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Chapter 9
The Endocrine System
General Characteristics
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chemicals released by cells enter the
bloodstream
target specific cells/organs
regulated by negative feedback
goal is to preserve homeostasis
Endocrine System
Two types of glands in the body
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Exocrine - secrete products through a duct
−
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sweat, oil, salivary glands
Endocrine - release hormones into the blood or
lymph
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pituitary, pancreas, thyroid
Hormones
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chemical substances secreted that regulate
metabolic activity of cells
Hormones
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amino acid-based
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proteins
−
peptides
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amines
steroids
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derived from cholesterol
prostaglandins
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derived from lipids
Hormone Action
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change plasma membrane permeability or
electrical state
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synthesis of proteins/enzymes
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activation or inactivation of enzymes
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stimulation of mitosis
Hormone Action
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each hormone affects only target cells or
organs
specific protein receptors
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internal receptors
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plasma membrane
Hormone Action
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internal receptors
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diffuse through membrane
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result in mRNA translation of new protein
plasma membrane
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bind to membrane receptor (protein)
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produces a second messenger to effect changes
Hormone Action
What causes endocrine glands to
release hormones?
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negative feedback mechanisms
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hormone secretion is triggered
increase in hormone levels inhibit further release
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example: low blood Ca2+
Endocrine Organs
Pituitary Gland
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where?
two functional lobes
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anterior pituitary: glandular
posterior pituitary: nervous
Pituitary Gland
Anterior Pituitary
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releases hormones
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two affect non-endocrine organs
tropic hormones: stimulate other endocrine glands
to secrete hormones
all are proteins
Non-endocrine Anterior Pituitary
Hormones
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Growth hormone (GH)
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growth of skeletal muscles and long bones
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pituitary dwarfism
gigantism
Prolactin (PRL) - (pro = for; lact = milk)
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milk production
Tropic Anterior Pituitary Hormones
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Adrenocorticotropic hormone (ACTH)
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regulates cortex of adrenal gland
Thyroid-stimulating hormone (TSH)
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growth and activity of thyroid
Gonadotropic Anterior Pituitary
Hormones
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regulate hormonal activity of gonads (ovaries
and testes)
follicle-stimulating hormone (FSH)
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♀ stimulates follicle development in ovaries
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♂ stimulates sperm development in testes
luteinizing hormone (LH)
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♀ triggers ovulation
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♂ stimulates testosterone production
Anterior Pituitary & Hypothalamus
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hypothalamus controls anterior pituitary
hypothalamic hormones released into blood of
portal system
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portal system = 2 capillary beds connected by
veins
Hypothalamus & Posterior Pituitary
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hormones
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oxytocin
antidiuretic hormone (ADH)
synthesized by
neurosecretory cells
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transport hormones down
axons to posterior pituitary
Posterior Pituitary
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technically not an endocrine gland
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oxytocin
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does not make the hormones it releases
stores hormones made by hypothalamus
uterine contractions, milk ejection
antidiuretic hormone (ADH)
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inhibits urine production
Lab
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Exercise 15: Spinal Cord & Nerves
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cow spinal cord demo
answer questions pg 126.
complete Review Sheet pp 301-302.
Exercise 16
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all activities
Pituitary Gland
Thyroid Gland
Thyroid Gland
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hormones
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thyroid hormone
calcitonin
follicles
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store sticky precursor to
hormones
Thyroid hormone
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T4 or thyroxine
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T3 or triiodothyronine
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both contain iodine
control glucose oxidation rate
goiter
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enlargement of thyroid gland due to lack of iodine
Calcitonin
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decreases blood calcium levels
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how?
PTH antagonist
Parathyroid glands
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posterior surface of thyroid
parathyroid hormone (PTH)
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regulates Ca2+ in blood
negative feedback mechanism
Calcitonin and PTH
Calcitonin and PTH
Adrenal Gland
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cortex
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glandular
medulla
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neural
Adrenal Cortex
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Corticosteroids
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mineralcorticoids
glucocorticoids
sex hormones
Adrenal Cortex
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Mineralcorticoids
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regulate mineral or salt content of blood
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aldosterone
K+ and Na+ ions
target organ: kidneys
Adrenal Cortex
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Glucocorticoids
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cortisone
cortisol
increase blood glucose levels
long term stressors
sex hormones
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androgens
estrogens
Adrenal Medulla
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neural
secretes catecholamines
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epinephrine (adrenaline)
norepinephrine
sympathetic nervous response = short term
stressor
glucocorticoids = long term stressor
Pancreas
A unique gland with both exocrine and endocrine
functions
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Exocrine: produces enzymes for digestion
Endocrine: produces hormones for blood glucose
regulation
Pancreas
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pancreatic islets
insulin
glucagon
Pancreas
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high blood glucose stimulates beta cells to
release insulin
insulin increases cells ability to move glucose
across cell membranes
Pancreas
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glucagon
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insulin antagonist
released by alpha cells
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low blood glucose stimulates release
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targets liver to break down glycogen to glucose