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Endocrine System
Human Anatomy & Physiology
University of Washington PMT
The Endocrine System
Endocrine System
 The Endocrine System
 Regulates long-term processes
 Growth
 Development
 Reproduction
 Uses chemical messengers to relay information and
instructions between cells
 Direct communication
 Paracrine communication
 Endocrine communication
Hormonal Action
 Target Cells
 Are specific cells that possess receptors needed to
bind and “read” hormonal messages
 Hormones
 Stimulate synthesis of enzymes or structural
proteins
 Increase or decrease rate of synthesis
 Turn existing enzyme or membrane channel “on” or
“off”
Hormone Actions
 “Lock and Key” approach: describes the
interaction between the hormone and its
specific receptor.
 Receptors for nonsteroid hormones are
located on the cell membrane
 Receptors for steroid hormones are found in
the cell’s cytoplasm or in its nucleus
Non Lipid Soluble
Hormonal Action
 Hormones and Plasma Membrane Receptors
 Bind to receptors in plasma membrane
 Cannot have direct effect on activities inside
target cell
 Use intracellular intermediary to exert effects
 First messenger:
 leads to second messenger
 may act as enzyme activator, inhibitor, or cofactor
 results in change in rates of metabolic reactions
Lipid Soluble Hormonal
Action
 Steroid Hormones:
 Lipid soluble
 Diffuse through cell membranes
 Endocrine organs
 Adrenal cortex
 Ovaries
 Testes
 Thyroid
Pituitary Gland
 A marble-sized gland
at the base of the
brain
 Controlled by the
hypothalamus or
other neural
mechanisms and
therefore the middle
man.
Pituitary Gland
The Pituitary Gland and its
Hormones
 Posterior Lobe
 Antidiuretic hormone (ADH)
 Oxytocin
 Anterior Lobe
 Adrenocorticotropic (ACTH)
 Growth hormone (GH)
 Thyroid-stimulating hormone (TSH)
 Follicle-stimulating hormone (FSH)
 Luteinizing hormone (LH)
 Prolactin (PRL)
Endocrine Reflexes
Hypothalamus
Pituitary Gland
Thyroid Gland
 Thyroid Gland
 Located along the midline of the neck
 Secretes two nonsteroid hormones
 Triiodothyronine (T3)
 Thyroxine (T4)
 Calcitonin: calcium metabolism (osteoblast)
 Regulates metabolism
 increases protein synthesis
 promotes glycolysis, gluconeogenesis, glucose uptake
Thyroid Gland
Thyroid Gland
Parathyroid Glands
 Embedded in
posterior surface of
the thyroid gland
 Parathyroid hormone
(PTH)
 Produced by chief
cells
 In response to low
concentrations of Ca2+
Parathyroid Gland
Suprarenal (Adrenal) Gland
 Lie along superior border of
each kidney
 Subdivided into:
 Superficial suprarenal cortex
 Stores lipids, especially
cholesterol and fatty acids
 Inner suprarenal medulla
 Secretory activities controlled by
sympathetic division of ANS
Suprarenal (Adrenal) Gland
 Adrenal Medulla
 Contains two types of secretory cells
 Epinephrine (70-75% of mass)
 Increase H.R. and B.P.
 Increase respiration
 Increase metabolic rate
 Increase glycogenolysis
 Bronchodilation
 Norepinephrine (20-25% of mass)
 Vasoconstriction
Suprarenal (Adrenal) Gland
 Adrenal Cortex
 Mineralocorticoids (Zona Glomerulosa)
 Aldosterone: maintains electrolyte balance
  Na+ reabsorption by kidneys &  K+ urinary loss
 Glucocorticoids (Zona Fasciculate)
 Cortisol (Hydrocortisone):
 Stimulates gluconeogenisis
 Mobilization of free fatty acids
 Anti-inflammatory agent
 Androgens (Zona Recticularis)
 Bone growth, muscle growth & blood formation
Pineal Gland
 Lies in posterior portion
of roof of third ventricle
 Contains pinealocytes
 Synthesize hormone
melatonin
 Inhibits reproductive
functions
 Protects against
damage from free
radicals
 Setting circadian
rhythms
Pancreas
 Exocrine / Endocrine
Gland
 Endocrine Pancreas
consists of “clusters”
of cells called Islets
of Langerhans
 4 types of cells of
endocrine pancreas
 Comprise only 1% of
entire pancreas
Pancreas
 Insulin
 A peptide hormone released by beta cells
 Affects target cells by:
 Accelerate glucose uptake
 Accelerate glucose utilization and enhances ATP
formation
 Stimulate glycogen formation
 Stimulate amino acid absorption and protein
synthesis
 Stimulate triglyceride formation in adipose tissue
Pancreas
 Glucagon
 Released by alpha cells
 Mobilizes energy reserves
 Affects target cells:
 Stimulates breakdown of glycogen in
skeletal muscle and liver tissue
 Stimulates breakdown of triglycerides in
adipose tissue
 Stimulates production of glucose in liver
Sex Organs (Testes &
Ovaries)
 Testes (Gonads)
 Produce androgens
in interstitial cells
 Testosterone is the
most important male
hormone
 Secrete inhibin in
nurse
(sustentacular) cells
 Support differentiation
and physical
maturation of sperm
 Ovaries (Gonads)
 Produce estrogens
 Principle estrogen is
estradiol
 After ovulation, follicle
cells
 Reorganize into
corpus luteum
 Release estrogens
and progestins,
especially
progesterone
Thymus
Produces thymosins
(blend of thymic
hormones)
That help develop and
maintain normal
immune defenses
Endocrine Tissues of
Other Organs
 Kidneys:
 Produce calcitriol and erythropoietin
 Produces enzyme renin
 Heart:
 Produces natriuretic peptides (ANP & BNP)
 When blood volume becomes excessive
 Action opposes angiotensin II
 Resulting in reduction of blood pressure &
volume
Hormone Interactions
 General Adaptation Syndrome (GAS)
 Also called stress response
 How body responds to stress-causing
factors
 Is divided into three phases:
1. Alarm phase
2. Resistance phase
3. Exhaustion phase