Review Sheet 18 Functional Anatomy of the Endocrine Glands
Learning Objectives
By the end of this section, you will be able to:
- Distinguish the types of intercellular advice, their importance, mechanisms, and effects
- Identify the major organs and tissues of the endocrine system and their location in the trunk
Communication is a process in which a sender transmits signals to one or more receivers to control and coordinate actions. In the man body, two major organ systems participate in relatively "long altitude" communication: the nervous system and the endocrine organisation. Together, these two systems are primarily responsible for maintaining homeostasis in the body.
Neural and Endocrine Signaling
The nervous system uses ii types of intercellular communication—electrical and chemic signaling—either by the direct action of an electrical potential, or in the latter case, through the action of chemical neurotransmitters such equally serotonin or norepinephrine. Neurotransmitters deed locally and rapidly. When an electric signal in the form of an action potential arrives at the synaptic terminal, they diffuse across the synaptic cleft (the gap between a sending neuron and a receiving neuron or muscle jail cell). Once the neurotransmitters collaborate (bind) with receptors on the receiving (post-synaptic) cell, the receptor stimulation is transduced into a response such as continued electrical signaling or modification of cellular response. The target prison cell responds within milliseconds of receiving the chemical "message"; this response then ceases very chop-chop once the neural signaling ends. In this way, neural communication enables body functions that involve quick, brief actions, such as motility, sensation, and cognition.In contrast, the endocrine system uses just one method of communication: chemical signaling. These signals are sent by the endocrine organs, which secrete chemicals—the hormone—into the extracellular fluid. Hormones are transported primarily via the bloodstream throughout the torso, where they bind to receptors on target cells, inducing a feature response. As a result, endocrine signaling requires more time than neural signaling to prompt a response in target cells, though the precise amount of time varies with different hormones. For instance, the hormones released when you are confronted with a dangerous or frightening situation, called the fight-or-flight response, occur by the release of adrenal hormones—epinephrine and norepinephrine—within seconds. In dissimilarity, information technology may have up to 48 hours for target cells to respond to certain reproductive hormones.
Interactive Link
Visit this link to watch an animation of the events that occur when a hormone binds to a jail cell membrane receptor. What is the secondary messenger made by adenylyl cyclase during the activation of liver cells past epinephrine?
In addition, endocrine signaling is typically less specific than neural signaling. The same hormone may play a role in a variety of unlike physiological processes depending on the target cells involved. For instance, the hormone oxytocin promotes uterine contractions in women in labor. It is also important in breastfeeding, and may be involved in the sexual response and in feelings of emotional attachment in both males and females.
In general, the nervous organisation involves quick responses to rapid changes in the external surround, and the endocrine system is usually slower acting—taking intendance of the internal environment of the body, maintaining homeostasis, and controlling reproduction (Table 17.1). So how does the fight-or-flight response that was mentioned before happen so quickly if hormones are commonly slower acting? It is because the two systems are connected. It is the fast action of the nervous system in response to the danger in the surroundings that stimulates the adrenal glands to secrete their hormones. Equally a result, the nervous system can crusade rapid endocrine responses to proceed upward with sudden changes in both the external and internal environments when necessary.
Endocrine and Nervous Systems
| Endocrine system | Nervous arrangement | |
|---|---|---|
| Signaling mechanism(s) | Chemical | Chemical/electrical |
| Master chemic signal | Hormones | Neurotransmitters |
| Distance traveled | Long or short | Always curt |
| Response fourth dimension | Fast or slow | Always fast |
| Environment targeted | Internal | Internal and external |
Tabular array 17.1
Structures of the Endocrine System
The endocrine system consists of cells, tissues, and organs that secrete hormones every bit a chief or secondary role. The endocrine gland is the major player in this system. The primary function of these ductless glands is to secrete their hormones directly into the surrounding fluid. The interstitial fluid and the blood vessels so transport the hormones throughout the body. The endocrine system includes the pituitary, thyroid, parathyroid, adrenal, and pineal glands (Figure 17.two). Some of these glands have both endocrine and non-endocrine functions. For example, the pancreas contains cells that function in digestion too as cells that secrete the hormones insulin and glucagon, which regulate claret glucose levels. The hypothalamus, thymus, centre, kidneys, stomach, small intestine, liver, skin, female ovaries, and male testes are other organs that contain cells with endocrine part. Moreover, adipose tissue has long been known to produce hormones, and recent research has revealed that even os tissue has endocrine functions.
Figure 17.2 Endocrine System Endocrine glands and cells are located throughout the body and play an important role in homeostasis.
The ductless endocrine glands are not to be confused with the torso's exocrine system, whose glands release their secretions through ducts. Examples of exocrine glands include the sebaceous and sweat glands of the peel. Every bit simply noted, the pancreas also has an exocrine function: most of its cells secrete pancreatic juice through the pancreatic and accompaniment ducts to the lumen of the small intestine.
Other Types of Chemical Signaling
In endocrine signaling, hormones secreted into the extracellular fluid diffuse into the blood or lymph, and can so travel bang-up distances throughout the torso. In contrast, autocrine signaling takes place within the same cell. An autocrine (auto- = "self") is a chemical that elicits a response in the same cell that secreted it. Interleukin-i, or IL-1, is a signaling molecule that plays an important role in inflammatory response. The cells that secrete IL-1 have receptors on their prison cell surface that bind these molecules, resulting in autocrine signaling.
Local intercellular advice is the province of the paracrine, likewise chosen a paracrine factor, which is a chemical that induces a response in neighboring cells. Although paracrines may enter the bloodstream, their concentration is mostly too low to elicit a response from afar tissues. A familiar case to those with asthma is histamine, a paracrine that is released by immune cells in the bronchial tree. Histamine causes the smooth muscle cells of the bronchi to constrict, narrowing the airways. Some other example is the neurotransmitters of the nervous system, which act only locally inside the synaptic fissure.
Career Connection
Endocrinologist
Endocrinology is a specialty in the field of medicine that focuses on the treatment of endocrine system disorders. Endocrinologists—medical doctors who specialize in this field—are experts in treating diseases associated with hormonal systems, ranging from thyroid disease to diabetes mellitus. Endocrine surgeons treat endocrine disease through the removal, or resection, of the affected endocrine gland.
Patients who are referred to endocrinologists may have signs and symptoms or blood examination results that propose excessive or dumb functioning of an endocrine gland or endocrine cells. The endocrinologist may order additional blood tests to decide whether the patient'due south hormonal levels are aberrant, or they may stimulate or suppress the office of the suspect endocrine gland and then accept blood taken for analysis. Treatment varies according to the diagnosis. Some endocrine disorders, such equally type 2 diabetes, may respond to lifestyle changes such as modest weight loss, adoption of a salubrious diet, and regular concrete activeness. Other disorders may require medication, such as hormone replacement, and routine monitoring by the endocrinologist. These include disorders of the pituitary gland that can affect growth and disorders of the thyroid gland that can effect in a variety of metabolic issues.
Some patients feel wellness problems as a result of the normal refuse in hormones that tin accompany aging. These patients tin consult with an endocrinologist to weigh the risks and benefits of hormone replacement therapy intended to boost their natural levels of reproductive hormones.
In addition to treating patients, endocrinologists may exist involved in research to ameliorate the agreement of endocrine system disorders and develop new treatments for these diseases.
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Source: https://openstax.org/books/anatomy-and-physiology/pages/17-1-an-overview-of-the-endocrine-system
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