1. The Endocrine System
Chapter 11

2. -Endocrine System
I. Function
A. Body’s source of hormones
B. Hormonally controls body function

3. II. Structure
A. Glands or gland cells
1. secretory cell or structure derived from epithelium, sources of hormones
2. 2 types
a. endocrine – ductless, secrete into bloodstream
b. exocrine – have ducts or tubes that secrete into epithelial tissue

4. Endocrine System Main Sources Pituitary gland Adrenal glands
Thyroid gland
Parathyroid glands
Pineal gland
Thymus gland
Figure 36.2
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5. 3. 9 main “glands”
a. hypothalamus – brain, controls pituitary
b. pituitary – brain, “master gland”
-posterior (stores and secretes hormones made in hypothalamus)
-anterior (makes and secretes its own hormones)
c. adrenals -
-medulla – inner portion cortex –outer portion
d. thyroid - throat
e. parathyroids - throat
f. gonads – lower abdomen, primary reproductive organs, secretes gametes and sex hormones
-testes (male) -ovaries (female)
g. pancreatic islets – endocrine clusters in the pancreas, abdomen
-alpha cells -beta cells -delta cells
h. thymus - chest
i. pineal - brain

6. The Hypothalamus Region in the forebrain
Contains hormone-secreting cells
Interacts with pituitary
pituitary gland

7. Pituitary Gland Pea-sized gland at base of hypothalamus Two lobes
Posterior lobe stores and secretes hormones synthesized in the hypothalamus
Anterior lobe produces and secretes its own hormones

8. 4. others
a. stomach and small intestine
b. liver
c. kidneys
d. heart

9. B. Hormones
1. secretory products of endocrine glands, endocrine cells and some neurons that the delivers to nonadjacent target cells
a. one type of signaling molecule (molecules that help integrate activities within and between cells)
-some other signaling molecules are:
-neurotransmitters – that we talked about in nervous system
-local signaling molecules – released by many cells in localized tissue
-phermones – secretions of exocrine glands that diffuse outside of the body and act on other individuals

10. 2. over 50 known hormones
3. we will study mainly vertebrate (human hormones), but invertebrates have hormones as well
4. each “gland” or endocrine organ secretes specific hormones (see chart below)
5. target cells – any cell with receptors for a signaling molecule that may chamge its activities in response to it

11. 6. antagonistic
a. many hormones work in pairs to “counteract” each other
b. classic examples
-glucagon and insulin
-calcitonin and parathyroid hormone
-epinephrine and norepinephrine

12. 7. 2 main types
a. steroid hormones
-lipid soluble so they can diffuse through the membranes
-can enter the cell and even the nucleus
-can affect gene expression by initiating or Inhibiting transcription
-ex. estrogens, androgens, progesterone, cortisol, aldosterone
b. peptide hormones
-water soluble, cannot diffuse through membrane
-bind to membrane receptor, don’t get inside cell
-second messenger is activated inside the cell, the second messenger affects gene expression
-cAMP is common second messenger -ex. glucagon, ADH, OCT, TRH, insulin, STH, PRL, FSH, LH, TSH

13. Two Main Hormone Types Steroid hormones Peptide hormones
Derived from cholesterol
Estrogens, progestins, androgens, cortisol, aldosterone
Peptide hormones
Peptides, proteins, or glycoproteins
Glucagon, ADH, oxytocin, TRH, insulin, somatotropin, prolactin, FSH, LH, TSH

14. hormone-receptor complex
Steroid Hormones
hormone
Most diffuse across the plasma membrane and bind to a receptor
Hormone-receptor complex acts in nucleus to inhibit or enhance transcription
receptor
hormone-receptor complex
Figure 36.3
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gene product

15. Protein Hormone Hormone binds to a receptor at cell surface
glucagon
glucagon receptor
Hormone binds to a receptor at cell surface
Binding triggers a change in activity of enzymes inside the cell
cyclic AMP
+ Pi
ATP
cAMP activates
protein kinase A
Protein kinase A converts phosphorylase
kinase to active form and inhibits an
enzyme required for glucagon synthesis.
Figure 36.4
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16. C. Mechanisms
1. feedback
a. positive feedback – rising levels stimulates further secretion
b. negative feedback – rising levels inhibits further secretion
2. environmental factors can affect hormone secretion
a. ex. pineal gland secretes melatonin in the absence of light and is therefore affected by time of day and seasons

17. Feedback Mechanisms Negative feedback Positive feedback
Increase in hormone triggers activities that inhibit further secretion
Positive feedback
Increase in hormone triggers activities that stimulate further secretion

18. 3. direct responses to internal environment
a. the pancreatic islets respond to blood sugar levels
- if blood sugar drops the pancreas secretes glucagon to raise blood sugar
- if blood sugar is high the pancreas secretes insulin to lower blood sugar
4. therefore, some endocrine glands react to chemical changes and are not controlled by hypothalamus and pituitary
5. hormones interact with protein receptors on target cells
a. different hormones act on different mechanisms in target cell
b. not all types of cells respond to a given signal

19. Responses to Hormones Vary
Different hormones activate different responses in the same target cell
Not all types of cells respond to a particular hormone

20. Local Signaling Molecules
Prostaglandins
Produced and secreted in response to local changes
Sixteen types with a variety of effects
Growth factors
Affect cell division rates in tissues