The pituitary & hypothalamus Mader Chapter 14.2 & 7

The master controllers of the endocrine system

The hypothalamus Hypothalamus—regulates the internal environment through the autonomic nervous system. Controls glandular secretions of the pituitary gland. Helps control heartbeat. Helps control body temperature. Helps control water balance. 14-6

Posterior pituitary - peptides Posterior Pituitary: Antidiuretic hormone (ADH)—regulates water reabsorption (H 2 O is returned to the bloodstream). Oxytocin—stimulates uterine contraction during childbirth and milk release. These hormones are produced in the hypothalamus by neurosecretory cells and are stored in the posterior lobe of the pituitary gland. Controlled by positive feedback. 14-7

The hypothalamic-pituitary axis

Anterior pituitary - peptides Anterior Pituitary-Targets: Thyroid-stimulating hormone (TSH)—stimulates the thyroid gland to produce thyroxine. Adrenocorticotropic hormone (ACTH)—stimulates the adrenal cortex to produce cortisol. Gonadotropic hormones—stimulate the gonads to produce gametes and hormones. Prolactin (PRL)—causes mammary glands to develop and produce milk. Melanocyte-stimulating hormone (MSH)—causes skin cells to produce melanin. Growth hormone (GH)—promotes skeletal and muscular growth. 14-8

Stress hormones Adrenal glands—sit on top of the kidneys. * Adrenal medulla: Epinephrine—prepares the body for quick action. “fight or flight” / short-term response to stress. * Adrenal cortex: Glucocorticoids—influence carbohydrate, protein, & fat metabolism. Aldosterone—promotes renal absorption of Na + and renal excretion of K +. *Kidneys—secrete renin which stimulates cortex to release aldosterone. *Cardiac cells—release ANH which inhibits the release of aldosterone

The Stress Response

Pituitary gonadotropin targets Gonads—reproductive organs. * Testes produce testosterone. Stimulates growth of penis and testes. Responsible for male secondary sex characteristics. Prompts larynx & vocal cords to enlarge. Responsible for muscular strength of males. * Ovaries produce estrogen and progesterone. Stimulates growth of the vagina and uterus. Responsible for secondary sex characteristics. Necessary for egg maturation. Regulates uterine cycle