Chapter 5.2 Flashcards
How does the hypothalamus control the pituitary gland
- it controls the pituitary gland through paracrine release of hormones into a portal system
- > this portal system directly connects the two organs
How is the release of hormones regulated by the hypothalamus
-it is regulated by negative feedback
What blood vessel system connects the anterior pituitary with the hypothalamus
- the hypophyseal portal system is a blood vessel system
- >that connects the hypothalamus to the anterior pituitary
List the hormones released by the anterior pituitary. There are 7.
1) ACTH
2) TSH
3) LH
4) FSH
5) Prolactin
6) Endorphins
7) Growth Hormone
List the hormones released by the hypothalamus. There are 4.
1) CRF
2) TRH
3) GnRH
4) PIF(prolactin inhibiting factor)->actually dopamine
5) GHRH
How does the hypothalamus communicate with the posterior pituitary gland
-posterior pituitary does not receive TROPIC hormones
through the hypophyseal system
->rather hypothalamus sends axons down the PITUITARY STALK directly onto the posterior pituitary
What two hormones are released by the posterior pituitary
- oxytocin
- > increases uterine contractions during labour
- > also increases milk letdown during lactation
- ADH
- > increases reabsorption of water in the collecting ducts of the kidney
- > it is released in response to increased plasma osmolarity or increased concentration of solutes within the blood
What are the four tropic hormones released by the anterior pituitary
1) FSH
2) LH
3) TSH
4) ACTH
What are the three direct hormones released by the posterior pituitary
1) Prolactin
- >stimulates milk production in mammary glands
- >blocked in release until placenta is removed
- >in this case, progesterone/estrogen/dopamine levels drop
2) Growth hormone
3) Endorphins
What is the mechanism of growth hormone
- prevents glucose uptake in certain tissues(those that are not growing)
- stimulates the breakdown of fatty acids
What is the result of too much or too little GH during childhood
Too much= gigantism
Too little= dwarfism
What does excess GH in adult stage result in
-results in acromegaly
Describe again how ADH works
- increased blood osmolarity(sensed by osmoreceptors)
- decrease blood volume(sensed by baroreceptors)
-mechanism occurs in the collecting duct
What kind of loop does oxytocin work off. Note that oxytocin can be released due to suckling on the nipple by infants
- it works off a positive feedback loop
- > release promotes uterine contractions
- > which promotes more oxytocin release
What are the two major functions of the thyroid hormone
-setting basal metabolic rate and calcium homeostasis
- metabolic rate is controlled by T3/T4
- calcium levels are controlled by calcitonin
How are T3 and t4 produced in the thyroid
-by the iodination of the amino acid tyrosine in the follicular cells of the thyroid
What does increased levels of T3 and T4 do. Note that it has to do with cellular respiration
- increased levels of T3/T4= increased cellular respiration
- >therefore, greater amount of protein and fatty acid turnover
What condition does a deficiency in iodine lead to
- it results in hypothyroidism
- >characterized by lethargy, decreased body temperature, slow respiratory/heart rate, cold intolerance and weight gain
What condition does an excess stimulation in iodine lead to
- it results in hyperthyroidism
- >increased body temperature, increased respiration, heart rate and weight loss(also heat intolerance)
What cells produce calcitonin? What is the role of calcitonin?(describe the three ways it reduces calcitonin)
- C cells produce calcitonin
- calcitonin acts to decrease plasma calcium levels in three ways
- > increased calcium excretion from the kidneys
- > decreased calcium absorption from the gut
- > increased storage of calcium in the bone
What stimulates the secretion of calcitonin from the C-cells
-high levels of calcium in the blood stimulate secretion of calcitonin from the C-cells
What is the role of PTH?
- antagonistic hormone to calcitonin
- it decreases the excretion of calcium by the kidneys
- increases absorption of calcium in the gut
- increases bone resorption
How are PTH and Vitamin D related
- PTH activates vitamin D
- >which is required for the absorption of calcium and phosphate in the gut
Does PTH have an effect on phosphate levels
- no
- >it just increases calcium levels
What are the role of glucocorticoids? Give two examples
- they are hormones that regulate glucose levels
- > they also affect protein metabolism
- > examples are: cortisol and cortisone
How do glucocorticoids relate to protein synthesis and gluconeogenesis
-they increase gluconeogenesis and decrease protein synthesis
How does glucocorticoids related to inflammation and immunological responses
-they decrease inflammation and immunologic responses
What are the roles of mineralcorticoids. Give an example of this type of hormone.
- used in salt and water homeostasis
- > their most profound effect are on the kidneys
- an example is aldosterone
- > increases sodium reabsorption in the distal convoluted tubule and the collecting duct of the nephron
How does aldosterone work in terms of blood pressure and plasma osmolarity? Also describe its relation to potassium and hydrogen ions.
- it increases blood pressure but does not affect plasma osmolarity
- it decreases the reabsorption of potassium and hydrogen ions in distal/collecting duct
- > promoting their excretion in urine
Where are angiotensin-converting enzymes located
-they are located in the lungs
Name the three corticosteroids
1) Glucocorticoids(sugar)
2) Mineralcorticoids(salt)
3) Cortical sex hormones(sex)
What is the role of glucagon? What cells is it produced by? When is it inhibited?
- it is produced by alpha cells
- it is secreted during times of fasting
- > when glucose levels run low
- > glucagon is released to convert glycogen to glucose
- > also increases gluconeogenesis
-it is inhibited when glucose levels are high
What is the role of insulin? What cells is it produced by? When is it inhibited?
- the role of insulin is antagonistic to glucagon
- it is secreted when blood glucose levels are high
- > secreted by beta cells
-it stimulates anabolic processes like fat and protein synthesis
What is aldestorone under the control of
- under the control of renin-angiotensin-aldosterone system
- > decreased blood pressure causes juxtaglomerular cells of the kidney to secrete renin
- > renin cleaves inactive plasma protein, angiotensionegen, to its active form, angiotensin 1
- > angiotensin 1 is converted to angiotensin 2 by angiotensin converting enzyme
- > angiotensin 2 stimulates the adrenal cortex to secrete aldosterone
Is the pancreas an exocrine and endocrine tissue
- yes
- > the exocrine tissue secrete substance directly into the ducts
- > the endocrine aspect there are hormone-producing cells grouped together into islets of Langerhans
- islets contain alpha, beta and delta cells
- > alpha cells secrete glucagon, beta cells secrete insulin and delta cells secrete somatostatin
What does underproduction of insulin lead to
- diabetes mellitus
- > characterized by hyperglycemia
- > glucose can result in urine
- > this can lead to excess excretion of water and an increase in urine volume
Do diabetics often report polyruia(increased frequency of urination) and polydipsia(increased thirst)
-yes
What are the two types of diabetes
Type 1
- > insulin dependant diabetes
- > caused by autoimmune destruction of the beta cells of the pancreas
- > these individuals produce little or no insulin because the majority of the beta cells are destroyed
Type 2
- > this is non insulin dependant diabetes
- > result of receptor level resistance to the effects of insulin
- > due to diet and obesity
What is somatostatin and how is it released
- it is an inhibitor of insulin and glucagon
- > high blood glucose and amino acid concentrations stimulate its secretion
-somatostatin can also decrease grwoth hormone secretion
How does the pineal gland know when to release melatonin
-because of its projections directly from the retina
Discuss erythripoietin, ANP, and thymosin
Erythripoietin
- > produced by the kidneys
- > stimulates red blood cell production in the bone marrow
Heart
- > releases ANP to help regulate salt and water balance
- > when cells in the atria are stretched from excess blood volume, they release ANP
- > this hormone promotes excretion of sodium and increases urine volume
- > lowers blood volume and pressure and has no effect on blood osmolarity
Thymosin
- > located behind the sternum
- > important for proper T-cell development and differentiation
