BIO_211_Ch_16_Lecture Notes TheEndocrineSystem

BIO_211_Ch_16_Lecture Notes TheEndocrineSystem - Bio 211 A...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Bio 211 A & P II Chapter 16 The Endocrine System 1 Chapter 16 The Endocrine System Endocrine System: Overview Acts with the nervous system to coordinate and integrate the activity of body cells Influences metabolic activities by means of hormones transported in the blood Responses occur more slowly but tend to last longer than those of the nervous system Endocrine glands: pituitary, thyroid, parathyroid, adrenal, and pineal glands Endocrine System: Overview Some organs produce both hormones and exocrine products (e.g., pancreas and gonads) The hypothalamus has both neural and endocrine functions Other tissues and organs that produce hormones include adipose cells, thymus, cells in the walls of the small intestine, stomach, kidneys, and heart Chemical Messengers Hormones: long-distance chemical signals that travel in the blood or lymph Autocrines: chemicals that exert effects on the same cells that secrete them Paracrines: locally acting chemicals that affect cells other than those that secrete them Autocrines and paracrines are local chemical messengers and will not be considered part of the endocrine system Chemistry of Hormones Two main classes 1. Amino acid-based hormones Amines, thyroxine, peptides, and proteins 2. Steroids Synthesized from cholesterol Gonadal and adrenocortical hormones Mechanisms of Hormone Action Hormone action on target cells 1 Alter plasma membrane permeability of membrane potential by opening or closing ion channels 2 Stimulate synthesis of proteins or regulatory molecules 3 Activate or deactivate enzyme systems 4 Induce secretory activity 5 Stimulate mitosis Mechanisms of Hormone Action Two mechanisms, depending on their chemical nature 1 Water-soluble hormones (all amino acid–based hormones except thyroid hormone) Cannot enter the target cells Act on plasma membrane receptors Coupled by G proteins to intracellular second messengers that mediate the target cell’s response Mechanisms of Hormone Action
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Bio 211 A & P II Chapter 16 The Endocrine System 2 2 Lipid-soluble hormones (steroid and thyroid hormones) Act on intracellular receptors that directly activate genes Plasma Membrane Receptors and Second-Messenger Systems cAMP signaling mechanism 1 Hormone (first messenger) binds to receptor 2 Receptor activates G protein 3 G protein activates adenylate cyclase 4 Adenylate cyclase converts ATP to cAMP (second messenger) 5 cAMP activates protein kinases Plasma Membrane Receptors and Second-Messenger Systems cAMP signaling mechanism Activated kinases phosphorylate various proteins, activating some and inactivating others cAMP is rapidly degraded by the enzyme phosphodiesterase Intracellular enzymatic cascades have a huge amplification effect Plasma Membrane Receptors and Second-Messenger Systems PIP 2 -calcium signaling mechanism Used by some amino acid–based hormones in some tissues Involves a G protein G protein activates phospholipase C enzyme
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 12

BIO_211_Ch_16_Lecture Notes TheEndocrineSystem - Bio 211 A...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online