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MCAT Biology > Chapter 5.2 > Flashcards

Chapter 5.2 Flashcards

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1
Q

How does the hypothalamus control the pituitary gland

A
  • it controls the pituitary gland through paracrine release of hormones into a portal system
  • > this portal system directly connects the two organs
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2
Q

How is the release of hormones regulated by the hypothalamus

A

-it is regulated by negative feedback

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3
Q

What blood vessel system connects the anterior pituitary with the hypothalamus

A
  • the hypophyseal portal system is a blood vessel system

- >that connects the hypothalamus to the anterior pituitary

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4
Q

List the hormones released by the anterior pituitary. There are 7.

A

1) ACTH
2) TSH
3) LH
4) FSH
5) Prolactin
6) Endorphins
7) Growth Hormone

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5
Q

List the hormones released by the hypothalamus. There are 4.

A

1) CRF
2) TRH
3) GnRH
4) PIF(prolactin inhibiting factor)->actually dopamine
5) GHRH

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6
Q

How does the hypothalamus communicate with the posterior pituitary gland

A

-posterior pituitary does not receive TROPIC hormones
through the hypophyseal system
->rather hypothalamus sends axons down the PITUITARY STALK directly onto the posterior pituitary

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7
Q

What two hormones are released by the posterior pituitary

A
  • 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
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8
Q

What are the four tropic hormones released by the anterior pituitary

A

1) FSH
2) LH
3) TSH
4) ACTH

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9
Q

What are the three direct hormones released by the posterior pituitary

A

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

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10
Q

What is the mechanism of growth hormone

A
  • prevents glucose uptake in certain tissues(those that are not growing)
  • stimulates the breakdown of fatty acids
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11
Q

What is the result of too much or too little GH during childhood

A

Too much= gigantism

Too little= dwarfism

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12
Q

What does excess GH in adult stage result in

A

-results in acromegaly

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13
Q

Describe again how ADH works

A
  • increased blood osmolarity(sensed by osmoreceptors)
  • decrease blood volume(sensed by baroreceptors)

-mechanism occurs in the collecting duct

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14
Q

What kind of loop does oxytocin work off. Note that oxytocin can be released due to suckling on the nipple by infants

A
  • it works off a positive feedback loop
  • > release promotes uterine contractions
  • > which promotes more oxytocin release
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15
Q

What are the two major functions of the thyroid hormone

A

-setting basal metabolic rate and calcium homeostasis

  • metabolic rate is controlled by T3/T4
  • calcium levels are controlled by calcitonin
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16
Q

How are T3 and t4 produced in the thyroid

A

-by the iodination of the amino acid tyrosine in the follicular cells of the thyroid

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17
Q

What does increased levels of T3 and T4 do. Note that it has to do with cellular respiration

A
  • increased levels of T3/T4= increased cellular respiration

- >therefore, greater amount of protein and fatty acid turnover

18
Q

What condition does a deficiency in iodine lead to

A
  • it results in hypothyroidism

- >characterized by lethargy, decreased body temperature, slow respiratory/heart rate, cold intolerance and weight gain

19
Q

What condition does an excess stimulation in iodine lead to

A
  • it results in hyperthyroidism

- >increased body temperature, increased respiration, heart rate and weight loss(also heat intolerance)

20
Q

What cells produce calcitonin? What is the role of calcitonin?(describe the three ways it reduces calcitonin)

A
  • 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
21
Q

What stimulates the secretion of calcitonin from the C-cells

A

-high levels of calcium in the blood stimulate secretion of calcitonin from the C-cells

22
Q

What is the role of PTH?

A
  • antagonistic hormone to calcitonin
  • it decreases the excretion of calcium by the kidneys
  • increases absorption of calcium in the gut
  • increases bone resorption
23
Q

How are PTH and Vitamin D related

A
  • PTH activates vitamin D

- >which is required for the absorption of calcium and phosphate in the gut

24
Q

Does PTH have an effect on phosphate levels

A
  • no

- >it just increases calcium levels

25
Q

What are the role of glucocorticoids? Give two examples

A
  • they are hormones that regulate glucose levels
  • > they also affect protein metabolism
  • > examples are: cortisol and cortisone
26
Q

How do glucocorticoids relate to protein synthesis and gluconeogenesis

A

-they increase gluconeogenesis and decrease protein synthesis

27
Q

How does glucocorticoids related to inflammation and immunological responses

A

-they decrease inflammation and immunologic responses

28
Q

What are the roles of mineralcorticoids. Give an example of this type of hormone.

A
  • 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
29
Q

How does aldosterone work in terms of blood pressure and plasma osmolarity? Also describe its relation to potassium and hydrogen ions.

A
  • 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
30
Q

Where are angiotensin-converting enzymes located

A

-they are located in the lungs

31
Q

Name the three corticosteroids

A

1) Glucocorticoids(sugar)
2) Mineralcorticoids(salt)
3) Cortical sex hormones(sex)

32
Q

What is the role of glucagon? What cells is it produced by? When is it inhibited?

A
  • 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

33
Q

What is the role of insulin? What cells is it produced by? When is it inhibited?

A
  • 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

34
Q

What is aldestorone under the control of

A
  • 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
35
Q

Is the pancreas an exocrine and endocrine tissue

A
  • 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
36
Q

What does underproduction of insulin lead to

A
  • diabetes mellitus
  • > characterized by hyperglycemia
  • > glucose can result in urine
  • > this can lead to excess excretion of water and an increase in urine volume
37
Q

Do diabetics often report polyruia(increased frequency of urination) and polydipsia(increased thirst)

A

-yes

38
Q

What are the two types of diabetes

A

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
39
Q

What is somatostatin and how is it released

A
  • 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

40
Q

How does the pineal gland know when to release melatonin

A

-because of its projections directly from the retina

41
Q

Discuss erythripoietin, ANP, and thymosin

A

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

MCAT Biology (30 decks)

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