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9. The Endocrine System. The Endocrine System. Second controlling system of the body Nervous system is the fast-control system Uses chemical messengers (hormones) that are released into the blood Hormones control several major processes Reproduction Growth and development - PowerPoint PPT Presentation
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© 2012 Pearson Education, Inc.
PowerPoint® Lecture Slides Prepared by Patty Bostwick-Taylor,Florence-Darlington Technical College
C H A P T E R 9
The Endocrine System
© 2012 Pearson Education, Inc.
The Endocrine System
•Second controlling system of the body•Nervous system is the fast-control system
•Uses chemical messengers (hormones) that are released into the blood•Hormones control several major processes•Reproduction•Growth and development•Mobilization of body defenses•Maintenance of much of homeostasis•Regulation of metabolism
© 2012 Pearson Education, Inc.
Hormone Overview
•Hormones are produced by specialized cells
•Cells secrete hormones into extracellular fluids
•Blood transfers hormones to target sites
•These hormones regulate the activity of other cells
© 2012 Pearson Education, Inc.
The Chemistry of Hormones
•Hormones are classified chemically as
•Amino acid–based, which includes
•Proteins
•Peptides
•Amines
•Steroids—made from cholesterol
•Prostaglandins—made from highly active lipids
© 2012 Pearson Education, Inc.
Mechanisms of Hormone Action
•Hormones affect only certain tissues or organs (target cells or target organs)
•Target cells must have specific protein receptors
•Hormone-binding alters cellular activity
© 2012 Pearson Education, Inc.
Effects Caused by Hormones
•Changes in plasma membrane permeability or electrical state
•Synthesis of proteins, such as enzymes
•Activation or inactivation of enzymes
•Stimulation of mitosis
•Promotion of secretory activity
© 2012 Pearson Education, Inc.
The Chemistry of Hormones
•Two mechanisms in which hormones act
•Direct gene activation
•Second-messenger system
© 2012 Pearson Education, Inc.
Direct Gene Activation (Steroid Hormone Action)•Diffuse through the plasma membrane of target cells
•Enter the nucleus
•Bind to a specific protein within the nucleus
•Bind to specific sites on the cell’s DNA
•Activate genes that result in synthesis of new proteins
© 2012 Pearson Education, Inc. Figure 9.1a
Steroidhormone
Cytoplasm Nucleus
Receptorprotein
Hormone-receptor complex
DNA
mRNA
Newprotein
Plasmamembraneof targetcell
(a) Steroid hormone action
1 2
3
4
5
6
© 2012 Pearson Education, Inc. Figure 9.1a, step 1
Steroidhormone
Cytoplasm Nucleus
1
© 2012 Pearson Education, Inc. Figure 9.1a, step 2
Steroidhormone
Cytoplasm Nucleus
Receptorprotein1 2
© 2012 Pearson Education, Inc. Figure 9.1a, step 3
Steroidhormone
Cytoplasm Nucleus
Receptorprotein
Hormone-receptor complex
1 2
3
© 2012 Pearson Education, Inc. Figure 9.1a, step 4
Steroidhormone
Cytoplasm Nucleus
Receptorprotein
Hormone-receptor complex
DNA
1 2
3
4
© 2012 Pearson Education, Inc. Figure 9.1a, step 5
Steroidhormone
Cytoplasm Nucleus
Receptorprotein
Hormone-receptor complex
DNA
mRNA
1 2
3
4
5
© 2012 Pearson Education, Inc. Figure 9.1a, step 6
Steroidhormone
Cytoplasm Nucleus
Receptorprotein
Hormone-receptor complex
DNA
mRNA
Newprotein
Plasmamembraneof targetcell
1 2
3
4
5
6
© 2012 Pearson Education, Inc.
Second-Messenger System (Nonsteroid Hormone Action)•Hormone binds to a membrane receptor
•Hormone does not enter the cell
•Sets off a series of reactions that activates an enzyme
•Catalyzes a reaction that produces a second-messenger molecule (such as cAMP)
•Oversees additional intracellular changes to promote a specific response
© 2012 Pearson Education, Inc. Figure 9.1b
Nonsteroidhormone (first messenger)
Cytoplasm
Enzyme
Receptorprotein
Plasma membraneof target cell
Secondmessenger
Effect on cellular function,
such as glycogenbreakdown
(b) Nonsteroid hormone action
ATP
cAMP
12
3
4
© 2012 Pearson Education, Inc. Figure 9.1b, step 1
Nonsteroidhormone (first messenger)
Cytoplasm
Receptorprotein
1
© 2012 Pearson Education, Inc. Figure 9.1b, step 2
Nonsteroidhormone (first messenger)
Cytoplasm
Enzyme
Receptorprotein
12
© 2012 Pearson Education, Inc. Figure 9.1b, step 3
Nonsteroidhormone (first messenger)
Cytoplasm
Enzyme
Receptorprotein
Secondmessenger
ATP
cAMP
12
3
© 2012 Pearson Education, Inc. Figure 9.1b, step 4
Nonsteroidhormone (first messenger)
Cytoplasm
Enzyme
Receptorprotein
Secondmessenger
Effect on cellular function,
such as glycogenbreakdown
ATP
cAMP
12
3
4
Plasma membraneof target cell
© 2012 Pearson Education, Inc.
Control of Hormone Release
•Hormone levels in the blood are mostly maintained by negative feedback
•A stimulus or low hormone levels in the blood triggers the release of more hormone
•Hormone release stops once an appropriate level in the blood is reached
© 2012 Pearson Education, Inc.
Hormonal Stimuli of Endocrine Glands
•Most common stimuli
•Endocrine glands are activated by other hormones
•Examples:
•Anterior pituitary hormones travel to target glands, such as the thyroid gland, to prompt the release of a particular hormone, such as thyroid hormone
© 2012 Pearson Education, Inc. Figure 9.2a
(a) Hormonal stimulus
The hypothalamus secretes hormones that…
Hypothalamus
…stimulatethe anteriorpituitary gland to secretehormonesthat…
Anteriorpituitarygland
Thyroidgland
Adrenalcortex
Gonad(Testis)
…stimulate other endocrine
glands to secrete hormones
1
2
3
© 2012 Pearson Education, Inc.
Humoral Stimuli of Endocrine Glands
•Changing blood levels of certain ions stimulate hormone release•Humoral indicates various body fluids such as blood and bile•Examples:•Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels• Insulin is produced in response to changing levels of blood glucose levels
© 2012 Pearson Education, Inc. Figure 9.2b
Capillary blood contains lowconcentration of Ca2+, whichstimulates…
…secretion of parathyroid hormone (PTH) by parathyroidglands
1
(b) Humoral stimulus
Capillary(low Ca2+
in blood)
Parathyroidglands PTH
2
Parathyroidglands
Thyroid gland(posterior view)
© 2012 Pearson Education, Inc.
Neural Stimuli of Endocrine Glands
•Nerve impulses stimulate hormone release
•Most are under the control of the sympathetic nervous system
•Examples:
•The release of norepinephrine and epinephrine by the adrenal medulla
© 2012 Pearson Education, Inc. Figure 9.2c
Preganglionic sympatheticfiber stimulates adrenal medulla cells…
…to secrete catecholamines(epinephrine and norepinephrine)
1
(c) Neural stimulus
CNS (spinal cord)
Preganglionicsympathetic fibers
Capillary
Medulla ofadrenalgland
2
© 2012 Pearson Education, Inc.
Major Endocrine Organs
•Pituitary gland
•Thyroid gland
•Parathyroid glands
•Adrenal glands
•Pineal gland
•Thymus gland
•Pancreas
•Gonads (Ovaries and Testes)
•Hypothalamus
© 2012 Pearson Education, Inc. Figure 9.3
Pineal gland
HypothalamusPituitary gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Ovary (female)
Testis (male)
© 2012 Pearson Education, Inc.
Pituitary Gland
•Size of a pea
•Hangs by a stalk from the hypothalamus in the brain
•Protected by the sphenoid bone
•Has two functional lobes
•Anterior pituitary—glandular tissue
•Posterior pituitary—nervous tissue
•Often called the “master endocrine gland”
© 2012 Pearson Education, Inc.
Hormones of the Anterior Pituitary
•Six anterior pituitary hormones
•Two affect non-endocrine targets
•Growth hormone
•Prolactin
•Four stimulate other endocrine glands (tropic hormones)
•Thyroid-stimulating hormone (thyrotropic hormone)
•Adrenocorticotropic hormone
•Two gonadotropic hormones
© 2012 Pearson Education, Inc.
Hormones of the Anterior Pituitary
•Characteristics of all anterior pituitary hormones
•Proteins (or peptides)
•Act through second-messenger systems
•Regulated by hormonal stimuli, mostly negative feedback
© 2012 Pearson Education, Inc. Figure 9.4
Releasing hormonessecreted into portalcirculation
Anterior pituitary
Hypophysealportal system
Growth hormone (GH)
Bones and muscles Prolactin (PRL)
Mammaryglands
Follicle-stimulatinghormone (FSH)and luteinizinghormone (LH)
Posterior pituitary
Hypothalamus
Adrenocorticotropichormone (ACTH)
Adrenal cortexThyrotropichormone (TH)
Thyroid
Testes or ovaries
HypothalamusHypothalamus
© 2012 Pearson Education, Inc.
Hormones of the Anterior Pituitary
•Growth hormone
•General metabolic hormone
•Major effects are directed to growth of skeletal muscles and long bones
•Plays a role in determining final body size
•Causes amino acids to be built into proteins
•Causes fats to be broken down for a source of energy
© 2012 Pearson Education, Inc.
Hormones of the Anterior Pituitary
•Growth hormone (GH) disorders
•Pituitary dwarfism results from hyposecretion of GH during childhood
•Gigantism results from hypersecretion of GH during childhood
•Acromegaly results from hypersecretion of GH during adulthood
© 2012 Pearson Education, Inc.
Pituitary dwarf (left), Giant (center), Normal height woman (right)
Figure 9.5
© 2012 Pearson Education, Inc.
Hormones of the Anterior Pituitary
•Prolactin (PRL)
•Stimulates and maintains milk production following childbirth
•Function in males is unknown
•Adrenocorticotropic hormone (ACTH)
•Regulates endocrine activity of the adrenal cortex
•Thyroid-stimulating hormone (TSH)
• Influences growth and activity of the thyroid gland
© 2012 Pearson Education, Inc.
Hormones of the Anterior Pituitary
•Gonadotropic hormones
•Regulate hormonal activity of the gonads
•Follicle-stimulating hormone (FSH)
•Stimulates follicle development in ovaries
•Stimulates sperm development in testes
•Luteinizing hormone (LH)
•Triggers ovulation of an egg in females
•Stimulates testosterone production in males
© 2012 Pearson Education, Inc.
Pituitary–Hypothalamus Relationship
•Hormonal release is regulated by releasing and inhibiting hormones produced by the hypothalamus•Hypothalamus produces two hormones•These hormones are transported to neurosecretory cells of the posterior pituitary•Oxytocin•Antidiuretic hormone
•The posterior pituitary is not strictly an endocrine gland, but does release hormones
© 2012 Pearson Education, Inc.
Hormones of the Posterior Pituitary
•Oxytocin
•Stimulates contractions of the uterus during labor, sexual relations, and breastfeeding
•Causes milk ejection in a nursing woman
© 2012 Pearson Education, Inc.
Hormones of the Posterior Pituitary
•Antidiuretic hormone (ADH)
• Inhibits urine production by promoting water reabsorption by the kidneys
• In large amounts, causes vasoconstriction leading to increased blood pressure
•Also known as vasopressin
© 2012 Pearson Education, Inc. Figure 9.6
Opticchiasma
Axon terminals
Anterior lobeof the pituitary
ADH
Kidney tubules
Hypothalamicneurosecretorycells
Hypothalamus
Arterial blood supply
Posterior lobe
Capillary bed
Venous drainage
Oxytocin
Mammary glandsUterine muscles
© 2012 Pearson Education, Inc.
Thyroid Gland
•Found at the base of the throat
•Consists of two lobes and a connecting isthmus
•Produces two hormones
•Thyroid hormone
•Calcitonin
© 2012 Pearson Education, Inc. Figure 9.7a
Thyroid cartilage
Common carotidartery
Trachea
Brachiocephalic artery
Aorta
(a) Gross anatomy of the thyroid gland, anterior view
Epiglottis
Isthmus ofthyroid gland
Left subclavianarteryLeft lobe of thyroid gland
© 2012 Pearson Education, Inc.
Thyroid Gland
•Thyroid hormone
•Major metabolic hormone
•Composed of two active iodine-containing hormones
•Thyroxine (T4)—secreted by thyroid follicles
•Triiodothyronine (T3)—conversion of T4 at target tissues
© 2012 Pearson Education, Inc. Figure 9.7b
Colloid-filledfollicles Follicle cells
Parafollicular cell
(b) Photomicrograph of thyroid gland follicles (125×)
© 2012 Pearson Education, Inc.
Thyroid Gland
•Thyroid hormone disorders•Goiters •Thyroid gland enlarges due to lack of iodine•Salt is iodized to prevent goiters
•Cretinism•Caused by hyposecretion of thyroxine•Results in dwarfism during childhood
© 2012 Pearson Education, Inc. Figure 9.8
© 2012 Pearson Education, Inc.
Thyroid Gland
•Thyroid hormone disorders (continued)
•Myxedema
•Caused by hypothyroidism in adults
•Results in physical and mental slugishness
•Graves’ disease
•Caused by hyperthyroidism
•Results in increased metabolism, heat intolerance, rapid heartbeat, weight loss, and exophthalmos
© 2012 Pearson Education, Inc. Figure 9.9
© 2012 Pearson Education, Inc.
Thyroid Gland
•Calcitonin
•Decreases blood calcium levels by causing its deposition on bone
•Antagonistic to parathyroid hormone
•Produced by parafollicular cells
•Parafollicular cells are found between the follicles
© 2012 Pearson Education, Inc. Figure 9.7b
Colloid-filledfollicles Follicle cells
Parafollicular cell
(b) Photomicrograph of thyroid gland follicles (125×)
© 2012 Pearson Education, Inc.
Parathyroid Glands
•Tiny masses on the posterior of the thyroid
•Secrete parathyroid hormone (PTH)
•Stimulate osteoclasts to remove calcium from bone
•Stimulate the kidneys and intestine to absorb more calcium
•Raise calcium levels in the blood
© 2012 Pearson Education, Inc. Figure 9.10
Calcitonin
Thyroid glandreleases calcitonin.
StimulusRising bloodCa2+ levels
Calcium homeostasis of blood: 9–11 mg/100 ml
Osteoclastsdegrade bonematrix andrelease Ca2+ into blood.
BALANCE
IMBALANCE
IMBALANCE
Calcitoninstimulatescalcium saltdeposit in bone.
StimulusFalling bloodCa2+ levels
BALANCE
Parathyroidglands releaseparathyroidhormone (PTH).
Thyroidgland
Parathyroidglands
PTH
© 2012 Pearson Education, Inc.
Adrenal Glands
•Sit on top of the kidneys
•Two regions
•Adrenal cortex—outer glandular region has three layers
•Mineralocorticoids secreted by outermost layer
•Glucocorticoids secreted by middle layer
•Sex hormones secreted by innermost layer
•Adrenal medulla—inner neural tissue region
© 2012 Pearson Education, Inc. Figure 9.11
Adrenal gland
Kidney
Adrenal gland• Medulla
Kidney
Me
du
lla
Co
rte
x
CapsuleMineralocorticoid-secreting area
Glucocorticoid-secreting area
Sex hormonesecreting area
Adrenalmedulla
Adrenalcortex
• Cortex
© 2012 Pearson Education, Inc.
Hormones of the Adrenal Cortex
•Mineralocorticoids (mainly aldosterone)
•Produced in outer adrenal cortex
•Regulate mineral content in blood
•Regulate water and electrolyte balance
•Target organ is the kidney
•Production stimulated by renin and aldosterone
•Production inhibited by atrial natriuretic peptide (ANP)
© 2012 Pearson Education, Inc. Figure 9.12
Decreased Na+ or
increased K+ in blood
Decreasedblood volumeand/or bloodpressure
Kidney
ReninIndirectstimulatingeffect viaangiotensin
Angiotensin II
Directstimulatingeffect
Increased absorptionof Na+ and water;
increased K+ excretion
Increased bloodvolume andblood pressure
Enhanced secretion of aldosterone targets kidney tubules
Mineralocorticoid-producing part of adrenal cortex
Inhibitoryeffect
Atrial natriureticpeptide (ANP)
ACTH
Heart
Increasedblood pressureor blood volume
Anterior pituitary
Corticotropin-releasing hormone
Hypothalamus
Stress
© 2012 Pearson Education, Inc.
Hormones of the Adrenal Cortex
•Glucocorticoids (including cortisone and cortisol)
•Produced in the middle layer of the adrenal cortex
•Promote normal cell metabolism
•Help resist long-term stressors
•Released in response to increased blood levels of ACTH
© 2012 Pearson Education, Inc. Figure 9.13
Short term
Spinal cord
Catecholamines(epinephrine and norepinephrine)
Adrenalmedulla
1. Increased heart rate2. Increased blood pressure3. Liver converts glycogen to glucose and releases glucose to blood4. Dilation of bronchioles5. Changes in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity6. Increased metabolic rate
1. Retention of sodium and water by kidneys2. Increased blood volume and blood pressure
1. Proteins and fats converted to glucose or broken down for energy2. Increased blood sugar3. Suppression of immune system
Short-term stress response Long-term stress response
Preganglionicsympatheticfibers
Nerve impulses
Hypothalamus
More prolongedStress
Releasing hormones
Corticotropic cells ofanterior pituitary
ACTH Adrenalcortex
Mineralocorticoids Glucocorticoids
© 2012 Pearson Education, Inc.
Hormones of the Adrenal Cortex
•Sex hormones
•Produced in the inner layer of the adrenal cortex
•Small amounts are made throughout life
•Mostly androgens (male sex hormones) are made but some estrogens (female sex hormones) are also formed
© 2012 Pearson Education, Inc.
Adrenal Glands
•Adrenal cortex disorders
•Addison’s disease
•Results from hyposecretion of all adrenal cortex hormones
•Bronze skin tone, muscles are weak, burnout, susceptibility to infection
•Hyperaldosteronism
•May result from an ACTH-releasing tumor
•Excess water and sodium are retained leading to high blood pressure and edema
© 2012 Pearson Education, Inc.
Adrenal Glands
•Adrenal cortex disorders
•Cushing’s syndrome
•Results from a tumor in the middle cortical area of the adrenal cortex
• “Moon face,” “buffalo hump” on the upper back, high blood pressure, hyperglycemia, weakening of bones, depression
•Masculinization
•Results from hypersecretion of sex hormones
•Beard and male distribution of hair growth
© 2012 Pearson Education, Inc.
Hormones of the Adrenal Medulla
•Produces two similar hormones (catecholamines)
•Epinephrine (adrenaline)
•Norepinephrine (noradrenaline)
•These hormones prepare the body to deal with short-term stress (“fight or flight”) by
• Increasing heart rate, blood pressure, blood glucose levels
•Dilating small passageways of lungs
© 2012 Pearson Education, Inc. Figure 9.11
Adrenal gland
Kidney
Adrenal gland• Medulla
Kidney
Me
du
lla
Co
rte
x
CapsuleMineralocorticoid-secreting area
Glucocorticoid-secreting area
Sex hormonesecreting area
Adrenalmedulla
Adrenalcortex
• Cortex
© 2012 Pearson Education, Inc.
Pancreatic Islets
•The pancreas is a mixed gland and has both endocrine and exocrine functions
•The pancreatic islets produce hormones
• Insulin—allows glucose to cross plasma membranes into cells from beta cells
•Glucagon—allows glucose to enter the blood from alpha cells
•These hormones are antagonists that maintain blood sugar homeostasis
© 2012 Pearson Education, Inc. Figure 9.14a
Stomach
Pancreas(a)
© 2012 Pearson Education, Inc. Figure 9.14b
(b)
Pancreaticislets
Exocrinecells ofpancreas
© 2012 Pearson Education, Inc. Figure 9.14c
Capillaries
Exocrinecells ofpancreas
Cord of beta (β) cells secretinginsulin into capillaries
Alpha (α)cells
(c)
© 2012 Pearson Education, Inc. Figure 9.15
Uptake of glucosefrom blood isenhanced in mostbody cells
Tissue cells
Glucose GlycogenPancreas
InsulinInsulin-secreting cellsof the pancreasactivated; releaseinsulin into the blood
Elevated bloodsugar level
Stimulus Bloodglucose level(e.g., aftereating fourjelly doughnuts)
Blood glucose risesto homeostaticset point; stimulusfor glucagonrelease diminishes
Liver breaksdown glycogenstores andreleasesglucose to theblood
Glucose Glycogen
LiverGlucagon
Glucagon-releasingcells of pancreasactivated; releaseglucagon into blood
Low blood sugar level
Stimulus Blood glucoselevel (e.g., afterskipping a meal)
BALANCE: Normal blood glucose level (about 90 mg/100 ml)
IMBALANCE
Liver takes upglucose and storesas glycogen
Blood glucosefalls to homeostaticset point; stimulusfor insulin releasediminishes
IMBALANCE
© 2012 Pearson Education, Inc.
Pineal Gland
•Found on the third ventricle of the brain
•Secretes melatonin
•Helps establish the body’s wake and sleep cycles
•Believed to coordinate the hormones of fertility in humans
© 2012 Pearson Education, Inc. Figure 9.3
Pineal gland
HypothalamusPituitary gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Ovary (female)
Testis (male)
© 2012 Pearson Education, Inc.
Thymus Gland
•Located posterior to the sternum
•Largest in infants and children
•Produces thymosin
•Matures some types of white blood cells
• Important in developing the immune system
© 2012 Pearson Education, Inc.
Gonads
•Ovaries
•Produce eggs
•Produce two groups of steroid hormone
•Estrogens
•Progesterone
•Testes
•Produce sperm
•Produce androgens, such as testosterone
© 2012 Pearson Education, Inc. Figure 9.3
Pineal gland
HypothalamusPituitary gland
Thyroid gland
Parathyroid glands
Thymus
Adrenal glands
Pancreas
Ovary (female)
Testis (male)
© 2012 Pearson Education, Inc.
Hormones of the Ovaries
•Estrogens
•Stimulate the development of secondary female characteristics
•Mature female reproductive organs
•With progesterone, estrogens also
•Promote breast development
•Regulate menstrual cycle
© 2012 Pearson Education, Inc.
Hormones of the Ovaries
•Progesterone
•Acts with estrogen to bring about the menstrual cycle
•Helps in the implantation of an embryo in the uterus
•Helps prepare breasts for lactation
© 2012 Pearson Education, Inc.
Hormones of the Testes
•Produce several androgens
•Testosterone is the most important androgen
•Responsible for adult male secondary sex characteristics
•Promotes growth and maturation of male reproductive system
•Required for sperm cell production
© 2012 Pearson Education, Inc.
Other Hormone-Producing Tissues and Organs
•Parts of the small intestine
•Parts of the stomach
•Kidneys
•Heart
•Many other areas have scattered endocrine cells
© 2012 Pearson Education, Inc.
Endocrine Function of the Placenta
•Produces hormones that maintain the pregnancy
•Some hormones play a part in the delivery of the baby
•Produces human chorionic gonadotropin (hCG) in addition to estrogen, progesterone, and other hormones
© 2012 Pearson Education, Inc.
•Most endocrine organs operate smoothly until old age•Menopause is brought about by lack of efficiency of the ovaries•Problems associated with reduced estrogen are common•Growth hormone production declines with age•Many endocrine glands decrease output with age
Developmental Aspects of the Endocrine System