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THE ENDOCRINE SYSTEM
READINGS: CHAPTER 45; 943–963
COORDINATION
• Animals use two systems to coordinate many of their functions:
• _____________________________ signals – _____________________________ system
– Useful for _____________________________ term changes
– Slow response time (_____________________________)
– Hormones travel through _____________________________
• _____________________________ signals – _____________________________ system
– _____________________________ term responses
– Very rapid response time (_____________________________)
– Action potentials travel along _____________________________
CHEMICAL SIGNALS
• Allow for communication between cells of the body
– To coordinate and regulate various functions
– Hormones are products of endocrine glands
• Hypothalamus
• Pituitary
• Thyroid & Parathyroid
• Pancreas
• Kidney
• Adrenal
• Testes/Ovaries
• _____________________________ signals
– A signal is produced, released, and binds to a receptor on the __________________________
• _____________________________ signals
– A signal is produced, released, and binds to a receptor on a ___________________________
• _____________________________ signals
– A signal is produced, released, enters the _____________________________, and binds to a
receptor on a _____________________________
– Neuroendocrine signals
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• _____________________________
– Chemical signals are released into the _____________________________ to modify
behaviour in _____________________________
A GLAND BY ANY OTHER NAME …
• Not all glands in our body are part of the endocrine system
• _____________________________ glands
– Secrete _____________________________ directly into circulation or other body fluids
– Those just mentioned
• Hormones travel to and act on target cells/tissues
• _____________________________ glands
– Secrete various products through _____________________________ to the external
environment
– Mucus glands, sebaceous, mammary, sweat, liver, pancreas
• Mucus, sweat, digestive enzymes
HORMONE STRUCTURE
• What exactly are hormones?
– _____________________________ or peptides – insulin
– _____________________________ derivatives – thyroid hormones (triiodothyronine)
– _____________________________ (cholesterol) derivatives – sex hormones
CONTROL OF SECRETION
•
Release of most hormones is highly _____________________________
– Only released when a response is _____________________________
– Dysregulation leads to _____________________________
•
Three mechanisms exist to regulate hormone secretion
– The action of a _____________________________ on an endocrine gland
– The action of the _____________________________ system on endocrine glands
– The action of a _____________________________ produced by one endocrine gland on
another gland
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NONHORMONAL REGULATION
• Blood _____________________________ levels and the _____________________________
– Cells in the islets of Langerhans detect blood sugar levels and respond
– Glucose is a non-hormone signal
– If levels are ________
• Alpha-cells secrete
• Glucagon _____________________________ blood sugar
– If levels are ________
• Beta-cells secrete
• Insulin _____________________________ blood sugar
NERVOUS REGULATION
• Neurons can _____________________________ glands and hormone-releasing cells
– _____________________________ release regulates hormone secretion by the target gland
• An external stimulus is perceived
• Sends a signal to the hypothalamus
• Release of hormones
HORMONAL REGULATION
• A fairly common regulatory mechanism
• The hypothalamus and pituitary gland release a lot of hormones which can regulate secretion by
other glands
– _____________________________ hormones
– _____________________________ hormones
• Hormones released by one gland travel to another and cause release of a second hormone
HORMONE EFFECTS
• In order for a target cell/tissue to respond to a hormone, the cell(s) must have a
_____________________________ to detect its presence
– Like _____________________________, these receptors are specific
– Without the right receptor, the cell _____________________________ the hormone
• This is important for the target specificity of hormones
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• Responses to hormones are generally _____________________________
– More hormone = _____________________________ response
= Amplitude-modulation
REGULATION OF RESPONSE
• Different cells have the ability to regulate their responses to hormones
• _____________________________ regulation of surface hormone receptors
– Have _____________________________ receptors
• _____________________________ regulation of surface hormone receptors
– Have _____________________________ receptors
INVERTEBRATE HORMONES
• Hydra
– A freshwater Cnidarian capable of regeneration
• If they lose a _____________________________ it isn't a big deal
• If they lose their entire head it’s ______________________________________________
• Coordination of mouth and tentacle regeneration
– _____________________________ is a hormone that promotes development of the
•
Insects use a series of hormones to coordinate two major events of moulting
• Getting rid of _____________________________
• Promote the production of the _____________________________
• Hormones secreted by brain and other glands
– _____________________________ hormone
– _____________________________ (a steroid hormone)
• Hormones also determine what the becomes
– _____________________________
– _____________________________ hormone
•
When it is time to moult brain hormone is released from the _____________________________
– Travels in the hemolymph to the _____________________________
– Causes release of _____________________________
– An example of hormonal regulation of hormone secretion
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• Ecdysone
– Travels in the hemolymph to the _____________________________
– Initiates_____________________________ of the old cuticle
– And _____________________________ of the new cuticle
• Juvenile hormone
– Not directly involved in moulting, but determines what the insect will ___________________
• _____________________________
– Concentration starts out _____________________________ in the larvae
• JH _____________________________ larval characteristics
– Concentration _____________________________ with age
• Lower concentration (__________________________) ___________________________
adult characteristics
• What if these hormones don’t work properly
– If no brain hormone or ecdysone:
• No _____________________________
– If no decrease in juvenile hormone:
• No _____________________________ into the adult form and therefore no
• Who would benefit from this?
– The plants that produce hormones which disturb this process
• Disrupt _____________________________ and _____________________________ in
insects
• Fewer insects to _____________________________
VERTEBRATE HORMONES
• The major vertebrate endocrine glands are the _____________________________ and
_____________________________
– Produce and secrete hormones which regulate most of the other glands
HYPOTHALAMUS & PITUITARY
• The pituitary gland develops in part as an extension of the hypothalamus
– The _____________________________ pituitary
– ___________________hypophysis
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• And in part from the back of the mouth
– The _____________________________ pituitary
– ___________________hypophysis
THE POSTERIOR PITUITARY
• Receives _____________________________ neural input from the hypothalamus
– Axons enter the neurohypophysis
• Neurons synthesize _____________________________
– Hormones that come from a nerve
• __________________________________________________________ (ADH)
– Travels to the kidney tubules to increase water _____________________________
• _____________________________
– Released during childbirth or suckling of newborn
– Effects contractions of:
• _____________________________ smooth muscle
• Smooth muscle in _____________________________
HORMONAL DISTURBANCE
• ADH is released when osmoreceptors detect increased blood _____________________________
(too many solutes)
– Effects on:
• Kidney tubules _____________________________ water reabsorption
• Diabetes insipidus
– The neurons in the posterior pituitary do not release ADH
• Not enough ___________________________________________________
– Copious amounts of dilute urine
• Water stays _____________________________
– Leads to increased osmolality of body fluids
THE ANTERIOR PITUITARY
• Connected indirectly to hypothalamus via a special pituitary _____________________________
system
– Veins which carry blood between _____________________________
– Neurosecretory cells of the hypothalamus can control the products of the anterior pituitary
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• Many different hormones
• _____________________________ hormones
– Have effects on glands
• _____________________________ hormones
– Those that don’t
• Hormones that effect glands _____________________________ targets
PITUITARY TROPIC HORMONES
• The gonadotropins have effects on both male and female reproductive organs
• Follicle-Stimulating Hormone (FSH)
– Ovary → __________________________________________________________
– Testes → __________________________________________________________
– Synthesis begins at puberty
• Luteinizing Hormone (LH)
– Ovary → _____________________________ and synthesis & release of
_____________________________ and _____________________________
– Testes → _____________________________ production
• Adrenocorticotropic Hormone (ACTH)
– Travels to the _____________________________
• Increases secretion of the _____________________________ hormones
• Thyroid-Stimulating Hormone (TSH)
– Secreted in response to thyroid-releasing hormone (TRH) produced by the hypothalamus
– Travels to the thyroid gland
• Stimulates thyroid follicular cells to _____________________________ the thyroid
hormones
PITUITARY NONTROPIC HORMONES
• Prolactin (PRL)
– Travels to mammary gland
• Stimulates _____________________________
– Blood levels follow _____________________________ during menstrual cycle & increase
during pregnancy
– Production continues as long as breast feeding
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• β Endorphins
– Analgesics produced in response to exercise
– Travel to _____________________________ in the brain
• The ‘runner’s high’ you get from torturing yourself
GROWTH HORMONE (GH)
• A hormone with both ________________________ and __________________________ effects
– Tropic effects include stimulation of liver to produce other
• Bone elongation & increased muscle mass
– Nontropic effects include
• Metabolic effects such as _____________________________
HORMONAL DISTURBANCE
• Growth hormone abnormalities
– Hypersecretion → _____________________________
– Hyposecretion → _____________________________
• Not the same as achondroplastic dwarfism in that long bones are proportional
THE THYROID GLAND
• The thyroid gland is situated just inferior to the larynx at the base of the neck
• Hormones are _____________________________ produced and stored in
– A lumen surrounded by endocrine cells
• _____________________________ (TH)
– Follicle cells synthesize thyroxine (_____) and triiodothyronine (_____)
• _____________________________
– Regulates blood Ca
++
levels
– Deposition at bones
THE THYROID HORMONES
• T3 is the active form
– T4 gets transformed to T3 before it works
• T3 acts on most cells of the body
– _______________________________________________________ leading to tissue growth
• Important homeostatic functions maintaining normal:
– Blood pressure
– Heart rate
– Muscle tone
– Intestinal motility
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HORMONAL DISTURBANCE
Hyperthyroidism
Hypothyroidism
• Graves’ Disease
• Nearly opposite of hyper-
• Increased metabolic rate
• May develop a goiter
– Weight loss, increased appetite
• Excessive sweating
• Increased heart rate
• Increased intestinal motility
– Bouts of intestinal hurry
• Weak skeletal muscles
• Increased iodide uptake
• Goiter
ADRENAL GLAND
• Two structurally and functionally separate components
– Adrenal medulla (_____________________________)
– Stimulation causes release of _____________________________ and
_____________________________
– Part of the fight-or-flight response
•
Secretion is stimulated by _____________________________
– Effects include:
•
↑ cardiac output
•
↑ blood flow to muscles (↓ to GI)
•
↑ glucose release (glycogen breakdown)
•
↓ digestive functions
ADRENAL GLAND
– Adrenal Cortex (_____________________________)
– Recall that hormone secretion is stimulated by ACTH
• Produces different types of steroid hormones
– Mineralocorticoids
– Androgens
– Glucocorticoids
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MINERALOCORTICOIDS
• The major mineralocorticoid is aldosterone
– Maintain ____________________________________________ balance in the body
ADRENAL ANDROGENS
• Such as androstenedione
– Stimulate growth of both _____________________________
– Increase _____________________________
GLUCOCORTICOIDS
• Hormones including cortisol
– Released in response to
(metabolic, disease, emotional, exams)
• Effects fall under three categories:
– _____________________________
• Gluconeogenesis, protein and fat metabolism
– _____________________________
• Maturation of fetal lungs
– _____________________________
• Suppression of immune system by decreasing numbers of WBCs
• A common treatment for a immune/inflammatory diseases
THE OVARIES
• After puberty, LH and FSH are released from the anterior pituitary and travel to the gonads
• LH binds to follicle interstitial cells → _____________________________ are synthesized
– ___________________________________________ sex characteristics
• LH & FSH stimulate _____________________________ of the follicle and cause the primary
oocyte to
meiosis I → secondary oocyte
– Meiosis isn’t completed until fertilization
• LH surge stimulates _____________________________
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THE TESTES
• LH binds to interstitial cells in testes → stimulating _____________________________
secretion
– ___________________________________________ sex characteristics
• Voice, hair
– Bone growth & muscle mass
• FSH binds to Sertoli cells → _____________________________________
THE PANCREAS
• The pancreas is a gland with both _____________________________ and
_____________________________ functions
– Exocrine → digestive enzymes and bicarbonate
• Two major endocrine hormones are produced in the islets of Langerhans:
•
_____________________________ cells → _____________________________
•
_____________________________ cells → _____________________________
• These 2 hormones work together to maintain a stable _____________________________ level
INSULIN
• Released in response to blood glucose
– After a meal
• Targets:
– liver, muscle, adipose tissue
• Causes:
– Increased glucose _____________________________
– Increased _____________________________ synthesis (storage)
– Effectively _____________________________ glucose from the blood
• Reasons:
– These effects occur after a meal _________________________________________________
– Promote cellular storage of excess nutrients
• Also stimulates ‘_____________________________ centre’ in hypothalamus
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GLUCAGON
• Released when blood glucose
– Between meals
• Targets:
– liver, and adipose tissue
• Causes:
– _____________________________ – breakdown of glycogen
– _____________________________ – synthesis of glucose
• Reasons:
– Mobilize stored nutrients preventing _____________________________
– Part of the sympathetic response to mobilize stored glucose for use when needed
DIABETES MELLITUS
• Literally means ‘running over with honey’
• Type I – _____________________________-dependent DM
~3%
– Autoimmune _____________________________ of the pancreatic beta cells
– _____________________________ in the blood to stimulate glucose uptake
– Controlled by insulin _____________________________
• Type II – _____________________________-dependent DM ~97%
– Beta cells work fine, insulin is produced
– _____________________________ for insulin are non-functional
– Controlled primarily by _____________________________
LIST OF FIGURES
45.2
45.6
45.7
45.8
45.12
45.13
45.15
Table 45.1