1. Biology 212 Anatomy & Physiology
Endocrine System

2. Endocrine System
Isolated organs & tissues (“endocrine glands”) which secrete chemical messages (“hormones”) into the blood which cause changes in cells and tissues (“targets”) elsewhere in the body.
Endocrine glands are ductless: they have a rich network of capillaries, and hormones are carried to target tissues & organs by the blood.

3. Hormones:
Three major chemical groups:
1) Peptides – Chains / rings of amino acids

4. Hormones:
Three major chemical groups:
2) Amines – Small molecules containing one or
more amine groups

5. Hormones:
Three major chemical groups:
3) Steroids – Formed from the lipid cholesterol by adding
specific sidechains

6. Endocrine System
Target cells & tissues respond to hormones relatively slowly (seconds, minutes, days) compared to much more rapid (milliseconds) responses to nervous stimulation

7. Hormones can produce a variety of changes in their target cells:
- Stimulate or inhibit cell differentiation
- Stimulate or inhibit cell division
- Activate or deactivate enzymes
- Stimulate or inhibit protein synthesis
- Stimulate or inhibit secretion
- Change permeability of plasma membrane

8. A specific hormone can only affect cells which have specific receptors for it on their plasma membranes.

9. Any single hormone can have only one effect on any specific target cells, but it may affect different types of target cells in different ways.
For example, epinephrine can:
Stimulate contraction of smooth muscle cells in
arterioles of intestines
Inhibit contraction of smooth muscle cells in
arterioles of leg muscles
Stimulate cardiac muscle cells to contract more quickly
Stimulate sweat glands to secrete sweat
Stimulate liver cells to release glucose into the blood
Stimulate fat cells to break down and release
fats into the blood

10. - Changing the amount of hormone circulating in the blood
The effect of a hormone on its target cells can be changed (increased or decreased) by:
- Changing the amount of hormone circulating in the blood
- Changing the number of receptors which the target cells
have for the hormone.
- Changing the specificity and affinity which these receptors
have for the hormone
Upregulation
Downregulation

12. Pituitary Gland
also called Hypophysis
Located in sella turcica of sphenoid bone
Two developmentally and functionally distinct parts, both under control of hypothalamus of brain

13. Anterior pituitary or adenohypophysis
Secretes 6 peptide hormones
Secretory cells regulated (stimulated or inhibited) by hormones produced in the hypothalamus and carried to it by hypothalamic – hypophyseal portal veins

14. 1) Growth Hormone (GH):
Stimulates growth of many organs
2) Thyroid Stimulating Hormone (TSH):
Stimulates thyroid gland to secrete its hormones
3) Adrenocorticotropic Hormone (ACTH):
Stimulates adrenal cortex to secrete its hormones
4) Prolactin (PRL):
Stimulates milk production by breast
5) Follicle Stimulating Hormone (FSH):
Stimulates development or eggs / sperm
6) Luteinizing Hormone (LH):
Stimulates testes to produce testosterone
Stimulates follicle of ovary to change to corpus luteum

15. Posterior pituitary or neurohypophysis
Secretes 2 peptide hormones
Secretory cells are really the axons whose cell bodies are located in the hypothalamus and whose axons pass through the hypothalamic-hypophyseal tract

16. 1) Oxytocin (OT):
Stimulates contraction of smooth muscle in breast
(lactation) and uterus (labor)
2) Antidiuretic Hormone (ADH):
Increases absorption of water in the kidney to
concentrate urine and decrease its volume

17. Thyroid Gland:
Located in neck, anterior to trachea.

18. Thyroid Gland:
Located in neck, anterior to trachea.
Secretes 2 similar amine hormones
Triiodothyronine
Tetraiodothyronine
and 1 peptide hormone
Calcitonin

19. Thyroid Gland:
Located in neck, anterior to trachea.
Secretes 2 similar amine hormones
Triiodothyronine
Tetraiodothyronine
and 1 peptide hormone
Calcitonin
Secretory cells for T3 and T4
arranged in hollow spheres
called follicles; Stimulated
by thyroid-stimulating hormone
from adenohypophysis.
Secretory cells for calcitonin
located between follicles;
Regulated by concentration of calcium in blood

20. Triiodothyronine (T3) & tetraiodothyronine (T4) increase metabolic rates of cells throughout the body by stimulating energy production by mitochondria.
Calcitonin (CT) stimulates osteoblasts to store additional calcium in the extracellular matrix of bone, thus lowering calcium levels in the blood

21. Parathyroid Glands:
Four small glands on
posterior surface of thyroid
Secretes one peptide: Parathyroid Hormone (PTH)
PTH increases concentration of calcium in blood:
- Stimulates osteocytes & osteoclasts to reabsorb calcium
from bone
- Inhibits kidneys from losing calcium through urine

22. Adrenal Glands:
Located in abdomen
Superior to kidneys
Each adrenal actually two
functionally distinct glands,
one (adrenal cortex)
wrapped around the other
(adrenal medulla)

23. Adrenal Medulla:
Actually a ganglion of the
sympathetic division of the
autonomic nervous system
Secretory cells stimulated by
preganglionic sympathetic neurons
and
Secrete two related amine
hormones called catecholamines

24. Since epinephrine and
norepinephrine are the
neurotransmitters normally
secreted by postganglionic
sympathetic neurons, they
produce all of the effects of
sympathetic nerve stimulation
on various organs

25. Adrenal Cortex:
Secretes more than twenty
different steroid hormones,
collectively called the
corticosteroids
Secretory cells arranged in three concentric layers, each of which secretes a specific group of corticosteroids.
From superficial to deep:
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis

26. Cells in zona glomerulosa secrete mineralocorticoids
which
regulate concentrations of various minerals (ions, electrolytes) in the blood by controlling their retention and removal by the kidneys.
Most common mineralocorticoid = Aldosterone

27. Cells in zona fasciculata secrete glucocorticoids
which
Regulate metabolism in many cells by:
a) stimulating breakdown of fat
b) stimulating breakdown of proteins
c) increasing concentrations of fatty acids, amino acids,
and glucose in the blood
Stimulate repair of damaged tissue
Most common glucocorticoids = cortisol & corticosterone

28. Cells in zona reticularis secrete gonadocorticoids, or
sex hormones, which supplement those secreted by testes and ovaries.
Mostly androgens (male hormones)
Some estrogens and progesterone (female hormones)
Most common = dehydroepiandrosterone & testosterone

29. Pancreas:
Located in abdomen
Posterior & inferior to stomach
Body of pancreas anterior to
aorta & inferior vena cava
Tail of pancreas extends left

30. Pancreas:
Primarily an exocrine gland
99% of cells secretes digestive enzymes into small intestine
but
1% = groups of endocrine
cells called pancreatic islets
or islets of Langerhans
Secrete two peptide hormones
Insulin
Glucagon
which are antagonistic to each
other in regulating blood glucose

31. Pancreatic Islets:
Alpha cells produce glucagon
Stimulated by low blood sugar
Causes increased blood sugar
by glycogen breakdown
gluconeogenesis
Beta cells produce insulin
Stimulated by high blood sugar
Causes decreased blood sugar
by glycogen synthesis

32. Diabetes Mellitus
Two forms:
INSULIN DEPENDENT (Type I; Juvenile-onset)
- Beta cells destroyed by body’s immune system,
not producing enough insulin
NON-INSULIN DEPENDENT (Type II; Adult-onset)
- Beta cells still producing insulin, but:
Insulin is defective & can’t act on target cells; or
- Target cells are defective & can’t recognize insulin
Hyperglycemia: Beta cells not producing enough insulin
Alpha cells producing too much glucagon
Hypoglycemia: Beta cells producing too much insulin
Alpha cells not producing enough glucagon

33. Gonads:
Produce most of the steroid sex hormones

34. Gonads:
Produce most of the steroid sex hormones
Testes:
Interstitial (Leydig) cells
produce androgens
mostly testosterone
Stimulated by luteinizing
hormone from adenohypophysis
Causes development of male
sexual characteristics & their
maintenance

35. Gonads:
Produce most of the steroid sex hormones
Ovaries:
As oocyte develops, it is
surrounded by follicular cells
which produce estrogens,
primarily estradiol
Stimulated by Follicle
Stimulating Hormone from
adenohypophysis.
Causes development of female sexual characteristics
Prepares uterus for pregnancy
Prepares breast for lactation

36. Gonads:
Produce most of the steroid sex hormones
Ovaries:
After ovulation, follicle changes
to corpus luteum, secretes
progesterone.
Stimulated by luteinizing
hormone from adenohypophysis
Maintains thick lining with uterus for pregnancy

37. Many other organs also contain cells & tissues
which secrete hormones.
Examples:
Kidney: Renin (blood pressure)
Erythropoietin (erythrocyte development)
Calciferol (blood calcium)
Heart: Atrial natriuretic hormone (blood sodium)
Liver: Angiotensin (blood pressure)
Thymus: Thymopoietin (lymphocyte development)
Stomach: Cholecystokinin (gall bladder contraction)
& Secretin (pancreas secretion)
Intestine: Gastrin (stomach function)