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Chapter 18 - Endocrine Glands

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What are the 8 main regulatory functions of the endocrine system?
1) metabolism and tissue maturation
2) Ion regulation
3) Water Balance
4) immune system regulation
5) heart rate and blood pressure regulation
6) control of blood glucose and other nutrients
7) control of reproductive functions
8) uterine contractions and milk release
Pituitary gland (hypophysis)
a major endocrine gland that secretes nine major hormones that regulate numerous body functions and the secretory activity of severtal other endocrine glands
Hypothalamus
a portion of the brain that regulates the secretions of the posterior pituitary gland
Infundibulum
a structure that connects the posterior pituitary to the hypothalamus;
releases many inhibiting and stimulating hormones
Posterior pituitary (neurohypophysis)
the posterior aspect of the pituitary gland;
develops from an outgrowth of the hypothalamus;
secretes oxytocin and ADH
Anterior pituitary (adenohypophysis)
an anterior aspect of the pituitary gland;
develops from an outgrowth of the roof of the oral cavity;
secretes numerous major hormones into the body
Neurohormone
hormones that are excreted from the nervous system; for example hormones secreted from the posterior pituitary are neurohormones
Hypothalamohypophysial portal system
one of two major portal systems in the body;
extends from a part of the hypothalamus to the anterior pituitary
Releasing hormones
tropic neurohormones secreted from the hypothalamus that acts on tissues in the anterior pituitary to increase hormonmal secretions
Inhibiting hormones
tropic neurohormones secreted from the hypothalamus that acts on tissues in the anterior pituitary to decrease hormonmal secretions
Growth hormone-releasing hormoone (GHRH)
a small peptide released from the hypothalamus that stimulates the secretion of growth hormone from the anterior pituitary gland
Growth hormone-inhibiting hormone (GHIH)
a small peptide released from the hypothalamus that inhibits the secretion of growth hormone from the anterior pituitary gland;
also called somatostatin
Thyroid-releasing hormone (TRH)
a small peptide released fom the hypothalamus that stimulates the secretion of thyroid-stimulating hormone from the anterior pituitary gland
Corticotropin-releasing hormone (CRH)
a peptide that is released from the hypothalamus that stimulates adrenocorticotropic hormone secretion from the anterior pituitary
Gonadotropin-releasing hormone (GRH)
a small peptide released from the hypothalamus that stimulates the release of LH and FSH from the anterior pituitary gland
Prolactin-releasing hormone (PRH)
a neurohormone released from the hypothalamus that stimulates the secretion of prolactin from the anterior pituitary gland
Prolactin-inhibiting hormone (PIH)
a neurohormone released from the hypothalamus that inhibits the secretion of prolactin from the anterior pituitary gland
Hypothalamohypophysial tract
a tract of neuron acons that run from the hypothalamus, through the infundibulum, to the posterior pituitary gland;
neurohormones are produced in the hypothalamus and transported in vesicles down the tract where they are stored until stimulated to release
Antidiuretic hormone (ADH)
a hormone that is released from the posterior pituitary that prevents the output of large amounts of urine; sometimes called vasopressin because it constricts blood vessels and raises blood pressure when large amounts are released
Osmoreceptors
specialized neurons that are sensitive to changes in the osmolality of a fluid;
aid in regulation of fluid concentration levels
Tropic hormones
hormones that are released from one gland and stimulate the release of hormone from a different gland which then exerts its effect on yet another tissue
Growth hormone (GH)
a hormone released from the anterior pituitary gland;
stimulates growth in most tissues, plays a major role in regulating growth and metabolism; direct effects include increased breakdown of lipids and decreased use of glucose as an energy source
also called somatotropin
Somatomedins
produced by the liver under the stimulation of GH; circulate in the blood and binds to receptors on target tissues, increased growth of cartilage and bone, as well as increased protein snythesis in bone
insulin-like growth factor I & II
somatomedins similar in structure and function to insulin
Thyroid-stimulating hormone (TSH)
also called thyrotropin;
secreted by the anterior pituitary, stimulates the synthesis and secretion of thyroid hormones from the thyroid gland;
glycoprotein consisting of alpha and beta subunits
Adrenocorticotropic hormone (ACTH)
a peptide hormone secreted from the anterior pituitary, works at the adrenal cortex and prompts secretion of corisol and other steroids; also acts at the skin with MSH
Lipotropin
hormones secreted from the anterior pituitary that bind to membrane-bound receptor molecules on adipose tissue cells;
cause fat breakdown and release of fatty acids into the circulatory system
Beta endorphins
secreted from the ant. pituitary;
hormone that has the same effect on the body as opiates; plays a role in analgesia in response to stress and exercise
Melanocyte-stimulating hormone (MSH)
a hormone secreted from the ant. pituitary that binds to membrane-bound receptors on skin melanocytes and stimulates increased melanin deposition in the skin
Gonadotropins
glycoprotein hormones capable of promoting growth and function of the gonads
Gonads
ovaries and testes
Luteinizing hormone (LH)
hormone secreted from the ant. pituitary into the blood;
when released with FSH, stimulats the production of gametes; controls the production of reproductive hormones
Follicle-stimulating hormone (FSH)
hormone secreted from the ant. pituitary into the blood;
when released with LH, stimulats the production of gametes; controls the production of reproductive hormones
Prolactin
hormone secreted from the ant. pituitary;
plays an important role in milk production in the mammary glands of lactating females;
can enhance progesterone secretion of the ovary after ovulation; regulated by a complex hypothalamic system
Thyroid gland
composed of two lobes connected by a narrow band of thyroid tissue
Isthmus (thyroid)
a narrow band of tissue connecting the two lobes of the thyroid gland
Follicles (thyroid)
small spheres whose walls are composed of a single layer of cuboidal epithelial cells;
highly vascular tissue;
lumen is filled with thyroglobulin;
Thyroglobulin
protein that is synthesized and secreted by cells of thyroid follicles;
thyroid hormones are stored in lumen in conjuction with these proteins
Parafollicular cells
found in spaces between thyroid follicles;
secretes calcitonin
Calcitonin
secreted from parafollicular cells and plays a role in reducing the concentration of calcium in the body fluids when calcium levels become elevated
Triiodothyronine (T3) & Tetraiodothyronine (T4)
thyroid hormones;
stimulates metabolism in many tissues throughout the body
Thyroxine-binding globulin
synthesized by the liver; found within the circulatory system, 70-75% of T3 and T4 bind to this protein; increases the half-life of thyroid hormone in the body
cretin
a mentally retarded person of short stature and distinctive form; results from the hyposecretion of thyroid hormone during development
Parathyroid glands
usually embedded in the posterior part of each lobe of the thyroid gland;
composed of two cell types, chief cells and oxyphils
Parathyroid hormone (PTH)
a polypeptide hormone that is important in the regulation of calcium levels in body fluids;
stimulates osteoclast activity in bone and can cause the number of osteoclasts to increase, resulting in bone resorption, release of calcium and phosphate, and thus an increase in the blood-calcium levels; induces calcium reabsorpiton in the kidneys
Adrenal glands
glands located near the superior poles of the kidneys;
composed of an inner medulla and an outer cortex;
Zona glomerulosa
a layer of the adrenal cortex that lies just deep to the capsule and is composed of small clusters of cells;
secretes mainly mineralocorticoids
Zona fasciculata
the thickest layer of the adrenal cortex; cells form long columns;
prodominent secretory product are the glucocorticoids
Zona reticularis
the deepest layer of the adrenal cortex;
secretes androgens
Epinephrine and Norepinephrine
two major hormones, related in structure, that are part of the sympathetic response; released from the adrenal medulla; funciton through binding with G protein sites;
effects are short lived, increase blood levels of glucose, increases fat breakdown and glycogen breakdown in muscle cells, increase heart rate, etc.
Mineralocorticoids
steroid hormone secreted by the zona glomerulosa of the adrenal cortex;
increase rate of Na+ reabsorption by kidneys, increases K+ and H+ excretion into urine; too much might result in alkalosis
Aldosterone
a mineralocorticoid secreted by the adrenal medulla
Glucocorticoids
primary secretion of the zona fasciculata of the adrenal cortex;
have metabolic, development, and anti-inflammatory effects in the body;
increase fat catabolism, decrease glucose and amino acid uptake in skeletal muscle, increase gluconeogenesis, increase protein degradation
Gluconeogenesis
the production of glucose in the liver from precursor molecules such as amino acids
Androgens
primary secretion of the zona reticularis of the adrenal cortex;
stimulates pubic and axillary hair growth and sexual drive in females; effects in males is negligible
Panreas
exocrine and endocrine gland that lies behind the peritoneum betwen the greater curvature of the stomach and the duodenum
Acini
cells in the exocrine portion of the pancreas
Pancreatic islets
the endocrine portion of the pancreas that produces hormones that enter the circulatory system;
composed of alpha and beta cells
Alpha cells (pancreas)
compose about 20% of the islets of Langerhans;
secrete the small polypeptide glucagon
Beta cells (panreas)
compose about 75% of the islets of Langerhans;
secretes a small protein hormone, insulin
Delta cells (pancreas)
secrete somatostatin
Insulin
a small protein hormone consisting of two polypeptide chains bound together;
secreted by the beta cells of the pancreas;
target the liver, adipose tissue, muscles, and the satiety center in the hypothalamus;
increases the number of cell receptors for amino acids and glucose, thereby increasing its ability to take up glucose
Glucagon
a small polypeptide hormone secreted by the alpha cells of the pancreas;
primarily influences the liver;
stimulates the release of glucose from the liver, thereby increasing blood-glucose levels
Testosterone
steroid hormone secreted by the testes; regulates the production of sperm cells by the testes and the development and maintenance of male reproductive organs and secondary sex characteristics
Inhibin
hormone secreted by the testes which inhibits the release of FSH from the ant. pituitary
Estrogen and progesterone
main hormones secreted by the ovaries;
along with FSH and LH, control the female reproductive cycle, prepare the mammary glands for lactation, and maintain pregnancy
Relaxin
secreted by the ovaries during pregnancy;
increases the flexibility of connective tissue of the symphysis pubis and help dilate the cervix
Pineal body
a gland located in the epithalamus of the brain;
secretes hormones that act on the hypothalamus or the gonads to inhibit reproductive funcionts; once thought to be the connection between mind and body; serves as a "third eye" in some animals
Melatonin
hormone secreted by the pineal body;
can decrease GnRH secretion from the hypothalamus and may inhibit reproductive funcitons through this mechanism; may also help regulate sleep cycles
Thymus
a gland located in the neck;
plays an important role in the development and maturation of the immune system

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