1. Ch .45 Hormones and the Endocrine System
Fig. 45-1
Ch .45 Hormones and the Endocrine System
Figure 45.1 What role do hormones play in transforming a caterpillar into a butterfly?
For the Discovery Video Endocrine System, go to Animation and Video Files.

2. Two systems coordinate communication throughout the body:
Nervous System:
nerve impulses
faster
Endocrine System
Chemical messages (hormones)
Slower but longer-acting responses (ex. reproduction)

3. Endocrine vs. Exocrine
Endocrine glands: are ductless and secrete hormones directly into blood
Exocrine glands: have ducts and secrete substances onto body surfaces or into body cavities (ex. tear, sweat, salivary, mucous)

4. Endocrine Glands Thyroid (provides T3 and T4) 2. Parathyroid (PTH)
Near larynx
Hormone = thyroxine (requires iodine)
Regulates body metabolism
2. Parathyroid (PTH)
Embedded in thyroid
Regulates Ca2+ and phosphate ions in blood
Thyroid gland
Parathyroid (PTH)
glands

5. Endocrine Glands 3. Hypothalamus 4. Pituitary (anterior and posterior)
receives information from the nervous system and initiates responses through the endocrine system
The pituitary gland is attached to the hypothalamus
4. Pituitary (anterior and posterior)
Located at the base of the brain
Produces growth hormone and gonadotrophic hormones (sex hormones)
Many stimulate activity of other endocrine tissues
Hypothalamus
Pituitary gland

6. Cerebrum Thalamus Pineal gland Hypothalamus Cerebellum Pituitary gland
Fig
Cerebrum
Thalamus
Pineal
gland
Hypothalamus
Cerebellum
Pituitary
gland
Spinal cord
Figure Endocrine glands in the human brain
Hypothalamus
Posterior
pituitary
Anterior
pituitary

7. Endocrine Glands 5. Adrenal Adrenal cortex Top of each kidney
Adrenal Medulla  EPINEPHRINE ”fight or flight” hormone
1. Reroutes blood
2. Increase heart rate
3. Strengthens muscle contraction
4. Enlarges airways
Adrenal cortex
mineralocorticoids: Na+ and water retention
Gluticocorticoids: increase blood sugar
Adrenal
glands

8. (b) Long-term stress response
Fig c
Adrenal cortex
Adrenal gland
Kidney
(b) Long-term stress response
Effects of mineralocorticoids:
Effects of glucocorticoids:
1. Retention of sodium ions and water by kidneys
1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose
Figure 45.21b Stress and the adrenal gland
2. Increased blood volume and blood pressure
2. Possible suppression of immune system

9. Endocrine Glands Pancreas 6. Pancreas
mostly exocrinedigestive enzymes
Islet of Langerhans-clusters of endocrine cells
Alpha (α) cells-secrete glucagon ( glucose)
Beta (β) cells-secrete insulin ( glucose)
7. Gonads-produce sex hormones
Control development and reproduction
Ex: testosterone, estrogen, progesterone
Controlled by gonadotrophs from pituitary
Ovaries
Testes

10. Endocrine Glands 8. Pineal Gland Near center of brain
Secretes melatonin
9. Thymus
Front of neck
Large during childhood
Thymosin-stimulates development of T-lymphocytes
Pineal gland
Thymus

11. II. Types of Chemical Signals
Neurotransmitters (local regulator)
Released from neuron and diffuse to target cell
play a role in sensation, memory, cognition, and movement
Ex: acetylcholine
Neurohormones are a class of hormones that originate from neurons in the brain and diffuse through the bloodstream
Neurohormone = oxytocin

12. 2. Pheromones
Communication signals between animals of the same species.
Animal attractants, territorial markers, alarm substances
Ex. Queen bee releases pheromone that prevents worker bees from giving young a special diet to make a new queen

13. 3. Prostaglandins (local regulator)
Modified fatty acids released into interstitial fluid to regulate nearby cells
help sperm reach an egg once in reproductive tract
Releases signal for uterus to contract at childbirth
Promote fever and inflammation
Assist in forming blood clots

14. 4. Endorphins
Released by pituitary and carried by blood
Target nerve cells
Inhibit perception of pain.
heroin and other opiates mimic endorphins and bind to these receptors in the brain
“Runners High” is also due to endorphin release

15. 5. Hormones-made in glands and carried by blood
Three major classes of molecules function as hormones in vertebrates:
Steroids-lipids, made from cholesterol (lipid-soluble)
Made in adrenal cortex and sex organs
Enter target cells
Ex: testosterone

16. b. Polypeptides (proteins and peptides)
Most hormones
Attach to cell receptors, often amplified (water-soluble hormones)
ex. insulin
c. Amines derived from amino acids
Derived from 1 amino acid (tyrosine or tryptophan)
Ex. epinephrine

17. Hormone action at the cellular level
The solubility of a hormone correlates with the location of receptors inside or on the surface of target cells
Water-soluble hormones are secreted by exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors
Lipid-soluble hormones diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells
Hormones can affect varied target cells differently
Signaling by any of these hormones involves three key events:
Reception
Signal transduction
Response

18. Water- soluble hormone Fat-soluble hormone Transport protein
Fig
Water-
soluble
hormone
Fat-soluble
hormone
Transport
protein
Signal receptor
TARGET
CELL OR
Signal
receptor
Figure 45.5 Receptor location varies with hormone type
Cytoplasmic
response
Gene
regulation
Cytoplasmic
response
Gene
regulation
(a)
NUCLEUS
(b)

19. Signal Transduction Pathways
Intracellular Receptors
Steroids-small lipid soluble
Binds to a receptor in cytoplasm or nucleus
Hormone receptor complex binds to an acceptor protein
Acceptor protein recognizes sections of DNA and stimulates transcription of specific genes
Ex. estrodial causes cells to make a protein in female bird that produces egg yolk

20. Hormone (estradiol) Estradiol (estrogen) receptor Plasma membrane
Fig
Hormone
(estradiol)
Estradiol
(estrogen)
receptor
Plasma
membrane
Hormone-receptor
complex
Figure 45.7 Steroid hormone receptors directly regulate gene expression
DNA
Vitellogenin
mRNA
for vitellogenin

21. 2. Thyroid hormones a. not a steroid but have receptors that are typically located in the nucleus b. ex. Thyroxine in humans stimulates and maintains metabolic processes; in frogs reabsorption of tail during metamorphosis
Figure 45.9 Specialized role of a hormone in frog metamorphosis

22. B. Membrane Receptors
Protein hormones unable to pass through cell membrane.
Binds to receptors on cell surface
~10,000 receptors on a target cell surface
Type 2 diabetes-insulin okay receptors not
3. Second Messenger-carries message inside
cAMP
Ca+2 (calmodulin)
4. Amplification-one molecule of hormone may start a cascade of enzyme catalyzed reactions releasing billions of desired molecules

23. Example: http://bcs.whfreeman.com/thelifewire/content/chp15/15020.html
Fig
Example:
Epinephrine
Adenylyl
cyclase
G protein
G protein-coupled
receptor
GTP
ATP
Second
messenger
cAMP
Figure 45.6 Cell-surface hormone receptors trigger signal transduction
Protein
kinase A
Inhibition of
glycogen synthesis
Promotion of
glycogen breakdown

24. (a) Short-term stress response
Fig b
Adrenal medulla
Adrenal gland
Kidney
(a) Short-term stress response
Effects of epinephrine and norepinephrine:
1. Glycogen broken down to glucose; increased blood glucose
2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate
Figure 45.21a Stress and the adrenal gland
5. Change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity

25. Epinephrine and norepinephrine
Trigger the release of glucose and fatty acids into the blood
Increase oxygen delivery to body cells
Direct blood toward heart, brain, and skeletal muscles, and away from skin, digestive system, and kidneys
The release of epinephrine and norepinephrine occurs in response to nerve signals from the hypothalamus

26. Multiple Effects of Hormones
The same hormone may have different effects on target cells that have
Different receptors for the hormone
Different signal transduction pathways
Different proteins for carrying out the response
A hormone can also have different effects in different species

27. Same receptors but different intracellular proteins (not shown)
Fig
Same receptors but different
intracellular proteins (not shown)
Different receptors
Epinephrine
Epinephrine
Epinephrine
Epinephrine
 receptor
 receptor
 receptor
 receptor
Glycogen
deposits
Vessel
dilates.
Vessel
constricts.
Glycogen
breaks down
and glucose
is released.
Figure 45.8 One hormone, different effects
(a) Liver cell
(b) Skeletal muscle
blood vessel
(c) Intestinal blood
vessel

28. Regulation of Hormone Pathways
A negative feedback loop inhibits a response by reducing the initial stimulus
Negative feedback regulates many hormonal pathways involved in homeostasis

29. Insulin and Glucagon: Control of Blood Glucose
Insulin and glucagon are antagonistic hormones that help maintain glucose homeostasis
The pancreas has clusters of endocrine cells called islets of Langerhans with alpha cells that produce glucagon and beta cells that produce insulin

30. Body cells take up more glucose. Insulin Beta cells of pancreas
Fig
Body cells
take up more
glucose.
Insulin
Beta cells of
pancreas
release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Blood glucose level
rises.
Blood glucose
level declines.
Figure Maintenance of glucose homeostasis by insulin and glucagon
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)

31. Target Tissues for Insulin and Glucagon
Insulin reduces blood glucose levels by
Promoting the cellular uptake of glucose
Slowing glycogen breakdown in the liver
Promoting fat storage

32. Blood glucose level rises.
Fig
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
STIMULUS:
Blood glucose level
falls.
Blood glucose
level rises.
Alpha cells of pancreas
release glucagon.
Figure Maintenance of glucose homeostasis by insulin and glucagon
Liver breaks
down glycogen
and releases
glucose.
Glucagon

33. Glucagon increases blood glucose levels by
Stimulating conversion of glycogen to glucose in the liver
Stimulating breakdown of fat and protein into glucose

34. Fig
Body cells
take up more
glucose.
Insulin
Beta cells of
pancreas
release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Blood glucose level
rises.
Blood glucose
level declines.
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
Figure Maintenance of glucose homeostasis by insulin and glucagon
STIMULUS:
Blood glucose level
falls.
Blood glucose
level rises.
Alpha cells of pancreas
release glucagon.
Liver breaks
down glycogen
and releases
glucose.
Glucagon

35. Diabetes Mellitus
Diabetes mellitus is perhaps the best-known endocrine disorder
It is caused by a deficiency of insulin or a decreased response to insulin in target tissues
It is marked by elevated blood glucose levels

36. Type I diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells
Type II diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors
Type 1 used to be called juvenile diabetes and is less common than Type 2 diabetes. Both can have injections but Type 1 starts with more initially (2/day).

37. Brain and nerveshypothalmuspituitary (anterior or porsterior)
The endocrine and nervous systems act individually and together in regulating animal physiology
Signals from the nervous system initiate and regulate endocrine signals
Brain and nerveshypothalmuspituitary (anterior or porsterior)
Oxytocin induces uterine contractions and the release of milk
Suckling sends a message to the hypothalamus via the nervous system to release oxytocin, which further stimulates the milk glands
Antidiuretic hormone (ADH) regulates kidney function

38. Mammary glands, uterine muscles
Fig
Hypothalamus
Neurosecretory cells of the hypothalamus
Axon
Posterior
pituitary
Anterior
pituitary
Figure Production and release of posterior pituitary hormones
HORMONE
ADH
Oxytocin
TARGET
Kidney tubules
Mammary glands, uterine muscles

39. This is an example of positive feedback, where the stimulus leads to an even greater response

40. Anterior Pituitary controlled by releasing and inhibiting hormones from the hypothalamus
Many of these are tropic hormones which stimulate the activity of other endocrine tissues.

41. Endocrine signaling regulates metabolism, homeostasis, development, and behavior
Two antagonistic hormones regulate the homeostasis of calcium (Ca2+) in the blood of mammals
Parathyroid hormone (PTH) is released by the parathyroid glands
Calcitonin is released by the thyroid gland

42. Falling blood Ca2+ level Blood Ca2+ level (about 10 mg/100 mL)
Fig
Active vitamin D
Stimulates Ca2+ uptake in kidneys
Increases Ca2+ uptake in intestines
PTH
Parathyroid gland (behind thyroid)
Stimulates Ca2+ release from bones
Figure The roles of parathyroid hormone (PTH) in regulating blood calcium levels in mammals
STIMULUS:
Falling blood Ca2+ level
Blood Ca2+ level rises.
Homeostasis:
Blood Ca2+ level (about 10 mg/100 mL)

43. PTH increases the level of blood Ca2+
It releases Ca2+ from bone and stimulates reabsorption of Ca2+ in the kidneys
It also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca2+ from food
Calcitonin decreases the level of blood Ca2+
It stimulates Ca2+ deposition in bones and secretion by kidneys