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Essentials of Human Anatomy & Physiology
Seventh Edition
Elaine N. Marieb
Chapter 9
The Endocrine System
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slides 9.1 – 9.48
The Endocrine System
Lecture Slides in PowerPoint by Jerry L. Cook
The Endocrine SystemThe Endocrine System
Second messenger system of the body
Uses chemical messages (hormones)that are released into the blood
Hormones control several majorprocesses
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processes
Reproduction
Growth and development
Mobilization of body defenses
Maintenance of much of homeostasis
Regulation of metabolism
Hormone OverviewHormone Overview
Hormones are produced by specializedcells
Cells secrete hormones intoextracellular fluids
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Cells secrete hormones intoextracellular fluids
Blood transfers hormones to target sites
These hormones regulate the activity ofother cells
The Chemistry of HormonesThe Chemistry of Hormones
Amino acid-based hormones
Proteins
Peptides
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Amines
Steroids – made from cholesterol
Prostaglandins – made from highlyactive lipids
Mechanisms of Hormone ActionMechanisms of Hormone Action
Hormones affect only certain tissues ororgans (target cells or organs)
Target cells must have specific protein
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Target cells must have specific proteinreceptors
Hormone binding influences the workingof the cells
Effects Caused by HormonesEffects Caused by Hormones
Changes in plasma membranepermeability or electrical state
Synthesis of proteins, such as enzymes
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Synthesis of proteins, such as enzymes
Activation or inactivation of enzymes
Stimulation of mitosis
Steroid Hormone ActionSteroid Hormone Action
Diffuse through the plasma membraneof target cells
Enter the nucleus
Bind to a specific protein within the
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Bind to a specific protein within thenucleus
Bind to specific sites on the cell’s DNA
Activate genes that result in synthesis ofnew proteins
Steroid Hormone ActionSteroid Hormone Action
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Figure 9.1a
Nonsteroid Hormone ActionNonsteroid Hormone Action
Hormone binds to a membrane receptor
Hormone does not enter the cell
Sets off a series of reactions thatactivates an enzyme
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activates an enzyme
Catalyzes a reaction that produces asecond messenger molecule
Oversees additional intracellularchanges to promote a specific response
Nonsteroid Hormone ActionNonsteroid Hormone Action
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Figure 9.1b
Control of Hormone ReleaseControl of Hormone Release
Hormone levels in the blood aremaintained by negative feedback
A stimulus or low hormone levels in the
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A stimulus or low hormone levels in theblood triggers the release of morehormone
Hormone release stops once anappropriate level in the blood is reached
Hormonal Stimuli of Endocrine GlandsHormonal Stimuli of Endocrine Glands
Endocrine glandsare activated by
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are activated byother hormones
Figure 9.2a
Humoral Stimuli of Endocrine GlandsHumoral Stimuli of Endocrine Glands
Changing bloodlevels of certain
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Figure 9.2b
levels of certainions stimulatehormone release
Neural Stimuli of Endocrine GlandsNeural Stimuli of Endocrine Glands
Nerve impulsesstimulate hormonerelease
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release
Most are undercontrol of thesympathetic nervoussystem
Figure 9.2c
Location of Major Endrocrine OrgansLocation of Major Endrocrine Organs
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Figure 9.3
Pituitary GlandPituitary Gland
Size of a grape
Hangs by a stalk from the hypothalamus
Protected by the sphenoid bone
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Protected by the sphenoid bone
Has two functional lobes
Anterior pituitary – glandular tissue
Posterior pituitary – nervous tissue
Hormones of the Anterior PituitaryHormones of the Anterior Pituitary
Six anterior pituitary hormones
Two affect non-endocrine targets
Four stimulate other endocrine glands(tropic hormones)
Characteristics of all anterior pituitary
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Characteristics of all anterior pituitaryhormones
Proteins (or peptides)
Act through second-messenger systems
Regulated by hormonal stimuli, mostlynegative feedback
Hormones of the Anterior PituitaryHormones of the Anterior Pituitary
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Figure 9.4
Growth Hormone (GH)Growth Hormone (GH)
General metabolic hormone
Major effects are directed to growth ofskeletal muscles and long bones
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skeletal muscles and long bones
Causes amino acids to be built intoproteins
Causes fats to be broken down for asource of energy
Functions of Other Anterior PituitaryFunctions of Other Anterior PituitaryHormonesHormones
Prolactin (PRL)
Stimulates and maintains milk productionfollowing childbirth
Function in males is unknown
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Function in males is unknown
Adrenocorticotropic hormone (ACTH)
Regulates endocrine activity of the adrenalcortex
Thyroid-stimulating hormone (TSH)
Influences growth and activity of the thyroid
Functions of Other Anterior PituitaryFunctions of Other Anterior PituitaryHormonesHormones
Gonadotropic hormones
Regulate hormonal activity of the gonads
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Follicle-stimulating hormone (FSH)
Stimulates follicle development inovaries
Stimulates sperm development intestes
Functions of Other Anterior PituitaryFunctions of Other Anterior PituitaryHormonesHormones
Gonadotropic hormones (continued)
Luteinizing hormone (LH)
Triggers ovulation
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Triggers ovulation
Causes ruptured follicle to become thecorpus luteum
Stimulates testosterone production inmales
Referred to as interstitial cell-stimulatinghormone (ICSH)
PituitaryPituitary -- Hypothalamus RelationshipHypothalamus Relationship
Release of hormones is controlled byreleasing and inhibiting hormonesproduced by the hypothalamus
Hypothalamus produces two hormones
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Hypothalamus produces two hormonesthat are transported to neurosecretorycells of the posterior pituitary
The posterior pituitary is not strictly anendocrine gland, but does releasehormones
Hormones of the Posterior PituitaryHormones of the Posterior Pituitary
Oxytocin
Stimulates contractions of the uterus duringlabor
Causes milk ejection
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Causes milk ejection
Antidiuretic hormone (ADH)
Can inhibit urine production
In large amounts, causes vasoconstrictionleading to increased blood pressure(vasopressin)
Hormones of the Posterior PituitaryHormones of the Posterior Pituitary
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Figure 9.5
Thyroid GlandThyroid Gland
Found at the base of the throat
Consists of two lobes joined by centralmass or isthmus
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mass or isthmus
Produces two hormones
Thyroid hormone
Calcitonin
Thyroid GlandThyroid Gland
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Figure 9.6
Thyroid HormoneThyroid Hormone
Major metabolic hormone
Composed of two active iodine-containing hormones
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containing hormones
Thyroxine (T4) – secreted by thyroidfollicles
Triiodothyronine (T3) – conversion of T4 attarget tissues
CalcitoninCalcitonin
Decreases bloodcalcium levels bycausing itsdeposition on bone
Antagonistic to
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Antagonistic toparathyroidhormone
Produced by C(parafollicular)cells
Figure 9.9
Parathyroid GlandsParathyroid Glands
Tiny masses on the posterior of thethyroid
Secrete parathyroid hormone
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Stimulate osteoclasts to remove calciumfrom bone and release it into the blood
Stimulate the kidneys and intestine toabsorb more calcium
Raises calcium levels in the blood
Adrenal GlandsAdrenal Glands
Two glands
Cortex – outer glandular region in threelayers
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layers
Medulla – inner neural tissue region
Sits on top of the kidneys
Hormones of the Adrenal CortexHormones of the Adrenal Cortex
Mineralocorticoids (mainly aldosterone)
Produced in outer adrenal cortex
Regulate mineral content in blood, water,and electrolyte balance
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and electrolyte balance
Target organ is the kidney
Production stimulated by renin andaldosterone
Production inhibited by atrial natriureticpeptide
Hormones of the Adrenal CortexHormones of the Adrenal Cortex
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Figure 9.10
Hormones of the Adrenal CortexHormones of the Adrenal Cortex
Glucocorticoids (including cortisone andcortisol)
Produced in the middle layer of the adrenalcortex
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cortex
Promote normal cell metabolism
Help resist long-term stressors
Released in response to increased bloodlevels of ACTH
Hormones of the Adrenal CortexHormones of the Adrenal Cortex
Sex hormones
Produced in the inner layer of the adrenalcortex
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cortex
Androgens (male) and some estrogen(female)
Hormones of the Adrenal MedullaHormones of the Adrenal Medulla
Produces two similar hormones(catecholamines)
Epinephrine
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Epinephrine
Norepinephrine
These hormones prepare the body todeal with short-term stress
Roles of the Hypothalamus and AdrenalRoles of the Hypothalamus and AdrenalGlands in the Stress ResponseGlands in the Stress Response
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Figure 9.12
Pancreatic IsletsPancreatic Islets
The pancreas is a mixed gland
The islets of the pancreas producehormones
Insulin – allows glucose to cross plasma
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Insulin – allows glucose to cross plasmamembranes into cells from beta cells
Glucagon – allows glucose to enter theblood from alpha cells
These hormones are antagonists thatmaintain blood sugar homeostasis
Pancreatic IsletsPancreatic Islets
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Figure 9.13
Pancreatic Hormones and Blood SugarPancreatic Hormones and Blood Sugar
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Figure 9.14
Pineal GlandPineal Gland
Found on the third ventricle of the brain
Secretes melatonin
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Helps establish the body’s wake and sleepcycles
May have other as-yet-unsubstantiatedfunctions
ThymusThymus
Located posterior to the sternum inupper thorax
Largest in infants and children
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Largest in infants and children
Produces thymosin
Matures some types of white blood cells
Important in developing the immune system
Hormones of the OvariesHormones of the Ovaries
Estrogens
Produced by Graafian follicles of the ovariesor the placenta
Stimulates the development of secondaryfemale characteristics
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female characteristics
Matures female reproductive organs
Helps prepare the uterus to receive a fertilizedegg
Helps maintain pregnancy
Prepares the breasts to produce milk
Hormones of the OvariesHormones of the Ovaries
Progesterone
Produced by the corpus luteum
Acts with estrogen to bring about the
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Acts with estrogen to bring about themenstrual cycle
Helps in the implantation of an embryo inthe uterus
Hormones of the TestesHormones of the Testes
Interstitial cells of testes are hormone-producing
Produce several androgens
Testosterone is the most importantandrogen
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androgen
Responsible for adult male secondary sexcharacteristics
Promotes growth and maturation of malereproductive system
Required for sperm cell production
Other HormoneOther Hormone--Producing TissuesProducing Tissuesand Organsand Organs
Parts of the small intestine
Parts of the stomach
Kidneys
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Heart
Placenta – temporary organ
Some tumors
Many other areas have scattered endocrinecells
Endocrine Function of the PlacentaEndocrine Function of the Placenta
Produces hormones that maintain thepregnancy
Some hormones play a part in the
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Some hormones play a part in thedelivery of the baby
Produces human chorionicgonadotropin (HCG) in addition toestrogen, progesterone, and otherhormones
Developmental Aspects of theDevelopmental Aspects of theEndocrine SystemEndocrine System
Most endocrine organs operate smoothlyuntil old age
Menopause is brought about by lack ofefficiency of the ovaries
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efficiency of the ovaries
Problems associated with reduced estrogenare common – osteoporosis
Growth hormone production declines with age
Many endocrine glands decrease output withage