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MCAT: Biology > Chapter 5: The Endocrine System > Flashcards

Chapter 5: The Endocrine System Flashcards

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1
Q

Based on their chemical identities, what are the three types of hormones?

A
  • Peptides
  • Steroids
  • Amino acid derivatives
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2
Q

What are peptide hormones derived from?

A
  • From larger precursor polypeptides that are cleaved during posttranslational modification
  • These smaller units are transported to the Golgi apparatus for further modifications that activate the hormone and direct it to the correct location in the cell
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3
Q

Why must peptide hormones bind to an extracellular receptor?

A

Because they are charged and cannot pass through the plasma membrane

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4
Q

Peptide hormones are considered _______ messengers.

A

first

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5
Q

At each step of a signaling cascade, there is the possibility of what?

A

Amplification

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6
Q

What are some common secondary messengers?

A

cAMP, inositol triphosphate (IP3), and calcium

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7
Q

What are the characteristics of the effects of peptide hormones? Why?

A

Rapid and short-lived because these hormones act through transient second messenger systems

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8
Q

Which hormones are quicker to turn on and off: peptide hormones or steroid hormones?

A

Peptide hormones, but their effects do not last without constant stimulation

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9
Q

Do peptide hormones require carriers?

A

No since they are generally water-soluble, they can travel freely in the bloodstream

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10
Q

What are steroid hormones derived from? What are they primarily produced by?

A
  • Derived from cholesterol

- Produced primarily by the gonads and adrenal cortex

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11
Q

Which hormones can easily cross cell membranes? Why%

A

Steroid hormones because they are derived from nonpolar molecules

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12
Q

Where are the receptors for steroid hormones usually found?

A

Intracellularly (cytosol) or intranuclearly (nucleus)

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13
Q

How do steroid hormones function?

A
  • Steroid-receptor intracellular complex undergoes conformational changes (ex: dimerization)
  • The receptor binds directly to DNA to alter gene transcription (increase or decrease) –> alterations in the amount of mRNA and protein present in a cell
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14
Q

Do steroid hormones require carriers?

A
  • Yes, since they are not water-soluble

- They must dissociate from their carrier to function

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15
Q

What are amino acid-derivative hormones derived from?

A

One or two amino acids, usually with a few additional modifications

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16
Q

How do catecholamines function? What kind of hormone are they? Give examples.

A
  • Amino acid-derivative hormones (epinephrine and norepinephrine)
  • Bind to G protein-coupled receptors
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17
Q

How do thyroid hormones function? What kind of hormone are they?

A
  • Amino acid-derivative hormones

- Bind intracellulary

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18
Q

What are the characteristics of the catecholamines?

A

Extremely fast onset but are short-lived

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19
Q

What are the characteristics of thyroxine and triiodothyronine?

A

Slower onset but a longer duration

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20
Q

What are direct hormones? What major effects do they have? Give an example.

A
  • Hormones that are secreted and then act directly on a target tissue
  • Major effects in non-endocrine tissues
  • Insulin released by the pancreas
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21
Q

What are tropic hormones? What major effects do they have? Give an example.

A
  • Hormones that require an intermediary to act
  • Major effects in other endocrine tissues
  • GnRH stimulates LH and FSH
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22
Q

Where do tropic hormones usually originate in?

A

Brain and anterior pituitary gland

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23
Q

Most peptide and amino acid-derivative hormones have names that end in what?

A

-in or -ine

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24
Q

Most steroid hormones have names that end in what?

A

-one, -ol, -oid

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25
Q

What structure regulates the pituitary gland? How?

A

The hypothalamus through tropic hormones

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26
Q

Where is the hypothalamus located?

A

In the forebrain, directly above the pituitary gland and below the thalamus

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27
Q

What is negative feedback?

A

Occurs when a hormone (or a product) later in the pathway inhibits hormones (or enzymes) earlier in the pathway

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28
Q

What system directly connects the hypothalamus with the anterior pituitary?

A

Hypophyseal portal system

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29
Q

GnRH, released by the hypothalamus, causes the release of what other hormones? From where?

A
  • FSH and LH

- From the anterior pituitary

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30
Q

GHRH, released by the hypothalamus, causes the release of what other hormones? From where?

A
  • Growth hormone

- From the anterior pituitary

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31
Q

THR, released by the hypothalamus, causes the release of what other hormones? From where?

A
  • Thyroid-stimulating hormone (TSH)

- From the anterior pituitary

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32
Q

Corticotropin-releasing factor (CRF), released by the hypothalamus, causes the release of what other hormones? From where?

A
  • Adrenocorticotropic hormone (ACTH)

- From the anterior pituitary

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33
Q

As long as the hypothalamus releases ____________, no __________ will be released.

A

prolactin-inhibiting factor (PIF)

prolactin

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34
Q

Prolactin-inhibiting factor is actually what?

A

Dopamine

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35
Q

What inhibits the hypothalamus and anterior pituitary from releasing CRF and ACTH?

A

ACTH causes the adrenal cortex to increase the levels of cortisol, which inhibits the secretion of CRF and ACTH in a negative feedback loop

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36
Q

What connects the hypothalamus to the posterior pituitary?

A

Neurons in the hypothalamus send their axons down the pituitary stalk directly into the posterior pituitary

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37
Q

What is the mnemonic to remember the products of the anterior pituitary?

A

F: FSH (tropic)
L: LH (tropic)
A: ACTH (tropic)
T: TSH (tropic

P: Prolactin (direct)
E: Endorphins (direct)
G: Growth hormone (direct)

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38
Q

What does nipple stimulation cause?

A

Activation of the hypothalamus

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39
Q

Activation of the hypothalamus by nipple stimulation leads to two effects. What are they?

A

1) Oxytocin is released from the posterior pituitary; contraction of the smooth muscle of the breast and ejection of milk through the nipple
2) Hypothalamus stops releasing dopamine onto the anterior pituitary

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40
Q

Where does bone growth originate?

A

In epiphyseal plates

41
Q

What does an excess of growth hormone released in childhood cause? What does a deficit cause?

A
  • Excess: gigantism

- Deficit: dwarfism

42
Q

What is acromegaly?

A

An excess of growth hormone in adults, which results in an increase in the size of small bones (hands, feet, head)

43
Q

What is the function of follicle-stimulating hormone? What type of hormone is it? What is the source?

A
  • Anterior pituitary
  • Peptide
  • Stimulates follicle maturation in females; spermatogenesis in males
44
Q

What is the function of luteinizing hormone (LH)? What type of hormone is it? What is the source?

A
  • Anterior pituitary
  • Peptide
  • Stimulates ovulation in females; testosterone synthesis in males
45
Q

What is the function of adrenocorticotropic hormone (ACTH)? What type of hormone is it? What is the source?

A
  • Anterior pituitary
  • Peptide
  • Stimulates the adrenal cortex to synthesize and secrete glucocorticoids
46
Q

What is the function of thyroid-stimulating hormone? What type of hormone is it? What is the source?

A
  • Anterior pituitary
  • Peptide
  • Stimulates the thyroid to produce thyroid hormones
47
Q

What is the function of prolactin? What type of hormone is it? What is the source?

A
  • Anterior pituitary
  • Peptide
  • Stimulates milk production and secretion
48
Q

What is the function of endorphins? What type of hormone is it? What is the source?

A
  • Anterior pituitary
  • Peptide
  • Decreases sensation of pain; can promote euphoria
49
Q

What is the function of growth hormone? What type of hormone is it? What is the source?

A
  • Anterior pituitary
  • Peptide
  • Stimulates bone and muscle growth; raises blood glucose levels
50
Q

What is the function of antidiuretic hormone (ADH; vasopressin)? What type of hormone is it? What is the source?

A
  • Hypothalamus (released by posterior pituitary)
  • Peptide
  • Stimulates water reabsorption in kidneys by increasing permeability of collecting duct
51
Q

What is the function of oxytocin? What type of hormone is it? What is the source?

A
  • Hypothalamus (released by posterior pituitary)
  • Peptide
  • Stimulates uterine contractions during labor and milk secretion during lactation; may promote bonding behavior
52
Q

What is the function of triiodothyronine (T3) and thyroxine (T4)? What type of hormone is it? What is the source?

A
  • Thyroid (follicular cells)
  • Amino acid-derivative
  • Stimulate metabolic activity
53
Q

What is the function of calcitonin? What type of hormone is it? What is the source?

A
  • Thyroid (parafollicular or C cells)
  • Peptide
  • Decreases blood calcium concentrations
54
Q

What is the function of parathyroid hormone (PTH)? What type of hormone is it? What is the source?

A
  • Parathyroids
  • Peptide
  • Increases blood calcium concentrations
55
Q

What is the function of glucocorticoids (cortisol and cortisone)? What type of hormone is it? What is the source?

A
  • Adrenal cortex
  • Steroid
  • Increase blood glucose concentrations; decrease protein synthesis; anti-inflammatory
56
Q

What is the function of mineralocorticoids (aldosterone)? What type of hormone is it? What is the source?

A
  • Adrenal cortex
  • Steroid
  • Increase water reabsorption in the kidneys by increasing sodium reabsorption; promote potassium and hydrogen ion excretion
57
Q

What is the function of epinephrine and norepinephrine? What type of hormone is it? What is the source?

A
  • Adrenal medulla
  • Amino acid-derivative
  • Increase blood glucose concentrations and heart rate; dilate bronchi; alter blood flow patterns
58
Q

What is the function of glucagon? What type of hormone is it? What is the source?

A
  • Pancreas (a-cells)
  • Peptide
  • Stimulates glycogen breakdown; increases blood glucose concentration
59
Q

What is the function of insulin? What type of hormone is it? What is the source?

A
  • Pancreas (B-cells)
  • Peptide
  • Lowers blood glucose concentrations and increases anabolic processes
60
Q

What is the function of somatostatin? What type of hormone is it? What is the source?

A
  • Pancreas (delta-cells)
  • Peptide
  • Suppresses secretion of glucagon and insulin
61
Q

What is the function of testosterone? What type of hormone is it? What is the source?

A
  • Testicals (and adrenal cortex)
  • Steroid
  • Develops and maintains male reproductive system and male secondary sex characteristics
62
Q

What is the function of estrogen? What type of hormone is it? What is the source?

A
  • Ovary (and placenta)
  • Steroid
  • Develops and maintains female reproductive system and female secondary sex characteristics
63
Q

What is the function of progesterone? What type of hormone is it? What is the source?

A
  • Ovary (and placenta)
  • Steroid
  • Promotes maintenance of the endometrium
64
Q

What is the function of melatonin? What type of hormone is it? What is the source?

A
  • Pineal gland
  • Peptide
  • Involved in circadian rhythms
65
Q

What is the function of erythropoietin? What type of hormone is it? What is the source?

A
  • Kidney
  • Peptide
  • Stimulates bone marrow to produce erythrocytes
66
Q

What is the function of atrial natriuretic peptide (ANP)? What type of hormone is it? What is the source?

A
  • Heart (atria)
  • Peptide
  • Promotes salt and water excretion
67
Q

What is the function of thymosin? What type of hormone is it? What is the source?

A
  • Thymus
  • Peptide
  • Stimulates T-cell development
68
Q

When is ADH secreted? (2)

A
  • In response to low blood volume (sensed by baroreceptors)

- In response to increased blood osmolarity (sensed by osmoreceptors)

69
Q

Which hormone has a positive feedback loop?

A

Oxytocin; its release promotes uterine contraction, which promotes more oxytocin release

70
Q

What synthesizes ADH and oxytocin?

A

The hypothalamus; the posterior pituitary just releases them

71
Q

What are the two major functions of the thyroid gland?

A

1) Setting basal metabolic rate

2) Calcium homeostasis

72
Q

The iodination of tyrosine occurs in which cells of the thyroid?

A

Follicular cells

73
Q

How are thyroid hormones capable of resetting the basal metabolic rate of the body?

A

By making energy production more or less efficient, and altering the utilization of glucose and fatty acids

74
Q

What characterizes hypothyroidism?

A

Lethargy, decreased body temperature, slowed respiratory and heart rate, cold intolerance, and weight gain

75
Q

What characterizes hyperthyroidism?

A

Heightened activity level, increased body temperature, increased respiratory and heart rate, heat intolerance, and weight loss

76
Q

Which cells in the thyroid produce calcitonin?

A

C-cells (parafollicular cells)

77
Q

What are the three ways in which calcitonin decreases plasma calcium?

A

1) Increased calcium excretion from the kidneys
2) Decreased calcium absorption from the gut
3) Increased storage of calcium in the bone

78
Q

What are the three ways in which PTH increases plasma calcium?

A

1) Decreased excretion of calcium by the kidneys
2) Increased absorption of calcium in the gut (via vitamin D)
3) Increased bone resorption

79
Q

How does parathyroid hormone affect phosphorus homeostasis?

A

It promotes its excretion in urine

80
Q

What promotes the release of glucocorticoids from the adrenal cortex?

A

CRF from the hypothalamus promotes release of ACTH from the anterior pituitary, which promotes release of glucocorticoids from the adrenal cortex

81
Q

What is the most noteworthy mineralocorticoid? What is its function?

A
  • Aldosterone
  • Increases sodium reabsorption in the distal convoluted tubule and collecting duct of the nephron
  • Increases blood volume and blood pressure
82
Q

Decreased blood pressure causes the _______________ cells of the kidney to secrete what?

A
  • juxtaglomerular

- rennin

83
Q

What is the function of rennin?

A

Cleaves an inactive plasma protein, angiotensinogen, to its active form, angiotensin I

84
Q

What is the function of angiotensin-converting enzyme? Where is it located?

A

Converts angiotensin I to angiotensin II in the lungs

85
Q

What is the function of angiotensin II?

A

Stimulates the adrenal cortex to secrete aldosterone, which increases blood pressure

86
Q

What are the 3 S”s of corticosteroids?

A
  • Salt (mineralocorticoids)
  • Sugar (glucocorticoids)
  • Sex (cortical sex hormone)
87
Q

Which organ has its hormones focused on the fight-or-flight response? Name its main hormones.

A
  • Adrenal medulla

- Epinephrine and norepinephrine

88
Q

Islets of Langerhans contain three types of cells, what are they? In which organ are they contained?

A
  • Alpha, beta, delta

- Pancreas

89
Q

Which hormones are capable of increasing plasma glucose?

A
  • Glucagon
  • Growth hormone
  • Glucocorticoids
  • Epinephrine
90
Q

Diabetes mellitus is characterized by ____glycemia

A

hyper

91
Q

Why is somatostatin produced by the hypothalamus?

A

It functions to decrease growth hormone secretion in addition to its effects on insulin and glucagon

92
Q

Erythropoietin is secreted in response to what?

A

Low oxygen levels in the blood

93
Q

Atrial natriuretic peptide is secreted in response to what?

A

When the cells in the atria are stretched from excess blood volume, which lowers blood volume and pressure

94
Q

What is the target organ of FSH and LH? Which hormones are released by the target organ?

A
  • Gonads (testes or ovaries)

- Testosterone or estrogen and progesterone

95
Q

What is the target organ of ACTH? Which hormones are released by the target organ?

A
  • Adrenal cortex

- Glucocorticoids (cortisol and cortisone)

96
Q

What is the target organ of prolactin?

A

Breast tissue

97
Q

What is the target organ of growth hormone?

A

Bone and muscle

98
Q

Which three hormones are primarily involved in water homeostasis?

A
  • Antidiuretic hormone (ADH): hypothalamus (released by posterior pituitary); increases blood volume
  • Aldosterone: adrenal cortex; increases blood volume
  • Atrial natriuretic peptide (ANP): heart; decreases blood volume

MCAT: Biology (12 decks)

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