Chapter 5: The Endocrine System Flashcards
The organs of the endocrine system are?
glands
____________ are signaling molecules that are secreted directly into the bloodstream to distant target tissues
hormones
What are the 3 types of chemical identities of hormones?
- peptides
- steroids
- amino acid derivatives
________ hormones are made up of amino acids, ranging in size from quite small (such as ADH) to relatively large (such as insulin).
peptide
Peptide hormones are all derived from what?
When are they cleaved into their peptides?
larger precursor polypeptides
post-translational modification
After post-translational modification, these smaller units are transported to the ________ ____________ for further modifications that activate the hormones and direct them to the correct locations in the cell.
Golgi apparatus
Why can’t peptide hormones go through the plasma membrane?
They are charged
If peptide hormones can’t pass through the membrane, how do they act?
They have to bind to an extracellular receptor
The peptide hormone is considered the first ________________.
messenger
As a first messenger, the peptide hormone binds to an ________________ receptor and triggers the transmission of a second signal known as the ____________ ________________.
extracellular; second messenger
What are 3 common second messengers?
- cAMP
- inositol triphsophate (IP3)
- Calcium
GPCR Pathway
The binding of a peptide hormone triggers a GPCR to either activate/inhibit an enzyme called ____________ ________, raising or lowering the levels of ________ accordingly.
adenylate cyclase; cAMP
cAMP can bind to intracellular targets, such as ________ ________ ____, which phosphorylates transcription factors like cAMP response element-binding protein (CREB) to exert the hormone’s ultimate effect.
protein kinase A
What does cAMP bind to? What does that target phosphorylate?
protein kinase A, CREB
How quick do peptide hormones take to come into effect and how long do they last?
Why?
What effect does this have?
Rapid but short lived
Because they act through second messenger cascades, which are transient
Makes it easier to turn on and off
What allows peptide hormones to travel freely in the bloodstream? Do they need carriers?
What is this in contrast to?
They can travel because they are water-soluble and do NOT need carriers
In contrast to steroid hormones, which are lipid-soluble
Steroid hormones are derived from ____________ and are produced by what two things?
cholesterol; gonads AND adrenal cortex
Since steroid hormones are derived from nonpolar molecules, is it easier or harder for them to cross the cell membrane?
easier
Steroid hormone receptors are usually where in relation to the cell?
Either intracellular (in cytosol) or intranuclear (in nucleus)
Once a steroid hormone binds, the steroid hormone-receptor complexes undergo conformational changes. The receptor then binds directly to ________, resulting in either increased o decreased transcription of particular genes, depending on the identity of the hormone.
DNA
A common form of conformational change is ________________, or pairing of two receptor-hormone complexes.
dimerization
How quick do steroid hormones take to come into effect and how long do they last?
Why?
Slower, but longer lived
They participate in gene regulation, causing alterations in the amount of mRNA and protein present in a cell by direct action on DNA
Steroid hormones are not water-soluble, so they must be carried around by ____________ to travel in the bloodstream.
proteins
Some transport proteins for steroids are very specific and carry only one hormone, while others are nonspecific, such as ________________.
albumin
Hormones are generally ____________ while attached to a carrier protein.
inactive
________ ________-derivative hormones are less common thn peptide and steroid hormones, but include hormones like epinephrine, norepinephrine, triiodothyronine, and thryoxine.
amino acid
Amino acid-derivative hormones are derived from (how many?) amino acids, usually with a few additional modificiations.
1-2
Which amino acid-derivative hormones are catecholamines?
epinephrine and norepinephrine
Hormones can also be classified by target tissue. What are 2 types?
direct hormones
tropic hormones
What characterizes direct hormones? What’s an example?
Acts directly on a target tissue
insulin
What characterizes tropic hormones? What’s an example?
Need an intermediary to act
Ex. gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH acts on the gonads to stimulate testosterone production in males and estrogen production in females.
What 2 hormones does gonadotropin-releasing hormone (GnRH) stimulate the release of?
luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
What does luteinizing hormone (LH) act on?
gonads
What does LH stimulate production of in females? males?
estrogen, testosterone
9 of them
What are the major endocrine glands?
- hypothalamus
- pituitary gland
- thyroid
- parathyroid glands
- adrenal glands
- pancreas
- gonads (testes and ovaries)
- pineal gland
The ________________ is the bridge between the nervous and endocrine systems.
hypothalamus
The hypothalamus regulates the ____________ gland through ________ hormones.
pituitary; tropic
The hypothalamus is located in the ____________, directly above the pituitary gland and below the thalamus.
forebrain
Since the hypothalamus and the pituitary are close to each other, the hypothalamus controls the pituitary through ____________ release of hormones into a portal system that directly connects the two organs.
paracrine
The hypothalamus secretes compounds into the ____________ ________ system, which is a blood vessesl system that directly connects the hypothalamus with the anterior pituitary.
hypophyseal portal
Hormones released from the hypothalamus travel directly to the anterior pituitary and cannot be found in appreciable concentrations in the systemic circulation
____________ is an alternative term for the pituitary
hypophysis
Once hormones are released from the hypothalamus into this portal bloodstream, they travel down the ____________ ________ and bind to receptors in the anterior pituitary, stimulating the release of other hormones.
pituitary stalk
GnRH is released by the hypothalamus then ________ and ________ are released by the anterior pituitary in response.
FSH and LH
When growth hormone-releasing hormone (GHRH) is released by the hypothalamus and ________ hormone is released by the anterior pituitary in response.
growth
GH
When thyroid-releasing hormone (TRH) is released by the hypothalamus and ________-____________ hormone is released by the anterior pituitary in response.
thyroid-stimulating
TSH
When corticotropin-releasing factor (CRF) is released by the hypothalamus and ____________________ hormone is released by the anterior pituitary in response.
adenocorticotropic
(ACTH)
An exception to this pattern of tropic hormones being released by the hypothalamus and hormones being released by the anterior pituitary in response IS - ____________-____________ factor, which is actually dopamine, is released by the hypothalamus and causes a decrease in prolactin secretion.
prolactin-inhibiting
Each tropic hormone causes the release of another hormone from an endocrine gland that has ____________ feedback effects.
negative
The release of CRF (tropic hormone) stimulates the anterior pituitary to secrete ________.
ACTH
ACTH will then cause the adrenal cortex to increase the level of ________ being secreted into the blood.
cortisol
To prevent excess cortisol secretion, cortisol inhibits the ____________ and ________ ____________ from releasing CRF and ACTH, respectively.
hypothalamus, anterior pituitary
Three-organ systems are commonly referred to as ________; e.g. hypothalamic-pituitary-adrenal.
axes
The ____________ pituitary does not receive tropic hormones through the hypophyseal portal system. Instead, neurons in the hypothalamus send their axons down the pituitary stalk directly into here.
posterior
What are two examples of hormones that are produced by the posterior pituitary after stimulated by neurons in the hypothalamus (and pituitary stalk)?
Oxytocin
Antidiuretic hormone (ADH)
________ stimulates uterine contractions during labor as well as milk letdown during lactation.
Oxytocin
____________ hormone, also known as vasopressin, increases reabsorption of water in the collecting ducts of the kidneys. It is secreted in response to increased plasma osmolarity, or increased concentration of solutes within the blood.
antidiuretic
What is another name for antidiuretic hormone?
vasopressin
What are the 2 parts that the pituitary gland is divided into?
Anterior and posterior
FLAT PEG
What are the 7 products of the anterior pituitary?
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Adrenocorticotropic hormone (ACTH)
Thyroid-stimulating hormone (TSH)
Prolactin
Endorphins
Growth hormone (GH)
Which 4 products of the anterior pituitary are tropic hormones?
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Adrenocorticotropic hormone (ACTH)
Thyroid-stimulating hormone (TSH)
Which 3 products of the anterior pituitary are direct hormones?
Prolactin
Endorphins
Growth hormone (GH)
The release of FSH and LH is stimulated by?
gonadotropin-releasing hormone (GnRH)
FSH and LH act on the ?
gonads
the release of ACTH is stimulated by ____ from the hypothalamus
CRF
The release of thyroid-stimulating hormone is stimulated by ________?
thyroid-releasing hormone
________ is more important in females than males, it does what?
proalctin; milk production
The release of ________ from the hypothalamus decreases the secretion of prolactin.
dopamine
High levels of estrogen and progesterone allow for the development of milk ducts in preparation for lactation, but it is not until shortly after the expulsion of the ____________, when estrogen, progesterone, and dopamine levels drop, that the block on milke production is removed and lactation begins.
placenta
____________ decrease the perception of pain.
endorphins
________ hormone (GH) promotes the growth of bone and muscle. Requires a lot of what?
growth; glucose
Growth hormone prevents ________ uptake in certain tissues (those that are not growing), and stimulates the breakdown of ____________ ________. This allows muscle and bone to use it.
glucose; fatty acids
Growth hormone release is stimulated by ________ from where?
growth hormone-releasing hormone; hypothalamus
Bone growth originates in special regions of the bone known as ____________ ____________, which seal shut during puberty.
epiphyseal plates
An excess of GH results in what? A deficit?
gigantism, dwarfism
In adults, GH can cause ________________, where smaller bones are affected.
acromegaly
The ____________ pituitary contains the nerve terminals of neurons with cell bodies in the hypothalamus.
posterior
The posterior pituitary receives and stores 2 hormones produced by the hypothalamus, which are?
- ADH
- oxytocin
ADH is secreted in response to what two possible things?
- low blood volume (sensed by baroreceptors)
- increased blood osmolarity (as sensed by osmoreceptors)
ADH acts at the level of the collecting duct - what does it do?
increases the permeability of the duct to water, which increases reabsorption of water from the filtrate in the nephron
Since ADH increases the reabsorption of water from the filtrate in the nephron, it causes greater water retention, which results in what two things?
- increased blood volume
- higher blood pressure
Oxytocin is unusual in that it has a ____________ feedback loop.
positive
The thyroid is controlled by what hormone from the anterior pituitary?
thyroid-stimulating hormone
The thyroid is on the front surface of the ________; it can be palpated (felt) as an organ near the base of the neck that moves up and down with swallowing.
trachea
The thyroid has 2 major functions, what are they?
- Setting basal metabolic rate
- Promoting calcium homeostasis
What 2 things does the thyroid release in order to setting basal metabolic rate?
- Triiodothyronine (T3) and
- Thyroxine (T4)
What does the thyroid release in order to promote calcium homeostasis?
calcitonin
How are triiodothyronine (T3) and thyroxine (T4) produced? Where?
The iodination of the amino acid tyrosine in the follicular cells of the thyroid
What does the number 3 and 4 of triiodothyronine and thyroxine signify?
the number of iodine cells attached to the tyrosine
Thyroid hormones are capable of resetting the ________ metabolic rate of the body by making energy production more or less efficient, as well as altering the utilization of glucose and fatty acids.
basal
Increased amounts of T3 and T4 leads to increased what?
cellular respiration
Increased amounts of T3 and T4 leads to increased cellular respiration, which leads to increased what? Why?
Increased protein and fatty acid turnover; it speeds up both synthesis and degradation of these compounds
High plasma levels of thyroid hormones will lead to decreased ____ and ____ synthesis.
TSH and TRH
A deficiency of iodine or inflammation of the thyroid may result in ________________, in which thyroid hormones are secreted in insufficient amounts or not at all
hypothyroidism
What characterizes hypothyroidism?
lethargy, decreased body temp, slowed respiratory and HR, cold intolerance, and weight gain
A deficiency in thyroid hormones as children will result in intellectual disability and developmental delay. This is called ?
cretinism
An excess of thyroid hormone, which may result from a tumor or thyroid overstimulation, is called
Hyperthyroidism
What characterizes hyperthyroidism?
Heightened activity level, increased body temperature, increased respiratory and HR, heat intolerance, and weight loss
In the thyroid gland, what are the 2 distinct cell populations within the gland?
- follicular cells
- C-cells (parafollicular cells)
C-cells produce what hormone?
Calcitonin
Calcitonin tones down calcium levels in the blood
What are 3 ways that calcitonin decreases plasma calcium?
- Increasing calcium excretion from the kidneys
- Decreasing calcium absorption from the gut
- Increasing storage of calcium in the bone
(low/high?) levels of calcium in the blood stimulates secretion of calcitonin from the C-cells
high
The ____________ are 4 small pea-sized structures that sit on the posterior surface of the thyroid.
parathyroid
The hormone produced by the parathyroid glands is ?
parathyroid hormone (PTH)
PTH serves as an ____________ hormone to calcitonin, as it raises blood calcium levels.
antagonistic
In what 3 ways does PTH raise blood calcium levels?
- Decreases excess calcium excretion by the kidneys
- Increases absorption of calcium in the gut (via vitamin D)
- Increases bone resorption (by freeing calcium)
As levels of plasma calcium rise, PTH secretion is ____________. Parathyroid hormone also promotes phosphorus homeostasis.
decreased
In what 2 ways does PTH promote phosphorus homeostasis?
- Increasing resorption of phosphate from the bone
- Reducing reabsorption of phosphate in the kidney
What is antagonist to PTH?
Calcitonin
PTH also activates vitamin ____, which is required for the absorption of calcium and phosphate in the gut.
D
The overall effect of PTH is a significant increase in blood. ________ levels with little effect on ________ .
calcium; phosphate
p. 197
the absorption of phosphate in the gut and its excretion in the kidney somewhat cancel each other
The ____________ ____________ are located on top of the kidneys.
adrenal glands
Each adrenal gland consists of what 2 things?
- cortex
- medulla
Each part of the gland is responsible for the secretion of different hormones. The adrenal cortex secretes ____________________.
corticosteroids
What are the 3 classes of corticosteroids?
- glucocorticoids
- mineralcorticoids
- cortical sex hormones
____________ are steroid hormones that regulate glucose levels. These also affect protein metabolism.
glucocorticoids
What are 2 common examples of glucosteroids?
- cortisol
- cortisone
What effect do cortisol and cortisone have on blood glucose? How do they act?
raise blood glucose;
1. increase gluconeogenesis
2. decrease protein synthesis
Cortisol is known as a stress hormone, how does it work?
Releases glucose in times of physical/emotional stress in order to increase blood sugar and provide a ready source of fuel
Glucocorticoid release is under the control of ________________ hormone.
adrenocorticotropic
____________-____________ factor from the hypothalamus promotes release of ACTH from the ____________ ____________, which promotes the release of ____________ from the adrenal cortex.
corticotropin-releasing; anterior pituitary; glucocorticoids
________________ are used in salt and water homeostasis.
mineralocorticoids
Mineralocorticoids act the most on which organ?
kidneys
The most noteworthy mineralocorticoid is ____________, which increases sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron.
aldosterone
aldosterone
Water follows Na+ into the bloodstream, increasing blood volume and pressure. Since water and sodium ions flow together, what remains unchanged?
plasma osmolarity
Aldosterone doesn’t change plasma osmolarity (only pressure and volume), which is in contrast to ADH, which only does what?
Increases water reabsorption (which decreases plasma osmolarity)
Aldosterone also decreases the reabsorption of ____________ and ____________ ions in these same segments of the nephron, promoting their excretion in the urine.
potassium, hydrogen
Aldosterone is primarily under the control of the ________-____________-____________ system.
renin-angiotensin-aldosterone
Decreased blood pressure causes the ________________ cells of the kidney to secrete ______, which cleaves an inactive plasma protein, ________________, to its active form, angiotensin I. Angiotensin I is then converted to angiotensin II by ____________-____________ enzyme in the lungs. Angiotensin II stimulates the adrenal cortex to secrete ___________. Once BP is restored, there is a decreased drive to stimulate renin release (negative feedback).
juxtaglomerular; renin; angiotensinogen; angiotensin-converting; aldosterone
The adrenal glands also make cortical sex hormones. What are they?
- androgens
- estrogens
Because the testes secrete large quantities of androgens, adrenal testosterone plays a ________ role in male physiology. Because the ovaries secrete far less androgens, females are more ____________ to disorders of cortical sex hormone production.
small; sensitive
3 S’s
What are the functions of the corticosteroids?
- salt (mineralocorticoids)
- sugar (glucocorticoids)
- sex (cortical sex hormones)
Nestled inside the adrenal cortex is the adrenal ____________. A derivative of the nervous system, this organ is responsible for the production of the sympathetic hormones ____________ and ____________________.
medulla; epinephrine and norepinephrine
Both epinephrine and norepinephrine are amino acid-derivatives hormones that belong to a larger class of molecules known as ________________.
catecholamines
Hormones released from the adrenal medulla affect the human on what scale?
system-wide
Epinephrine can increase the breakdown of ____________ to glucose (glycogenolysis) in both liver and muscles, as well as increase the ________ metabolic rate.
glycogen; basal
Both epinephrine and norepinephrine will increase ________ ________, dilate the ________, and shunt blood flow to the systems that would be used in a sympathetic response.
heart rate; bronchi
Cortisol is understood to mediate ________-term stress responses, while catecholamines are understood to control ________-term stress responses.
long; short
Cortisol actually increases the synthesis of ________________.
catecholamines
The pancreas has both exocrine and endocrine functions. Exocrine tissues secrete substances where?
Directly into ducts
From an endocrine standpoint, small clusters of hormone-producing cells are grouped together into ________ of ____________ throughout the pancreas.
islets of Langerhans
Islets contain 3 distinct types of cells, what are they?
alpha, beta, and delta
What hormone do alpha-cells secrete?
glucagon
What hormone do beta-cells secrete?
insulin
What hormone do delta cells secrete?
somatostatin
________ is secreted during times of fasting.
glucagon
When glucose levels are low, glucagon increases glucose production by triggering ____________, ________________, and the degradation of protein and fat.
glycogenolysis, gluconeogenesis
In addition to low blood glucose concentrations, certain gastrointestinal hormones, such as ____________ and ________, increase glucagon release from alpha-cells. When blood glucose concentrations are high, glucagon release is ____________.
cholecystokinin and gastrin; inhibited
____________ is antagonistic to glucagon is released when blood glucose levels are high.
Insulin
Insulin induces what?
- muscle and liver cells to take up glucose and store it as glycogen for later use
Because insulin is active when glucose levels are high, it stimulates ________ processes, such as fat and protein synthesis.
anabolic
In excess, insulin will cause ____________, which is characterized by low blood glucose concentration.
hypoglycemia
Underproduction, insufficient secretion, or insensitivity to insulin can all results in ____________ ____________, which is clinically characterized by ________________.
diabetes mellitus; hyperglycemia
In the kidneys, excessive glucose in the filtrate will overwhelm the nephron’s ability to reabsorb glucose, resulting in its presence in the urine.
Because glucose is an osmotically active particle and does not readily cross the cell membrane, the presence of glucose in the filtrate leads to excess excretion of water and an increase in?
urine volume
Patients who have diabetes often report ____________ (increased frequency of urination) and ________________ (increased thirst)
polyuria, polydipsia
Type ____ (insulin-dependent) diabetes mellitus is caused by autoimmune destruction of the beta-cells of the pancreas, resulting in low or absent insulin production.
I
body does not make enough insulin
Type ____ (non-insulin dependent) diabetes mellitus is the result of receptor-level resistance to the effects of insulin.
II
body cannot use insulin properly
____________ is an inhibitor of both insulin and glucagon secretion.
somatostatin
What stimulates somatostatin secretion?
- High blood glucose
- High amino acid concentrations
What produces somatostatin? What does it affect?
hypothalamus; decreases growth hormone secretion in addition to its effects on insulin and glucagon
The ________ secrete testoserone in response to stimulation by gonadotropins (LH and FSH)
testes
What does testosterone do?
Causes sexual differentiation of the male during gestation and also promotes the development and maintenance of secondary sex characteristics in males
The ________ secrete estrogen and progesterone in response to gonadotropins.
ovaries
____________ is involved in development of the female reproductive system during gestation and also promotes the development and maintenance of secondary sex characteristics in females.
estrogen
The ________ gland is located deep within the brain and secretes the hormone melatonin.
pineal
The kidneys play a role in water balance. ADH increases water permeabilitiy in the ____________ duct, and the renin-angiotensin-aldosterone system increases ________ and water reabsorption in the distal ____________ tubule and collecting duct.
collecting; sodium; convulted
The kidneys also produce ____________, which stimulates bone marrow to increase production of erythrocyes (red blood cells). It is secreted in response to low oxygen levels in the blood.
erythropoietin
The heart releases ________ ____________ peptide to help regulate salt and water balance. When cells in the atria are stretched from excess blood volume, they release this peptide.
atrial natriuretic peptide (ANP)
ANP promotes excretion of ________ and therefore increases urine volume. This is antagonistic to ____________ because it lowers blood volume and pressure, and has no effect on blood osmolarity.
sodium; aldosterone
The thymus, located directly behind the sternum, releases ____________, which is important for proper T-cell development and differentiation.
thymosin
Review list of hormones on Table 5.1
page 206-207
