CH 17 – FUNCTIONAL ORGANIZATION OF THE ENDOCRINE SYSTEM
I. INTRODUCTION
A. CONTROL SYSTEMS – closely linked, work together (Fig. 17.2, p. 582)
1. NERVOUS SYSTEM – Elec & Chem, Rapid, Frequency Modulated
2. ENDOCRINE SYSTEM – Chem, Long-term, Amplitude Modulated
B. GLANDULAR SYSTEM – scattered
1. EXOCRINE a. Tubes & ducts
b. Secrete onto Epithelium
2. ENDOCRINE a. Ductless glands (Fig. 17.1, p. 581)
w/in to separate b. Secrete into blood or by diffusion
II HORMONES or LIGANDS – Gk “to set in motion,” = chemical messengers
A. CLASSES OF CHEMICAL MESSENGERS - 4
(KNOW Tab. 17.1, p. 580)
B. CHEMICAL NATURE OF HORMONES (Tab. 17.2 p. 585)
1. LIPID SOLUBLE = LIPID/FATTY ACIDS – Cholesterol based – Testosterone 2. WATER SOLUBLE =
a. PROTEIN/GLYCOPROTEINS/POLYPEPTIDES – Insulin
b. AMINO ACID DERIVATIVES – Epinephrine
C. TARGET TISSUES – have specific receptors for hormones (Fig. 17.10, p. 591)
III. CONTROL OF SECRETION
A. CAUSES
1. HUMORAL – Food in stomachè églucose in bloodè é INSULIN
èglucose uptakeè êglucose in blood (Fig. 17.5, p. 587)
2. NEURAL – Symp. N.S. è éepinephrine (Fig. 17.6, p. 588)
3. HORMONAL – TRHè TSHè THYROXINE (Fig. 17.7, p. 588)
B. TIME PATTERNS (Fig. 17.4, p. 586)
1. CHRONIC – constant, THYROID
2. ACUTE – as needed, in response to stimuli, INSULIN
3. EPISODIC/CYCLIC – regular cycle, FSH
C. REGULATION (Fig. 17.8, p. 589)
1. POSITIVE FEEDBACK – rare, increases deviation, OXYTOCIN
2. NEGATIVE FEEDBACK – common, “thermostat”, restores deviation
a. Amplitude modulation éhormone è éaction by target
b. Due to é or ê in [hormone]
c. i.e. éBlood sugar è éInsulin and vice versa
3. CONCENTRATION - More hormone, more effect on target & vice versa.
a. Plasma binding proteins – maintain equilibrium (p. 593, bottom)
4. ½ LIFE
a. Time to remove ½ of hormone from body
b. Protein & A.A. (H20 soluble) have SHORT ½ life
c. Lipid (H20 insoluble) LONGER ½ life
5. UP & DOWN (Fig. 17.11, p. 592)
a. DOWN - ê # of receptors (a)
i.e. GnRH è P:ituitary è ê # GnRH receptors in pituitary
b. UP - é # of receptors (b)
i.e. éFSH è é # LH receptors in ovaries
IV. RECEPTORS
A. SPECIFIC – only sensitive to 1 hormone
B. PROTEINS
C. 2 CLASSES: ON or IN cell (OVERVIEW Fig. 17.12, p. 593)
1. MEMBRANE-BOUND RECEPTORS
a. Protein & A.A. hormones (large or H20 soluble, can’t get
thru plasma membrane)
b. Hormone + receptor è change in PM permeability
c. 10 Messenger (= Extracellular hormone) è
20 Messenger =Intracellular messenger
i. Ca+2/Calmodulin,
ii. cAMP
iii. G proteins
è turn on enzymesèresponse
èopen/close ion channel è response
d. Cascade response (Fig. 17.20, p. 600)
e. Short-term, rapid response
f. Examples: Epinephrine (Tab 17.3, p. 592)
& Insulin
2. NUCLEAR/INTRACELLULAR RECEPTORS (Fig. 17.13, p. 594)
a. Lipid (Small or H20 insoluble, can diffuse thru membrane)
b. Receptor INSIDE NUCLEUS
c. Hormoneè thru membrane into cell è nucleusè turns on gene
è response
d. Long-term, slower response, but prolonged
e. Example: sex hormones (Tab 17.3, p. 592)