chapter 42 ~ the endocrine system Flashcards
Long-distance signaling molecules
Hormones
Hormones are secreted into the ECF by the cells of endocrine glands
Classical endocrine signaling
Ductless secretory organs
Endocrine glands
Release their secretions into ducts that lead outside the body or into the cavity of the digestive tract
Exocrine glands
Specialized neurons called neurosecretory neurons release a hormone called neurohormone into the circulatory system when appropriately stimulated
Neuroendocrine signaling
A cell releases a signaling molecule that diffuses through the ECF and acts on nearby cells
Paracrine regulation
When a local regulator acts on the same cells that produced it
Autocrine regulation
Involved in classical endocrine and neuroendocrine signaling. Most are based on tyrosine. With one exception (thyroxine, which passes through the plasma membrane and binds to a receptor inside the target cell), they are hydrophilic and diffuse readily into the blood and ECF. They bind to receptors at the cell surface. Include dopamine, epinephrine, and norepinephrine
Amine hormones
Consist of amino acid chains ranging in length from three to more than two hundred. Some have carbohydrate groups attained to the chain. Involved in classical endocrine and neuroendocrine signaling, as well as act in paracrine and autocrine manners. Released into the ECF and enter the blood. Include insulin, gonadotropin releasing hormone, and growth hormones.
Peptide hormones
A large group of peptide hormones that regulate the division and differentiation of many cell types in body. Act in both paracrine and autocrine manners, as well as in classical endocrine signaling
Growth factors
Involved in classical endocrine signaling. Hydrophobic molecules derived from cholesterol. Combine with hydrophilic carrier proteins to form water soluble complexes that can diffuse through the ECF and enter the bloodstream. On contacting a cell they are released from the carrier proteins and pass through the plasma membrane of the target cell and bind to internal receptors in the nucleus or cytoplasm. Include aldosterone, cortisol, and sex hormones
Steroid hormones
Involved in paracrine and autocrine regulation. Include prostaglandins
Fatty acid derived molecules
A fatty acid derived molecule and important local regulator that can be secreted by virtually every cell and is present essentially at all times. They generally induce contraction or relaxation of smooth muscle cells, and also may intensify pain and inflammation
Prostaglandins
A product of the pathway inhibits an earlier step in the pathway
Negative feedback
A region of the brain located in the floor of the cerebrum
Hypothalamus
Consisting mostly of two fused lobes, is suspended just below the hypothalamus by a slender stalk of tissue that contains both neurons and blood vessels
Pituitary gland
Contains axons and nerve endings of neurosecretory neurons that originated in the hypothalamus
Posterior pituitary
Contains non neuronal endrocine cells that form a distinct gland
Anterior pituitary
Peptide neurohormones from the hypothalamus that control the secretion of hormones from the anterior pituitary, are carried in the blood from the hypothalamus to the anterior pituitary in a portal vein, secretion is controlled by neurons containing receptors that monitor the blood to defect changes in body chemistry and temperature, negative feedback pathways regulate secretion
Releasing hormones and inhibiting hormones
A special vein that connects the capillaries of the hypomalamus and anterior pituitary. it provides a critical link between the brain and the endocrine system, ensuring that most of the blood reaching the anterior pituitary first passes through the hypothalamus
Portal vein
Secreted by the anterior pituitary, influences reproductive activities and parental care in vertebrates, in mammals stimulates development of the secretory cells of mammary glands during late pregnancy and stimulates milk synthesis after a female mammal gives birth
Prolactin PRL
Secreted by the anterior pituitary, stimulates cell division, protein synthesis, and bone growth in children and adolescents, causing body growth, stimulates protein synthesis and cell division in adults by binding to target tissues, mostly liver cells, causing them to release insulin like growth factor, controls many metabolic processes in mammals of all ages including the conversion of glycogen to glucose and fats to fatty acids, stimulates body cells to take up fatty acids and amino acids and limits the rate at which muscle cells take up glucose
Growth hormones GH
Secreted by liver cells, a peptide that directly stimulates growth processes
Insulin-like growth factor
A deficiency in GH secretion during childhood, those affected remain small in saltire through the childhood into adulthood
Pituitary dwarfs
Overproduction of GH during childhood of adolescence, often due to a tumor of the anterior pituitary, those affected may grow above 8 ft in height
Pituitary giants
Secreted by the anterior pituitary, stimulates the thyroid gland to grow size and secrete thyroid hormones
Thyroid stimulating hormone TSH
Secreted by the anterior pituitary, triggers hormone secretion by cells in the adrenal cortex
Adrenocorticotropic hormone ACTH
Secreted by the anterior pituitary, controls egg development and the secretion of sex hormones in female mammals, and sperm production in males
Follicle stimulating hormone FSH
Secreted by the anterior pituitary, regulates part of menstrual cycle in human females and secretion of sex hormones in males
Luteinizing hormone LH
FSH and LH, regulate the activity of the gonads
Gonadotropins
Produced by the anterior pituitary but is secreted little to none adult humans, effects skin cells that contain the black pigment melanin
Melanocyte-stimulating hormone MSH
Peptide hormones produced by the hypothalamus and pituitary, are released by the anterior pituitary, act as neurotransmitters in the PNS in pathways that control pain, inhibiting the perception of pain
Endorphins
Secreted by the posterior pituitary, stimulated kidney cells to absorb more water from urine, increasing the volume of the blood. Is released when sensory receptor cells of the hypothalamus detect an increase in the blood,s osmotic pressure during periods of body dehydration or after a salty meal, and also when an injury results in heavy blood loss or some other event triggers a severe drop in blood pressure. Secretion is reduced by alcohol and stimulated by nicotine and emotional stress
Antidiuretic hormone ADH
Secreted by the posterior pituitary, stimulated the ejection of milk from the mammary glands of a nursing mother. Release is stimulated by a positive feedback mechanism. Plays a key role in childbirth. In males, it is secreted into a seminal fluid by the testes and stimulates contractions of the uterus that aid movement of sperm through the female reproductive tract during sexual intercourse
Oxytocin
A product of the pathway stimulates secretion of more product
Positive feedback
Located in the front of the throat in humans, secretes the same hormones in all vertebrates
Thyroid gland
The primary circulating thyroid hormone, concentration kept at a balanced level by negative feedback loops, is converted to T3 once inside a cell to combine with internal receptors, alters gene expression, vital to growth, development, maturation, and metabolism in all vertebrates, interact with GH, increase sensitivity of many body cells to effects of epinephrine and norepinephrine
Thyroxine T4
The thyroid secretes this in smaller amounts, closely related to T4, concentration kept at a balanced level by negative feedback loops, enters cells and binds to internal receptors to alter gene expression, vital to growth, development, maturation, and metabolism in all vertebrates, interacts with GH, increase sensitivity of many body cells to effects of epinephrine and norepinephrine
Triiodothyronine T3
Thyroid hormones trigger this in amphibians, the change in body form from tadpole to adult
Metamorphosis
Low thyroid output, causes affected individuals to be sluggish mentally and physically, have a slow heart rate and weak pulse, and often feel confused and depressed
Hypothyroidism
Stunted growth and diminished intelligence, a result of hypothyroidism in infants and children
Cretinism
Overproduction of thyroid hormones in human adults, produces nervousness and emotional instability, irritability, insomnia, weight loss, and a rapid, irregular heartbeat
Hyperthyroidism
The most common form of hyperthyroidism, characterized by inflamed, protruding eyes in addition to the symptoms of hyperthyroidism
Graves’ disease
Enlargement of the thyroid caused by insufficient iodine in the diet
Goiter
A peptide hormone secreted by the thyroid in mammals that lowers the level of ca 2+ in the blood by inhibiting the ongoing dissolution of calcium from bone. Secretion is stimulated when ca 2+ levels in blood rise above the normal range is inhibited when they fell below
Calcitonin
Occur only in tetrapod vertebrates. Mammals have four located on the posterior surface of the thyroid gland. They produce one hormone
Parathyroid glands
Secreted in response to a fall in blood ca 2+ levels and stimulates bone cells to dissolve the mineral matter of bone tissues releasing calcium and phosphate ions into the blood. Also stimulates enzymes in the kidney that convert vitamin D Into its fully activated form in the body
Parathyroid hormone PTH
A steroid like molecule that increases the absorption of ca 2+ and phosphates from ingested food by promoting the synthesis of a calcium binding protein in the intestine and also increases the release of ca 2+ from bone in response to PTH
Vitamin D
In mammals, consist of two distinct regions, the adrenal medulla and the adrenal cortex
Adrenal glands
The central region of the adrenal gland that contains secretory cells of neural crest origin
Adrenal medulla
The tissue surrounding the adrenal gland that contains endocrine cells
Adrenal cortex
Chemical compounds derived from the amino acid tyrosine that circulate in the bloodstream
Catecholamines
Secreted from sympathetic neurons and the adrenal medulla when the body encounters stress. Prepares the body for handling stress or physical activity by increasing heart rate, releasing glucose and fatty acids for fuel, dilating blood vessels to increase blood flow in the heart, skeletal muscles (one of these hormones constricts these but the other is secreted in greater quantities), and lungs, constricting blood vessels elsewhere which raises blood pressure, reduces water loss, and slows digestive processes, and dilates airways to increase the flow of air. Binds to receptors in the plasma membranes of its target cells
Epinephrine and norepinephrine
Secreted by the adrenal cortex, steroid hormones, help maintain glucose levels in the blood by stimulating the synthesis of glucose from non- carbohydrate sources, reducing glucose uptake by body cells except those in CNS, and promoting the breakdown of fats and proteins for alternative fuel, secretion is under control of the hypothalamus via ACTH
Glucocorticoids
The major glucocorticoid secreted by the adrenal cortex
Cortisol
Secreted by the adrenal cortex, steroid hormones, increase the amount of Na + reabsorbed from fluids processed by kidneys and absorbed from foods in the intestine. Also reduce the amount of Na + secreted by salivary and sweat glands and increase the rate of K + excretion by the kidneys. Secretion is linked to blood volume
Mineralocorticoids
The primary mineralocorticoid secreted by the adrenal cortex
Aldosterone
Secreted by the adrenal cortex in small amounts and gonads in larger amounts, steroid sex hormones responsible for the maintenance of male reproductive systems and masculine characteristics, synthesized primarily by gonads
Androgens
Testes and ovaries, the primary sources of sex hormones in vertebrates
Gonads
In male vertebrates, secretes androgens
Testes
The principal androgen, the male sex hormone, stimulates puberty and the development of secondary sexual characteristics including facial and body hair, muscle development, changes in voice, and development of sex drive. Synthesis and secretion is controlled by LH from the anterior pituitary, which is controlled by GnRH from the hypothalamus
Testosterone
Secreted by the hypothalamus, controls the release of LH from the anterior pituitary
Gonadotropin-releasing hormone GnRH
Synthetic derivatives of androgens
Anabolic androgens steroids AAS
Under the stimulatory influence of FSH, produce estrogens
Ovaries
Steroid hormones that stimulate and control the development and maintenance of female reproductive systems
Estrogens
The principal estrogen, stimulates maturation of sex organs at puberty and the development of the secondary sexual characteristics
estradiol
The primary progestin produced by the ovaries, is a steroid hormone that prepares and maintains the uterus for implantation of a fertilized egg and the subsequent growth and development of an embryo. Synthesis and secretion is controlled by LH which is controlled by GnRH
Progesterone
A relatively large gland just behind the stomach, mostly secretes digestive enzymes into the small intestine as an exocrine gland but has a small amount of endocrine cells that form islets of langerhans
Pancreas
Endocrine cells in the pancreas that secrete the peptide hormones insulin and glucagon into the bloodstream
Islets of langerhans
A peptide hormone secreted by beta cells in the islets, and acts mainly on cells of skeletal muscles, liver cells, and adipose tissue. It lowers circulating blood glucose, fatty acid, and amino acid levels and promotes their storage. Also inhibits degradation of compounds into their building blocks
Insulin
A peptide hormone secreted by alpha cells in the islets, stimulates glycogen, fat, and protein degradation, promotes the use of amino acids and other non carbohydrates as the input of glucose synthesis
Glucagon
A disease that results from problems with insulin productive or action. Type 1 results from insufficient insulin secretion by the pancreas. Type 2 results from reduced responsiveness to the hormone in target cells
Diabetes mellitus
Found at different locations in the brains of vertebrates, in mammals roughly at the center
Pineal gland
A peptide hormone secreted by the pineal gland in mammals that helps to maintain daily biorhythms. Secretion is regulated by an inhibitory pathway, where light hitting the eyes generates signals to inhibit secretion, targets a part of the hypothalamus called the suprachiasmatic nucleus
Melatonin
Pigment- containing cells of the skin in some fish, amphibians, and reptiles, where melatonin produces changes in skin color
Melanophores
Located in the hypothalamus, it is the primary biological clock coordinating body activity to a daily cycle
Suprachiasmatic nucleus
A peptide hormone secreted by neurosecretory neurons in the brains of insects to regulate molting and metamorphosis
Prothoracicotropic hormone PTTH
A steroid hormone secreted by the prothoracic glands of insects to regulate molting and metamorphosis
Ecdysone
A terpenoid (unsaturated hydrocarbon) secreted by the corpora allata, a pair of glands just behind the brain of insects to regulate molting and metamorphosis. If this is high, the molt produces a larger lava. If it is low, the molt leads to pupation and the emergence of an adult
Juvenile hormone JH
A peptide neurohormone that is secreted before growth reaches the stage at which the exoskeleton is shed in crustaceans by a gland in the eye stalks that inhibits ecdysone secretion. As body size increases to where a molt is required, this is inhibited
Molt inhibiting hormone MIH
