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Chapter 45 Endocrine System

Biology, 7th Edition (Book & CD-ROM)

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Chapter 45 Endocrine System I. Endocrine system and nervous system A. Nervous system 1. Conveys high-speed electrical signals along neurons 2. Controls the movement of body parts in response to sudden environmental changes. a. Quick immediate response B. Endocrine system 1. Slower responses, but longer lasting 2. Kinds of stimuli a. Stress b. Dehydration c. Low blood glucose level 3. Endocrine glands a. Secrete chemical messenger right into extracellular fluid b. Ductless C. Overlap between the two 1. Neurosecretory cells- nerve cells that release hormones into the blood via extracellular fluid a. Its hormones are called neurohormones 2. Epinephrine a. Produced by adrenal medulla b. It is a fight or flight hormone and a neurotransmitter 3. Nervous system plays a role in responses (day/night cycle, reproductive cycle) by adjusting secretion from endocrine glands D. Controlled pathways and feedback loops 1. Review a. Receptor/sensor detects a stimulus b. Sends the information to the control center i Control center compares incoming information to a set point/desired value c. Control center sends out a signal that directs an effector to respond d. Outgoing signal = effector signal, acts on effector tissues. It’s a hormone which acts on effector tissues and elicits specific changes 2. Three Pathways 1
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i The stimulus is given to the sensory neuron in the hypothalamus, and the neurosecretory cell in the hypothalamus secretes neurohormones, whose target cells are the endocrine cells. The endocrine cells receive the neurohormones, produce hormones of their own, and send them off their way into the blood vessel to attach to a target effector and produce a response. 3. Feedback a. Negative Feedback i Response reduces the initial stimulus ii Prevents overreaction by the system and wild fluctuations b. Positive stimulus i Reinforces stimulus and leads to a greater response ii When baby sucks on mom’s breast, sensory nerve cells in the nipples travel down a pathway, and the response is to secrete milk. The more sucking, the more milk produced. II. Hormones A. Introduction
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