Chemical Signals Maintain Homeostasis

 

 

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Importance of the Endocrine System

 

Pituitary Hormones:

 

-         Thyroid-stimulating hormone (TSH): stimulates release of thryoxine from thyroid; thyroxine regulates cell metabolism

-         Adrenocorticotropic hormone (ACTH): stimulates release of hormones involved in stress responses

-         Growth hormone: promotes growth

-         Follicle-stimulating hormone (FSH): in females, stimulates follicle development in ovaries; in males, promotes the development of sperm cells in testes

-         Luteinizing hormone (LH): in females, stimulates ovulation and formation of the corpus luteum; in males, stimulates the production of the sex hormone testosterone

-         Prolactin (PRL): stimulates and maintains milk production in lactating females

-         Oxytocin: initiates strong contractions; triggers milk release in lactating females

-         Antidiuretic hormone (ADH): increases water reabsorption by kidneys

 

Hormones That Affect Blood Sugar

 

-         Insulin: increases permeability of cells to glucose; increases glucose uptake; allows for the conversion of glucose to glycogen; brings about a decrease in blood sugar

-         Glucagon: promotes the conversion of glycogen to glucose; brings about an increase in blood sugar

-         Epinephrine and norepinephrine: promotes the conversion of glycogen to glucose; brings about an increase in blood sugar; brings about an increase in heart rate, and cell metabolism

-         Cortisol: promotes the conversion of amino acids to glucose; promotes the breakdown of fats to fatty acids; decreases glucose uptake by the muscles; brings about an increase in blood sugar in response to stress

 

Hormones That Affect Metabolism

 

-         Thyroxine: regulates the rate at which glucose is oxidized within body cells

-         Calcitonin: lowers calcium levels in the blood

-         Parathyroid hormone (PTH): raises calcium levels in the blood

-         Growth Hormone: promotes protein synthesis by increasing the uptake of amino acids by cells; causes a switch in cellular fuels from glucose to fatty acids

 

Adjustments to Stress

 

-         The endocrine and nervous systems interact to help the body cope with stress.

-         More than 16 different types of prostaglandins are secreted in response to changes in the internal environment.

-         Anabolic steroids are one of the many types of chemicals used to enhance athletic performance.

-         It is difficult to detect banned drugs like growth hormone and erythropoietin because the body naturally produces them.

 

Female Reproductive Hormones

 

-         Estrogen: inhibits growth of facial hair; initiates secondary female characteristics, and causes thickening of the endometrium.

-         Progesterone: inhibits ovulation, inhibits uterine contractions, and stimulates the endometrium.

-         Follicle-stimulating hormone (FSH): stimulates the development of the follicle cells in the ovary.

-         Luteinizing hormone: stimulates ovulation and the formation and maintenance of the corpus luteum.

 

 

 

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