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8/12/2019 Ch13 Endocrine
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The Endocrine System
chemical messages (hormones) that are released into
the blood
Hormones control several major processes
Reproduction - gametogenesis, sexual desire
Growth and development
Maintenance of homeostasis - salts, water, blood
pressure, RBCs
Regulation of metabolism - digestion, stress
responses
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Endocrine System Characteristics
Access to every cell
Each hormone acts only on specific cells(target cells) that have matching receptors
Endocrine control slower than nervous
system
Endocrine and nervous systems interact
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Classification of Hormones: Steroid
Steroid Hormones:
Lipid soluble, derived from cholesterol
Enter target cells
Activate specific genes to produce proteins
Slower acting: minutes to hours
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Steroid Hormones:
QuickTime™ and aCinepak decompressor
are needed to see this picture.
How does a steroid hormone cause changes in cells?
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Hormones: Nonsteroid
Amino acid-based hormones
proteins, peptides, amines
Water soluble
Bind to receptors on target cell surface Work via second messengers to activate
existing enzymes
Faster action: seconds to minutes
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Non-Steroid Hormones:
How does a non-steroid hormone cause changes in cells?
QuickTime™ and aCinepak decompressor
are needed to see this picture.
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Control of Hormone Release
Hormone levels are
maintained by negativefeedback
Low hormone levels or
a stimulus triggers therelease of more hormone
Hormone release stops
once an appropriate levelin the blood is reached
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1. Hormonal Stimulus
Endocrine glands are
activated by other
hormones Most common signal-
coordinates response of
several glands
Figure 9.2a
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2. Humoral Stimulus
Changing blood
levels of certain ionsstimulate hormone
release
PTH - to raise Ca++
Calcitonin - to
decrease Ca++
Insulin - to decrease
glucose
Figure 9.2b
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3. Neural Stimulus
Nerve impulses
stimulate hormonerelease
Usually by sympathetic
nervous system
Figure 9.2c
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Location of Major Endocrine Organs
Figure 9.3
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Pituitary - Hypothalamus Relationship
Release of anterior pituitary
hormones is controlled by
hormones from hypothalamus
Hypothalamus produces two
hormones that are stored in the
posterior pituitary
posterior pituitary releases
hormones when neurally
stimulated by hypothalamus
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Hormones of the Posterior Pituitary
Oxytocin
Stimulates contractions ofthe uterus during labor
Causes milk ejection
Antidiuretic hormone (ADH)
Can inhibit urine production
In large amounts, causes
vasoconstriction
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Hormones of the Anterior Pituitary
Six anterior pituitary
hormones; common
characteristics:
Proteins (or peptides)
Act through second-messenger systems
Regulated by
hormonal stimuli,
mostly negative
feedback
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Growth Hormone (GH)
General metabolic hormone
Major effects are directed to growth ofskeletal muscles and long bones
Causes amino acids to be built into proteins
Causes fats to be broken down for a source of
energy
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Functions of Other Anterior Pituitary
Hormones
Prolactin (PRL) Stimulates milk production following childbirth
Function in males is unknown
Adrenocorticotropic hormone (ACTH)
Regulates the adrenal cortex (affects salt,
glucose levels)
Thyroid-stimulating hormone (TSH)
Influences thyroid gland
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Functions of Other Anterior Pituitary
Hormones
Gonadotropic hormones - appear at puberty
Follicle-stimulating hormone (FSH)
Stimulates follicle development (ovaries)
and sperm development (testes)
Luteinizing hormone (LH)
Triggers ovulation
Stimulates testosterone production in males
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Thyroid Gland
Found at the base of the
throat
Produces two hormones
Thyroid hormone -
controls metabolism
Calcitonin - affects
Ca++ levels in blood
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Calcitonin
Decreases blood
calcium levels bycausing calcium
deposition in bone
(in children)
Antagonistic to PTH,
parathyroid hormone
Figure 9.9
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Adrenal Glands
Two glands
Cortex – outerglandular region in
three layers
Medulla – inner
neural tissue region
Sits on top of thekidneys
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Hormones of the Adrenal Cortex
Mineralocorticoids (mainly aldosterone)
Regulate mineral content in blood, water,and electrolyte balance via kidney action
Glucocorticoids (cortisone, cortisol)
Promote normal cell metabolism
Help resist long-term stressors
depress inflammatory response
Androgen, estrogen
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R l f th H th l d Ad l
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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 9.12
Roles of the Hypothalamus and Adrenal
Glands in the Stress Response
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Pancreatic Islets
Figure 9.13
Insulin – allows
glucose to cross
plasma membranesinto cells
Glucagon – allows
glucose to enter the blood
Somatostatin
pancreas is a mixed gland
islet cells produce hormones:
Di b
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Diabetes
Diabetes mellitus - “sweet siphon”
Type I - lack of insulin
juvenile
Type II - resistant to effects of insulin Adult onset
Oth H S
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Other Hormone Sources
Thymus: thymosin and thymopoietin, assist
maturation of T lymphocytes Pineal gland: melatonin
Heart: atrial natriuretic hormone (ANH)
Digestive system: gastrin, secretin,
cholecystokinin
Kidney: erythropoietin, renin