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Endocrine System
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Endocrine System
• Primary function: produce ____________
• Works together with ______________ system to maintain
homeostasis.
• Hormones act on specific target cells to produce specific effects
• No _________, use circulatory system.
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Endocrine System vs. Nervous System
Characteristic
Endocrine System
Nervous System
General Function
Maintain homeostasis
Maintain homeostasis
Reaction to stimuli
slow
rapid
Duration of effect
long
short
Target tissues
throughout body
muscles and glands
Chemical
messenger
hormone
neurotransmitter
Messenger
producing cell
endocrine gland
neurons
Distance to
target cells
long (via bloodstream)
short (across synaptic space)
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Exocrine/Endocrine Glands
Gland
Exocrine
Pancreas
Ovary
Testes
Kidney
digestive enzymes
egg
sperm
urine
Endocrine
insulin, glucagon
estrogen, progesterone
testosterone
erythropoietin
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• Chemical messengers produced
by endocrine glands
• Absorbed into blood vessels and
will contact all cells of the body.
Hormones
• Only produces effects on cells
containing specific receptors
• __________ cell
• ‘Lock and key’ arrangement
causes a change in activity of target
cell
• Growth hormone—all cells
• Prolactin—mammary tissue
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Control of Hormone
Secretion
___________ feedback systems (like a
thermostat)
• If hormone level is low:
•Appropriate endocrine gland is
stimulated to produce more hormone
• Once adequate hormone concentration is
attained in the bloodstream:
•Stimulation of endocrine gland is
reduced and production of the hormone
is stopped/reduced
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Hypothalamus
• Part of ___________________ section of
brain
• Controls activities of pituitary gland
 Portal system of blood vessels links
hypothalamus with anterior portion of
pituitary gland
•Neurosecretory cells in hypothalamus
secrete releasing and inhibiting
hormones into portal blood vessels
•Specific for a particular anterior pituitary
hormone Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.
Hypophyseal Portal System
GHRH, GHIH (Don’t memorize)
Thyrotropin releasing hormone (TRH)
Gonadaotropin releasing hormone (GnRH)
PRH, PIH
Corticotropin releasing hormone (CRH)
Growth hormone
Thyroid stim hormone (TSH)
Follicle stim hormone (FSH)
Luteinizing hormone (LH)
Prolactin
Adrenocorticotropic hormone (ACTH)
Melanocyte stim hormone (MSH)
Posterior
pituitary
Oxytocin
Antidiuretic hormone (ADH)
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Hypothalamus
• Modified neurons in hypothalamus
secrete Antidiuretic Hormone (ADH)
and Oxytocin
• Transported to posterior pituitary
(along neurons) for storage
• Released into the bloodstream by
nerve impulses from hypothalamus
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• Two separate glands with different
structures, functions, and
embryological origins
Pituitary Gland
(Hypophysis)
•Anterior pituitary _______hypophysis; rostral
portion
• Composed of glandular tissue
• Produces hormones
•Posterior pituitary _______hypophysis; caudal
portion
• Composed of neurosecretory cells
• Stores and releases hormones
produced in hypothalamus
Rostral
Caudal
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HORMONES MADE BY THE ANTERIOR PITUITARY
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Growth Hormone (GH)
• Promotes bone and muscle growth in young animals, but targets
all cells of the body.
• Helps regulate metabolism of proteins, carbohydrates, and lipids
in animals of all ages.
• Proteins are synthesized via _______bolism
• Lipids are released from storage and go through _______bolism for
energy use by the body.
• Since GH promotes the use of lipids for energy, glucose accumulates
in the blood. This is known as the hyperglycemic effect.
• It is important for the animal to have normal production of ____________
by the pancreas to counteract the hyperglycemia
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Prolactin
• Helps trigger and maintain
_____________ in females
• Secretion of milk by mammary
glands
• Prolactin production continues as long
as the animal is stimulated by nursing
or milking
1. Baby sucks/stimulates
2. ↓PIH, ↑PRH
3-4. Stimulates milk glands
• When prolactin stimulation stops:
• Milk production stops
• Mammary gland shrinks to
nonlactatingMosby
size
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ThyroidStimulating
Hormone (TSH)
• Stimulates growth/development of
thyroid gland and causes thyroid to
produce its hormones.
• Secretion regulated by:
•Feedback (neg) from thyroid
gland hormone
•Thyroid hormone levels too lowTSH production increases
•Thyroid hormone levels too highTSH production diminishes
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• Stimulates growth/development of
adrenal cortex and the release of its
hormones
• Regulated by levels of cortisol:
Adrenocorticotropic
Hormone (ACTH)
•When low or patient is stressed,
the hypothalamus will produce CRF
which causes anterior pituitary to
release ACTH
•When elevated, negative feedback
will cause CRF and ACTH levels to
be reduced.
• NOTE: administering steriods that mimic
the effects of cortisol (ex: prednisone,
dexamethasome) can also cause
negative feedback
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•Females—stimulates
growth/development of ovarian
follicles
• Males- stimulates
____________________
in the testes
•Also stimulates the cells lining
the follicles to produce/secrete
_______________
•Used to superovulate
FollicleStimulating
Hormone
(FSH)
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• Completes follicular development in
ovary
Luteinizing
Hormone (LH)
• Increasing amounts of estrogen
feedback to the anterior pituitary and
cause reduced production of FSH and
increased production of LH
•
LH levels reach a peak when follicle is
fully mature
• causes _______________________
• In males, LH stimulates interstitial cells
to produce ___________________
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HORMONES STORED BY THE POSTERIOR PITUITARY
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• Reduces urine volume, prevents diuresis
• Receptors detect changes in concentration of blood (due to
dehydration - hemoconcentration)
• Release of ADH causes kidneys to reabsorb more water from urine
and return it to bloodstream
• Urine becomes more concentrated
• ADH deficiency causes Diabetes ______________ (PU/PD occurs)
Antidiuretic
Hormone (ADH)
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► Works via POSITIVE feedback
Oxytocin
► Effect on uterus:
• _______________ during breeding and
parturition
 Helps to transport spermatozoa to oviduct
 Causes delivery of fetus and placenta
► Effect on active mammary glands:
• Stimulation of teat/nipple by nursing or
milking causes oxytocin release into
bloodstream
 Causes contraction of myoepithelial cells
around mammary gland alveoli and small
ducts. This forces milk into lower parts of
gland, making it accessible (________
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__________________).