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Transcript
Endocrine System
Hormones
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
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
– slow, long-lasting response
– nervous system
• system of neurons
– transmits “electrical” signal &
release neurotransmitters to
target tissue
– fast, short-lasting response
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
target cell
Classes of Hormones
• Protein-based hormones
– polypeptides
• small proteins: insulin, ADH
insulin
– glycoproteins
• large proteins + carbohydrate: FSH, LH
– amines
• modified amino acids: epinephrine, melatonin
• Lipid-based hormones
– steroids
• modified cholesterol: sex hormones,
aldosterone
How do hormones act on target
cells
• Lipid-based hormones
– hydrophobic & lipid-soluble
• diffuse across membrane & enter cells
• bind to receptor proteins in cytoplasm & nucleus
• bind to DNA as transcription factors
• Protein-based hormones
– hydrophilic & not lipid soluble
•
•
•
•
can’t diffuse across membrane
receptor proteins in cell membrane
trigger secondary messenger pathway
activate internal cellular response
– enzyme action, uptake or secretion of molecules…
Action of lipid (steroid)
hormones
steroid hormone
target cell
S
S
cytoplasm
S
1
2
blood
protein
carrier
receptor protein
4
transcription
factor
S
3
DNA
nucleus
mRNA
5 protein
plasma membrane
ex: growth factors (hair, bone, muscle, gametes)
Action of protein hormones
signal-transduction pathway
1
protein
hormone
P
signal
plasma membrane
activates ion channel
or enzyme
2° messenger
receptor
protein
transduction
ATP
activates
enzyme
cytoplasm
target cell
2
secondary
messenger
system
activates
enzyme
produces an action
3
response
Signal Transduction pathway
1
protein hormone P
activates
enzyme
G protein
cAMP
receptor
protein
2
GTP
cytoplasm
3
ATP
activates
enzyme
activates
enzyme
produces an action
secondary
messenger
system
4
5
Action of epinephrine
(adrenalin)
1
epinephrine
activates
adenylyl cyclase adrenal gland
G protein
cAMP
receptor
protein
2
GTP
cytoplasm
liver cell
3
ATP
activates
protein kinase-A
activates
phosphorylase
glycogen
5
4
glucose
released
to blood
Benefits of a 2° messenger
system
signal
1
Activated adenylyl cyclase
receptor protein
2
Not yet
activated
amplification
4
3
GTP
amplification
cAMP
amplification
5
G protein
protein kinase
6
Amplification!
FAST response!
amplification
enzyme
7
amplification
product
Maintaining homeostasis
hormone 1
lowers
body condition
gland
high
specific body condition
low
raises
body condition
gland
hormone 2
Negative Feedback
Model
Nervous System Control Feedback
Controlling Body Temperature
nerve signals
brain
sweat
high
body temperature
low
brain
constricts surface shiver
blood vessels
nerve signals
dilates surface
blood vessels
Regulation of Blood Sugar
Feedback
insulin
liver stores
sugar
body
cells take
up sugar
from blood
pancreas
high
liver
blood sugar level
low
triggers
hunger
liver
releases
sugar
liver
pancreas
glucagon
reduces
appetite
Blood Osmolarity
Feedback
ADH
pituitary
increased
water
reabsorption
increase
thirst
nephron
high
blood osmolarity
blood pressure
nephron
adrenal
gland
low
increased
water & salt
reabsorption
JuxtaGlomerular
Apparatus
nephron
(JGA)
renin
aldosterone
Stimulates production
angiotensin
Nervous & Endocrine systems
linked
• 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
hypothalamus
anterior
pituitary
posterior
Hypothalamus
thyroid-stimulating
hormone
(TSH)
Thyroid gland
antidiuretic
posterior hormone
pituitary (ADH)
anterior
pituitary
Kidney
tubules
Muscles
of uterus
Adrenal
cortex
gonadotropic
hormones:
folliclestimulating
hormone (FSH)
& luteinizing
hormone (LH)
Melanocyte
in amphibian
Bone
and muscle
Testis
Ovary
Mammary
glands
in mammals
Homology in hormones
What does this tell you about these hormones?
How could these hormones have different effects?
same gene family
gene duplication?
prolactin
mammals
milk
production
birds
fat
metabolism
fish
amphibians
salt &
water
balance
metamorphosis
& maturation
growth
hormone
growth
& development
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
tyrosine
+
iodine
thyroxine
Goiter
Iodine deficiency
causes thyroid to
enlarge as it tries to
produce thyroxine
Regulation of Blood Calcium
Feedback
calcitonin
 kidney
filters Ca++
Ca++ deposited
in bones
high
blood calcium level

uptake
in intestines
Ca++
(10 mg/100mL)
low
activated Vitamin D
bones
release Ca++
 kidney
reabsorbs Ca++
parathyroid
Parathyroid hormone
Feedback
Female reproductive cycle
egg
matures &
is released
(ovulation)
estrogen
builds up
uterus lining
corpus
luteum
ovary
Progestins
fertilized egg
FSH & LH
maintains
uterus lining
HCG
yes
pregnancy
GnRH
hypothalamus
no
corpus luteum breaks down
progesterone drops
menstruation
progesterone
maintains
uterus lining
Any Questions??
Robert Wadlow
1918-1940
8' 11"