Lecture Outline

CHAPTER OVERVIEW: This chapter introduces the basic concepts of endocrine control and the function of chemical messengers. Negative feedback, amplitude modulation and frequency modulation are reviewed. The cellular mechanisms of endocrine action; membrane-bound receptors, intracellular receptors, second messengers, and up and down regulation are explained in detail. The chemical nature of hormones is used as means of explaining the differences in half-life and mechanism of action among hormones.

OUTLINE (two fifty-min. lectures):

 Chapt. Object.

Topic Outline, Chapter 17

 

Figures & Tables

Trnspcy. Acetates

Trnspcy.

Masters

1

 I. Introduction

      1. One of Bodyís Major Control Systems

II. General Characteristics of the Endocrine System

      
 

    A. Endocrine Glands

Fig. 17.1, p. 522

TA-214

  

2

      1. Secretions Called Hormones
      
 

      2. Transported in Blood
      
 

      3. Target Tissue(s) has(have) Response(s)
      
 

    B. Differences Between Endocrine and Nervous Systems

Fig. 17.2, p. 523

    

3

      1. Amplitude v. Frequency Modulation

Fig. 17.2a, p.523

    
 

      2. Rate of Target Tissue Response

Fig. 17.2b, p.523

    
 

      3. Duration of Target Tissue Response
      

2, 3

    C. Continuum of Chemical Messengers

Table 17.1, p. 524

    
 

      1. Hormones
      

4

      2. Neurohormones
      
 

      3. Intercellular Chemical Signals
      
 

      4. Autocrine Chemical Signals
      
 

      5. Paracrine Chemical Signals
      
 

      6. Pheromones
      
         
 

III. Chemical Structure of Hormones

Table 17.2, p.525; Fig. 17.3, p.526

    
 

    A. Protein-based
      
 

    B. Lipids
      
 

      1. Steroids - Estrogens, Testosterone
      

5

IV. Control of Secretion Rate

Fig. 17.4, p.527

    
 

    A. Rate Usually Not Constant
     
 

    B. Homeostatic Control of Secretion

Fig. 17.5, p.527

TA-215

  
 

      1. Negative Feedback

Fig. 17.7, p.528

TA-217

  
 

      2. Auto-Regulation
      
 

    C. Other Control Mechanisms of Hormone Secretion
      
 

      1. Non-hormone Substance
      
 

      2. Nervous Stimulation
      
 

      3. Another Hormone

 

      4. Positive Feedback

Fig. 17.6, p.528, Predict Quest. 1

Fig. 17.7, p.528

TA-216

TA-217

 

  
 

    D. Patterns of Secretion

Fig. 17.8, p.529

TA-218

  
 

      1. Chronic Secretion
      
 

      2. Acute Secretion
      
 

      3. Cyclic Secretion
      
         
 

V. Transport and Distribution in the Body

Fig. 17.9, p.529

TA-219

  
 

    A. Dissolved in Plasma
      
 

    B. Bound to Transport Proteins
      
 

    C. Circulate with Blood

Fig. 17.10, p.530

TA-220

  
 

      1. Movement of Lipid-Soluble Hormones
      
 

      2. Movement of Water-Soluble Hormones
      
         
 

VI. Metabolism and Excretion

     

6

    A. Definition of Hormone Half-Life

Table 17.3, p.530; Predict Quest.2

    
 

    B. Water-Soluble Hormones
      
 

      1. Short Half-Lives - Rapid Degradation
      
 

      2. Blood Levels Change Rapidly
      
 

      3. Actions of Rapid Onset & Short Duration
      
 

    C. Lipid-Soluble Hormones
      
 

      1. Longer Half-Lives
      
 

        a. Bound to Plasma Proteins
      
 

        b. Stay in Blood Longer
      
 

      2. Blood Levels Relatively Constant
      

7

    D. Removal of Hormones from Blood
      
 

      1. Direct Excretion in Urine or Bile
      
 

      2. Modified Before Excretion
      
 

        a. Metabolized
      
 

        b. Conjugation by Liver
      
 

      3. Active Transport and Recycling
      

8

VII. Interactions of Hormones With Their Target Tissues

      
 

    A. General Role of Hormone Receptors

Fig. 17.11, p.531

TA-221

  
 

      1. Made of Protein or Glycoprotein
      
 

      2. Three-Dimensional Shape Confers Specificity
      
 

      3. Specific Response of Target Tissue Depends on Type of Receptor(s) Present

Predict Quest. 3

    

8

    B. Number of Receptors Affects Response
      
 

      1. Down Regulation Decreases Tissue Responsiveness

Fig. 17.12a, p.532

TA-222

  
 

      2. Up Regulation Increases Tissue Responsiveness

Fig. 17.12b, p.532

TA-222

  
         

9

VIII. Classes of Hormone Receptors

      

10

    A. Membrane-Bound Hormone Receptors
      

12

13

11
      1. Receptors that Directly Control Membrane Channels

        a. Ligand-Gated Ion Channels

      2. Hormone Receptors that Directly Synthesize Intracellular Mediator Molcules
      3. Hormones that Activate G Proteins
        a. Alpha Subunit Bound to GTP Alters Cell Activity

Fig. 17.13, p.533

Table 17.4, p.533

Fig. 17.14, p.534

 

Fig. 17.15, p.534

 

    
 

        b. Can Open Ca2+ Channels
      
 

          1). Influx of Ca2+
      
 

          2). Calcium Ions Bind to Calmodulin or Other Regulatory Protein
      
 

          3). Ca2+/Calmodulin Complex Alters Cell's Functions
      
 

        c. Can Activate Adenylate Cyclase

Fig. 17.16, p.535; Predict Quest. 4

    
 

          1). cAMP Produced from ATP
      
 

          2). Activates Protein Kinases (Phosphokinases) Which Alter Cell Function
      
 

          3). cAMP removed by Action of Phosphodiesterase
      
 

        d. Can Activate Phospholipase C

Fig. 17.17, p.536

    
 

          1). Diacylglycerol (DAG) and Inositol Triphosphate (IP3) Produced from Phosphoinositol
      
 

          2). DAG Regulates Enzyme Function
      
 

          3). IP3 Releases Ca+2 from Sarcoplasmic Reticulum and Opens Plasma Membrane Ca+2 Channels
      
 

      4. Hormone Receptors That Phosphorylate Enzymes

Fig. 17.18; Table 17.5, p.536

    
 

        a. Cascade Effect Magnifies Cell Response in Second Messenger Systems
      

9, 14

    B. Intracellular Hormone Receptors

Fig. 17.19, p.537; Tab1e 17.6, p.538

    
 

      1. Binds with Lipid-Soluble Hormones

Predict Quest. 5

    
 

        a. Receptor in Cytoplasm or Nucleus
      
 

        b. Receptor-Hormone Complex Interacts with DNA in Nucleus
      
 

      2. mRNA Synthesis Increased
      
 

      3. New Protein Synthesis Results
      
 

      4. Latent Period of Hours Between Binding of Hormone and Measurable Response
      
 

      5. Receptor-Hormone Complexes Degraded Within Cell
      
         

IMPORTANT CONSIDERATIONS: The logical separation of the material into two presentations occurs between the general issues of hormones (secretion and control) and the detail of the mechanisms of action of hormones at their target cells.

The concept of regulation (especially at the cellular level) is often unfamiliar to students. Presenting the general framework of how control systems operate helps organize both the details of how the nervous and endocrine systems influence the functioning of other cells and the mechanisms which regulate the secretion of hormones. Some sort of organization is needed to keep this information from being simply a meaningless collection of facts for students.

Relate the functions of the endocrine system to those that have already been discussed for the nervous system and the neuronal regulation of body functions. Discuss both the similarities and differences between endocrine and neuronal control and relate these differences to the kind of body functions being regulated; hormonal control of metabolic rate v. neuronal control of the withdrawal reflex, for example. The role of amplitude modulation and frequency modulation can also be related to the difference in type of cell activity being controlled and the mechanism of action at the receptors on the postsynaptic membrane or target tissue.

A clear understanding of the structural differences among the hormones will be helpful to students when differences in mechanism of action are discussed later.

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