chapter 45 ~ chemical signals in animals endocrine system ~ hormones
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Chapter 45 ~ Chemical Signals in Animals Endocrine system ~ Hormones. growth hormones. Regulatory systems. Hormone ~ chemical signal secreted into body fluids (blood) communicating regulatory messages Target cells ~ body cells that respond to hormones - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 45 ~ Chemical Signals in AnimalsEndocrine system ~Hormones
growth hormones
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Regulatory systems• Hormone~ chemical signal secreted into
body fluids (blood) communicating regulatory messages
• Target cells~ body cells that respond to hormones
• Endocrine system/glands~ hormone secreting system/glands (ductless); exocrine glands secrete chemicals (sweat, mucus, enzymes) through ducts
• Neurosecretory cells~ actual cells that secrete hormones
• Feedback mechanisms ~ negative and positive
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Local regulators: cells adjacent to or near point of secretion
• Growth factors ~ proteins for cell proliferation
• Nitric oxide (NO) ~ neurotransmitter; cell destruction; vessel
dilation• Prostaglandins ~
modified fatty acids secreted by placenta and immune system; also found in semen
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• 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
Regulation
growth hormones
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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
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Regulation by chemical messengers
axon
endocrine gland
receptor proteins
target cell
• Neurotransmitters released by neurons• Hormones release by endocrine glands
receptor proteins
hormone carried by blood
neurotransmitter
Lock & Keysystem
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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
insulin
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Mode of Action: Chemical Signaling• 1- Plasma membrane reception •
signal-transduction pathways (neurotransmitters, growth factors, most hormones)
• 2- Cell nucleus reception • steroid hormones, thyroid hormones, some local regulators
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nucleus
target cell
DNAmRNA
protein
blood
proteincarrier
S
S
S
S
Action of lipid (steroid) hormones
binds to receptor protein
cytoplasm
becomes transcription factor
ex: secreted protein = growth factor (hair, bone, muscle, gametes)
2
4
6
cross cell membrane
1
steroid hormone
mRNA read by ribosome5
plasma membrane
protein secreted7
3
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Action of protein hormones
activatesenzyme
activatesenzyme
activates enzyme
ATP
produces an action
P1
2
3
cytoplasm
receptor protein
response
signal
secondarymessengersystem
signal-transduction pathway
acts as 2° messenger
target cell
plasma membrane
binds to receptor protein
proteinhormone
ATPactivatescytoplasmicsignal
cAMP
GTP
activatesG-protein
transduction
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Benefits of a 2° messenger system
Amplification!
signal
receptor proteinActivated adenylyl cyclase
amplification
amplification
amplification
amplification
GTP G protein
product
enzyme
protein kinase
cAMP
Not yetactivated
1
2
4
35
6
7
FAST response!
amplification
Cascade multiplier!
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Maintaining homeostasis
high
low
hormone 1
lowersbody condition
hormone 2
gland
specific body condition
raisesbody condition
gland
Negative FeedbackModel
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Vertebrate Endocrine System• Tropic hormones ~ a
hormone that has another endocrine gland as a target
• Hypothalamus~pituitary• Pituitary gland• Pineal gland• Thyroid gland• Parathyroid glands• Thymus• Adrenal glands• Pancreas• Gonads (ovary, testis)
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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
pituitary
posterior
anterior
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Thyroid gland
hypothalamus
anteriorpituitary
gonadotropic hormones:follicle-stimulatinghormone (FSH) & luteinizing hormone (LH)
Mammaryglandsin mammals
Musclesof uterus
Kidneytubules
posteriorpituitary
thyroid-stimulating hormone(TSH)
antidiuretic hormone(ADH)
Adrenalcortex
Boneand muscle
Testes Ovaries
Melanocytein amphibian
adrenocorticotropic
hormone (ACTH)melanocyte-stimulating hormone
(MSH)
oxytocin
prolactin (PRL)
grow
th ho
rmon
e (GH)
tropic hormones = target endocrine glands
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The hypothalamus & pituitary, I• Releasing and inhibiting hormones• Anterior pituitary:• Growth (GH)~bones
√gigantism/dwarfism √acromegaly
• Prolactin (PRL)~mammary glands; milk production
• Follicle-stimulating (FSH) &• Luteinizing (LH)~ovaries/testes• Thyroid-stimulating (TSH)~ thyroid • Adrenocorticotropic (ACTH)~ adrenal
cortex • Melanocyte-stimulating (MSH) • Endorphins~natural ‘opiates’; brain
pain receptors
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The pituitary, II
• The posterior pituitary:• Oxytocin~
uterine and mammary gland cell contraction
• Antidiuretic (ADH)~ retention of water by
kidneys
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The pineal, thyroid, & parathyroid• Melatonin~ pineal gland;
biological rhythms
• Thyroid hormones: Calcitonin~ lowers blood calcium Thyroxine~ metabolic processes
• Parathyroid (PTH)~ raises blood calcium
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Regulation of Blood Calcium
blood calcium level(10 mg/100mL)
calcitonin
parathyroid hormone (PTH)
Ca++ uptakein intestines
high
low
FeedbackEndocrine System Control
kidney reabsorption of Ca++
bones release Ca++
kidney reabsorption of Ca++
Ca++ depositedin bones
activated Vitamin D
thyroid
parathyroid
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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
thyroxines
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The 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)
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liver
pancreas
liver
Regulation of Blood Sugar
blood sugar level(90mg/100ml)
insulin
body cells takeup sugar from blood
liver storesglycogen
reducesappetite
glucagon
pancreas
liver releasesglucose
triggershunger
high
low
FeedbackEndocrine System Controlislets of Langerhans beta islet cells
islets of Langerhansalpha islet cells
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The adrenal glands• Adrenal medulla (catecholamines): •epinephrine & norepinephrine~
increase basal metabolic rate (blood glucose and pressure)
• Adrenal cortex (corticosteroids): •glucocorticoids (cortisol)~ raise
blood glucose •mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+
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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