Introduction to the Endocrine System P

Hormones Hormone- chemical regulators produced by cells in one part of the body that affect cells in another part of the body Hormon- Greek – to excite or to set into motion Growth hormone- regulates the development of long bones. (Robert Wadlow)

Hormones Non-target hormones: affect many cells throughout the body eg. Insulin causes many cells to absorb glucose Target Hormones: affect specific cells or tissues only eg. Gastrin affects the stomach only Receptors on an individual cell may vary – Liver cells and muscle cells have many receptors for hormone insulin – Fewer receptor sites are found on less active cells such as bone and cartilage

Hormones 2 main classification of hormones: Steroid Hormones Protein Hormones

Steroid Hormones 1.Steroid hormone diffuses through the cell membrane. 2.Hormone binds to receptor proteins in the cytoplasm 3.Lipid hormones bind to DNA as transcription factors. 4.Causes conformational change and initiates transcription of DNA 5.mRNA is made 6.Translation of a new protein

Protein Hormones 1.Protein hormone binds to receptors on the plasma membrane 2.Binding causes conformational change, initiating production of enzyme adenylyl cyclase 3.Adenylyl cyclase causes the cell to convert ATP into cyclic adenosine monophosphate (cAMP) 4.cAMP activates enzymes to carry out normal function

Glands 2 types of glands: Exocrine glands- secrete hormones into ducts that lead directly to outside world eg. Sweat glands, salivary glands Endocrine glands- secrete hormones directly into the bloodstream or to target cells eg. Adrenal gland

Major Endocrine Glands 1.Pineal gland 2.Pituitary gland 3.Thyroid gland 5. Adrenal gland 6. Pancreas 7. Ovary 8. Testis

Pituitary Gland: The Master Gland Exercises control over other endocrine glands (hence master gland) 2 lobes make up the pituitary: – Posterior Lobe – Anterior Lobe

Pituitary Gland: The Master Gland Posterior- hypothalamus produces hormones – ADH- stored in pituitary and released into blood when needed Anterior- produces its own hormones - hypothalamus regulates release of hormones like posterior lobe – Eg. Growth hormone (GH) inhibitors of hormones- somatostatin inhibits secretion of somatotropin (GH)

Reproductive Hormones The male reproductive system : Testosterone: stimulates spermatogenesis along with lowering of voice, strengthening of muscles, fat distribution and protein synthesis Body uses a negative feedback system to control the level of testosterone

Male Reproductive System Pituitary produces and stores: – Follicle- stimulating hormone (FSH)- stimulates production of sperm cells – Lutenizing hormone (LH)- promotes production of testosterone by the interstitial cells Hypothalamus activates these hormones during puberty when it secretes gonadotropin- releasing hormone (GnRH)

Male Reproductive System Once high levels of testosterone are detected: – High levels of testosterone inhibits hypothalamus – Decrease in GnRH – Decrease in LH – Testosterone in normal range FSH regulated through inhibin which inhibits the secretion of FSH in the pituitary

Female Reproductive System Females have set number of eggs Follicles in ovaries comprised of primary oocyte (undergoes meiosis) and granulosa cells (nutrients for oocyte) – ~ follicles at puberty in 2 ovaries – Dominant follicle during reproductive cycle is released – Release of secondary oocyte= ovulation

Female Reproductive System Hypothalamus releases GnRH during puberty GnRH activates FSH (promotes development of follicles in the ovary) and LH (promotes ovulation and formation of corpus luteum) – Follicles in ovary secrete estrogen – Corpus luteum- secretes estrogen and progesterone Increased estrogen from follicles inhibits FSH secretion and rises LH secretion causing ovulation Remaining follicles  corpus luteum

Female Reproductive System Corpus luteum- secretes estrogen (breasts, thickening of endometrium) and progesterone (thickens endometrium, stimulates ovulation) Increased estrogen and progesterone inhibit FSH and LH Hypothalamus GnRH Anterior Pituitary FSH LH Growing follicle Corpus luteum estrogen Progesterone, estrogen ovulation Inc progesterone, estrogen inhibit FSH, LH