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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
• 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
Let Sleeping Bears Lie
• 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
• Body temperature regulation requires adjustment to heat gained from or lost to an animal’s environment
Heat is gained or lost in four ways
Figure 25.1
Convection Radiation
Evaporation
Conduction
• 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
AP Biology 2004-2005
Chapter 45.
Endocrine SystemHormones
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
growth hormones
AP Biology 2004-2005
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
AxonNeurotransmitter
Endocrine gland
Receptor proteins
Hormonecarried by blood
Target cell
Neurotransmitters released by neurons Hormones release by endocrine glands
AP Biology 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 bind to DNA as transcription factors
AP Biology 2004-2005
Nucleus
Cytoplasm
Steroid hormone (S) passes through plasma membrane.
Inside target cell, the steroid hormone binds to a specific receptor protein in the cytoplasm or nucleus.
Hormone-receptor complex enters nucleus & binds to DNA, causing gene transcription
Protein is produced.
Protein synthesis is induced.
Plasma membrane
DNAmRNA
Protein
Steroidhormone
Blood plasma
Proteincarrier
1
2
2
3
3
5
5 4
4
S
S
S
1S
Action of steroid (lipid) hormones
AP Biology 2004-2005
How do hormones act on target cellsSignal molecule
Cell surface receptorenzyme
G proteincAMP
Targetprotein
Nucleus
Cytoplasm
ATP
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.
AP Biology 2004-2005
Action of protein hormones
3
4
GTPactivatesenzyme
activatesenzyme
activatesenzyme
Receptorprotein
cAMP
Proteinhormone
ATP
1
2
Cytoplasm
Produces an action
proteinmessengercascade
G protein
AP Biology 2004-2005
adrenal gland
Action of epinephrine (adrenalin)
3
4
GTPactivates
protein kinase-A
activatesphosphorylase
activates adenylyl cyclase
Receptorprotein cAMP
Epinephrine
ATP
1
2
Cytoplasm
G protein
Liver cell
GlucoseGlycogen
releasedto blood
AP Biology 2004-2005
Benefits of a 2° messenger system
Amplification!
Signal molecule Receptor protein Activated adenylyl cyclase
Amplification
Amplification
Amplification
Amplification
GTP G protein
2
1
3
4
5
6
7
Enzymatic product
Enzyme
Protein kinase
cAMP
Not yetactivated
AP Biology 2004-2005
Ductless glands release hormones into blood
Tropic hormones= a hormone that has another endocrine gland as a target
Endocrine system
Duct glands = exocrine(tears, salivary)
AP Biology 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” endocrine system secretes broad range
of hormones regulating other glands
AP Biology 2004-2005
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 Testis
Ovary
Melanocytein amphibian
Adrenocorticotropic
hormone (ACTH) Melanocyte-stimulating hormone(MSH)
OxytocinProlactin (PRL)
Gro
wth
hor
mon
e (G
H)
AP Biology 2004-2005
AP Biology 2004-2005
Homology in hormones
prolactin
mammals birds amphibiansfish
milkproduction
fatmetabolism
metamorphosis& maturation
salt &water
balance
growthhormone
growth& development
What does this tell you about these hormones?
same gene family
AP Biology 2004-2005
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
Anterior pituitary
Inhibition
–
Inhibition
Target glands
Hypothalamus
Releasing hormones(TRH, CRH, GnRH)
Tropic hormones(TSH, ACTH, FSH, LH)
–
(thyroid, adrenal cortex, gonads)
Hormones
AP Biology
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 2004-2005
- triggers release of glucose by liver
- stimulates appetite
Regulating blood sugar levels
- triggers uptake of glucose by body cells
- triggers storage in liver
- depresses appetite
pancreas
pancreas
beta islet cells
alpha islet cells
Islets of LangerhansAlpha cells: •glucagon~ raises
blood glucose levelsBeta cells: •insulin~ lowers
blood glucose levelsType I diabetes mellitus (insulin-
dependent; autoimmune disorder)Type II diabetes mellitus (non-insulin-dependent; reduced responsiveness
in insulin targets)
AP Biology 2004-2005
Regulating blood osmolarityIf amount of dissolved material in blood is too high, need to dilute blood
ADH
Dehydration Lowers blood volume & pressure
Increased waterretention
Increasedvasoconstrictionleading to higherblood pressureReduced
urine volume
Osmotic concentrationof blood increases
ADH synthesized in hypothalamus
ADH released from posterior pituitary into blood
Osmoreceptors NegativefeedbackNegative
feedback
AP Biology 2004-2005
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
tyrosineiodine
thyroxine
AP Biology 2004-2005
GoiterIodine deficiency causes thyroid to enlarge as it tries to produce thyroxine
AP Biology 2004-2005
Homology in hormones
Days from emergence of forelimb
TRH rises
TRH TSH Thyroxine
–35 –30 –25 –20 –15 –10 –5 0 +5 +10
Th
yro
xin
e s
ecre
tio
n r
ate
Thyroxine stimulates metamorphosis in amphibians
AP Biology 2004-2005
Regulating blood calcium levels
Increased blood Ca++
Thyroid
ParathyroidsLow blood Ca++
Parathyroidhormone (PTH)
Increased absorptionof Ca++ from intestine due to PTH activation of Vitamin D
Reabsorption of Ca++ &excretion of PO4
Osteoclasts dissolve CaPO4crystals in bone, releasing Ca++
–Negativefeedback
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
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
• 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
Let Sleeping Bears Lie
• 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
• Body temperature regulation requires adjustment to heat gained from or lost to an animal’s environment
Heat is gained or lost in four ways
Figure 25.1
Convection Radiation
Evaporation
Conduction
• 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