Chapter 17: FUNCTIONAL ORGANIZATION OF THE ENDOCRINE SYSTEM
I.
HORMONES AND THEIR SUMMARIZED FUNCTIONS
GLAND
SUMMARIZED FU NCTION
HORMONE
(Target tissues are underscored.)
Hypothalamus
Growth hormone R.H. (GH-RH) Releases GH from anterior pituitary
Thyrotropin R.H. (TRH)
Releases TSH from anterior pituitary
Corticotropin R.H.(CRH)
Releases ACTH from anterior pitu­
itary
Releases FSH and LH from anterior
pituitary
Inhibits PRL from anterior pituitary
Gonadotropin R.H. (GnRH)
Prolactin Inhibiting H. (PIH)
Increases growth in most tissues
Anterior Pituitary Growth H. (GH)
Thyroid-stimulating H. (TSH)
Increases thyroxine from thyroid
gland
Adrenocorticotropic H. (ACTH) Increases cortisol from adrenal
cortex
Luteinizing H. (LH)
Stimulates ovary or testis
Follicle-stimulating H. (FSH)
Stimulates ovary or testis
Prolactin (PRL)
Stimulates milk production of breasts
Melanocyte-stimulating H.(MSH) Increases melanin synthesis by
melanocytes
Posterior Pituitary Antidiuretic H. (ADH)
Increased retention of water by
kidneys
Milk ejection by breasts, contraction
of uterus
Oxytocin (OT)
91 92 HORMONES AND THEIR SUMMARIZED FUNCTIONS, continued
GLAND
HORMONE
SUMMARIZED FUNCTION
(Target tissues are underlined.)
Thyroid Gland
Thyroxine (Thyroid H.; TH)
Calcitonin
Parathyroid Gland Parathyroid hormone (PTH)
Adrenal Medulla
Adrenal Cortex
Pancreas
Increases metabolic rate of most
cells
Lowers blood calcium levels by
inhibiting osteoclasts
Raises blood calcium levels via action
on bone. kidney. and small intestine
Epinephrine (E)
Enhances sympathetic response in
organs with sympathetic receptors
Norepinephrine (NE)
Enhances sympathetic response in
organs with sympathetic receptors
Cortisol
Increases protein and fat breakdown
in most tissues. increases stress
response
Aldosterone
Retention of sodium ion by kidney
Insulin
Lowers blood glucose by allowing it
to enter most body cells
Glucagon
Raises blood glucose levels by
causing glucose release from liver
Estrogen
Promotes reproductive capability of
primary and secondary sex organs
Progesterone
Promotes reproductive capability of
breasts and uterus; sustains
pregnancy
Testosterone
Promotes reproductive capability of
primary and secondary sex organs
Ovary
Testis
93 HORMONES AND THEIR SUMMARIZED FUNCTIONS, continued
GLAND
HORMONE SUMMARIZED FUNCTION
(Target tissues are underlined.)
Pineal Body
Melatonin (Fig.18.20 [18.19]) Affects the day/night cycle (and
reproductive readiness in some
mammals and birds)
Thymus gland
Thymosin Development of immune system
A number of other organs of the body that are not usually classified primarily as
endocrine glands in fact do secrete hormones. The following is a list of some of these
organs and some of their secretions.
ORGAN
HORMONE
SUMMARIZED FUNCTION
(Target tissues are underscored.)
Heart
Atrial Natriuretic H.
Causes kidneys to excrete sodium ion
Stomach
Gastrin
Increases digestive activity of the
stomach
Small Intestine
Secretin
Increases secretions of liver and pancreas
Cholecystokinin (CCK)
Increa.ses secretions of pancreas and con­
traction of gall bladder
Kidney
Erythropoietin
Stimulates red cell production in bone
marrow
Body fat
Leptin
Signals satiety to the hypothalamus
Estrogen
Promotes reproductive capability of
primary and secondary sex organs
Human chorionic
Gonadotropin
Signals corpus luteum to increase its
hormones
Placenta
Progesterone
Estrogen
94 II.
GENERAL PRINCIPLES OF ENDOCRINE FUNCTION
A. Def.: Endocrine organ: secretes hormones into blood, which transports
them to target cell, causing an effect
B.
Overview
ENDOCRINE GLAND
Synthesis
Storage
Hormone
Release
DISPOSAL ORGAN
Liver or kidney
Disposal of hormone Feedback
signal
Desired
response
BLOOD
Binding
proteins
Hormone +
binding
protein
(Fig. 17.3, 9th ed)
TARGET CELL
C.
Nervous system vs. endocrine system:
1.
Control center
2.
Speed of response
3.
Duration of response
4.
Effectors
5.
Signal strength (Fig. 17.2)
6.
Repair
Nervous System Endocrine System
95 D.
Hormones' chemistry (Table 17.2)
1.
2.
E.
F.
Lipid-soluble
a.
Steroids (from cholesterol)
b.
Thyroxine (from amino acid)
Water soluble
a.
Amines (from amino acids, except TH)
b.
Proteins or polypeptides (very short amino acid chains)
Patterns of hormone secretions (Fig. 17.4 [17.8])
1.
Chronic: Constant
2.
Acute: Responds to specific stimulus
3.
Episodic (Cyclic): Daily or monthly cycles
Target cell (Fig. 17.10 [17.11 )
1.
Def.:
2.
Ex.:
96 III.
CONTROL OF HORMONE SECRETION
A.
Control by humeral stimuli (Fig. 17.5 [17.4])
1.
Non-hormone molecules regulates hormone
2. Ex: Insulin
High blood glucose
Pancreas
Insulin
_ _ _ _ blood glucose
Movement of glucose into cells
_ _ _ _ _ _ _ _ _ Feedback
3.
B.
Ex: Parathyroid hormone (See p. 32, this Notebook)
Control by neural stimuli (Fig. 17.6 [17.5])
1.
Adrenal medulla (Fig. 18.14)
Stress
JJ. ANS JJ. Sympathetic neurons
JJ.
Adrenal medulla -> Epinephrine and norepinephrine
Hvpo'ftlAlAM1C
~EURON CELL BOOIES
2.
Posterior pituitary (Fig. 18.4)
a.
Structure
b.
Function
.
"
'
.. ......... '" .,
·
.·
,
POSTERIOR
PITUITARY
..... _--_ .... ­
97 C.
Control by hormonal stimuli:
Hypothalamus controlling anterior pituitary hormones
(Fig. 17.17 [17.6]; Fig. 18.10 [18.3, p. 611])
1.
Hypothalamus and anterior pituitary anatomy
OPTIC
CHIASMA
INFUNDIBULUM ---..:.­
,
,,
•
•
,
,,
,
,, ,
,,
HYPOTHALAMO­
HYPOPHYSEAL.
PORTAL SYSTEM
ANTERIOR . - . ' - - - ,
PITUITARY
•,,
,,
-­
2.
Ex.:
....
Thyroxine
Cold, low metabolism
Increased metabolism
Hypothalamus
Thyroid stimulating hormone
releasing hormone (TRH)
Pituitary
All body cells
Thyroxine
Thyroid stimulating hormone (TSH)
_ _ _ _ feedback
Thyroid gland
98 IV.
HORMONE RECEPTORS AND MECHANISM OF ACTION
A.
Hormone receptors (Fig. 17. 10 [1 7. 14]):
B.
Regulation of receptors
1.
2.
C.
Down-regulation (Fig. 17.11 [12a]):
a.
Loss of receptors
b.
Cause:
c.
Effect: Target cell becomes _ _ _ _ _ sensitive to hormone
d.
Ex.:
Up-regulation (Fig. 17.11B [17.12b])
a.
Increased number of receptors to a particular hormone
b.
Cause:
c.
Effect: Target cell becomes _ _ _ _ _ sensitive to hormone
d.
Ex.:
Classes of receptors
1.
Nuclear receptors (Fig. 17.12a; 17.13[17.21])
a.
Steroid hormones and TH
b.
Solubility:
c.
Activate DNA
d.
Response time:
99
2. Membrane-bound receptors (Fig. 17.12b [17.15])
a. Protein or peptide hormones, E and NE
b. Size and solubility:
c. Activate intracellular regulatory molecules [mediators] which
activate enzymes or change membrane permeability
d. Cascade effect (Fig. 17.20 [17.22)
d. Response time:
V. PROSTAGLANDINS
A. Def.: Three series of biologically active fatty acid derivatives, secreted by
virtually all cells, and producing local effects.
B. Secreted into interstitial fluid
C. Effects
Pg1
a. Smooth muscle contraction
b. Blood clotting
c. Inflammation
Aspirin
Series
Pg2
Pg3