Download Steroid hormones

Introductory Questions #8
1)
2)
3)
4)
5)
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. 947-948)
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
Homeostasis & Osmoregulation
Chapter
The liver is vital in homeostasis
• It assists the kidneys by
– making urea from ammonia
– breaking down toxic chemicals
Homeostasis: regulation of internal environment
• Thermoregulation
internal temperature
• Osmoregulation
solute and water balance
• Excretion
nitrogen containing waste
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
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
• 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
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
• 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
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
Chapter 45.
Endocrine System
Hormones
AP Biology
2004-2005
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
AP Biology
2004-2005
growth hormones
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
AP Biology
2004-2005
Regulation by chemical messengers
 Neurotransmitters released by neurons
 Hormones release by endocrine glands
Endocrine gland
Axon
Neurotransmitter
Hormone
carried
by blood
Receptor
proteins
AP Biology
Target cell
2004-2005
Classes of Hormones
 Protein-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
AP Biology
2004-2005
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

AP Biology
bind to DNA as transcription factors
2004-2005
Action of steroid (lipid) hormones
Cytoplasm
S
Steroid
S hormone
Blood plasma
S
1
Protein
carrier
Plasma membrane
1 Steroid hormone (S) passes
2
through plasma membrane.
2
Inside target cell, the steroid
hormone binds to a specific
receptor protein in the
cytoplasm or nucleus.
3
Hormone-receptor complex
enters nucleus & binds to DNA,
causing gene transcription
4
Protein synthesis is induced.
5
Protein is produced.
2004-2005
4
S
DNA
Nucleus
AP Biology
3
mRNA
5 Protein
How do hormones act on target cells
 Protein-based hormones

hydrophilic & not lipid
soluble
Signal molecule
Cell surface receptor
enzyme
 can’t diffuse across
cAMP
membrane

trigger secondary (2°)
messenger pathway
G protein
ATP
 transmit “signal” across
membrane
 “signal transduction”
 usually activates a series of
2° messengers
 multi-step “cascade”

Nucleus
activate cellular response
 enzyme action, uptake or
AP Biology
Target
protein
secretion of molecules, etc.
Cytoplasm
2004-2005
Action of protein hormones
1
Protein
hormone
activates
enzyme
G protein
cAMP
Receptor
protein
3
2
ATP
GTP
Cytoplasm
AP Biology
activates
enzyme
activates
enzyme
4
Produces an action
protein
messenger
cascade
2004-2005
Action of epinephrine (adrenalin)
Liver cell
1
Epinephrine
activates
adenylyl cyclase adrenal gland
G protein
Receptor
protein
cAMP
2
3
ATP
GTP
activates
protein kinase-A
activates
phosphorylase
4
released
to blood
Cytoplasm
AP Biology
Glycogen
Glucose
2004-2005
Benefits of a 2° messenger system
1
Signal molecule
Receptor protein
Activated adenylyl cyclase
Not yet
activated
2 Amplification
4 Amplification
3
GTP
cAMP
5
G protein
Protein kinase
6 Amplification
Amplification!
AP Biology
Enzyme
7 Amplification
Enzymatic product
2004-2005
Endocrine system
 Ductless glands
release hormones
into blood
 Tropic hormones=
a hormone that
has another
endocrine gland
as a target
Duct glands = exocrine
AP Biology
(tears,
salivary)
2004-2005
Major vertebrate hormones (1)
AP Biology
2004-2005
Major vertebrate hormones (2)
AP Biology
2004-2005
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”


AP Biology
endocrine system
secretes broad range
of hormones
regulating other
glands
2004-2005
Hypothalamus
Thyroid-stimulating
Antidiuretic
Hormone
Posterior
hormone
(TSH)
pituitary (ADH)
Thyroid gland
Anterior
pituitary
Kidney
tubules
Muscles
of uterus
Adrenal
cortex
Gonadotropic
hormones:
Folliclestimulating
hormone (FSH)
& luteinizing
hormone (LH)
Melanocyte
in amphibian
Bone
and muscle
AP Biology
Testis
Ovary
Mammary
glands
in mammals
2004-2005
AP Biology
2004-2005
Homology in hormones
What does this tell you about these hormones?
same gene family
prolactin
mammals
milk
production
AP Biology
birds
fat
metabolism
fish
amphibians
salt &
water
balance
metamorphosis
& maturation
growth
hormone
growth
& development
2004-2005
Hormones & Homeostasis
 Negative feedback Inhibition Hypothalamus

stimulus triggers
control mechanism
that inhibits further
change
 body temperature
 sugar metabolism
 Positive feedback

stimulus triggers
control mechanism
that amplifies effect
 lactation
AP Biology
 labor contractions
–
Releasing hormones
(TRH, CRH, GnRH)
Inhibition
Anterior pituitary
Tropic hormones
(TSH, ACTH, FSH, LH)
Target glands
(thyroid, adrenal cortex, gonads)
Hormones2004-2005
–
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)
AP Biology
Regulating blood sugar levels
beta islet cells
pancreas
Islets of Langerhans
Alpha cells:
•glucagon~ raises
blood glucose levels
Beta cells:
•insulin~ lowers
blood glucose levels
Type I diabetes mellitus (insulindependent; autoimmune disorder)
Type II diabetes mellitus (non-insulindependent; reduced responsiveness
in insulin targets)
- triggers
release of
glucose by
liver
- stimulates
appetite
AP
Biology
- triggers uptake
of glucose by
body cells
- triggers
storage in liver
- depresses
appetite
pancreas
alpha islet cells
2004-2005
Regulating blood osmolarity
If amount of
dissolved
material in
blood is too
high, need to
dilute blood
Dehydration
Osmotic concentration
of blood increases
Negative
feedback
Osmoreceptors
Negative
feedback
ADH synthesized
in hypothalamus
ADH
Increased
water
retention
AP Biology
Lowers
blood
volume
& pressure
Reduced
urine
volume
ADH released from
posterior pituitary
into blood
Increased
vasoconstriction
leading to higher
blood pressure
2004-2005
Regulating metabolism
 Hypothalamus

TRH = TSH-releasing hormone
 Anterior Pituitary

TSH = thyroid stimulating hormone
 Thyroid


produces thyroxine hormones
metabolism & development







AP Biology
bone growth
mental development
metabolic use of energy
blood pressure & heart rate
muscle tone
digestion
reproduction
tyrosine
iodine
thyroxine
2004-2005
Goiter
Iodine deficiency
causes thyroid to
enlarge as it tries to
produce thyroxine
AP Biology
2004-2005
Thyroxine secretion rate
Homology in hormones
–35
Thyroxine stimulates metamorphosis in amphibians
TRH
TSH
Thyroxine
TRH rises
–30
–25
–20
–15
–10
–5
0
+5
+10
Days from emergence of forelimb
AP Biology
2004-2005
Regulating blood calcium levels
Thyroid
Low blood Ca++
–
Negative
feedback
Increased absorption
of Ca++ from intestine
due to PTH activation
of Vitamin D
AP Biology
Parathyroids
Parathyroid
hormone (PTH)
Reabsorption of Ca++ &
excretion of PO4
Increased blood Ca++
Osteoclasts
dissolve CaPO4
crystals in
bone, releasing
Ca++
2004-2005
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)
• uterine lining growth
Any Questions??
AP Biology
2005-2006