Endocrine System Overview target cell hormone bloodstream receptor

Endocrine System Overview target cell hormone bloodstream receptor • Glands: Major organs of the endocrine system • Glands make hormones – Hormones: chemical signals • Hormones move through bloodstream • Hormone binds to cell receptor • Target cells produce proteins not a target cell

• Steroid hormones vs. Nonsteroid hormones. – Steroid hormones enter the cell and bind within. – Nonsteroid hormones do not enter the cell, they bind in the membrane. Steroid hormone diffuses through the cell membrane Nonsteroid hormone binds to receptor on the cell membrane. Non-steroid hormone receptor Steroid hormone binds to a receptor within the cell. receptor nucleus The hormone and receptor enter the nucleus and bind to DNA Steroid hormone causes DNA to make proteins Receptor stimulates a second messenger with in the cell. Second messenger starts a series of chemical reactions in the cytoplasm. Second messenger reactions activate enzymes. second messenger Chemical reactions activated enzymes

Major Glands HYPOTHALAMUS PITUITARY THYROID THYMUS ADRENAL GLANDS PANCREAS FEMALE GONADS : OVARIES MALE GONADS : TESTES All the below create hormones • Hypothalamus – Stimulates the pituitary gland to release hormones – Controls growth, reproduction, body temp • Pituitary gland – Controls cell growth and [H 2 O] in blood – Stimulates other glands • Thyroid gland – Regulates metabolism, growth, development • Thymus – Allows WBCs to mature to fight infection • Adrenal Glands – Controls “fight or flight” response – Increases breathing, alertness, blood pressure – Epinephrine • Pancreas – Controls glucose level in blood – Insulin, glucagon • Gonads: influence sexual development – Testes (males): testosterone – Ovaries: Estrogen, progesterone

• Releasing hormones stimulate other glands to produce hormones. – allow glands to communicate with one another – are used in temperature regulation

Hormonal imbalances can cause severe illness. • Abnormal hormone levels affect homeostasis. • Hormonal imbalances might be treated with surgery or medicine. • Steroids, a pituitary tumor, or some prescription drugs can make the pituitary overactive and indirectly cause problems.

Pituitary gland hypothalamus Thyroid thymus Adrenal glands pancreas ovaries testes