Body temperature is the balance between the heat produced by the body and the heat lost from the body. In humans, as other mammals, the core temperature of the body remains constant despite the temperature of the surrounding environment. For the body to function optimally, the temperature must be maintained within narrow limits. There are two kinds of body temperature: core temperature and surface temperature. Core temperature is the temperature of the deep tissues of the body. It normally remains constant at about 98. 6 degrees Fahrenheit (37.0 degrees Celsius). However, body temperature varies from person to person and is affected by factors such as exercise, sleep, eating and drinking, and time of day.
The body's surface temperature rises and falls in response to the environment. Body temperature is maintained by the hypothalamus, which constantly monitors bloodtemperature and activates mechanisms to compensate for changes. When the body's surface temperature falls, the hypothalamus sends nerve impulses to the skin to stimulate shivering, which generates heat by muscle activity, and to restrict the blood vessels in the skin, which limits heat loss. When the surface temperature rises, the hypothalamus stimulates the sweat glands in the skin to produce sweat and dilates the blood vessels in the skin to increase heat loss. There is a danger to life should the body temperature drop and remain below 95 degrees Fahrenheit (35 degrees Celsius) or rise and remain at or above 106 degrees Fahrenheit (41 degrees Celsius). Chemical reactions in the body increase an average of about 120% for every 10 degree rise in temperature. Research Body Temperature
The infundibulum, also called the pituitary stalk or neural stalk, is the stem-like structure of grey matter which attaches the pituitary gland to the hypothalamus on the under surface of the brain. Research Infundibulum
The optic chiasm is located on the undersurface of the hypothalamus near the pituitary gland. The optic nerves cross in an 'X' formation at the optic chiasm. This is where the fibres from the medial (or nasal) half of each retina cross and join the optic tract of the opposite side and continue to the brain. Research Optic Chiasm
The pituitary gland (or hypophysis),is a gland within the brain concerned with regulating growth and regulating other ductless glands. The pituitary gland , consists of three lobes, the anterior lobe, the intermediate lobe, which in primates is present for only a short part of the life span, and the posterior lobe. It is situated at the base of the brain and has been called the master controlling gland of the body. The anterior and the posterior lobes of the pituitary secrete different hormones. The anterior lobe secretes various hormones that stimulate the function of other endocrine glands, for example, adrenocorticotropic hormone, or ACTH, which stimulates the adrenal cortex; thyroid- stimulating hormone, or thyrotropin, known as TSH; follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which stimulate the sex glands; and prolactin, which, with other special hormones, influences milk production of the mammary gland.
In addition, the anterior pituitary is the source of growthhormone, also called somatotropin, which promotes the development of body tissues, particularly of bone matrix and muscle, and influences carbohydrate metabolism. The anterior pituitary also secretes a hormone called melanocyte-stimulating hormone, which regulates the intensity of pigmentation in pigmented cells. In the 1970s scientists found that the anterior pituitary also produces substances called endorphins. These are peptides that act on the peripheral and central nervous systems to reduce sensitivity to pain. The hypothalamus, secretes an antidiuretic hormone named vasopressin, which is stored in the posterior lobe of the pituitary gland. The posterior lobe of the pituitary also stores another hormone secreted by the hypothalamus. This hormone, known as oxytocin, stimulates muscular contractions, especially of the uterus, and ejection of milk from lactating mammary glands. Not long ago it was found that secretion of three anterior pituitary hormones is under regulation of the hypothalamus: thyrotropin secretion is stimulated by thyrotropin-releasing factor (TRF), and luteinizing- hormone secretion by luteinizing-hormone releasing hormone (LHRH). Release of growthhormone is inhibited by somatostatin, which is also made by the pancreas. Research Pituitary gland
The sweat that dampens the skin comes from the eccrine glands. They lie in the subcutaneous tissue (hypodermis) just under the dermis. The human body has between two and three million eccrine glands that secrete moisture on the skin primarily to cool the body through evaporation. The eccrine glands react to signals from the hypothalamus in the brain. Research Sweat Gland
The sweat pores allow loss of fluid as part of temperature control of the body. As a rise in external temerature is sensed by the nerve endings in the skin, the message is relayed to the hypothalamus, the temperature-regulating area of the brain. The brain then sends nerve impulses to the sweat glands stimulating them to release sweat until the skin receptors detect that the skin's temperature is back to normal. The brain then sends messages to stop the release of sweat. Research Sweat Pore
The thalamus is located in the midportion of the diencephalon, a structure between the cerebrum and midbrain which also contains the epithalamus, the hypothalamus, and the subthalamus and surrounds the third ventricle. The
thalamus contains nerve centers responsible for optic and auditory reflexes, equilibrium, and posture. The hypothalamus contains the optic chiasm, the infundibulum, and the posterior lobe of the pituitary gland. It houses centers responsible for maintaining and regulating metabolism, body temperature, and emotions which affect heart rate, appetite, sexual arousal, and blood pressure. Research Thalamus
The thyroid is an endocrine gland near the larynx in vertebrates. It influences growth and development. The thyroid gland in human beings is a brownish-red organ having two lobes connected by an isthmus; it normally weighs about 28 g and consists of cuboidal epithelial cells arranged to form small sacs known as vesicles or follicles. The vesicles are supported by connective tissue that forms a framework for the entiregland. In the normal thyroid gland, the vesicles are usually filled with a colloid substance containing the protein thyroglobulin in combination with the two thyroid hormones thyroxine, also called tetraiodothyronine (T4), and triiodothyronine (T3). These hormones are composed of the amino acid tyrosine, containing four and three iodine atoms, respectively.
The amount of thyroglobulin secreted by the thyroid is controlled by the thyroid- stimulating hormone (TSH) of the pituitary gland. Pituitary TSH, in turn, is regulated by a substance called thyroid-stimulating hormone releasing factor (TRF), which is secreted by the hypothalamus. Thyroglobulin is especially rich in iodine. Although the thyroid gland constitutes about 0.5 percent of the total human body weight, it holds about 25 percent of the total iodine in the body, which is obtained from food and water in the diet. Iodine usually circulates in the blood as an inorganic iodide and is concentrated in the thyroid to as much as 500 times the iodide level of the blood. Research Thyroid More information about Thyroid
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Body Temperature
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