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• Anatomy is the study of the structure of an organism
• Physiology is the study of the functions an organism performs
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Physical laws and the environment constrain animal size and shape
Physical laws and the need to exchange materials with the environment place limits on the range of animal forms
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Exchange with the Environment
• An animal’s size and shape directly affect how it exchanges energy and materials with its surroundings
• Exchange occurs as substances dissolved in the aqueous medium diffuse and are transported across the cells’ plasma membranes
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LE 40-3
Diffusion
Mouth
Diffusion
Two cell layersSingle cell
Diffusion
Gastrovascularcavity
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LE 40-4
Digestivesystem
Circulatorysystem
Excretorysystem
Interstitialfluid
Cells
Nutrients
Heart
Animalbody
Respiratorysystem
Blood
CO2FoodMouth
External environment
O2
50 µ
m
A microscopic view of the lung reveals that it is much more spongelike than balloonlike. This construction provides an expansive wet surface for gas exchange with the environment (SEM).
10 µm
Inside a kidney is a mass of microscopic tubules that exchange chemicals with blood flowing through a web of tiny vessels called capillaries (SEM).
The lining of the small intestine, a digestive organ, is elaborated with fingerlike projections that expand the surface area for nutrient absorption (cross-section, SEM).
Unabsorbedmatter (feces)
Metabolic wasteproducts (urine)
Anus
0.5 cm
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• Most animals are composed of specialized cells organized into tissues that have different functions
• Tissues make up organs, which together make up organ systems
Animal form and function are correlated
at all levels of organization
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• Different tissues have different structures that are suited to their functions
• Tissues are classified into four main categories: epithelial, connective, muscle, and nervous
Tissue Structure & Function
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Epithelial Tissue
• Epithelial tissue covers the outside of the body and lines the organs and cavities within the body
• It contains cells that are closely joined
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Connective Tissue
• Connective tissue mainly binds and supports other tissues
• It contains sparsely packed cells scattered throughout an extracellular matrix
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Muscle Tissue
• Muscle tissue consists of long cells called muscle fibers, which contract in response to nerve signals
• It is divided in the vertebrate body into three types: skeletal, cardiac, and smooth
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Nervous Tissue
• Nervous tissue senses stimuli and transmits signals throughout the animal
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• Bioenergetics, the flow of energy through an animal, limits behavior, growth, and reproduction
• It determines how much food an animal needs• Studying bioenergetics tells us much about an
animal’s adaptations
Bioenergetics
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Energy Sources and Allocation
• Animals harvest chemical energy from food
• Energy-containing molecules from food are usually used to make ATP, which powers cellular work
• After the needs of staying alive are met, remaining food molecules can be used in biosynthesis
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LE 40-7
Externalenvironment
Organic moleculesin food
Animalbody Digestion and
absorption
Nutrient moleculesin body cells
Carbonskeletons
Cellularrespiration
Biosynthesis:growth,
storage, andreproduction
Cellularwork
ATP
Heat
Heat
Heat
Energylost in urine
Heat
Energylost in feces
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• Metabolic rate is the amount of energy an animal uses in a unit of time
• One way to measure it is to determine the amount of oxygen consumed or carbon dioxide produced
Quantifying Energy Use
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Chapter 40
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• An animal’s metabolic rate is closely related to its bioenergetic strategy
• Birds and mammals are mainly endothermic: Their bodies are warmed mostly by metabolic heat.
• Endotherms typically have higher metabolic rates
Bioenergetic Strategies
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• Amphibians and reptiles other than birds are ectothermic: They gain their heat mostly from external sources
• Ectotherms generally have lower metabolic rates
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Animals regulate their internal environment within relatively narrow limits
• The internal environment of vertebrates is called the interstitial fluid and is very different from the external environment
• Homeostasis is a balance between external changes and the animal’s internal control mechanisms that oppose the changes
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• Regulating and conforming are two extremes in how animals cope with environmental fluctuations
• A regulator uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation
• A conformer allows its internal condition to vary with certain external changes
Regulating and Conforming
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Thermoregulation: Maintaining body temperature within certain boundaries,
even when surrounding temperature is very different.
Homeostasis: A dynamic state of stability
between an animal's internal environment and its external environment
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Thermoregulators keep core body temperature
within certain limits
Thermoconformers change body temperature
with the temperature outside of its body
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• Mechanisms of homeostasis moderate changes in the internal environment
• A homeostatic control system has three functional components:
• receptor• control center• effector
Mechanisms of Homeostasis
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• Most homeostatic control systems function by negative feedback, where buildup of the end product shuts the system off
• In positive feedback, a change in a variable triggers mechanisms that amplify rather than reverse the change
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• Ectotherms include most invertebrates, fishes, amphibians, and non-bird reptiles
• Endotherms include birds and mammals• In general, ectotherms tolerate greater variation
in internal temperature than endotherms
Ectotherms and Endotherms
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LE 40-12
River otter (endotherm)
Largemouth bass (ectotherm)
Ambient (environmental) temperature (°C)0 10 20 30 40
40
Bo
dy
tem
per
atu
re (
°C)
30
20
10
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• Endothermy is more energetically expensive than ectothermy
• Endothermy buffers the animal’s internal temperatures against external fluctuations
• Endothermy also enables the animal to maintain a high level of aerobic metabolism
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LE 40-13
Radiation
Evaporation
Conduction
Convection
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Insulation• Insulation is a major thermoregulatory
adaptation in mammals and birds
• Insulation reduces heat flow between an animal and its environment
• Examples are skin, feathers, fur, and blubber
• In mammals, the integumentary system acts as insulating material
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• Many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin
• In vasodilation, blood flow in the skin increases, facilitating heat loss
• In vasoconstriction, blood flow in the skin decreases, lowering heat loss
Circulatory Adaptations
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• Many marine mammals and birds have an arrangement of blood vessels called a countercurrent heat exchanger
• Countercurrent heat exchangers are important for reducing heat loss
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LE 40-15
Blood flow
VeinArtery
Pacific bottlenose dolphin
Canadagoose
VeinArtery
33°
27°
18°
9°
35°C
30°
20°
10°
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Adjusting Metabolic Heat Production
• Some animals can regulate body temperature by adjusting their rate of metabolic heat production
• Many species of flying insects use shivering to warm up before taking flight
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• Mammals regulate body temperature by negative feedback involving several organ systems
• In humans, the hypothalamus (a part of the brain) contains nerve cells that function as a thermostat
Feedback Mechanisms in Thermoregulation
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LE 40-21Thermostat inhypothalamusactivates coolingmechanisms.
Increased bodytemperature (suchas when exercising
or in hotsurroundings)
Body temperaturedecreases;thermostat
shuts off coolingmechanisms.
Sweat glands secretesweat that evaporates,cooling the body.
Blood vesselsin skin dilate:capillaries fillwith warm blood;heat radiates fromskin surface.
Body temperatureincreases;thermostat
shuts off warmingmechanisms.
Decreased bodytemperature
(such as whenin cold
surroundings)
Blood vessels in skin constrict, diverting bloodfrom skin to deeper tissuesand reducing heat lossfrom skin surface.
Skeletal muscles rapidlycontract, causing shivering,which generates heat.
Thermostat in hypothalamusactivateswarmingmechanisms.
Homeostasis:Internal body temperatureof approximately 36–38°C
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Torpor and Energy Conservation
• Torpor is a physiological state in which activity is low and metabolism decreases
• Torpor enables animals to save energy while avoiding difficult and dangerous conditions
• Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity
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• Estivation, or summer torpor, enables animals to survive long periods of high temperatures and scarce water supplies
• Daily torpor is exhibited by many small mammals and birds and seems adapted to feeding patterns
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Chapter 45
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Overview: The Body’s Long-Distance Regulators
• Animal hormones are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body
• Hormones reach all parts of the body, but only target cells are equipped to respond
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The endocrine system and the nervous system act individually and together
in regulating an animal’s physiology
• Animals have two systems of internal communication and regulation: the nervous system and the endocrine system
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• The nervous system conveys high-speed electrical signals along specialized cells called neurons
• The endocrine system secretes hormones that coordinate slower but longer-acting responses
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Control Pathways and Feedback Loops• There are three types of hormonal control
pathways: simple endocrine, simple neurohormone, and simple neuroendocrine
• A common feature is a feedback loop connecting the response to the initial stimulus
• Negative feedback regulates many hormonal pathways involved in homeostasis
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LE 45-2a
Targeteffectors
Response
Simple endocrine pathway
Glycogenbreakdown,glucose releaseinto blood
Liver
Bloodvessel
Pancreassecretesglucagon ( )
Endocrinecell
Low bloodglucose
Receptorprotein
Stimulus
Pathway Example
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LE 45-2b
Targeteffectors
Response
Simple neurohormone pathway
Stimulus
Pathway Example
Suckling
Milk release
Smooth musclein breast
Neurosecretorycell
Bloodvessel
Posterior pituitarysecretes oxytocin( )
Hypothalamus/posterior pituitary
Sensoryneuron
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LE 45-2c
Targeteffectors
Response
Simple neuroendocrine pathway
Stimulus
Pathway Example
Milk production
Bloodvessel
Hypothalamus
Sensoryneuron
Mammary glands
Endocrinecell
Bloodvessel
Anteriorpituitarysecretesprolactin ( )
Hypothalamussecretes prolactin-releasinghormone ( )
Neurosecretorycell
Hypothalamicneurohormonereleased inresponse to neural andhormonalsignals
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Hormones and other chemical signals bind to target cell receptors,
initiating pathways that culminate in
specific cell responses
• Hormones convey information via the bloodstream to target cells throughout the body
• Three major classes of molecules function as hormones in vertebrates:– Proteins and peptides– Amines derived from amino acids– Steroids
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• Signaling by any of these hormones involves three key events:– Reception– Signal transduction– Response
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Cell-Surface Receptors for Water-Soluble Hormones
• The receptors for most water-soluble hormones are embedded in the plasma membrane, projecting outward from the cell surface
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LE 45-3
SECRETORYCELL
Hormonemolecule
Signal receptor
VIABLOOD
VIABLOOD
TARGETCELL TARGET
CELLSignaltransductionpathway
OR
Cytoplasmicresponse
DNA
NUCLEUS
Nuclearresponse
Receptor in plasma membrane Receptor in cell nucleus
DNA
NUCLEUS
mRNA
Synthesis ofspecific proteins
Signaltransductionand response
Signalreceptor
Hormonemolecule
SECRETORYCELL
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• Binding of a hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm or a change in gene expression
• The same hormone may have different effects on target cells that have– Different receptors for the hormone– Different signal transduction pathways– Different proteins for carrying out the response
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• The hormone epinephrine has multiple effects in mediating the body’s response to short-term stress
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LE 45-4
Different receptors different cell responses
Epinephrine
receptor
Epinephrine
receptor
Epinephrine
receptor
Vesselconstricts
Vesseldilates
Intestinal bloodvessel
Skeletal muscleblood vessel
Liver cell
Different intracellular proteins different cell responses
Glycogendeposits
Glycogenbreaks downand glucoseis releasedfrom cell
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Intracellular Receptors for Lipid-Soluble Hormones
• Steroids, thyroid hormones, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus
• Protein-receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes
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Paracrine Signaling by Local Regulators
• In paracrine signaling, nonhormonal chemical signals called local regulators elicit responses in nearby target cells
• Types of local regulators:– Neurotransmitters– Cytokines and growth factors– Nitric oxide– Prostaglandins
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• Prostaglandins help regulate aggregation of platelets, an early step in formation of blood clots
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• The hypothalamus and the pituitary gland control much of the endocrine system
The hypothalamus and pituitary integrate many functions
of the vertebrate endocrine system
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LE 45-6
Testis(male)
Ovary(female)
Adrenal glands
Pancreas
Parathyroid glands
Thyroid gland
Pituitary gland
Pineal gland
Hypothalamus
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Relation Between the Hypothalamus and Pituitary Gland
• The hypothalamus, a region of the lower brain, contains neurosecretory cells
• The posterior pituitary, or neurohypophysis, is an extension of the hypothalamus
• Hormonal secretions from neurosecretory cells are stored in or regulate the pituitary gland
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LE 45-7
Mammary glands,uterine muscles
Hypothalamus
Kidney tubules
OxytocinHORMONE
TARGET
ADH
Posteriorpituitary
Neurosecretorycells of thehypothalamus
Axon
Anteriorpituitary
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Posterior Pituitary Hormones
• The two hormones released from the posterior pituitary act directly on nonendocrine tissues
• Oxytocin induces uterine contractions and milk ejection
• Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys
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Anterior Pituitary Hormones
• The anterior pituitary produces both tropic and nontropic hormones
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Tropic Hormones• The four strictly tropic hormones are
– Follicle-stimulating hormone (FSH)– Luteinizing hormone (LH)– Thyroid-stimulating hormone (TSH)– Adrenocorticotropic hormone (ACTH)
• Each tropic hormone acts on its target endocrine tissue to stimulate release of hormone(s) with direct metabolic or developmental effects
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Nontropic Hormones
• Nontropic hormones produced by the anterior pituitary:– Prolactin– Melanocyte-stimulating hormone (MSH)
-endorphin
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• Prolactin stimulates lactation in mammals but has diverse effects in different vertebrates
• MSH influences skin pigmentation in some vertebrates and fat metabolism in mammals
• Endorphins inhibit pain
Nontropic Hormones
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Growth Hormone
• Growth hormone (GH) has tropic and nontropic actions
• GH promotes growth directly and has diverse metabolic effects
• GH stimulates production of growth factors
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The hypothalamus
and
anterior pituitary
control secretion of
thyroid hormones
through two
negative feedback loops
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Thyroid Hormones
• The thyroid gland consists of two lobes on the ventral surface of the trachea
• It produces two iodine-containing hormones: triiodothyronine (T3) and thyroxine (T4)
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• Thyroid hormones stimulate metabolism and influence development and maturation
• Hyperthyroidism, excessive secretion of thyroid hormones, can cause Graves’ disease in humans
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• The thyroid gland also produces calcitonin, which functions in calcium homeostasis
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Parathyroid Hormone and Calcitonin: Control of Blood Calcium
• Two antagonistic hormones, parathyroid hormone (PTH) and calcitonin, play the major role in calcium (Ca2+) homeostasis in mammals
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• Calcitonin stimulates Ca2+ deposition in bones and secretion by kidneys, lowering blood Ca2+ levels
• PTH, secreted by the parathyroid glands, has the opposite effects on the bones and kidneys, and therefore raises Ca2+ levels
• PTH also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca2+ from food
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Insulin and Glucagon: Control of Blood Glucose
• The pancreas secretes insulin and glucagon, antagonistic hormones that help maintain glucose homeostasis
• Glucagon is produced by alpha cells
• Insulin is produced by beta cells
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LE 45-12
Beta cells ofpancreasrelease insulininto the blood.
Insulin
Liver takesup glucoseand stores itas glycogen.
STIMULUS:Rising blood glucose
level (for instance, aftereating a carbohydrate-
rich meal)
Blood glucose leveldeclines to set point;stimulus for insulinrelease diminishes.
Homeostasis:Blood glucose level
(about 90 mg/100 mL)
STIMULUS:Dropping blood glucoselevel (for instance, after
skipping a meal)
Blood glucose levelrises to set point;
stimulus for glucagonrelease diminishes.
Liver breaksdown glycogenand releasesglucose into theblood.
Body cellstake up moreglucose.
Alpha cells of pancreasrelease glucagon into the blood.
Glucagon
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Target Tissues for Insulin
• Insulin reduces blood glucose levels by– Promoting the cellular uptake of glucose
– Slowing glycogen breakdown in the liver
– Promoting fat storage
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• Glucagon increases blood glucose levels by– Stimulating conversion of glycogen to
glucose in the liver
– Stimulating breakdown of fat and protein into glucose
Target Tissues for Glucagon
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Diabetes Mellitus
• Diabetes mellitus is perhaps the best-known endocrine disorder
• It is caused by a deficiency of insulin or a decreased response to insulin in target tissues
• It is marked by elevated blood glucose levels
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• Type I diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells
• Type II diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors
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Adrenal Hormones: Response to Stress
• The adrenal glands are adjacent to the kidneys
• Each adrenal gland actually consists of two glands:
• the adrenal medulla• adrenal cortex
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Catecholamines from the Adrenal Medulla
• The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline)
• These hormones are members of a class of compounds called catecholamines
• They are secreted in response to stress-activated impulses from the nervous system
• They mediate various fight-or-flight responses
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Stress Hormones from the Adrenal Cortex
• Hormones from the adrenal cortex also function in response to stress
• They fall into three classes of steroid hormones:– Glucocorticoids, such as cortisol, influence glucose
metabolism and the immune system
– Mineralocorticoids, such as aldosterone, affect salt and water balance
– Sex hormones are produced in small amounts
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Gonadal Sex Hormones
• The gonads, testes and ovaries, produce most of the sex hormones: – androgens– Estrogens– progestins
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• The testes primarily synthesize androgens, mainly testosterone, which stimulate development and maintenance of the male reproductive system
• Testosterone causes increase in muscle and bone mass and is often taken as a supplement to cause muscle growth, which carries health risks
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• Estrogens, most importantly estradiol, are responsible for maintenance of the female reproductive system and the development of female secondary sex characteristics
• In mammals, progestins, which include progesterone, are primarily involved in preparing and maintaining the uterus
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Melatonin and Biorhythms
• The pineal gland, located in the brain, secretes melatonin
• Light/dark cycles control release of melatonin
• Primary functions of melatonin appear to relate to biological rhythms associated with reproduction