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.

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Posterior pituitary - peptides

Posterior Pituitary: Antidiuretic hormone (ADH)—regulates water

reabsorption (H2O 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.

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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.

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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.

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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.

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