The Human Endocrine System
Action of Steroid Hormones Hormone diffuses through cell membrane of target cell Hormone combines with receptor molecule They move into the nucleus and attach to DNA DNA activates a gene to produce a specific protein
Action of Steroid Hormones One Messenger system
Action of Protein Hormones Hormone attaches to receptor on cell membrane of target cell This causes cyclic AMP to be formed which acts as a messenger within the cell Cyclic AMP activates enzymes in the cytoplasm which creates the desired hormonal effect
Action of Protein Hormones Two Messenger System
Negative Feedback Is a type of control system that regulates hormone production Works similar to a thermostat on your furnace When the desired change is detected, the original action is inhibited
Negative Feedback
Endocrine Glands: Pituitary Is often referred to as “master gland” because it controls the secretions of most of the other glands Is located in the brain directly below the hypothalamus Is composed of two lobes - the posterior lobe and the anterior lobe
hypothalamus pituitary gland
Endocrine Glands: Thyroid Is located in the neck just below the larynx and in front of the trachea. Parathyroid glands consist of 4 tiny ovals embedded in the back of the thyroid gland. They regulate calcium and phosphate metabolism.
hypothalamus pituitary gland parathyroid thyroid thymus
Endocrine Glands: Adrenal There is one adrenal gland sitting on top of each kidney. Each adrenal gland is composed of an outer layer called the cortex and an inner layer called the medulla
hypothalamus pituitary gland parathyroid thyroid thymus adrenal gland
Endocrine Glands: Pancreas The pancreas has small clusters of hormone-secreting cells called islets of Langerhans The hormones of the pancreas mainly control glucose levels in the body: Beta cells produce insulin which causes body cells to take up glucose from the blood. Alpha cells produce glucagon which causes the liver to store excess blood glucose as glycogen.
hypothalamus pituitary gland parathyroid thyroid thymus adrenal gland pancreas
Endocrine Glands: Gonads Ovaries Produce egg cells and release female sex hormones Testes Produce sperm cells and release male sex hormones
hypothalamus pituitary gland parathyroid thyroid thymus adrenal gland pancreas ovaries testes