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Ch. 45—Hormones and the Endocrine System. The Endocrine System. Includes hormones-secreting cells and tissues Endocrine glands secrete hormones into body fluids Hormones cause a response in target cells. Positive Feedback. ‘A’ produces more of ‘B’ which produces more of ‘A’
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The Endocrine System • Includes hormones-secreting cells and tissues • Endocrine glands secrete hormones into body fluids • Hormones cause a response in target cells
Positive Feedback • ‘A’ produces more of ‘B’ which produces more of ‘A’ • More gets you more • See bottom of pg. 254
Negative Feedback • More gets you less • See top of pg. 254
Cell Surface Receptors • Integral membrane proteins • Communication between cell and outside • Triggers a signal transduction pathway • Series of events that respond to the signal • Ex: binding of epinephrine to liver cells which leads to conversion of glycogen to glucose
Intracellular Receptors • Located inside the cell (rather than on its cell membrane) • Acts as a transcription factor • a protein that binds to specific DNA sequences and controls the flow of DNA to mRNA (transcription)
Hypothalamus • Portion of the brain • Link the nervous system to the endocrine system via the pituitary gland • Responsible for metabolic processes (autonomic nervous system) • Controls body temp, hunger, thirst, fatigue, sleep
Posterior Pituitary • Stores and secretes oxytocin and vasopressin (or antidiuretic hormone) • synthesized by the hypothalamus • See table 9.1
Anterior Pituitary • Secretes hormones that act on target organs (adrenal gland, liver, bond, thyroid, gonads) • Regulates several physiological processes • Stress, growth, reproduction, lactation *See FSH and LH in Table 9.1