Endrocrine System Flashcards
Organs of endocrine system are called?
Glands
Where are hormones secreted into?
Bloodstream
Do hormones target close or far tissues?
Far
What are the three chemical identities of hormones?
- Peptides
- Steroids
- Amino Acid Derivatives
Are peptide hormones charged? How does this affect the way they leave and enter cells?
Yes - leave cells by exocytosis and then bind to extracellular receptors
First and second messengers in peptide hormones
First messenger - peptide hormone itself, binds to a receptor and triggers the transmission of a second signal
Second messenger - this second signal triggered by the peptide hormone
Examples of second messengers
cAMP
IP3
Calcium
What type of hormone is insulin?
Peptide hormone
What type of hormone is ADH?
Peptide hormone
What enzyme affects the levels of cAMP?
Adenylate cyclase
What receptor affects the levels of cAMP?
G-protein coupled receptors
Are peptide hormone responses fast or slow?
Fast
Are peptide hormone responses long or transient?
Transient (due to secondary messenger cascades)
Are peptide hormones hydrophobic or hydrophilic? How does this affect the way they travel through the body?
Hydrophilic - can travel freely in the bloodstream
What are steroid hormones derived from?
Cholesterol
Where are steroids produced?
Gonads and adrenal cortex
Are steroid hormones charged? How does this affect the way they leave and enter cells?
No - they can easily cross the cell membrane and have receptors within the cell
What do steroid receptors do in the cell once bound?
Undergo a conformational change and bind directly to DNA
Are steroid hormone responses fast or slow?
Slow
Are steroid hormone responses long or transient?
Long
Are steroid hormones hydrophobic or hydrophilic? How does this affect the way they travel through the body?
Hydrophobic - must travel on proteins through the blood
Are steroid hormones active when bound to a carrier protein?
No
Examples of amino acid derived hormones?
Epi
Norepi
What are examples of catecholamines?
Epi and norepi
What receptors do catecholamines bind to?
G-protein coupled receptors
What receptors do thyroid hormones bind to?
Intracellular
What are tropic hormones?
Hormones that require an intermediary and do not directly affect the muscle/bone
What gland does the hypothalamus have a direct affect on?
Pituitary - anterior and posterior
How are the hypothalamus and anterior pituitary connected?
Hypophyseal portal system - release of hormones
Where is GnRH released from and what gland and hormone does it affect?
Released from hypothalamus and acts on anterior pituitary to release FSH and LH
Where is GHRH released from and what gland and hormone does it affect?
Released from hypothalamus and acts on anterior pituitary to release GH
GHRH hormone
Growth-hormone-releasing hormone
GnRH hormone
Gonadatropin-releasing hormone
Where is TRH released from and what gland and hormone does it affect?
Released from hypothalamus and acts on anterior pituitary to release TSH
TRH hormone
Thyroid-releasing hormone
TSH hormone
Thyroid-stimulating hormone
Where is CRF released from and what gland and hormone does it affect?
Released from hypothalamus and acts on anterior pituitary to release ACTH
CRF hormone
Corticotropin releasing factor
ACTH hormone
Adrenocorticotropic hormone
Where is PIF released from and what gland and hormone does it affect?
Released from hypothalamus and acts on anterior pituitary to decrease prolactin secretion
PIF hormone
Dopamine - Prolactin-inhibiting factor
Axes in endocrine system
Three-organ systems
How are the hypothalamus and posterior pituitary connected?
Neurons in hypothalamus send neurons directly to anterior pituitary
What hormones does the posterior pituitary release?
Oxytocin and ADH
ADH hormone
Antidiuretic hormone
Oxytocin effects
Stimulates uterine contractions, lactation, bonding behavior
ADH effects
Increase reabsorption of water in the collecting ducts of kidneys
What is ADH secreted in response to in the blood?
Increased blood osmolarity - provides water to decrease this osmolarity
Where is prolactin secreted from?
Anterior pituitary
What does prolactin do?
Stimulate milk production in the mammary glands
How does lactation begin after birth?
Delivery of the placenta leads to a significant decrease in estrogen, progesterone, and dopamine - this (esp dopamine) decrease allows prolactin to stimulate milk production
Where are endorphins secreted from?
Anterior pituitary
Where is growth hormone secreted from?
Anterior pituitary
Acromegaly
Growth of small bones in adults due to effects of lasting growth hormone after the large bones have closed during puberty
What hormone has an unusual positive feedback loop?
Oxytocin
What are the two main functions of the thyroid?
- Setting basal metabolic rate
2. Promoting calcium homeostasis
What molecules does the thyroid release to set metabolic rate?
T3 and T4
What molecules does the thyroid release to promote calcium homeostasis?
Calcitonin
How are T3 and T4 produced?
Iondination of tyrosine
Where does Iondination of tyrosine occur?
Follicular cells of thyroid
How do increased levels of T3 and T4 affect metabolism?
Increase the rate of cellular respiration and thus increase the rate of synthesis and degradation of proteins and fatty acids
Cretinism
Intellectual disability and developmental delay caused by deficiency in thyroid hormones
Where in the thyroid is calcitonin produced?
C-cells
Parafollicular cells
What does calcitonin do to blood calcium levels?
Decreases
How does calcitonin affect blood calcium levels?
- Increase excretion from kidneys
- Increasing storage in bones
- Decreasing calcium absorption in gut
PTH hormone
Parathyroid hormone
PTH function
- Raises blood calcium levels (opposite mechanism of calcitonin)
- Phosphorus homeostasis
- Activation of vitamin D
What is the function of vitamin D?
Absorption of calcium and phosphate in the gut
Where are the adrenal glands located?
On top of the kidneys
What type of hormone does the adrenal cortex secrete?
Cortiocosteroids
Three classes of corticosteroids
Glucocorticoids
Mineralocorticoids
Cortical sex hormones
What is the function of glucocorticoids?
Regulate blood glucose levels and affect protein metabolism
Where are glucocorticoids secreted from?
Adrenal cortex
What are two glucocorticoids?
Cortisol and cortisone
What class of hormones is cortisol?
Glucocorticoid
What class of hormones is cortisone?
Glucocorticoid
How do cortisol and cortisone function?
Increase glucogenesis and decrease protein synthesis
What controls the release of glucocorticoids?
ACTH (which is stimulated by CRF)
What is the function of mineralocorticoids?
Affect salt and water homeostasis primarily through the kidney
What is an important mineralocorticoid?
Aldosterone
What is the function of aldosterone?
Increase sodium and water resorption - osmolarity remains the same, increases blood volume and pressure
What is a difference between aldosterone and ADH?
ADH changes blood osmolarity by only affecting water and aldosterone does not by affecting both sodium and water
What controls the release of mineralocorticoids?
Renin (kidney) - angiotensin (I to II in the lungs) - aldosterone system
Are males or females more sensitive to disorders of cortical sex hormone pathways?
Females - males get a lot of testosterone from the testes and don’t rely on the adrenal glands as much as females
What class of enzymes are androgens and testosterone?
Cortical sex hormones, corticosteroids, adrenal hormones
Where are epi and norepi produced?
Adrenal medulla
What two hormones are important to stress response and what are the differences between the two?
Cortisol - long term and slow response
Catecholamines (epi and norepi) - short term and long response
What are islets of Langerhans?
Small clusters of hormone-producing cells in the pancreas
What types of cells do the islets of Langerhans contain?
Alpha - Glucagon
Beta - Insulin
Delta - Somatostatin
Where specifically is glucagon secreted from?
Alpha cells in the islets of Langerhans in the pancreas
Where specifically is insulin secreted from?
Beta cells in the islets of Langerhans in the pancreas
Where specifically is somatostatin secreted from?
Delta cells in the islets of Langerhans in the pancreas
When is glucagon secreted?
Fasting - increases glucose production
Would hyperglycemia be caused by increased or decreased insulin activity?
Decreased
What cells would be affected in someone with Type-I diabetes?
Beta cells in the islets of Langerhans in the pancreas
What is the function of somatostatin?
Inhibitor of insulin and glucagon
What does the pineal gland secrete?
Melatonin