1. Regulation Why are hormones needed?
chemical messages from one body part to another
communication needed to coordinate whole body
daily homeostasis & regulation of large scale changes
solute levels in blood
glucose, Ca++, salts, etc.
metabolism
growth
development
maturation
reproduction
growth hormones

2. Regulation & Communication
Animals rely on 2 systems for regulation
endocrine system
system of ductless glands
secrete chemical signals directly into blood
chemical travels to target tissue
target cells have receptor proteins
slow, long-lasting response
nervous system
system of neurons
transmits “electrical” signal & release neurotransmitters to target tissue
fast, short-lasting response
Hormones coordinate slower but longer–acting responses to stimuli such as stress, dehydration, and low blood glucose levels. Hormones also regulate long–term developmental processes by informing different parts of the body how fast to grow or when to develop the characteristics that distinguish male from female or juvenile from adult. Hormone–secreting organs, called endocrine glands, are referred to as ductless glands because they secrete their chemical messengers directly into extracellular fluid. From there, the chemicals diffuse into the circulation.

3. Regulation by chemical messengers
Neurotransmitters released by neurons
Hormones release by endocrine glands
endocrine gland
neurotransmitter
axon
hormone carried by blood
receptor proteins
receptor proteins
Lock & Key system
target cell

4. Classes of Hormones Protein-based hormones Lipid-based hormones
polypeptides
small proteins: insulin, ADH
glycoproteins
large proteins + carbohydrate: FSH, LH
amines
modified amino acids: epinephrine, melatonin
Lipid-based hormones
steroids
modified cholesterol: sex hormones, aldosterone
insulin

5. How do hormones act on target cells
Lipid-based hormones
hydrophobic & lipid-soluble
diffuse across cell membrane & enter cells
bind to receptor proteins in cytoplasm & nucleus
bind to DNA as transcription factors
turn on genes
Protein-based hormones
hydrophilic & not lipid soluble
can’t diffuse across cell membrane
bind to receptor proteins in cell membrane
trigger secondary messenger pathway
activate internal cellular response
enzyme action, uptake or secretion of molecules…

6. Action of lipid (steroid) hormones
target cell
blood S 1 S
cross cell membrane
protein
carrier S 2
binds to receptor protein
becomes transcription factor 5 3 S
plasma membrane 4
DNA
mRNA 6 7
ex: secreted protein = growth factor (hair, bone, muscle, gametes)

7. Question #1
Why would being non-polar allow steroid hormones to move through the cell membrane?
When a substance is nonpolar, it can interact with / flow through other nonpolar things. The hydrophobic tails of the membrane’s phospholipids are nonpolar. Therefore, steroid hormones can move right through the cell membrane.
B. What type of receptors would steroid hormones bind to (options = plasma membrane receptors or intracellular receptors)? Why?
They would bind to intracellular receptors because it is able to pass through the cell membrane and move directly into the cell. Thus, they would bind to a intracellular receptor. Only signal molecules that cannot pass through the membrane bind to plasma membrane receptors.

8. Action of protein hormones
signal-transduction pathway
Action of protein hormones 1
signal
protein hormone P
plasma membrane
binds to receptor protein
activates
G-protein
activates enzyme
cAMP
acts as 2° messenger
ATP
transduction
GTP
transduction: the action or process of converting something and especially energy or a message into another form
activates cytoplasmic signal
ATP
activates
enzyme 2
secondary
messenger system
activates
enzyme
produces an action 3
response
target cell

9. Ex: Action of epinephrine (adrenaline)
adrenal gland
signal 1
epinephrine
activates G protein 3
activates adenylyl cyclase
receptor
protein
in cell membrane
GDP
cAMP
transduction 4
ATP 2
GTP
activates
protein kinase-A 5
activates GTP
activates
phosphorylase kinase
cytoplasm
released to blood
activates
glycogen phosphorylase 7
liver cell
glycogen 6
glucose
response

10. Question #2
Amines (ex: epinephrine): modified from the amino acid tyrosine ; they are water-soluble (aka polar) so they CANNOT pass through the cell membrane
A. Why would being polar prevent amine hormones from moving through the cell membrane?
Polar and nonpolar substances do not mix or interact. Because the inside of the cell membrane is nonpolar, only nonpolar things can pass through it. Polar substances are repelled by the hydrophobic tails of the phospholipids.
B. What type of receptors would amine hormones bind to? Why? They would bind to plasma receptor proteins since they cannot pass through the membrane to access the intracellular receptors (which are inside the cell). 

11. Question #3
Full Proteins or Single Polypeptides (ex: oxytocin… used to induce labor): vary in size ; they are water-soluble so they CANNOT pass through the cell membrane.
A. Why would being water soluble (i.e. being attracted to water) prevent protein hormones from moving through the cell membrane?
If a substance is attracted to water, it is either charged or polar. Again, polar substances cannot interact/pass through nonpolar substances. This prevents protein hormones from passing through the hydrophobic membrane interior.
B. What type of receptors would protein hormones bind to?
Plasma membrane receptors for the reason stated in #2B above.

12. Question #4 The hormone is passing through the cell membrane.
Describe what is occurring in each of the six steps shown in the image to the left.
The hormone is passing through the cell membrane.
The hormone binds with an intracellular receptor.
The intracellular receptor protein is activated as a transcription factor and passes through the nuclear membrane.
The hormone-receptor complex transcribes a segment of DNA into mRNA.
The mRNA leaves the nuclear membrane.
A ribosome translates the mRNA into the desired protein.

13. Question #4 What type of hormone is being used? How do you know?
It must be a steroid since that is the only nonpolar hormone molecule, meaning that it can pass through the membrane and bind to an intracellular receptor.
Which parts of the pathway shown in the image to the left represent reception, transduction and response?
Step 1 & 2= reception. Step 3, 4, & 5= transduction. Step 6 = response.

14. Describe how this image is different from the previous image.
The initial hormone cannot pass through the membrane, so it binds to a plasma membrane receptor rather than an intracellular receptor.
What type of hormone is being used? How do you know?
It must either be an Amine or Protein hormone because it is polar/water-soluble and cannot pass through the cell membrane.
Which parts of the pathway shown in the image to the left represent reception, transduction and response?
The triangle fitting into the membrane receptor is reception. The second messengers represent transduction. The transcription factor being activated would be considered the response.

15. Benefits of a 2° messenger system1
signal
Activated adenylyl cyclase
receptor protein 2
Not yet
activated
amplification 4
amplification 3
cAMP
amplification 5
GTP
G protein
protein kinase 6
amplification
Amplification!
enzyme
Cascade multiplier! 7
amplification
FAST response!
product

16. Feedback
Feedback is a property of all open systems.

17. Negative Feedback
Negative feedback: any situation where the output of a process decreases the occurrence of that process. Regulatory in nature. Negative feedback maintains homeostasis of the system.

18. Maintaining homeostasis
hormone 1
gland
lowers body condition
high
specific body condition
low
raises body condition
gland
Negative Feedback Model
hormone 2

19. Regulation of Blood Sugar
Endocrine System Control
Feedback
Regulation of Blood Sugar
islets of Langerhans beta islet cells
insulin
body cells take up sugar from blood
liver stores glycogen
reduces appetite
pancreas
liver
high
blood sugar level
(90mg/100ml)
low
liver releases glucose
triggers hunger
pancreas
liver
islets of Langerhans alpha islet cells
glucagon

20. Question #5
In response to high blood glucose levels (ex: after a meal), your pancreas releases the hormone insulin into the bloodstream. Insulin causes liver cells to take in glycogen. In the liver cells, glucose molecules join together to form glycogen, a large energy-storage polysaccharide (i.e. big carbohydrate). Bringing glucose molecules into the liver cell to be stored causes blood glucose levels to drop.
In response to low blood glucose levels (ex: if you haven’t eaten a meal in a while), your pancreas releases glucagon into the bloodstream. Glucagon causes glycogen in liver cells to be broken down into individual glucose molecules. These glucose molecules are released into the blood, thereby raising blood glucose levels.
Is this system an example of positive or negative feedback? Explain your answer
Is this system an example of positive or negative feedback? Explain your answer

21. Question #6
Diabetes is a disease in which there is an error in the blood glucose control system. There are two forms of diabetes—Type 1 diabetes and Type 2 diabetes A. With Type 1 diabetes, the pancreas cannot produce insulin. How will this affect blood glucose levels? B. With Type 2 diabetes, the pancreas can produce insulin, but the receptors on the liver cells that cause the liver cells to respond to insulin are dysfunctional. How will this affect blood glucose levels?

22. Regulation of Blood Calcium
Are the hormones calcitonin and parathyroid hormone part of a negative or positive feedback loop? How do you know?  
They are part of a negative feedback loop because the product inhibits / reduces / stops the initial stimulus. Initial stimulus = blood calcium too high, Response = Thyroid gland releases calcitonin, End Result = blood calcium lowers. The product of this feedback loop reduces the initial stimulus.
Where does calcitonin store the excess calcium moved from the blood? In other words, what tissue in your body is primarily made of calcium? Bones

23. osmoreceptors in hypothalamus
Endocrine System Control
Feedback
Blood Osmolarity
increase thirst
osmoreceptors in hypothalamus
ADH
increased water reabsorption
nephron
pituitary
high
nephron
blood osmolarity
blood pressure
JuxtaGlomerular Apparatus
low
nephron
(JGA)
increased water & salt reabsorption
adrenal gland
angiotensin
aldosterone

24. Ex. Operons in gene expression

25. Ex. Temperature Regulation in Mammals

26. Ex. Population Growth

27. Positive Feedback
Positive feedback: any situation where the output of a process increases the occurrence of that process. Amplifying in nature. Positive feedback causes transformation in the system.

28. Ex. Animal Birth
The rabbit test was an early pregnancy test developed in 1927 by Bernhard Zondek and Selmar Aschheim. The original test actually used mice. The test consisted of injecting the tested woman's urine into a female rabbit, then examining the rabbit's ovaries a few days later, which would change in response to a hormone only secreted by pregnant women. The hormone, human chorionic gonadotropin (hCG), is produced during pregnancy and indicates the presence of a fertilized egg; it can be found in a pregnant woman's urine and blood. The rabbit test became a widely used bioassay (animal-based test) to test for pregnancy. The term "rabbit test" was first recorded in 1949 but became a common phrase in the English language. Xenopus frogs were also used in a similar "frog test".
Modern pregnancy tests still operate on the basis of testing for the presence of the hormone hCG. Due to medical advances, use of a live animal is no longer required.
It is a common misconception that the injected rabbit would die only if the woman was pregnant. This led to the phrase "the rabbit died" being used as a euphemism for a positive pregnancy test. In fact, all rabbits used for the test died, because they had to be surgically opened in order to examine the ovaries. While it was possible to do this without killing the rabbit, it was generally deemed not worth the trouble and expense.

29. Is the hormone oxytocin (involved in human labor) part of a negative or positive feedback loop? How do you know?
Oxytocin is part of a positive feedback loop. Once the baby’s head pushes against the cervix, the pressure impulses are sent to the brain which then stimulates the release of oxytocin. Oxytocin then stimulates muscular (uterine) contractions which pushes the baby’s head farther down on the cervix. This cycle repeats. In a positive feedback loop, the product strengthens or reinforces the original stimulus.

30. Ex. Fruit Ripening

31. Question #7
A ripening apple releases the hormone ethylene. Nearby apples come in contact with the ethylene hormone and ripen in response. As they ripen, they release more ethylene. Is this system an example of positive or negative feedback? Explain your answer.

32. Question #8
What are the pros and cons of using the endocrine system as a method of cell signaling?

33. Nervous & Endocrine systems linked
Hypothalamus = “master nerve control center”
nervous system
receives information from nerves around body about internal conditions
releasing hormones: regulates release of hormones from pituitary
Pituitary gland = “master gland”
endocrine system
secretes broad range of “tropic” hormones regulating other glands in body
hypothalamus
posterior
pituitary
anterior

34. tropic hormones = target endocrine glands hypothalamus
thyroid-stimulating
hormone
(TSH)
posterior
pituitary
antidiuretic
hormone
(ADH)
Thyroid gland
anterior
pituitary
adrenocorticotropic
hormone (ACTH)
Kidney
tubules
oxytocin
Muscles
of uterus
gonadotropic
hormones:
follicle-
stimulating
hormone (FSH)
& luteinizing
hormone (LH)
growth hormone (GH)
melanocyte-stimulating hormone
(MSH)
prolactin (PRL)
Adrenal
cortex
tropins (tropic hormones) stimulate growth in target organs/cells (tropic means nourishment) When the target organ is another gland, tropic hormones cause them to produce & release their own hormones.
Melanocyte
in amphibian
Mammary
glands
in mammals
Bone
and muscle
Ovaries
Testes

35. Any Questions??
Robert Wadlow
8' 11"