Exocrine gland cell

The vesicles are intimately involved in the release of the transmitter into the synaptic or neuroeffector cleft in response to an action potential. Following release, the transmitter must diffuse to the effector cells, where it interacts with receptors on these cells to produce a response. The distance between the varicosities and the effector cells varies considerably from tissue to tissue. Smooth muscle, cardiac muscle, and exocrine gland cells do not contain morphologically specialized regions comparable to the end plate of skeletal muscle. 

The action of administered acetylcholine on effector systems innervated by parasympathetic postganglionic neurons (smooth muscle cells, cardiac muscle cells, and exocrine gland cells) resembled the actions produced by the naturally occurring plant alkaloid muscarine. The actions of both acetylcholine and muscarine on the visceral effectors are similar to those produced by parasympathetic nerve stimulation. Furthermore, the effects of acetylcholine, muscarine, and parasympathetic nerve stimulation on visceral effectors are antagonized by atropine, another plant alkaloid. 

As well as excitable cells, other cell types such as liver cells may also have receptors, which can be affected by chemicals, although usually with less dramatic results. Thus, liver cells have oci adrenergic receptors, activation of which causes metabolic effects such as increased glycogenolysis and increased intracellular Ca2+. The muscarinic receptor in exocrine gland cells is influenced by acetylcholine, hence excess secretions occur with acetylcholinesterase inhibitors such as organophosphates (see chap. 7). 

CP-channels with even smaller conductance have been described for the lacrimal and other exocrine glands [76,77]. These channels have a conductance of 1-2 pS. Unlike the ICOR-channel they appear to be blocked by millimolar concentrations of furosemide [77]. Most recent and only partially published data from my own laboratory obtained with the above modified nystatin technique [50,133,134] indicate that the respiratory epithelial cells and colonic carcinoma cells possess these types of small CP channels, and that these channels are involved in hormonal regulation of CP-conductance (cf. section 5). These CP-channels are regulated by cytosolic Ca. Hormonally induced increases in cytosolic Ca lead to an abrupt increase in the probability of these small CP-channels being open, yet they have no effect on the ICOR-channel. Data of this kind reinforce that the physiological importance of these small CP-channels may have been grossly underestimated. 

The pancreas is a gland in the abdomen lying in the curvature of the stomach as it empties into the duodenum. The pancreas functions primarily as an exocrine gland, although it also has endocrine function. The exocrine cells of the pancreas are called acinar cells. They produce an alkaline fluid known as pancreatic... 

Cystic fibrosis (CF) is a hereditary disease of abnormal fluid secretion. It affects cells of the exocrine glands, such as intestine, sweat glands, pancreas, reproductive tract, and especially the respiratory tract. The disease affects about 1 in 2500 infants of the Caucasian population to varying degrees of seriousness. Patients produce thickened mucus that is difficult to get out of the airway. This leads to chronic lung infection, which progressively destroys pulmonary function. 

CF is caused by the absence of a protein called cystic fibrosis transmembrane conductance regulator (CFTR). This protein is required for the transport of chloride ions across cell membranes. On the molecular level, there is a mutation in the gene that encodes for CFTR. As a result, CFTR cannot be processed properly by the cell and is unable to reach the exocrine glands to assume its transport function. 

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. 

Mecfianism of Action A cholinergic agonist that binds to muscarinic receptors of effector cells, thereby increasing secretion of exocrine glands, such as salivary glands. Therapeutic Effect Relieves dry mouth. 

Nicotinic Muscarinic Autonomic ganglia All parasympathetic effector cells Visceral and bronchiole smooth muscle Cardiac muscle Exocrine glands (salivary, intestinal, lacrimal] Sweat glands Mediate transmission to postganglionic neuron Contraction (generally] Decreased heart rate Increased secretion Increased secretion... 

As stated by Blomquist et al. (1998) in their chapter, the line of demarcation between glandular or cuticular release of semiochemical signals is not always clear . This statement echoes an earlier one by Blum (1985), who reported that insect exocrine glands consisting of modified epidermal cells located throughout the body could perform de novo biosynthesis and secretion of behavioral chemicals. Later, Blum (1987) put forth a unified chemoso-ciality concept proposing that epicuticular lipids carried numerous exocrine compounds and that the cuticle could be compared to a thin layer phase. Nevertheless, it is known that in various non-social insects epicuticular hydrocarbons are synthesized by modified cells often associated with the epidermis, the oenocytes (see above), and that these oenocytes can be located in several sites within insects. 

Figure 5.1 Schematic illustration of the structure of the wall of different classes of blood capillaries. (1) Continuous capillary (as found in the general circulation). The endothelium is continuous with tight junctions between adjacent endothelial cells. The subendothehal basement membrane is also continuous. (2) Fenestrated capillary (as found in exocrine glands and the pancreas). The endothelium exhibits a series of fenestrae which are sealed by a membranous diaphragm. The subendothehal basement membrane is continuous. (3) Discontinuous (sinusoidal) capillary (as found in the liver, spleen and bone marrow). The overlying endothelium contains numerous gaps of varying size. The subendothehal basement is either absent (hver) or present as a fragmented interrupted structure (spleen, bone marrow)...

The pathway of secretory proteins and glycoproteins (protein with attached carbohydrate) through exocrine (secretory) gland cells in which secretory vacuoles are present is well established. However, the exact pathway of exchange of the membranes between the various organelles is less clear and could be either one or a combination of both of the schemes shown in Fig. 1-7. 

Sjogren s syndrome an autoimmune disorder affecting the salivary and lacrimal glands. In this disorder, immune cells attack host exocrine glands that are responsible for the production of tears and saliva. 

The liver functions as an exocrine gland, with each hepatocyte continually secreting a small amount of bile into tiny bile canaliculi located between adjacent pairs of parenchymal cells. These tiny vessels form a continuous network from lobule to lobule... 

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