Ch. 5: The Endocrine System Flashcards
What are peptide hormones?
- derived from larger precursor proteins that are cleaved during posttranslational modification
- modified by the golgi that activates the hormones
- charged (polar) and cannot pass through the plasma membrane so binds to an extracellular recetor (first messenger) which triggers a second signal (second messenger), —- signal cascade that can induce amplification of the signal
- rapid onset of effects but short lived
- since polar can travel freely in the blood and do not need a special carrier
What are steroid hormones?
- derived from cholesterol
- produced by gonads and adrenal cortex
- nonpolar and can easily cross teh cell membrane
- intracellular or intranuclear receptors
- after binding the steroid hormone-receptor complex undergoes conformational changes and the receptor can bind directly DNA
- increased or decreased transcription of particular genes
- slower and longer lived effect than peptide hormones since there is gene regulation
What are amino acid-derivative hormones?
- epinephrine, norepinephrine, triiodyothyronine, thyroxine
- derived from one or two amino acids with modifications
What are direct hormones?
secreted and act directly on target tissue
major effects on non-endocrine tissues
What are tropic hormones?
require an intermediary to act
major effects on other endocrine tissues
What is the role of the hypothalamus in the endocrine system?
uses tropic hormones to regulate the pituitary gland
can cause whole body effects
What is negative feedback?
occurs when a hormone/product later in the pathway inhibits hormones/enzymes earlier in the pathway
stop production of substances that are already present in sufficient quantities
What is the hpophyseal portal system?
blood vessel system that directly connects the hypothalamus with the anterioir pituitary
The hypothalamus secretes…
How does the anterior pituitary gland respond to GnRH?
FSH and LH
The hypothalamus secretes…
How does the anterior pituitary gland respond to GHRH?
growth hormone (GH)
The hypothalamus secretes…
How does the anterior pituitary gland respond to TRH (thyroid-releasing hormone)?
thyriod-stimulatin hormone TSH
The hypothalamus secretes…
How does the anterior pituitary gland respond to CRF (corticotropin-releasing factor)?
adrenocorticotropic hormone ACTH
The hypothalamus secretes…
How does the anterior pituitary gland respond to prolactin-inhibiting factor (PIF or dopamine)?
inhibit release of prolactin
How does the posterioir pituitary recieve signals?
neurons in the hypothalamus send their axons down the pituitary stalk directly into the posterioir pituitary
the release oxytocin (uterine contractions in labor and lactation) and ADH/vasopressin (increases reabsorption of water in collectin ducts of the kidneys)
What are the products of the anterioir pituitary?
FLAT PEG
Follicle stimulating hormone (FSH)
Luteinizing hormone (LH)
Adrenocorticotropic hormone (ACTH)
Thyriod-stimulating hormone (TSH)
Prolactin
Endorphins
Growth hormone (GH)
FLAT - tropic hormones
PEG - direct hormones
What does FSH do?
promotes development of ovarian follicles and spermatogenesis
What does LH do?
promotes ovulation and testosterone production
What does ACTH do?
promotes synthesis and release of glucocorticoids from adrenal cortex
What does TSH do?
promotes synthesis and release of triiodothyronine and thyroxine from the thyroid
What does prolactin do?
promotes milk production
What do endorphines do?
decrease perception of pain and produce euphoria
What does GH do?
promotes growth of bone and muscle
What does the posterioir pituitary do?
has nerve terminals of neurons with cell bodies in hypothalamus
recieves and stores ADH and oxytocin
does not syntehsize any hormones
What does ADH/vasopressin do?
secreted in response to low blood volume or increased blood osmolarity
increases reabsorption of water in collecting duct of nephron
increases blood volume and decreases blood osmolarity
What does oxytocin do?
promotes uterine contractions during childbirth and promotes milk ejection in lactation
unusual to have a positive feedback loop
What controls the thyroid?
thyroid stimulating hormone from anterioir pituitary
What is the role of the thyroid?
set basal metabolic rate and promote calcium homeostasis
What are triiodothyronine (T3) and thyroxine (T4)?
- produced by follicular cells
- contain iodine
- increase basal metabolic rate
- alter use of glucose and fatty acids
What is calcitonin?
- poduced by parafollicular cells
- decreases plasma calcium levels by promoting calcium excretion in the kidneys, decreaes calcium absorption in the gut, and promoting calcium storage in bone
What are parathyroid glands?
four small structures that sit on posterioir surface of thyroid
produce parahyroid hormone (PTH)
What does PTH do?
- raises blood calcium levels by decreasing excretion of calcium by the kidneys and increases absorption of calcium in the gut and increases bone resorption
- activates vitamin D to have calcium and phosphate absorption in the gut
What are the adrenal glands?
on top of the kidneys
adrenal cortex secretes corticosteroids (glucocorticoids, mineralocorticoids, and cortical sex hormones)
adrenal cortex
What are glucocorticoids?
regulate glucose levels and affect protein metabolism
Ex. cortisol and cortisone (increase gluconeogenesis and decrease protein synthesis to raise blood glucose, inhibit the immune system, and participate in stress response)
release is stimulated by ATCH
adrenal cortex
What are mineralocorticoids?
used in salt and water homeostasis, most effects are on kidneys
mineralcorticoid
What does aldosterone do?
- increases sodium reabsorption in distal convoluted tubule and collecting duct of the nephron
- water follows sodium cations into the bloodstream and increases blood volume and pressure
- increases potassium and hydrogen ion excretion
- activity is regulated by the renin-angiotenisin-aldosterone system
Explain the renin-angiotensin-aldosterone system.
- decreased blood pressure
- juxtaglomerular cells in kidney secrete renin
- antiotensinogen into angiotenin I
- angiotensin I into andiotensin II by antiotensin-converting enzyme (ACE)
- antiotensin II stimultes adrenal cortex
- aldosterone is released
- increases blood pressure and cardiac output
- decreased drive to stimulate renin (negative feedback)
Wat are cortical sex hormones?
Ex. androgens and estrogens
What is the adrenal medulla?
inside the adrenal cortex
production of epinephrine and norepinephrine (catecholamines)
glycogenolysis: increase metabolic rate, increase heart rate, dilate bronchi, shunt blood flow to the systems
What does the pancreas do?
exocrine (secrete substances directly into ducts) and endocrine functions
hormone producing cells are group together into islets of Langerhans throughout the pancreas
islets have alpha, belta and delta cells
secreted by alpha cells
What is glucagon?
glucagon increases glucose production when glucose levels are low
stimulatin protein and fat degradation, glycogenolysis and gluconeogenesis
secreted by beta cells
What is insulin?
secreted when blood glucose leves are high and causes muscle and liver cells to take up glucose and store it as glycogen for later
secreted by delta cells
What is somatostatin?
inhibitor of both insulin and glucagon secretion
secreted by high blood glucose and amino acid concentrations
What is the role of the testes?
secrete testosterone in response to LH and FSH
What is the role of the ovaries?
secrete estrogen and progesterone in response to LH and FSH (gonadotropins)
What is the pineal gland?
located in the brain and secretes melatonin
What is erythropoietin?
produced by the kidneys in response to low oxygen levels in blood
stimulates bone marrow to increase production of red blood cells
What is atrial natriuretic peptide (ANP)?
released by the heart
promotes excretion of salt and wate rin the kidneys in response to stretching of the atria (high blood volume)
What is thymosin?
released by the thymus
helps with proper T0cell deveopment and differentiation
