Chapter 37 Integration and Control

Chapter 37 Integration and Control - Chapter 37 Integration...

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Chapter 37 Integration and Control: Endocrine Systems I. “The Endocrine System” A. In the early 1900s, Bayliss and Starling first demonstrated that a hormone (later named secretin) released into the blood triggers secretion of pancreatic juices. B. Starling coined the word hormone for internal secretions released into the bloodstream that influence the activities of other tissues and organs. C. The sources of hormones may be collectively called the “endocrine system,” which shows intimate connections with the nervous system. II. Hormones and Other Signaling Molecules A. Signaling molecules are hormones and secretions that can bind to target cells and elicit in them a response. B. There are four main types of signaling molecules: 1 Hormones are secreted from endocrine sources and some neurons, and are then transported by the blood to remote targets. 2 Transmitter substances are secreted from neurons and act on immediately adjacent target cells for a short time. 3 Local signaling molecules are secreted from cells of many different tissues; they act locally and are swiftly degraded. 4 Pheromones, which are secreted by exocrine glands, have targets outside the body; they integrate social activities between animals. III. The Hypothalamus-Pituitary Connection A. The hypothalamus and pituitary gland work jointly as the neuroendocrine control center. 1 The hypothalamus is a portion of the brain that monitors internal conditions and emotional states. 2 The pituitary is connected to the hypothalamus by a stalk. a. The posterior lobe of the pituitary consists of nervous tissue and releases two neurohormones made in the hypothalamus. b. The anterior lobe consists of glandular tissue and secretes six hormones and controls the release of others. c. An intermediate lobe (not in humans) produces secretions that induce color changes in fur color of vertebrates. B. Posterior Lobe Secretions 1 Neuron cell bodies in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin, which are released from axon endings in the capillary bed of the posterior lobe. 2 ADH acts on the walls of kidney tubules to control the body’s water and solute levels. 3 Oxytocin triggers uterine muscle contractions to expel the fetus and acts on mammary glands to release milk.
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Chapter 37 Integration and Control - Chapter 37 Integration...

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