Transcript Endocrine System

Endocrine System
Modified from:
http://www2.kumc.edu/instruction/nursing/nrsg812/endocrine/
Images from:
http://www.endocrineweb.com/
gened.emc.maricopa.edu/bio/bio181/BIOBK/BioBookENDOCR.html
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Mechanisms of Hormone Action
• Certain secretory cells release chemical agents
(hormones) for the purpose of mediating
biologic responses in distant Target Cells.
• Hormones sources
– Single amino acid (catecholamines)
– Chains amino acids (peptide hormones of
hypothalamus)
– Cholesterol (steroids)
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Mechanisms of Hormone Action
• Hormones control and integrate many body
functions with this system.
• In general, hormonal control regulates the
metabolic functions of the body, the types of effects
that occur inside the cell and determined the
character of the cell itself.
• The endocrine system works with the nervous
system to regulate: metabolism, water and salt
balance, blood pressure, response to stress, and
sexual reproduction.
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3 Forms of Hormonal Communication
1. Endocrine = hormones are secreted into blood to
regulate the function of distant target cell
2. Paracrine = endocrine cells secrete into surrounding
extracellular space. Target cells are neighbors
3. Neuroendocrine = Directly into blood (norepin), &
into brain interstitial space (Vasopressin)
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Endocrine System
• Endocrine System Hormones/Glands whose functions
are solely endocrine include:
• pituitary (hypophysis)
• pineal
• thyroid
• parathyroids
• adrenals
• pancreas
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Hypothalamus and Pituitary
• Pituitary has direct
neural and blood
connection to the
hypothalamus
• Hypothalamus sends
releasing factors to
anterior pituitary
• Hypothalamus
stimulates posterior
pituitary via neural
pathway
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Hypothalamus
• Hypothalamus can synthesize and release
hormones from its axon terminals into the blood
circulation.
• controls pituitary function and thus has an
important, indirect influence on the other glands
of the endocrine system.
• exerts direct control over both the anterior and
posterior portions of the pituitary gland.
• regulates pituitary activity through two pathways:
a neural pathway and a portal venous pathway. 7
Hypothalamus
• Neural pathways extend
from the hypothalamus to
the posterior pituitary
lobe, where the hormones
are stored and secreted.
• Portal venous pathways
connect the hypothalamus
to the anterior pituitary
lobe, carry releasing and
inhibiting hormones
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Pituitary Gland
• Pituitary Gland is located at the base of the
skull in an indentation of the sphenoid bone.
• Is joined to the hypothalamus by the pituitary
stalk (neurohypophyseal tract) and consists of
the anterior pituitary and the posterior
pituitary
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Anterior pituitary gland (adenohypophysis)
• Called the master gland, because its anterior lobe
has direct control over the secretion of:
• ADH - antidiuretic hormone (vasopressin)
• ACTH - adrenocorticotrophic hormone
• TTH - thyrotrophic hormone
• GH - growth hormone
• FSH - follicle stimulating hormone
• LH - leutinizing hormone
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Posterior pituitary
• Stores and secretes hormones made in the
hypothalamus and contains many nerve fibers.
• ADH (Antidiuretic Hormone/Vasopressin), which
controls the rate of water excretion into the urine
• Regulates Na+ & K+ reabsorption in the kidneys
this influences blood volume & blood pressure
• Oxytocin, which, among other functions, helps
deliver milk from the glands of the breast.
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Adrenal Glands
• Adrenal Glands
have an outer
cortex and an
inner medulla.
• The adrenal
cortex and
medulla are
major factors in
the body's
response to
stress.
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Kidneys—Renal Hormones
• Renin is an hormone/enzyme
(released from juxtaglomerular
cells)
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Thyroid Gland
• Thyroid function is regulated by the
hypothalamus and pituitary, feedback
controls an intrinsic regulator mechanism
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Thyroid Problems
• Thyroid gland enlargement may or may not be
associated with abnormal hormone secretion.
• An enlarged thyroid gland can be the result of:
• iodine deficiency (Goiter)
• inflammation, or
• benign or malignant tumors
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Parathyroid Glands
• There are 4 parathyroid glands
located behind the thyroid.
• Parathyroid Glands are important in
calcium metabolism phosphorus
metabolism
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Pancreas
• endocrine gland, secreting the hormones
insulin and glucagon, exocrine gland,
producing digestive enzymes.
• Secretes insulin, glucagon (regulate blood
sugar)
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Cellular Mechanisms of Hormone Action
• Hormonal interaction with target cells begin with
reversible binding to specific receptors
1. Interactions with membrane receptor (protein)
2. Interactions with nuclear receptors (steroid)
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Amino Acid Based Hormones
• Bind to receptor sites on cell membranes
• Amino acid hormone binding causes changes to
occur receptor can activate carrier molecules which
transport substances across the membrane
• receptor can activate second messengers
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Second Messengers
• Second Messengers set a series of reactions in
motion
• Activate adenylate cyclase, generates cAMP from
ATP
• cAMP activates other proteins within the cell
increases glycogenolysis & lipolysis
• Open Ca2+ ion channels, activates calmodulin
• Hydrolyzes phospholipase C into inositol
triphosphate & diacylglycerol
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Steroid Hormones
• Steroid hormones are produced
by chemical modification
of cholesterol
•Major classes steroid hormones
•glucocorticoids (cortisol)
•mineralocorticoids (aldosterone)
•androgens (testosterone)
•estrogens (estradiol)
•Vitamin D metabolites
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Steroid Hormones
• Diffuse into cell and influence DNA
• Bind to a protein associated with DNA
• Cause DNA to increase synthesis of specific
amino acids
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Feedback Loops
• The release of a hormone is often triggered by
a change in the concentration of some
substance in the body fluids.
• Each hormone has a corrective effect,
eliminating the stimulus, which then leads to a
reduction in hormone secretion.
• This process is called a negative feedback
homeostatic control system to keep hormones
at normal levels. (if levels increased it would be
called positive feedback)
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Blood Sugar Control
• Insulin and glucagon are produced by small groups
of cells in the pancreas (islets of Langerhans).
• Beta cell make insulin (beta cells) and Alpha cells
that make glucagon
• Insulin is released when the blood sugar rises too
high. Insulin tells the cells to use sugar.
• Glucagon is produced when the blood sugar is
falling too low. Glucagon tells the liver to release
sugar that was stored there when the blood sugar
was higher.
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