spinal cord to the thalamus and are thence relayed to the post-central gyrus of the brain (or sensory cortex). Visceral reflex arcs use visceral afferent fibres to convey impulses to the cord, but the efferent limb of such a visceral reflex is the autonomic nervous system. Although visceral reflexes are under higher central control, it is usually impossible to bring them under the control of the will. 

The intermediate length systems include the tuberoinfundibular system, which projects from the arcuate and periventricular nuclei into the intermediate lobe of the pituitary and the median eminence. This system is responsible for the regulation of such hormones as prolactin. The inter hypothalamic neurons send projections to the dorsal and posterior hypothalamus, the lateral septal nuclei and the medullary periventricular group, which are linked to the dorsal motor nucleus of the vagus such projections may play a role in the effects of dopamine on the autonomic nervous system. 

The 1998 OECD test guidelines for the oral 28-/90-day studies (see Table 4.12) examine a number of simple nervous system endpoints, e.g., clinical observations of motor and autonomous nervous system activity, and histopathology of nerve tissue. It should be recognized that the standard 28-/90-day tests measure only some aspects of nervous system stmcture and function, while other aspects, e.g., learning and memory and sensory function is not or only superficially tested. Primarily the standard 28-/90-day tests are intended as a screening for neurotoxicity and depending on the results, further testing may be needed. 

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. 

Anatomical differences between the peripheral somatic and autonomic nervous systems have led to their classification as separate divisions of the nervous system. These differences are shown in Figure 9.1. The axon of a somatic motor neuron leaves the CNS and travels without interruption to the innervated effector cell. In contrast, two neurons are required to connect the CNS and a visceral effector cell of the autonomic nervous system. The first neuron in this sequence is called the preganglionic neuron. The second neuron, whose cell body is within the ganglion, travels to the visceral effector cell it is called the postganglionic neuron. 

The nervous system is conventionally divided into the central nervous system (CNS the brain and spinal cord) and the peripheral nervous system (PNS neuronal tissues outside the CNS). The motor (efferent) portion of the nervous system can be divided into two major subdivisions autonomic and somatic. The autonomic nervous system (ANS) is largely independent (autonomous) in that its activities are not under direct conscious control. It is concerned primarily with visceral functions such as cardiac output, blood flow to various organs, and digestion, which are necessary for life. The somatic subdivision is largely concerned with consciously controlled functions such as movement, respiration, and posture. Both systems have important afferent (sensory) inputs that provide information regarding the internal and external environments and modify motor output through reflex arcs of varying size and complexity. 

Nicotinic receptors are part of a transmembrane polypeptide whose subunits form cation-selective ion channels (see Figure 2-9). These receptors are located on plasma membranes of postganglionic cells in all autonomic ganglia, of muscles innervated by somatic motor fibers, and of some central nervous system neurons (see Figure 6-1). 

The PNS is further divided into functional sections known as the autonomic and somatic systems. The autonomic nervous system is also called the involuntary system. It regulates, without conscious effort, the visceral motor and sensory organs and muscles, as well as other smooth muscle and glands. The somatic is the voluntary nervous system which... 

Studies of neuromuscular junctions of the autonomic nervous system as early as 1904 led to the suggestion that adrenaline might be released at the nerve endings. Later it was shown that, while adrenaline does serve as a transmitter at neuromuscular junctions in amphibians, it is primarily a hormone in mammals. Nevertheless, it was through this proposal that the concept of chemical communication in synapses was formulated. By 1921, it was shown that acetylcholine is released at nerve endings of the parasympathetic system, and it later became clear the motor nerve endings of the somatic system also release acetylcholine. 

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