1. Introductory Questions #8
Name the nine major endocrine glands found in the body. Which one is called the “master gland”?
Name three major local regulators that act on nearby target cells. (pgs )
Name three key molecules that play a role in the signal transduction pathway (typical reactions in the endocrine system).
How is the anterior part of the pituitary gland different from the posterior part? Name the hormones secreted from each area. Which region secretes fewer types of hormones?
Using the table on pg. 949, name the hormone(s) that:
-Raises blood-calcium levels
-maintains metabolic processes

2. Homeostasis & Osmoregulation
Chapter

3. The liver is vital in homeostasis
It assists the kidneys by
making urea from ammonia
breaking down toxic chemicals

4. Homeostasis: regulation of internal environment
Thermoregulation internal temperature
Osmoregulation solute and water balance
Excretion nitrogen containing waste

5. Regulation of body temperature
Thermoregulation
4 physical processes:
Conduction~transfer of heat between molecules of body and environment
Convection~transfer of heat as water/air move across body surface
Radiation~transfer of heat produced by organisms
Evaporation~loss of heat from liquid to gas
Sources of body heat:
Ectothermic: determined by environment
Endothermic: high metabolic rate generates high body heat

6. Let Sleeping Bears Lie Bears don’t technically hibernate
They do enter a dormant state, when their body temperature drops by several degrees
Bears are endotherms
Endothermic animals derive most of their body heat from metabolism
Ectothermic animals warm themselves mainly by absorbing heat from their surroundings

7. Excretion is the disposal of metabolic wastes
Dormant bears have internal homeostatic mechanisms that compensate for fluctuations in the external environment
Thermoregulation maintains the body temperature within a tolerable range
Osmoregulation controls the gain and loss of water and dissolved solutes
Excretion is the disposal of metabolic wastes

8. Heat is gained or lost in four ways
Body temperature regulation requires adjustment to heat gained from or lost to an animal’s environment
Convection
Radiation
Evaporation
Conduction
Figure 25.1

9. Fur and feathers help the body retain heat
Hormonal changes may increase heat production by raising the metabolic rate
Fur and feathers help the body retain heat
Shivering, as these honeybees are doing, also increases metabolic heat production
Figure 25.2A

10. Regulation during environmental extremes
Torpor~ low activity; decrease in metabolic rate
1- Hibernation long term or winter torpor (winter cold and food scarcity); bears, squirrels
2- Estivation short term or summer torpor (high temperatures and water scarcity); fish, amphibians, reptiles
Both often triggered by length of daylight

11. Endocrine System Hormones
Chapter 45.
Endocrine System
Hormones

12. Regulation Why are hormones needed?
chemical messages from one body part to another
communication needed to coordinate whole body
homeostasis & regulation
metabolism
growth
development
maturation
reproduction
growth hormones

13. Regulation & Communication
Animals rely on 2 systems for regulation
endocrine system
ductless gland which secrete chemical signals directly into blood
chemical travels to target tissue
slow, long-lasting response
nervous system
system of neurons, central nerve system
transmits “electrical” signal 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.

14. Regulation by chemical messengers
Neurotransmitters released by neurons
Hormones release by endocrine glands
Endocrine gland
Axon
Neurotransmitter
Hormone
carried
by blood
Receptor
proteins
Target cell

15. 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

16. How do hormones act on target cells
Lipid-based hormones
lipid-soluble
diffuse across membrane & enter cells
bind to receptor proteins in cytoplasm & then this hormone-receptor complex moves into nucleus
bind to receptor proteins in nucleus
bind to DNA as transcription factors

17. Action of steroid (lipid) hormones
Cytoplasm
Blood plasma
Steroid
hormone S S 1
Protein
carrier S 2
Plasma membrane 1
Steroid hormone (S) passes through plasma membrane. 2
Inside target cell, the steroid hormone binds to a specific receptor protein in the cytoplasm or nucleus. 4 S 3
Hormone-receptor complex enters nucleus & binds to DNA, causing gene transcription 3
DNA
mRNA 5
Protein 4
Protein synthesis is induced.
Nucleus 5
Protein is produced.

18. How do hormones act on target cells
Protein-based hormones
hydrophilic & not lipid soluble
can’t diffuse across membrane
trigger secondary (2°) messenger pathway
transmit “signal” across membrane
“signal transduction”
usually activates a series of 2° messengers
multi-step “cascade”
activate cellular response
enzyme action, uptake or secretion of molecules, etc.
Signal molecule
Cell surface receptor
enzyme
cAMP
G protein
ATP
Target protein
Nucleus
Cytoplasm

19. Action of protein hormones1
Protein
hormone
activates enzyme
G protein
Receptor
protein
cAMP 3 2
ATP
activates
enzyme
protein
messenger cascade
GTP
activates
enzyme 4
Cytoplasm
Produces an action

20. Action of epinephrine (adrenalin)
Liver cell 1
Epinephrine
activates adenylyl cyclase
adrenal gland
G protein
Receptor
protein
cAMP 3 2
ATP
activates
protein kinase-A
GTP
activates
phosphorylase 4
released to blood
Cytoplasm
Glycogen
Glucose

21. Benefits of a 2° messenger system1
Receptor protein
Activated adenylyl cyclase
Signal molecule
Not yet
activated 2
Amplification 4
Amplification
cAMP 3 5
GTP
G protein
Protein kinase 6
Amplification
Amplification!
Enzyme 7
Amplification
Enzymatic product

22. Endocrine system
Ductless glands release hormones into blood
Tropic hormones= a hormone that has another endocrine gland as a target
Duct glands = exocrine
(tears, salivary)

23. Major vertebrate hormones (1)

24. Major vertebrate hormones (2)

25. Endocrine & Nervous system links
Hypothalamus = “master control center”
nervous system
receives information from nerves around body about internal conditions
regulates release of hormones from pituitary
Pituitary gland = “master gland”
endocrine system
secretes broad range of hormones regulating other glands

26. Melanocyte-stimulating hormone
Thyroid gland
Hypothalamus
Anterior
pituitary
Gonadotropic
hormones:
Follicle-
stimulating
hormone (FSH)
& luteinizing
hormone (LH)
Mammary
glands
in mammals
Muscles
of uterus
Kidney
tubules
Posterior
Thyroid-stimulating
Hormone
(TSH)
Antidiuretic
hormone
(ADH)
Adrenal
cortex
Bone
and muscle
Testis
Ovary
Melanocyte
in amphibian
Adrenocorticotropic
hormone (ACTH)
Melanocyte-stimulating hormone
(MSH)
Oxytocin
Prolactin (PRL)
Growth hormone (GH)

28. metamorphosis & maturation
Homology in hormones
What does this tell you about these hormones?
prolactin
same gene family
growth hormone
mammals
birds
fish
amphibians
milk production
fat metabolism
salt & water balance
metamorphosis & maturation
growth & development
The most remarkable characteristic of prolactin (PRL) is the great diversity of effects it produces in different vertebrate species. For example, prolactin stimulates mammary gland growth and milk synthesis in mammals; regulates fat metabolism and reproduction in birds; delays metamorphosis in amphibians, where it may also function as a larval growth hormone; and regulates salt and water balance in freshwater fishes. This list suggests that prolactin is an ancient hormone whose functions have diversified during the evolution of the various vertebrate groups.
Growth hormone (GH) is so similar structurally to prolactin that scientists hypothesize that the genes directing their production evolved from the same ancestral gene. Gene duplication!

29. Hormones & Homeostasis
Negative feedback
stimulus triggers control mechanism that inhibits further change
body temperature
sugar metabolism
Positive feedback
stimulus triggers control mechanism that amplifies effect
lactation
labor contractions
Inhibition
Hypothalamus –
Releasing hormones
(TRH, CRH, GnRH)
Inhibition
Anterior pituitary –
Tropic hormones
(TSH, ACTH, FSH, LH)
Target glands
(thyroid, adrenal cortex, gonads)
Hormones

30. Regulating blood sugar levels
Islets of Langerhans
Alpha cells:
•glucagon~ raises blood glucose levels
Beta cells:
•insulin~ lowers blood glucose levels
Type I diabetes mellitus
(insulin-dependent; autoimmune disorder)
Type II diabetes mellitus
(non-insulin-dependent; reduced responsiveness in insulin targets)

31. Regulating blood sugar levels
beta islet cells
triggers uptake of glucose by body cells
triggers storage in liver
- depresses appetite
pancreas
Islets of Langerhans
Alpha cells: •glucagon~ raises blood glucose levels
Beta cells: •insulin~ lowers blood glucose levels
Type I diabetes mellitus (insulin-dependent; autoimmune disorder)
Type II diabetes mellitus (non-insulin-dependent; reduced responsiveness in insulin targets)
- triggers release of glucose by liver
- stimulates appetite
pancreas
alpha islet cells

32. Regulating blood osmolarity
If amount of dissolved material in blood is too high, need to dilute blood
Dehydration
Lowers
blood
volume
& pressure
Osmotic concentration
of blood increases
Osmoreceptors
Negative
feedback
Negative
feedback
ADH synthesized in hypothalamus
ADH
ADH released from posterior pituitary into blood
Increased
water
retention
Increased
vasoconstriction
leading to higher
blood pressure
Reduced
urine volume

33. Regulating metabolism
Hypothalamus
TRH = TSH-releasing hormone
Anterior Pituitary
TSH = thyroid stimulating hormone
Thyroid
produces thyroxine hormones
metabolism & development
bone growth
mental development
metabolic use of energy
blood pressure & heart rate
muscle tone
digestion
reproduction
The thyroid gland produces two very similar hormones derived from the amino acid tyrosine: triiodothyronine (T3), which contains three iodine atoms, and tetraiodothyronine, or thyroxine (T4), which contains four iodine atoms. In mammals, the thyroid secretes mainly T4, but target cells convert most of it to T3 by removing one iodine atom. Although both hormones are bound by the same receptor protein located in the cell nucleus, the receptor has greater affinity for T3 than for T4. Thus, it is mostly T3 that brings about responses in target cells.
tyrosine
iodine
thyroxine

34. Goiter
Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine

35. Homology in hormones Thyroxine stimulates metamorphosis in amphibians
TRH
TSH
Thyroxine
Thyroxine secretion rate
TRH rises
–35
–30
–25
–20
–15
–10 –5 +5
+10
Days from emergence of forelimb

36. Regulating blood calcium levels
Thyroid
Low blood Ca++
Parathyroids –
Parathyroid
hormone (PTH)
Negative
feedback
PTH activates Vitamin D into hormone that enables calcium absorption from intestines. This is why Vitamin D deficiency causes rickets = poor bone formation
Increased absorption
of Ca++ from intestine due to PTH activation of Vitamin D
Reabsorption of Ca++ &
excretion of PO4
Osteoclasts
dissolve CaPO4
crystals in bone, releasing Ca++
Increased blood Ca++

37. The Gonads Steroid hormones: precursor is cholesterol
Androgens (testosterone)
sperm formation
male secondary sex characteristics; gonadotropin
Estrogens (estradiol)
uterine lining growth
female secondary sex characteristics
gonadotropin
Progestins (progesterone)

38. Any Questions??