Autonomic nervous system central connections

Enteric nerves control intestinal smooth muscle action and are connected to the brain by the autonomic nervous system. IBS is thought to result from dysregulation of this brain-gut axis. The enteric nervous system is composed of two gan-glionated plexuses that control gut innervation the submucous plexus (Meissner s plexus) and the myenteric plexus (Auerbach s plexus). The enteric nervous system and the central nervous system (CNS) are interconnected and interdependent. A number of neurochemicals mediate their function, including serotonin (5-hydroxytryptamine or 5-HT), acetylcholine, substance P, and nitric oxide, among others. 

The autonomic nervous system consists of central connections, visceral afferent fibers, and visceral efferent fibers. The hypothalamus is where the principal integration of the entire autonomic nervous... 

There are two main parts to die nervous system die central nervous system (CNS) and the autonomic nervous system (ANS). The CNS is the major integrating system of the body. The ANS connects the spinal cord at each vertebra and connects the CNS to each muscle and to glands. The ANS is divided classically into two systems the S3mipathetic and parasympathetic (Cordell, 1981). 

S-HT occurs in the central nervous system of all vertebrates and seems to be concentrated in the phylogenetically older parts of the brain connected with the autonomic nervous system and the reticular formation (Table 2). The use of histofluorescence techniques has made it possible to confirm the finding of uneven regional S-HT distribution based on chemical and biochemical assays. S-HT neurons have now been visualized (Fig. 7 and Fig. 10 in Sect B, Chap. S.2). Most S-HT neurons seem to be located in the nuclei of the raphe system and their axons travel towards several parts of the brain and the spinal cord. These axons are particularly concentrated in the medial forebrain bundle (MFB) (Fig. 7X which can be selectively destroyed, leading to a significant decrease in S-HT in some areas of the brain. Diurnal and seasonal variations in S-HT levels in several areas of the brain have been demonstrated. 

The nervous system can be divided into three parts the central nervous system (CNS), the peripheral nervous system (PNS), and the autonomic nervous system (ANS) (Dawson et al. 2003). The CNS consists of the brain and spinal cord. The PNS resides outside the CNS and forms a network to collect information from sensory responses. The ANS is identified by primary ganglia of the head and neck, sympathetic chain and adrenal gland (Gabella and Larry 2009). The primary function of the nervous system is to receive input from the environment and innervate muscle tissues in response. To accomplish this task, neurons, which are the basic unit of the functional nervous system (Dawson et al. 2003), form a highly specific interconnecting network from the brain to the spinal cord. There are 12 paired cranial nerve and 31 paired spinal nerve connections between the CNS and the PNS, which result in motor/ efferent, sensory/afferent, or mixed function. Furthermore, internal environments such as cardiorespiratory activities, glandular secretions, vasodilatation and genital erectile tissue responses are monitored by an array of visceral receptors, chemoreceptors, and stretch receptors via autonomic nerves from the CNS (Keller et al. 2009). 

The ENS is connected to the central nervous system by extrinsic parasympathetic and sympathetic motor neurons, and by extrinsic spinal and vagal sensory neurons. Through these bidirectional connections, the ENS can be monitored and modified. Despite the presence of these extrinsic nerve connections, the ENS can also function autonomously in some intestinal regions. Neural transmission within the ENS is controlled by a large variety of neurotransmitters and neuromodulatory peptides, such as serotonin, norepinephrine, acetylcholine, ATP, and nitric oxide. Most of these... 

The gastrointestinal (GI) tract is in a continuous contractile, absorptive, and secretory state. The control of this state is complex, with contributions by the muscle itself, local nerves (i.e., the enteric nervous system, ENS), the central nervous system (CNS), and humoral pathways. Of these, perhaps the most important regulator of physiological gut function is the ENS (Figure 37-1), which is an autonomous collection of nerves within the wall of the Gl tract, organized into two connected networks of neurons the myenteric (Auerbach s) plexus, found between the circular and longitudinal muscle layers, and the submucosal (Meissner s) plexus, found below the epithehum. The former is responsible for motor control, while the latter regulates secretion, fluid transport, and vascular flow. 

The peripheral nervous system (those nerves outside the central nervous system or CNS) of vertebrates is made up of both sensory (afferent) and motor (efferent) nerves (figure). Each of these includes a bundle of nerve cells that connect to different sensors and actuators in the body. Motor nerves can be either somatic (mostly voluntary) or autonomic (mostly involuntary). 

The brain stem is the main connection between the superior parts of the central nervous system (CNS) and the spinal cord. All nervous impulses ascending from the cord to the CNS or descending from the CNS to the cord pass through the brain stem. Within the brain stem are the nuclei of the cranial nerves and the autonomic centers. Significant damage to the brain stem is inconsistent with the continuation of life. 

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