17-chapt20 lecture anim - Nassau Community College. – Insulin lowers the blood sugar level, while...
Transcript of 17-chapt20 lecture anim - Nassau Community College. – Insulin lowers the blood sugar level, while...
8/30/2013
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Chapter 20
Lecture and
Animation Outline
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20.1 Overview of the Endocrine System
• The endocrine system consists of glands and tissues that secrete hormones.
• Hormones are chemicals that affect other glands
or tissues, located far away from the sites of hormone production.
• Like the nervous system, the endocrine system influences other organ systems in maintaining
homeostasis.
– Influence on cellular metabolism, growth and development
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20.1 Overview of the Endocrine System
• Growth factors – hormones that promote
cell division and mitosis
• Local hormones – not carried by the blood
– Affect tissues locally
– Ex: prostaglandins
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20.1 Overview of the Endocrine System
• Endocrine glands
– Have no ducts
– Secrete hormones into tissue fluid
– Hormones diffuse into the bloodstream
• Exocrine glands
– Secrete their products through ducts
• Ex: salivary glands send saliva to the mouth through salivary ducts
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Hormones and Homeostasis
• Homeostasis requires cooperation between
the endocrine and nervous systems.
Endocrine System Nervous System
Secretes hormones into
the blood
Transmits nerve impulses
Slower response Faster response
More prolonged response Less prolonged response
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Hormones and Homeostasis
• The blood concentration of a substance prompts an endocrine gland to secrete its
hormones.
– Ex: The parathyroid gland secretes a hormone when blood Ca+2 level falls below normal.
– Osteoclasts respond to hormone by slowly
releasing Ca+2 from bone.
– It take time for the response, but it is long-lasting.
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The Endocrine SystemCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
hypothalamus
pituitary gland(hypophysis)
thymus gland
thyroid gland
parathyroid glands(posterior surface o f thyroid)
adrenal glands
pancreas
ovary (female)
testis(male)
pineal gland
Figure 20.1
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Hormones and Homeostasis
• Production of most hormones controlled by
two things
– Negative feedback
• Sensitive to either the
condition it regulates or the blood level of the hormone it
is producing
– Action of other hormones
• Insulin and glucagon
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
stimulus
Sensor
Homeostasis
response to stimulusdata to control center
change of internal
conditionsnegative feedback
and return to normal
Control center
Effect
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Hormones and Homeostasis
• Example of negative feedback
– As the blood glucose level rises, the pancreas
secretes insulin.
– Insulin causes the liver to store glucose, and glucose is removed from the blood.
– The stimulus for insulin production is, thereby,
inhibited.
– The pancreas stops secreting insulin.
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Hormones and Homeostasis
• Hormone regulation by release of an
antagonistic hormone
– The effect of insulin is offset by the secretion of glucagon.
– Insulin lowers the blood sugar level, while
glucagon raises it.
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The Action of Hormones
• Hormones act on target cells.
– May increase uptake of a substance
– May bring about alteration of structure of target cell
• Hormones fall into two chemical classes.
– Peptide hormones – peptides, proteins, glycoproteins or modified amino acids
– Steroid hormones – same complex of four rings, but varying side chains
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The Action of Hormones
• Hormones function as chemical signals.
– Chemical signals - a means of communication between cells, body parts, or even individuals
• Typically affect the metabolism of target cells with
appropriate receptors
– For peptide hormones, receptors on cell surface
– For steroid hormones, receptors inside cell (cytoplasm or
nucleus)
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
receptors
capillary
hormone
target cells
Figure 20.2
nontarget cell
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The Action of Hormones
• The peptide hormone initiates a chemical signaling process after binding to its receptor; it serves as the first messenger.
• The activated receptor leads to the production of a second messenger, (cAMP is most common).
• The 2nd messenger sets in motion an enzymatic cascade.
• Each enzyme, in turn, activates another enzyme.
• During each step in the cascade, more reactions occur (1000-fold response possible).
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Peptide
Hormone Action
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ATP
1. Epinephrine binds to a
receptor in the plasma
membrane.
capillary
epinephrine
(first messenger)
activated
enzymereceptor protein
2. Binding leads to
activation of an
enzyme that changes
ATP to cAMP.
cAMP
(second messenger)
glucose
(leaves cell
and goes
to blood)
3. cAMP activates an
enzyme cascade.
plasma
membrane
4. Many molecules of
glycogen are broken
down to glucose,
which enters thebloodstream.
glycogen
Figure 20.3
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The Action of Hormones
• The steroid hormone has an alternate way because it can diffuse through the target cell membrane.
• The hormone can bind to its receptor either in the
cytoplasm or nucleus.
• The hormone receptor complex then binds to DNA to activate transcription of a certain gene into mRNA.
• mRNA translation results in enzymes or other
proteins that can carry out a response to the hormone.
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Steroid Hormone
Action
2. Hormone binds
to receptor inside
nucleus.
nucleus
cytoplasm
1. Hormone diffuses
through plasma
membrane because
it is lipid soluble.
steroid
hormone
plasma
membrane
DNAreceptor
protein
mRNA
protein
ribosome
mRNA
4. mRNA moves to
ribosomes, and protein
synthesis occurs.
3. Hormone-receptor
complex activates
gene and synthesis
of a specific mRNAmolecule.
Figure 20.4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Pheromones
• Pheromones are chemical signals that act between individuals of the same species.
– Effects better known in animals other than humans
• Ex: female moths release an attractant that acts on male
moths even miles away
– Humans do produce pheromones
• Airborne chemicals released by scalp, oral cavity, axilla, genital areas
• Possibly plays role in mate attraction
• Axillary secretions can affect the menstrual cycle
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20.2 Hypothalamus and Pituitary Gland
• The hypothalamus regulates the internal environment in two ways.
– Through the autonomic nervous system
• Heartbeat, blood pressure, appetite, body temperature, water balance
– Through control of pituitary gland secretions
• Posterior pituitary
• Anterior pituitary
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Posterior Pituitary
• Neurons in the hypothalamus called neurosecretory
cells produce antidiuretic hormone (ADH) and
oxytocin.
– Hormones travel down axons and are stored in
axon terminals in the posterior pituitary.
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Posterior Pituitary
• ADH - Antidiuretic hormone
– Released from posterior pituitary in response to increased concentration of blood (not enough
water)
– Causes increased reabsorption of water in the kidneys
• As water reabsorption occurs, the blood concentration becomes normal and ADH is shut off.
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Posterior Pituitary
• Oxytocin
– Causes uterine contractions and milk letdown
during lactation
– Neurological impulses from pressure and irritation
of uterus causes oxytocin release
• Oxytocin causes contractions which causes more pressure and irritation� more oxytocin� more contractions
– An example of positive feedback
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Anterior Pituitary
• A portal system, consisting of two capillary networks connected by a vein, lies between the
hypothalamus and the anterior pituitary.
– Hypothalamus controls the anterior pituitary by
producing
• Hypothalamic-releasing hormones
– Stimulates the anterior pituitary gland to release certain
hormones
• Hypothalamic-inhibiting hormones
– Prevents the secretion of certain hormones
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Anterior Pituitary
• Three anterior pituitary hormones have target effects on other glands.
– Thyroid-stimulating hormone (TSH) stimulates the thyroid gland to produce thyroid hormones.
– Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to produce glucocorticoids.
– Gonadotrophic hormones (FSH and LH) stimulate the gonads to produce estrogen and testosterone.
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20.2 Hypothalamus and
Pituitary Gland
• Anterior Pituitary
– In each instance, the blood level of the last hormone in the hypothalamus-anterior pituitary-target gland control system exerts negative feedback over secretions of the first two structures.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
target gland
feedbackinhibits
release ofhormone 1
feedbackinhibits
release ofhormone 2
target gland hormone(hormone 3)
stimulating hormone(hormone 2)
anterior pituitary
releasing hormone(hormone 1)
hypothalamus
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Anterior Pituitary
• Three anterior pituitary hormones do not affect other glands.
– Prolactin (PRL) stimulates the mammary glands to synthesize milk.
– Melanocyte-stimulating hormone (MSH) stimulates the pigment-producing melanocytes of the skin.
– Growth hormone (GH) stimulates bone and muscle growth and increases protein synthesis and fat metabolism.
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Hypothalamus and the PituitaryCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1. Neurosecretory cells produce
hypothalamic- releasing and
hypothalamic-inhibiting hormones.
2. These hormones are secreted into
a portal system.
3. Each type of hypothalamic
hormone either stimulates or
inhibits production and secretionof an anterior pituitary hormone.
4. The anterior pituitary secretes
its hormones into the bloodstream,
which then delivers them tospecific cells, tissues, and glands.
Adrenal cortex:
adrenocorticotropic
hormone (ACTH)
Thyroid:
thyroid-stimulating
hormone (TSH)Anterior pituitary
optic
chiasma
1. Neurosecretory cells produce
ADH and oxytocin.
2. These hormones move down
axons to axon endings.
3. When appropriate, ADH and
oxytocin are secreted from axon
endings into the bloodstream.
portal system
Posterior pituitary
Kidney tubules:
antidiuretic
hormone (ADH)
Smooth muscle
in uterus:
oxytocin
Mammary glands:
oxytocin
Ovaries, testes:
gonadotropic
hormones (FSH, LH)
Bones, tissues:
growth hormone
(GH)
Mammary glands:
pr olactin (PRL)
hypothalamus
Figure 20.5
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20.3 Thyroid and Parathyroid Glands
• The thyroid gland is a large gland located
in the neck.
– Attached to the trachea just below larynx
• The parathyroid glands are embedded in
the posterior surface of the thyroid gland.
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Thyroid Gland
• Thyroid gland has many follicles, each a small spherical structure of thyroid cells that produce
– Triiodothyronine (T3) (three iodine atoms)
– Thyroxine (T4) (four iodine atoms)
• Thyroid requires iodine to produce these hormones
– Iodine deficiency causes simple goiter
• T3 and T4 increase metabolic rate
– Stimulate most body cells to metabolize glucose and utilize more energy
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Thyroid Gland
• Thyroid gland also produces calcitonin
– Calcium-regulating hormone
– Produced in response to increased blood calcium levels
– Causes uptake of calcium by bone
• Calcium is important in muscle contraction, nerve
conduction, and blood clotting
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Parathyroid Gland
• Parathyroid glands produce parathyroid hormone (PTH)
– Causes an increase in blood calcium and a decrease in blood phosphate
– Increases osteoclast activity and the reabsorption of calcium by the kidneys
• Also stimulates activation of vitamin D needed for calcium absorption in the digestive tract
– When blood calcium levels increase, PTH is shut off
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Regulation of Blood
Calcium Level
calcitonin
Bones
take up Ca2+
from blood.
Thyroid gland
secretes
calcitonininto blood.
Blood Ca2+
lowers.
Homeostasis (normal blood Ca2+)
Blood Ca2+
rises.
activated
vitamin D
Parathyroid
glands
release PTHinto blood.
parathyroid
hormone
(PTH)
Intestines
absorb Ca2+
from digestivetract.
Kidneys
reabsorb Ca2+
from kidneytubules.
Bones
release Ca2+
into blood.
Figure 20.6
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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20.4 Adrenal Glands
• The adrenal glands sit atop the kidneys.
– Two parts of the adrenal gland that function independently
– Adrenal medulla (outer portion)
• Under the control of the nervous system
– Adrenal cortex (inner portion)
• Under the control of adrenocorticotropic hormone (ACTH), an anterior pituitary hormone
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Adrenal Medulla
• The hypothalamus initiates nerve impulses by way of the brain stem, spinal cord, and sympathetic
nerves to the adrenal medulla.
• The adrenal medulla secretes two hormones
– Epinephrine (adrenaline)
– Norepinephrine (NE)
• Epinephrine and norepinephrine bring rapid short-term changes.
– Response to stress (fight or flight response)
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Adrenal Cortex
• Hormones of the adrenal cortex result in long-term changes.
– Two types of hormones
• Glucocorticoids
– Regulate carbohydrate, protein, and fat metabolism leading to an increase in blood glucose level
• Mineralocorticoids
– Regulate salt and water balance leading to an
increases in blood volume and blood pressure
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Adrenal Cortex: Glucocorticoids
• Cortisol is the principal glucocorticoid hormone stimulated by ACTH.
• Actions
– Promotes breakdown of muscle proteins to amino acids
• Liver uses amino acids to make glucose
– Promotes metabolism of fatty acids, spares glucose
– Overall: Promotes a rise in blood glucose
• Beneficial under stress
– Counteracts inflammatory response• Can also suppress the immune system
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Adrenal Cortex: Mineralocorticoids
• Mineralocorticoid secretion is not controlled
by the anterior pituitary.
– Aldosterone is the principal mineralocorticoid hormone that targets the kidney.
• Increases absorption of Na+, excretion of K+
• Regulates blood volume and pressure
• Secretion controlled through release of renin from the kidney
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Adrenal Cortex: Mineralocorticoids
• Renin
– Released when blood Na+ levels and blood pressure are low
– Activates angiotensinogen to angiotensin I
– Converts angiotensin I to angiotensin II by enzyme in lung capillaries
– Angiotensin II stimulates adrenal cortex to release aldosterone
– Effect: Angiotensin II constricts arterioles
Aldosterone causes the kidneys to reabsorb sodium.
Blood pressure rises.
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Regulation of
Blood Pressure
and Volume
atrial natriuretic
hormone (ANH)
Heart secretes
atrial natriuretic
hormone (ANH)into blood.
Kidneys excrete
Na+ and water
in urine.
Blood pressure
drops.
Homeostasis (normal blood pressure)
Blood pressure
rises.
Kidneys
reabsorb Na+
and water fromkidney tubules.
Kidneys secrete
renin into blood.
renin
angiotensin
I and II
Adrenal cortex
secretes
aldosteroneinto blood.
aldosterone
Figure 20.8
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Adrenal Cortex: Mineralocorticoids
• Atrial natriuretic hormone (ANH)
– Produced when atria of the heart are stretched
• Represents an increase in blood volume
– Inhibits the release of aldosterone
– Results in natriuresis: excretion of Na+ in the urine
– Water follows passively so blood volume and
therefore pressure decreases
44
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
hypothalamus
epinephrine
Stress Response:
Long Term
Protein and fat metab-
olism instead of
glucose breakdown.
Reduction of
inflammation; immune
cells are suppressed.
Sodium ions and water
are reabsorbed by
kidney.
Blood volume and
pressure increase.
Glucocorticoids
Stress Response:
Short Term
Heartbeat and blood
pressure increase.
path of nerve
impulses
spinal cord
(cross section)
neurosecretory
cells produce
hypothalamic-
releasing
hormone
Mineralocorticoids
anterior
pituitary
secretes
ACTH
ACTH
Blood glucose level rises.
Muscles become
energized.
adrenal medulla adrenal cortexmineralocorticoids
glucocorticoids
stress
norepinephrine
neuron
cell body
Figure 20.7
Sympathetic Fibers
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20.5 Pancreas
• Pancreas is composed of two types of tissue
– The exocrine portion secretes digestive enzymes released into the small intestine by ducts.
– Pancreatic islets are the endocrine portion of the gland.
• Three types of endocrine islet cells
– Alpha cells produce glucagon
– Beta cells produce insulin
» Regulation of blood glucose levels
– Delta cells produce somatostatin
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20.5 Pancreas
• Insulin– Released after eating
– Stimulates uptake of glucose by cells• Especially muscle, liver, and adipose cells
• Decreases blood glucose
• Glucagon– Released before eating when glucose is low
– Targets liver and adipose tissue
– Increases blood glucose
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Regulation of
Blood Glucose
Level
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
insuli
n
Glucose levelrises.
After eating,
pancreas
secretes insulininto blood.
Before eating,
pancreas secretes
glucagon intoblood.
glucagon
Liver breaks
Down glycogen
to glucose.Glucose enters
blood.
Adipose tissue
breaks downfat.
Homeostasis (normal blood glucose)
Glucose level
drops.
Muscle cells
store glycogen
and build protein.
Adipose tissue
uses glucose
from blood toform fat.
Liver stores
glucose from
blood asglycogen.
Figure 20.9
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20.5 Pancreas
• Somatostatin
– Also known as growth hormone inhibiting hormone
– Also produced by cells in the stomach and small intestine
– Main effects
• Inhibit release of growth hormone by the anterior pituitary
• Suppress the release of various hormones produced by the digestive system, including insulin and glucagon
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20.6 Other Endocrine Glands
• The gonads are the testes in males and
the ovaries in females.
• The gonads are endocrine glands.
• Other glands and certain tissues also produce hormones.
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Testes and Ovaries
• Testes
– Produce sperm and androgens (e.g., testosterone)
– Responsible for male secondary sex characteristics
• Beard growth, enlargement of vocal cords and larynx
– Stimulate oil production by oil glands
– Involved in pattern baldness
– Responsible for increased muscle development
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Testes and Ovaries
• Some athletes take supplemental amounts of illegal anabolic steroids.
– Include testosterone or related chemicals
– Many side effects from taking anabolic steroids
• Acne
• Body odor
• Baldness
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The Side Effects of
Anabolic Steroid UseCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
deepening of voice in women
balding in men and
women; hair on face and
chest in women
breast enlargement in men and
breast reduction in women
liver
dysfunction
and cancer
kidney disease and
retention of fluids,
called "steroid bloat"
reduced testicular
size, low sperm count,
and impotency
stunted growth in
adolescents by causing
premature ossification
of growth plates
in women, increased
size of ovaries;
cessation of ovulation
and menstruation
high blood cholesterol and
atherosclerosis; high blood
pressure and damage to heart
severe acne
'roid mania–
delusions and hallucinations;
depression upon withdrawal
Figure 20.10
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Testes and Ovaries
• Ovaries
– Produce eggs, estrogen, and progesterone
– Estrogen
• Stimulates growth of uterus and vagina
• Required for egg maturation
• Responsible for secondary sex characteristics
– Breast development along with progesterone
– Fat distribution
– Body hair
– Progesterone
• Regulation of uterine cycle along with estrogen
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Thymus and Pineal Glands
• Thymus gland
– Largest and most active during childhood
– Secretes thymosins, hormones involved with maturation of T-lymphocytes
• Pineal gland
– Produces melatonin
• Involved with sleep/wake cycles and circadian rhythms
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Hormones from Other Tissues
• Some organs usually not considered endocrine glands can secrete hormones.
• The heart produces natriuretic hormone.
• The stomach and small intestine produce
hormones that regulate digestive secretions.
• Other tissues secrete hormones.
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Leptin
• Leptin
– Leptin is a protein hormone produced by adipose
tissue.
– Leptin stimulates the satiety center in the hypothalamus to signal that an individual has had enough to eat.
– It is thought that leptin in obese individuals may be ineffective.
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Growth Factors
• Growth factors• Stimulate mitosis in tissues
• Some released in blood, others act locally
– Granulocyte-macrophage colony-stimulating factor
• Produced by many different tissues
• Causes bone marrow stem cells to produce granulocytes
and macrophages
– Platelet-derived growth factor
• Wound healing
– Epidermal growth factor and nerve growth factor
• Wound healing
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Prostaglandins
• Prostaglandins
– Produced from arachidonic acid
– Act locally; effects depend on location
• Muscle contractions in uterus
• Mediation of pyrogens’ effects
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20.8 Disorders of the Endocrine System
• The endocrine glands play a major role in regulating the development and function of many
body systems.
• An increase or decrease in production of a hormone can cause significant disease.
• Cancer often causes an increase in hormone secretion by affecting the gland.
• Various conditions that destroy glands result in
decreased secretion of a hormone.
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Disorders of the Pituitary Gland
• Diabetes insipidus (DI)
– The posterior pituitary secretes too little ADH. (antidiuretic hormone)
• Large amounts of urine are produced, resulting in dehydration.
• Pituitary dwarfism
– Too little growth hormone is secreted by the anterior pituitary.
• Condition is characterized by small stature but normal proportions.
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Disorders of the Pituitary Gland
• Gigantism
– Excess growth hormone is produced during childhood.
– Gigantism also promotes the development of
diabetes mellitus.
Figure 20.11
62
Disorders of the Pituitary Gland
• Acromegaly
– Excess growth hormone in adulthood
– Long bones cannot grow, so the effect is
noticeable in the hands, feet, and facial bones
Figure 20.12
Age 9 Age 16 Age 33 Age 52
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(all): Reprinted from Clinical Pathological Conference, American Journal of Medicine, Vol. 20, page 133, “Acromegaly, Diabetes, Hypermetabolism, Proteinuria
and Heart Failure,” copyright 1956, with permission from Elsevier.
63
Disorders of the Pituitary Gland
• Cushing Syndrome
– Excess production of ACTH (usually by tumor)
– Adrenal cortex then produces excess cortisol
• Protein is metabolized, fat is deposited in the midsection
Before treatment Four months after treatment
Figure 20.13
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Disorders of the Thyroid, Parathyroid and Adrenal Glands
• Hypothyroidism
– Not enough thyroid hormone is produced.
– Failure of thyroid function in infancy or childhood results in congenital hypothyroidism.
• Individuals are short and stocky; mental retardation results if treatment does not begin within 1st two months of life
– Treatment consists of the administration of thyroid hormones.
65
a. Congenital hypothyroidism b. Simple goiter c. Exophthalmic goiter
affected eye
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a: © Medical-on-Line/Alamy; b: © Biophoto Associates/Photo Researchers, Inc.; c: © Dr. P. Marazzi/SPL/Photo Researchers, Inc.
66
Disorders of the Thyroid, Parathyroid and Adrenal Glands
• Hashimoto thyroiditis is a form of hypothyroidism that occurs in adults.
– The immune system produces antibodies that destroy the thyroid gland.
– Myxedma is a group of clinical symptoms in adults not treated for the condition.
• Symptoms include: weight gain, hair loss, constipation or slow heart rate
– Treatment is the administration of thyroid hormones.
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Disorders of the Thyroid, Parathyroid
and Adrenal Glands
• Goiter– Lack of dietary iodine
makes the thyroid unable to produce sufficient T3
and T4.
– The thyroid gland is consequently constantly stimulated by TSH.
– The result is an enlarged thyroid gland.
Figure 20.14b. Simple goiter
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Biophoto Associates/Photo Researchers, Inc.
68
Disorders of the Thyroid, Parathyroid
and Adrenal Glands
• Hyperthyroidism
– Results from oversecretion of thyroid hormones
• Graves disease arises from
antibodies reacting with the TSH receptor, mimicking
effect of TSH.
– Symptoms include
protruding eyes,
nervousness, hyperactivity, and
abnormal heart rhythms.
Figure 20.14
c. Exophthalmic goiter
affected eye
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Dr. P. Marazzi/SPL/Photo Researchers, Inc.
69
Disorders of the Thyroid, Parathyroid
and Adrenal Glands
• Disorders of the parathyroid
– Insufficient parathyroid production results in a drop in blood calcium levels.
– The body shakes from continuous muscle contraction (tetany).
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Disorders of the Thyroid, Parathyroid
and Adrenal Glands
• Disorders of the adrenal glands
– Addison disease
• The most common cause is destruction of the adrenal cortex by
the immune system.
• Symptoms include weakness, weight loss, abdominal pain, and
a bronzing of the skin.
• Decreased production of mineral corticoids can affect Na+ and K+ levels, which can adversely affect the heart.
Figure 20.15
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a: © Custom Medical Stock Photo; b: © NMSB/Custom Medical Stock Photos
a. b.
71
Diabetes Mellitus
• Diabetes mellitus
– Affects an estimated 25.8 million Americans, or 8.3% of the population (as of 2010)
– Affects ability to regulate glucose metabolism
• Type 1 sufferers do not produce enough insulin.
• Type 2 sufferers cannot use insulin produced.
– As blood glucose rises, glucose and water are lost in the
urine
– Cells do not take up the glucose
– Causes increased thirst, increased hunger
• A glucose tolerance test is often used for diagnosis.
72
Glucose Tolerance TestCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1 2 3
250
300
Blo
od
Glu
co
se
(m
g/1
00
ml)
150
50
100
200
renal threshold
diabeticnondiabetic
glucose
givenTime (hours)
Figure 20.16
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Diabetes Mellitus
• Two types of diabetes mellitus
– Type 1 – insulin-dependent• Lack of insulin may be due to exposure to environmental
agent, such as a virus, or an autoimmune condition.
• As cells break down fats for energy, ketones build up in
the blood.
– Ketoacidosis�coma�death
• Insulin overdose can cause hypoglycemia,
unconsciousness
– Immediate ingestion of glucose required to counteract
74
Diabetes Mellitus
• Two types of diabetes mellitus
– Type 2
• Insulin-resistant
• Linked to obesity - adipose tissue may produce a substance that impairs insulin receptor function
• Insulin levels often low - cells may not have sufficient insulin receptors
• Controlled by diet, exercise, medications
75
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Diabetes Mellitus
• Diabetics need to monitor their blood sugar several times daily, regardless of which diabetes
type they have.
• Monitoring is usually done by poking a finger to obtain blood drops to be tested using an external device.
• New testing devices are being introduced.
• Insulin pumps are replacing the needle and
syringe as an injection method.
77Figure 20.17b.
a.
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(both): Courtesy of Insulet Corporation
78
Diabetes Mellitus
• Long-term complication of diabetes
– Blindness
– Kidney disease
– Cardiovascular disorders
• Can lead to reduced blood flow to limbs (gangrene)
– Diabetic coma in pregnancy (if not managed)
• The child has a higher risk of being stillborn or dying shortly after birth.