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Transcript of Chapter 16 A

PowerPoint Lecture Slides prepared by Janice Meeking, Mount Royal College

CHAPTER

16

The Endocrine System: Part A

Copyright 2010 Pearson Education, Inc.

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

Copyright 2010 Pearson Education, Inc.

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 heartCopyright 2010 Pearson Education, Inc.

Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands (on dorsal aspect of thyroid gland) ThymusAdrenal glands

Pancreas

Ovary (female)Testis (male)

Copyright 2010 Pearson Education, Inc.

Figure 16.1

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 systemCopyright 2010 Pearson Education, Inc.

Chemistry of Hormones Two main classes1. Amino acid-based hormones Amines, thyroxine, peptides, and proteins 2. Steroids

Synthesized from cholesterol Gonadal and adrenocortical hormones

Copyright 2010 Pearson Education, Inc.

Mechanisms of Hormone Action Hormone action on target cells1. 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 mitosisCopyright 2010 Pearson Education, Inc.

Mechanisms of Hormone Action Two mechanisms, depending on their chemical nature1. Water-soluble hormones (all amino acidbased 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 cells response

Copyright 2010 Pearson Education, Inc.

Mechanisms of Hormone Action2. Lipid-soluble hormones (steroid and thyroid hormones)

Act on intracellular receptors that directly activate genes

Copyright 2010 Pearson Education, Inc.

Plasma Membrane Receptors and SecondMessenger Systems cAMP signaling mechanism1. 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

Copyright 2010 Pearson Education, Inc.

Plasma Membrane Receptors and SecondMessenger 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

Copyright 2010 Pearson Education, Inc.

1 Hormone (1st messenger)

binds receptor. G protein (GS)

Adenylate cyclase

Extracellular fluid

5 cAMP acti-

Receptor GDP Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin2 Receptor 3 G protein 4 Adenylate

vates protein kinases.Inactive protein kinase Active protein kinase Triggers responses of target cell (activates enzymes, stimulates cellular secretion, opens ion channel, etc.) Cytoplasm

activates G protein (GS).

activates adenylate cyclase.

cyclase converts ATP to cAMP (2nd messenger).

Copyright 2010 Pearson Education, Inc.

Figure 16.2

1 Hormone (1st messenger)

Extracellular fluid

binds receptor.

Receptor

Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin

Cytoplasm

Copyright 2010 Pearson Education, Inc.

Figure 16.2, step 1

1 Hormone (1st messenger)

Extracellular fluid

binds receptor. G protein (GS)

Receptor GDP Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin2 Receptor

activates G protein (GS).

Cytoplasm

Copyright 2010 Pearson Education, Inc.

Figure 16.2, step 2

1 Hormone (1st messenger)

binds receptor. G protein (GS)

Adenylate cyclase

Extracellular fluid

Receptor GDP Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin2 Receptor 3 G protein

activates G protein (GS).

activates adenylate cyclase.

Cytoplasm

Copyright 2010 Pearson Education, Inc.

Figure 16.2, step 3

1 Hormone (1st messenger)

binds receptor. G protein (GS)

Adenylate cyclase

Extracellular fluid

Receptor GDP Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin2 Receptor 3 G protein 4 Adenylate

activates G protein (GS).

activates adenylate cyclase.

cyclase converts ATP to cAMP (2nd messenger). Cytoplasm

Copyright 2010 Pearson Education, Inc.

Figure 16.2, step 4

1 Hormone (1st messenger)

binds receptor. G protein (GS)

Adenylate cyclase

Extracellular fluid

5 cAMP acti-

Receptor GDP Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin2 Receptor 3 G protein 4 Adenylate

vates protein kinases.Inactive protein kinase Active protein kinase Triggers responses of target cell (activates enzymes, stimulates cellular secretion, opens ion channel, etc.) Cytoplasm

activates G protein (GS).

activates adenylate cyclase.

cyclase converts ATP to cAMP (2nd messenger).

Copyright 2010 Pearson Education, Inc.

Figure 16.2, step 5

Plasma Membrane Receptors and SecondMessenger Systems PIP2-calcium signaling mechanism Used by some amino acidbased hormones in some tissues Involves a G protein G protein activates phospholipase C enzyme

Copyright 2010 Pearson Education, Inc.

Plasma Membrane Receptors and SecondMessenger Systems Phospholipase splits membrane phospholipid PIP2 into two second messengers: diacylglycerol (DAG) and IP3 DAG activates protein kinases; IP3 triggers release of Ca2+

Ca2+ alters enzymes or channels or binds to the regulatory protein calmodulin

Copyright 2010 Pearson Education, Inc.

Intracellular Receptors and Direct Gene Activation Steroid hormones and thyroid hormone1. Diffuse into their target cells and bind with intracellular receptors 2. Receptor-hormone complex enters the nucleus 3. Receptor-hormone complex binds to a specific region of DNA 4. This prompts DNA transcription to produce mRNA 5. The mRNA directs protein synthesis

Copyright 2010 Pearson Education, Inc.

Steroid hormone Extracellular fluid

Plasma membrane

1 The steroid hormone

Cytoplasm Receptor protein

diffuses through the plasma membrane and binds an intracellular receptor. Receptorhormone complex2 The receptor-

Nucleus

Hormone response elements DNA mRNA

hormone complex enters the nucleus.3 The receptor- hormone

complex binds a hormone response element (a specific DNA sequence).4 Binding initiates

transcription of the gene to mRNA.

5 The mRNA directs

protein synthesis. New protein

Copyright 2010 Pearson Education, Inc.

Figure 16.3

Steroid hormone Extracellular fluid

Plasma membrane

1 The steroid hormone

Cytoplasm Receptor protein

diffuses through the plasma membrane and binds an intracellular receptor. Receptorhormone complex

Nucleus

Copyright 2010 Pearson Education, Inc.

Figure 16.3, step 1

Steroid hormone Extracellular fluid

Plasma membrane

1 The steroid hormone

Cytoplasm Receptor protein

diffuses through the plasma membrane and binds an intracellular receptor. Receptorhormone complex2 The receptor-

Nucleus

hormone complex enters the nucleus.

Copyright 2010 Pearson Education, Inc.

Figure 16.3, step 2

Steroid hormone Extracellular fluid

Plasma membrane

1 The steroid hormone

Cytoplasm Receptor protein

diffuses through the plasma membrane and binds an intracellular receptor. Receptorhormone complex2 The receptor-

Nucleus

Hormone response elements DNA

hormone complex enters the nucleus.3 The receptor- hormone

complex binds a hormone response element (a specific DNA sequence).

Copyright 2010 Pearson Education, Inc.

Figure 16.3, step 3

Steroid hormone Extracellular fluid

Plasma membrane

1 The steroid hormone

Cytoplasm Receptor protein

diffuses through the plasma membrane and binds an intracellular receptor. Receptorhormone complex2 The receptor-

Nucleus

Hormone response elements DNA mRNA

hormone complex enters the nucleus.3 The receptor- hormone

complex binds a hormone response element (a specific DNA sequence).4 Binding initiates

transcription of the gene to mRNA.

Copyright 2010 Pear