Endocrine System Flashcards
The endocrine system and the nervous system control and integrate body function to maintain:
Homeostasis
The ___________ sends its messages along _________ which are ___________ .
Nervous system
Nerve fibers
Selective neural responses
The ___________ sends its ________ messages in the form of ______ via the ____________ .
Endocrine system
Chemical
Hormones
Bloodstream
Nervous system:
Initiates responses ______
________ responses
Acts via _________ and __________
Acts at ___________ determined by ___________
Neurotransmitters act over very ____________
Rapidly
Short-duration
Action potential & neurotransmitter
Specific locations & axon pathways
Short distances
Endocrine system:
Initiates responses _________
___________ responses
Acts via ________ released into the _______
Acts at _____________ targets can be anywhere blood reaches
Hormones act over __________
Slowly
Long duration
Hormones & blood
Diffuse locations
Long distances
Endocrine system functions
Growth and development
Maintain homeostasis
- metabolic function
- chemical reactions
- cell membrane transportation
Respond to emergencies
Endocrinology
In the endocrine system hormones are secreted from ______ and into the ______
Endocrine glands
Tissue
Hormones in the endocrine system then stimulate ______ or ______ in their ___________
Change or growth
In their specific target tissue
Purely endocrine glands
Pineal gland
Pituitary
Thyroid
Adrenals
Not purely endocrine gland
Pancreas
Glands that are neuroendocrine:
Hypothalamus
Hormones are _______ messengers of the endocrine system
Chemical
They are _______ chemical signals and travel in ______ or ____
Long-distance
Blood or lymph
What are the two main classes of hormones?
Amino acid-based
Steroids
Amin acid-based hormones are?
Amino acid derivatives, peptides and proteins
Steroid hormones are?
Synthesized from cholesterol
Hormones circulate _______. Only cells, _______, with receptors for that hormone are affected
Systemically
Target cells
Hormones alter target cell activity by _______ or ______ cellular processes
Stimulating or inhibiting
Hormones typically produce one or more of the following:
- Alter plasma membrane permeability or membrane potential or both by opening or closing ion channels
- stimulates synthesis of enzymes and other proteins within the cell
- activates or deactivates enzymes
- induces secretory activity
- stimulates mitosis
Hormones act either as ___________ hormones or ________ hormones
Water-soluble
Lipid-soluble
Water-soluble hormones are all _____________ hormones except _________ hormone
Amino acid-base
Thyroid
Water-soluble hormones act on:
Plasma membrane receptors
Water-soluble hormones exert effects through ________
Second-messenger systems
Water-soluble hormones are coupled with a regulatory molecules called
G proteins
Water-soluble hormones cannot
Enter cell
Lipid-soluble hormones are
Steroid and thyroid hormones
Lipid-soluble hormones act on
I trace lunar receptors that directly activate genes
Water-soluble hormones consist of:
All amino acid-based hormones except thyroid hormone
Water-soluble hormones sources
All other endocrine glands
Are water-soluble hormones stored in secretory vesicles ?
Yes
How are water-soluble hormones transported in blood?
Usually free in plasma
How long is water-soluble hormones in half-life in blood?
Short (most can be removed by kidneys)
What is the location of water-soluble hormones receptors?
On plasma membrane
Water-soluble hormones mechanism of action at target cell
Usually act through second-messenger systems
Lipid-soluble hormones consist of
All steroid hormones and thyroid hormone
Lipid-soluble hormones sources are:
Adrenal cortex, gonads, and thyroid gland
Are lipid-soluble hormones stored in secretory vesicles?
No
How are lipid-soluble hormones transported in blood?
Bound to plasma proteins
How long is lipid-soluble hormones half-life in blood?
Long (most need to be metabolized by liver)
What is the location of lipid-soluble hormones receptors?
Usually inside cell
What is the mechanism of action at target cell for the lipid-soluble hormones?
Activate genes, causing synthesis of new proteins
Endocrine glands are stimulated to synthesize and release hormones in response to one of three stimuli:
Humoral stimuli
Neural stimuli
Hormonal stimuli
Humoral stimuli is responsible for:
Changing blood levels of ion and nutrients directly stimulates secretion of hormones
An example of humoral stimuli is:
Ca2+ in blood
Declining blood Ca2+ concentration stimulates ___________
Parathyroid glands to secrete PTH
PTH causes Ca2+ concentration to ______________
Rise and the stimulus is removed
Which statement correctly describes the interaction between a hormone and its target cell?
A. Insulin, a water-soluble hormone, binds to a receptor in the plasma membrane of the target cell.
B. Prolactin, a water-soluble hormone, binds to a receptor within the nucleus of a target cell.
C. Testosterone, a lipid-soluble hormone, binds to a G protein in the target cell that directly activates a gene.
D. Estrogen, a lipid-soluble hormone, exerts its signaling effects on the target cell through an intracellular second-messenger
A. Insulin, a water-soluble hormone, binds to a receptor in the plasma membrane of the target cell.
In neural stimuli nerve fibers stimulate __________
Hormone release
Neural stimuli:
Sympathetic nervous system fibers stimulate __________ to secrete ____________
Adrenal medulla
Catecholamines
Hormonal stimuli:
Hormonal stimulate ___________ to release __________
Other endocrine organs
Their hormones
Hypothalamic hormones stimulate ____________
Release of most anterior pituitary hormones
Anterior pituitary hormones stimulate ______________
Targets to secrete still more hormones
Hypothalamic—pituitary target _______________
Endocrine organ feedback loop
Hormones from final target organs inhibit release of ________
Anterior pituitary hormones
The nervous system can adjust ______________________
Hormone levels when needed
The nervous system can override _____________________
Normal endocrine controls
Hormones can be removed from blood by:
- degrading enzymes
- kidneys
- liver
Half-life:
The time required for the level of hormone in the blood level to decrease by half
Half-life varies anywhere from ______________
A fraction of a minute to a week depending on the hormone
Up-regulation:
Target cells form more receptors in response to low hormone levels
Down-regulation:
Target cells lose receptors in response to high hormone levels
Desensitizes the target cells to prevent them from:
Overreacting to persistently high levels of hormone
The hormonal ‘set point’ that needs to be maintained to regulate homeostasis are:
Hormonal release & hormonal inhibition
NEGATIVE feedback system:
Occurs when a change in one direction produces a change in the other
A negative feedback loop response will _____________________
Reverse or cause the opposite effect of the original stimulus
POSITIVE feedback system (rare):
Occurs when a change in one direction is followed by another change in the SAME direction
Examples of of feedback systems
Puberty, aging, pregnancy, the environment, genetics and certain diseases / medications
Cyclical variations in hormone release are:
- growth hormone levels are higher at night
- cortisol varies with happiness / stress
Elevated blood glucose levels stimulate cells of the pancreas to secrete the hormone insulin. The pancreas is responding to which type of stimulus?
A. Neural
B. Humoral
C. Hormonal
D. Paracrine
B. Humoral
Posterior pituitary hormones:
Oxytocin & antidiuretic hormone
Oxytocin is stimulated by . . .
Impulses from hypothalamic neurons in response to stretching of the uterine cervix or suckling of infant at breast
Oxytocin is inhibited by . . .
Lack of appropriate neural stimuli
Oxytocin target organ and effects:
Uterus which stimulates uterine contractions, initiates labor
Breast which initiates milk ejection
Effects of hyposecretion and hyper secretion in oxytocin:
Unknown
Antidiuretic hormone stimulated by . . .
Impulses from hypothalami’s neurons in response to increased blood solute concentration or decreased blood volume; also stimulated by pain, some drugs, low blood pressure
Antidiuretic hormone is inhibited by . . .
Adequate hydration of the body and by alcohol
Antidiuretic hormone target organ and effects:
Kidneys which stimulate kidney tubule cells to reabsorb water from the forming urine back into blood
Antidiuretic hormone effects of hyposecretion and hyper secretion
Hypo: diabetes insipidus
Hyper: syndrome of inappropriate ADH secretion
Anterior pituitary hormones:
Growth hormone
Thyroid-stimulating hormone
Adrenocorticotropic hormone
Growth hormone is stimulated by . . .
GHRH release which is triggered by low blood levels of GH as well as by a number of secondary triggers including deep sleep, hypoglycemia, increases in blood levels of amino acids, low levels of fatty acids, exercise and other types of stressors
Growth hormone is inhibited by . . .
Feedback inhibition exerted by GH and insulin-like growth factors and by hyperglycemia, hyper lipids is, obesity and emotional deprivation via either increased GHIH or decreased GHRH release
Growth hormone target organs and effects:
Liver, muscle, bone, cartilage and other tissues; anabolic hormone; stimulates somatic growth; mobilizes fats; spares glucose
Growth-promoting effects mediated indirectly by IGFs
Growth hormone effects of hyposecretion and hyper secretion
Hypo: pituitary dwarfism in children
Hyper: gigantism in children; acromegaly in adults
Thyroid-stimulating hormone is stimulated by . . .
TRH and in infants indirectly by cold temperature
Thyroid-stimulating hormone is inhibited by . . .
Feedback inhibition exerted by thyroid hormones on anterior pituitary and hypothalamus and by GHIH
Thyroid-stimulating hormone target organ and effects:
Thyroid gland: stimulates thyroid gland to release thyroid hormones
Thyroid-stimulating hormone effects of hyposecretion and hyper secretion
Hypo: hypothyroidism; may cause myxedema
Hyper: hyperthyroidism; effects similar to those of Graves’ disease, in which antibodies mimic TSH
Adrenocorticotropic hormone is stimulated by . . .
CRH; stimuli that increase CRH release include fever, hypoglycemia, and other stressors
Adrenocorticotropic hormone is inhibited by . . .
Feedback inhibition exerted by glucocorticoids
ACTH target organ and effects:
Adrenal cortex which promotes release of glucocorticoids and androgens (mineralocorticoids to a lesser extent)
ACTH effects of hyposecretion and hyper secretions
Hypo: rare
Hyper: cushing’s disease
Thyroid-stimulating hormone is a tropic hormone that is also called . . .
Thyrotropin
Thyroid hormone is the body’s . . .
Major metabolic hormone
Thyroid hormone is found in two forms:
T4 (thyroxine)
T3 (triiodothyronine)
T4 (thyroxine):
Major form
T4 must be converted to T3 at the tissue level
Thyroid hormone affects . . .
Virtually every cell in the body
Thyroid hormone increases . . . And this is referred to as . . .
Basal metabolic rate and heat production
Calorigenic effect
Hypersecretion of TH: most common type is . . .
Grave’s disease
Grave’s disease is an autoimmune disease that the. . .
Body makes abnormal antibodies directed against thyroid follicular cells
Grave’s disease antibodies . . .
Mimic TSH, stimulating TH release
Grave’s disease symptoms include . . .
Exophthalmos: eyes protrude as tissue behind eyes become edematous & fibrous
Elevated metabolic rate
Sweating
Rapid & irregular heartbeats
Nervousness
Weight loss despite adequate food
Grave’s disease treatments include . . .
Surgical removal of thyroid or radioactive iodine to destroy active thyroid cells
The adrenal gland is . . . And is also referred to as . . .
Paired, pyramid-shaped organs atop kidneys
Suprarenal glands
The adrenal gland is two glands in one and they are:
Adrenal cortex & adrenal medulla
Adrenal cortex is . . .
Three layers of glandular tissue that synthesize and secrete several different hormones (aldosterone, cortisol)
Adrenal medulla is . . .
Nervous tissue that is part of the sympathetic nervous system
Adrenal cortex is part of the adrenal gland that produced over ____ different hormones collectively called __________
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Corticosteroids
Adrenal cortex hormones:
Mineralocorticoids
Glucocorticoids
Mineralocorticoids is primarily . . .
Aldosterone, which regulates sodium ion reabsorption and potassium excretion by the kidneys
Sodium ion reabsorption usually leads to . . .
Water reabsorption and raised blood volume and blood pressure
Release of aldosterone is stimulated by . . .
The renin-angiotensin-aldosterone mechanism, rising potassium ion levels in the blood and ACTH
Glucocorticoids are primarily . . .
Cortisol which helps the body resist stressors by increasing blood glucose, fatty acid and amino
High levels of glucocorticoids can lead to . . .
Depress the immune system and the inflammatory response
ACTH is the major stimulus for . . .
Glucocorticoid release
Aldosterone causes:
Sodium reabsorption
Water reabsorption
Potassium excretion
Net increase in blood volume
Renin-angiotensin-aldosterone mechanism
Decreased blood pressure stimulates special cells in the kidneys
Renin cells release into . . .
The blood
Renin cleaves off part of the plasma protein called . . .
Angiotensinogen that triggers enzyme cascade resulting in conversion to angiotensin II
Angiotensin II is a potent stimulator of . . .
Aldosterone release
Three major mechanisms controlling aldosterone release (important!!)
- Renin-angiotensin-aldosterone
- Plasma concentration of K+
- Adrenocorticotropic-tropic hormone
Cortisol is released in response to . .
ACTH
Excessive levels of glucocorticoids leads to:
- depress cartilage and bone formation
- inhibit inflammation by decreasing the release of inflammatory chemicals
- depress immune system
- disrupt normal cardiovascular, neural, and gastrointestinal functions
Cushing’s syndrome / disease is . . .
Depresses cartilage / bone formation and immune system; inhibits inflammation; disrupts neural, cardiovascular, and gastrointestinal function
Cushing’s syndrome causes:
Tumor on pituitary, lungs, pancreas, kidney or adrenal cortex; overuse of corticosteroids
Cushingoid signs:
“Moon” face and “buffalo hump”
Cushing’s treatment:
Removal of tumor, discontinuation of drugs
Addison’s disease:
Usually involves deficits in both glucocorticoids and mineralocorticoids
Addison’s disease is the decrease in . . .
Plasma glucose and Na+ levels
Symptoms of Addison’s disease
Weight loss, severe dehydration and hypotension
Addison’s disease treatment
Corticosteroid replacement therapy
Early sign of Addison’s disease
Characteristic bronzing of skin due to high level of ACTH, which triggers melanin production in melanocytes
Adrenal medulla produces
Catecholamines (epinephrine and norepinephrine) in response to sympathetic nervous system stimulation
Effects of Catecholamines:
- vasoconstriction
- increased heart rate
- increased blood glucose levels
- blood diverted to the brain, heart, and skeletal muscle
Short-Term Stress:
The hypothalamus activates the adrenal medulla via neural stimuli
Short-Term Stress Steps:
- Action potentials triggered by the hypothalamus in response to stressors activate the sympathetic nervous system
- APs travel along preganglionic sympathetic axons to the adrenal medulla
- The adrenal medulla secretes Amin acid-based hormones: epinephrine (80%) and some norepinephrine (20%)
- Epinephrine and norepinephrine reinforce other sympathetic responses to ready the body for exertion
Long-Term Stress:
The hypothalamus activates the adrenal cortex via hormonal stimuli. This greatly reinforces the continuing short-term stress response
Long-Term Stress Steps:
- Stressors cause hypothalamic neurons to release corticotropin-releasing hormone
- CRH travels via the portal system of blood vessels to the anterior pituitary
- Anterior pituitary cells release Adrenocorticotropic hormone
- ACTH travels in blood to the adrenal cortex
- The adrenal cortex synthesizes and releases glucocorticoids
Short-term stress has effects on:
Cardiovascular
Respiratory
Metabolic
Long-term stress has effect on:
Metabolic & renal
Hyposecretion - Epinephrine and norepinephrine are not essential to life therefore . . .
There are no problems associated with hyposecretion
Hypersecretion leads to symptoms of the uncontrolled sympathetic nervous system such as:
Hyperglycemia
Increased metabolic rate
Rapid heart beat
Palpitations
Hypertension
Intense nervousness
Sweating
Select the hormone synthesized by the adrenal medulla.
A. epinephrine
B. Androgen
C. Cortisol
D. Aldosterone
A. Epinephrine
How is aldosterone classified?
A. glucocorticoid
B. mineralocorticoid
C. catecholamine
D. gonadocorticoid
B. Mineralocorticoid
Which adrenal gland hormone is correctly paired with one of its effects?
A. cortisol;kidneysretain sodium and water
B. Norepinephrine suppresses immune system
C. cortisol;increasesblood glucose level
D. aldosterone;dilates airways
C. cortisol;increasesblood glucose level
Pineal gland is a. . .
Small gland hanging from roof of third ventricle
_________ secretes __________, derived from serotonin
Pinealocytes
Melatonin
Melatonin may affect:
- timing of sexual maturation and puberty
- day/night cycles
- physiological processes that show rhythmic variations
- production of antioxidant & detoxification in cells
Pancreas has both ________ and ________ cells
Exocrine
Endocrine
______________ produce enzyme-rich juice for digestion
Acinar cells
______________ contain endocrine cells
Pancreatic islets
____________ produce __________
Alpha cells
Glucagon
___________ produce _________
Beta cells
Insulin
Glucagon is . . .
Extremely potent hyperglycemic agent
Glucagon is triggered by . . .
Decreased blood glucose levels, rising amino acid levels or sympathetic nervous system
Raises blood glucose levels by targeting liver to:
- break down glycogen into glucose (glycogenolysis)
- synthesize glucose from lactic acid and other non carbohydrates (gluconeogenesis)
- release glucose into blood
Insulin lowers blood glucose levels in three ways:
- enchanted membrane transport of glucose into fat and muscle cells
- inhibits breakdown of glycogen to glucose
- inhibits conversion of amino acids or fats to glucose
Adipose tissue cells release:
Lepton
Resistin
Adiponectin
Gastrointestinal tract has enteroendocrine cells secrete these hormones:
Gastric
Ghrelin
Secretin
Cholecystokinin (CCK)
Incretins
Skin secretes:
Calcitriol
Which Hormone is the most important for regulating calcium balance in the blood?
A. parathyroid hormone
B. Calcitronin
C. Calcitriol
D. Thyroid hormone
A. parathyroid hormone
How do cells of the pancreas respond to rising glucose levels?
A. Alpha cells release glucagon, which stimulates glycogen breakdown.
B. Acinar cells release insulin, which stimulates glucose uptake by cells
C. Exocrine cells release proinsulin, which inhibits the breakdown of glycogen to glucose.
D. Beta cells release insulin, which stimulates glycogen formation in the liver
D. Beta cells release insulin, which stimulates glycogen formation in the liver
