Prolonged starvation can cause permanent organ damage and, untreated, leads to death. Individuals experiencing starvation lose substantial fat and muscle mass, called catabolysis, when the body breaks down its own fat and muscle for energy. Vitamin deficiency, diarrhea, skin rashes, edema, and heart failure are also common results of starvation.
In a state of starvation, other motivators—such as the desire for sleep, sex, and social activities— decrease. Individuals suffering from starvation may experience irritability, lethargy, impulsivity, hyperactivity, and more apathy over time. Privacy Policy. Skip to main content. Biological Foundations of Psychology. Search for:. The Endocrine System.
The Endocrine System The endocrine and nervous systems work together to act as a communication system for the human body. Learning Objectives Outline the structure and function of the endocrine system.
The endocrine system differs from the nervous system in that its chemical signals are slower-moving and longer-lasting. Hormones act as chemical messengers within the body, telling it to perform specific physical and mental functions.
There are eight major endocrine glands, each performing a different function: the pituitary gland, the thyroid, the thymus gland, the adrenal gland, the ovaries female and testes male , the pancreatic islets, and the pineal gland.
The HPA axis is a complex set of direct influences and feedback interactions among three organs crucial to endocrine function: the hypothalamus, the pituitary gland, and the adrenal glands.
Key Terms polypeptide : Any polymer of same or different amino acids joined via peptide bonds. The Endocrine System and Stress The hypothalamic-pituitary-adrenal axis regulates stress in vertebrates. Key Takeaways Key Points Stress is a useful response to dangerous situations but can damage the body if sustained.
The HPA axis regulates the stress response by producing cortisol through a complex series of feedback loops. Prenatal stress can affect HPA regulation in children. The Endocrine System and Hunger Hunger is divided into long-term and short-term regulation, each stimulating different hormone responses from the hypothalamus.
Learning Objectives Compare the factors involved in long-term and short-term hunger regulation. Key Takeaways Key Points Hunger is the physical sensation of desiring food, and appears to increase activity and movement in many animals. The sensation of hunger is controlled by the hypothalamus and hormones, and is divided into long-term and short-term regulation. Long-term regulation of hunger prevents energy shortfalls. It is the fast action of the nervous system in response to the danger in the environment that stimulates the adrenal glands to secrete their hormones.
As a result, the nervous system can cause rapid endocrine responses to keep up with sudden changes in both the external and internal environments when necessary. The endocrine system consists of cells, tissues, and organs that secrete hormones as a primary or secondary function. 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 then transport the hormones throughout the body. The endocrine system includes the pituitary, thyroid, parathyroid, adrenal, and pineal glands Figure. Some of these glands have both endocrine and non-endocrine functions. For example, the pancreas contains cells that function in digestion as well as cells that secrete the hormones insulin and glucagon, which regulate blood glucose levels.
The hypothalamus, thymus, heart, kidneys, stomach, small intestine, liver, skin, female ovaries, and male testes are other organs that contain cells with endocrine function. Moreover, adipose tissue has long been known to produce hormones, and recent research has revealed that even bone tissue has endocrine functions. Examples of exocrine glands include the sebaceous and sweat glands of the skin.
As just noted, the pancreas also has an exocrine function: most of its cells secrete pancreatic juice through the pancreatic and accessory ducts to the lumen of the small intestine. In endocrine signaling, hormones secreted into the extracellular fluid diffuse into the blood or lymph, and can then travel great distances throughout the body. In contrast, autocrine signaling takes place within the same cell.
Interleukin-1, 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 cell surface that bind these molecules, resulting in autocrine signaling.
Local intercellular communication is the province of the paracrine , also called a paracrine factor, which is a chemical that induces a response in neighboring cells. Although paracrines may enter the bloodstream, their concentration is generally too low to elicit a response from distant tissues.
A familiar example 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.
Another example is the neurotransmitters of the nervous system, which act only locally within the synaptic cleft. Endocrinologist Endocrinology is a specialty in the field of medicine that focuses on the treatment of endocrine system disorders. These hormones tell a boy's body when it's time to make the changes associated with puberty , like penis and height growth, deepening voice, and growth in facial and pubic hair.
Working with hormones from the pituitary gland, testosterone also tells a boy's body when it's time to make sperm in the testes.
A girl's gonads , the ovaries OH-vuh-reez , are in her pelvis. Estrogen is involved when a girl starts puberty. During puberty, a girl will have breast growth, start to accumulate body fat around the hips and thighs, and have a growth spurt.
Estrogen and progesterone are also involved in the regulation of a girl's menstrual cycle. These hormones also play a role in pregnancy. Insulin helps keep the body supplied with stores of energy. The body uses this stored energy for exercise and activity, and it also helps organs work as they should.
Reviewed by: Larissa Hirsch, MD. Larger text size Large text size Regular text size. What Is the Endocrine System? What Does the Endocrine System Do? Endocrine glands release hormones into the bloodstream. This lets the hormones travel to cells in other parts of the body. This branch of medicine — relating to the study of the endocrine system — is called endocrinology and is practiced by endocrinologists. The field is rapidly expanding due to understanding of the cellular pathways that hormones stimulate and the discovery of new hormones and their actions.
An exocrine gland, unlike an endocrine gland, is a gland that secretes substances electrolytes, proteins or enzymes straight to a target site via ducts or tube. Some examples include:. The pancreas is both an endocrine and exocrine organ. It releases certain enzymes to aid in digestion delivered to the gut via the pancreatic duct. The endocrine pancreas also releases hormones such as insulin and glucagon, which are hormones predominantly related to glucose metabolism, into the blood stream.
A hormone can be thought of as a key, and its target site such as an organ has specially shaped locks on the cell walls. If the hormone fits the cell wall, then it will work. The hormones can set off a cascade of other signaling pathways in the cell to cause an immediate effect for instance, insulin signaling leads to a rapid uptake of glucose into muscle cells or a more delayed effect glucocorticoids bind to DNA elements in a cell to switch on the production of certain proteins, which takes a while to produce.
The endocrine system is a tightly regulated system that keeps the hormones and their effects at just the right level. The release of hormones is regulated by other hormones, proteins or neuronal signals. The released hormone then has its effect on other organs. This effect on the organ feeds back to the original signal to control any further hormone release. The pituitary gland is well known for its feedback loops.
Numerous problems can occur in the endocrine system. These can be considered as excessive or deficient hormone production. Endocrine organs are also prone to tumours adenomas which can over produce hormones. Some problems of the endocrine system include:. This page has been produced in consultation with and approved by:.
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