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Human Physiology > Endocrine system > Flashcards

Endocrine system Flashcards

1
Q

what are the two communication systems in the body?

A

endocrine and nervous systems

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2
Q

In what two ways does communication of the endocrine system differ from communication in the nervous system?

A

route of communication

onset and duration of effects

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3
Q

what are the nine glands of the endocrine system?

A

pineal, hypothalamus, pituitary, thyroid, parathyroid, thymus, adrenal, pancreas, ovary/testis

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4
Q

Endocrine glands are ___ and require that ___ are released from a gland, and are transported in the ___/___ or other extracellular fluid to a ___ tissue.

A

ductless; hormones; blood/plasma; target

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5
Q

In order for there to be a response to a hormone or endocrine signal, what must the cells of a target tissue express?

A

functional receptors for that particular hormone

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6
Q

T/F. Specificity of responses is due to the presence of receptors, rather than the source of the signal.

A

True.

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7
Q

What are the three (four) major classes of hormones based on chemical structure?

A
  1. peptide and protein hormones
  2. steroid hormones
  3. amine hormones
  4. Eicosanoids
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8
Q

Peptide hormones are species specific and variability can exist due to ___.

A

glycosylations - affects the binding of hormones to the receptor

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9
Q

T/F. Peptides do not function as neurotransmitters. They only function as hormones.

A

False, the function as BOTH hormones and neurotransmitters. Examples include somatostatin and serotonin (5-HT).

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10
Q

In peptide hormone synthesis, the ___ is synthesized on ___ and includes extra amino acids and foldings.

A

preprohormone; ribosomes

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11
Q

The preprohormone forms the ___ by cleaving extra amino acids in the ___. Later it is packed into ___ ___ in the Golgi apparatus. Now, the hormone is called a ___.

A

prohormone; RER; secretory vesicles; hormone

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12
Q

When the hormone is secreted, what else is also released?

A

secretion of prohormone fragments from additional cleavage within the vesicle

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13
Q

what does packaging and storing peptide hormones permit?

A

the storage of large quantities for rapid release.

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14
Q

What does the use of precursor molecules prevent and limit?

A

prevents intracellular degradation

limits feedback efforts on the endocrine cells

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15
Q

Steroid hormones are ___ hormones, and are relatively ___ molecules.

A

lipid; small

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16
Q

T/F. Glandular sources of steroids are common.

A

False, glandular sources are rather limited.

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17
Q

What are the primary steroid producing organs?

A

gonads (ovaries/testes), adrenal CORTEX, and placenta

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18
Q

Where are steroids derived from?

A

cholesterol by a series of enzymatic reactions to produce FIVE different classes of steroids.

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19
Q

What are the five classes of steroids?

A
  1. progestagens
  2. androgens
  3. estrogens
  4. glucocorticoids
  5. mineralcorticoids
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20
Q

How is cholesterol produced?

A

de novo synthesis from acetyl CoA

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21
Q

T/F. Cholesterol is not a feature of all cells.

A

False, it is a feature of all cells because of cholesterol’s role as a membrane component.

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22
Q

Where is most of the cholesterol used for synthesis of steroid hormones derived from?

A

low density lipoproteins (LDLs)

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23
Q

LDLs in ___ are endocytosed into the steroidogenic cell and lysed to produce cholesterol ___ which are fairly ___-soluble.

A

circulation; esters; water

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24
Q

why is it a good thing that cholesterol esters are water-soluble?

A

so that they can be stored in lipid droplets. This causes the cells to appear white or fatty

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25
Q

The LDL is delivered to a ___ where the cholesteryl ___ is cleaved to yield free cholesterol to be utilized for membrane synthesis or is converted to ___ hormones and ___ acids.

A

lysosome; ester; steroid; bile

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26
Q

T/F. Cholesterol taken up by the cell inhibits the cell’s own cholesterol synthesis.

A

True.

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27
Q

How is steroid hormone synthesis is stimulated?

A

by peptide hormones from other glands

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28
Q

Once a steroid cell has been stimulated, what is the signaling cascade that results in the presence of free cholesterol in the cytoplasm?

A
  1. activate a G protein coupled receptor
  2. activate adenyl cyclase
  3. Increase cAMP
  4. activate PKA which stimulates the activity of cholesterol esterases
  5. Release of cholesterol from intracellular stores
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29
Q

What facilitates intracellular transport of cholesterol by binding to cholesterol and transporting it through the watery cytoplasm to the mitochondria?

A

steroid acute regulatory protein (StAR)

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30
Q

T/F. Steroid hormones cross the outer but not inner membrane of the mitochondria.

A

False, it crosses BOTH the outer and inner membranes

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31
Q

How and where is cholesterol converted into steroids?

A

by P450 enzymes in the mitochondria

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32
Q

What are P450 enzymes?

A

these are cytochrome P450 enzymes that add -OH or cleave C-C

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33
Q

Where are steroids shuffled for further enzyme modification?

A

SER

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34
Q

How do different cells or tissues make different steroids?

A

due to differences in the enzymes the cell synthesizes

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35
Q

T/F. Steroids are water-soluble so they are stored until needed.

A

False, steroids are LIPID-soluble so they are not stored and none of the intermediates can be stored.

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36
Q

How is the synthesis of steroids regulated?

A

by regulating the peptide hormone that stimulates their synthesis, the synthesis of steroidogenic enzymes, and/or the number of steroidogenic cells.

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37
Q

List the simplified pathway for steroid biosynthesis.

A
  1. cholesterol
  2. progestagens (progesterone)
  3. corticosteroids OR androgens (testosterone)
  4. estrogens (estradiol)
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38
Q

What type of hormones are derived from the amino acid tyrosine?

A

amine hormones

39
Q

what are the four amine hormones?

A

T3/T4, norepinephrine, epinephrine, dopamine

40
Q

Thyroid hormones are synthesized in the ___ gland where ___ and ___ are produced by the ___ of tyrosine at one or two carbons and combining iodinated molecules.

A

thyroid; T3; T4; iodination

41
Q

Catecholamines or catecholaminergic hormones are synthesized in the ___ ___ or ___.

A

adrenal MEDULLA; hypothalamus

42
Q

Match

  1. Norepinephrine (NE) (noradrenaline)
  2. Epinephrine (E) (adrenaline)
  3. Dopamine (DA)

A. Adrenal medulla
B. Hypothalamus

A
  1. A
  2. A
  3. B
43
Q

Catecholamines are common ___ so other neurons, like the ___ nervous system, make them.

A

neurotransmitters; autonomic

44
Q

T/F. NE, E, & DA are peptide-like with respect to solubility and receptors.

A

True, they are hydrophilic/polar

45
Q

T/F. Most hormones are secreted in short bursts with the timing of the bursts controlled by an upstream signal.

A

True. NO hormone is released in between vesicular release or the next round of steroid synthesis.

46
Q

The pattern of secretion produces variability in blood concentrations of hormones. Why does this produce a decrease in hormone concentrations between bursts?

A

due to clearance or metabolism of circulating hormones. example of T and LH

47
Q

What is the circadian secretion due to?

A

reduced pulsatility, but can also be due to changes in amplitude. example GH and cortisol

48
Q

Patterns of secretion are controlled by what three factors?

A
  1. plasma concentrations of a nutrient, eg GH and glucose
  2. neural control, eg neurons have rhythmic firing pattern
  3. hormonal control, eg GnRH - LH - T
49
Q

T/F. Hydrophilic hormones readily dissolve in plasma when being transported.

A

True.

50
Q

Lipophilic hormones require ___ proteins to increase their ___ in the plasma.

A

carrier; solubility

51
Q

Where are carrier or binding proteins synthesized?

A

liver

52
Q

How does the use of carriers affect the availability of hormone?

A

hormone must be released from carrier in order to bind to receptor
[free hormone] is a function of [binding protein]

53
Q

How are binding proteins protective?

A

they protect the hormone from degradation and clearance

54
Q

What organs contain enzymes that break down or inactivate a hormone? How is the done?

A

Liver and kidneys, but some degradation occurs in the blood due to the action of circulating enzymes
hydrolysis or sulfation
*note that in some cases, circulating prohormones are activated

55
Q

Which type of hormones are highly susceptible to enzymatic degradation? Which are not and why?

A

Catecholamines and peptides are highly susceptible to enzymatic degradation
Steroid and thyroid hormones are less susceptible because they attach to binding proteins in the blood.

56
Q

The amount of hormone circulating in the blood is a function of what?

A

what has been synthesized/secreted combined with the rate of clearance.

57
Q

Peptide and catecholamine receptors (for hydrophilic hormones) are found where? Why?

A

They are on the cell surface/in plasma membrane because they are too large and/or too hydrophobic to pass through membrane

58
Q

Peptide and catecholamine receptor activation causes a signal transduction pathway that facilitates a response within the cell to an extracellular signal known as what?

A

a second messenger system

59
Q

What do ionotropic responses open?

A

ion channels, Ca2+, Na+, K+

60
Q

___ responses alter cell activity, ___ proteins including second messengers move things around like receptors and vesicles.

A

Metabotropic; phosphorylate

61
Q

T/F. Both rapid AND delayed responses are possible with peptide hormones and catecholamines.

A

True.

62
Q

Which type of response includes responses to Ca2+ influx and protein phosphorylation? Which type occurs when the second messenger system alters protein synthesis?

A

rapid

delayed

63
Q

Where are receptors for lipophilic hormones found?

A

Steroid or thyroid hormone receptors are found intracellularly and/or in the nucleus.

64
Q

Receptor + ___ forms a DNA-binding protein that regulates ___. These responses are ___ because protein synthesis takes time.

A

ligand; transcription; delayed

65
Q

T/F. There are membrane receptors for steroid hormones.

A

True. These receptors control rapid, non-genomic responses.

66
Q

What is the central control of the endocrine function?

A

the hypothalamus and pituitary glands

67
Q

What forms the floor of the diencephalon and surrounds the 3rd ventricle?

A

hypothalamus

68
Q

The ___ gland lies below the hypothalamus in a depression in the sphenoid bone called the ___ ___. What is another name for this gland?

A

pituitary; sella turcica; hypophysis

69
Q

The ___ is the stalk of tissue that connects the pituitary gland to the base or ___ ___ of the hypothalamus.

A

infundibulum; median eminence

70
Q

Which structure contains several nuclei or clusters of neuronal cell bodies?

A

the hypothalamus

71
Q

The anterior pituitary gland or ___ develops from an outpocketing of the ___ ___ that pinches off from the ___ of the mouth and lies above the ___.

A

adenohypophysis; oral ectoderm; roof; palate

72
Q

The ___ pituitary gland or neurohypophysis buds off the ___ of the hypothalamus and is suspended below the brain by the ___.

A

posterior; floor; infundibulum

73
Q

Which portion of the pituitary gland contains the axon terminals of neurons within two hypothalamic nuclei that passed thru the infundibulum?

A

posterior pituitary gland

74
Q

What two hormones are released from the posterior pituitary gland?

A

oxytocin and vasopressin

75
Q

T/F. Oxytocin and vasopressin are steroid hormones.

A

False, they are peptide hormones.

76
Q

Posterior pituitary hormones are synthesized in the neuronal cell bodies in the ___ and ___ nuclei and secretory vesicles are stored in the axon terminals within the posterior pituitary.

A

supraoptic; paraventricular nuclei

77
Q

Posterior pituitary hormones are released into ___ of the systemic circulation in response to ___ ___ in the hypothalamic neurons.

A

capillaries; action potentials

78
Q

T/F. The posterior pituitary synthesizes hormones in addition to receiving some from the hypothalamus.

A

False, NO hormones are synthesized in the posterior pituitary - it is simply the site of release for hormones synthesized in the hypothalamus.

79
Q

What are the functions of oxytocin and vasopressin?

A

Oxytocin stimulates smooth muscle contraction

Vassopressin (or antidiuretic hormone) has actions in the kidney and blood vessels to regulate blood pressure.

80
Q

T/F. The anterior pituitary gland is an extension of the hypothalamus.

A

False, it is NOT an extension of the hypothalamus, but it is regulated by hormones secreted by hypothalamic neurons.

81
Q

Hypothalamic neurons secrete ___ or releasing hormones whose axon terminals lie in the ___ ___. At the base of this structure are the ___ blood vessels.

A

hypophysiotropic; median eminence; portal

82
Q

How do hypothalamic hormones get transported to the anterior pituitary?

A

they are transported in the blood within the portal vessels of the anterior pituitary

83
Q

T/F. Releasing hormones are only stimulatory.

A

False, most are stimulatory but there are a few inhibitory ones.

84
Q

In the anterior pituitary there are ___ (5/6) different cell types that produce ___ (5/6) PRIMARY hormones in response to different hypophysiotropic hormones.

A

5; 6

85
Q

T/F. Hypophysiotropic hormones are often found elsewhere in the nervous system and they are NOT all peptides.

A

True. Dopamine is not a peptide hormone, it is a catecholamine.

86
Q

What is often referred to as the neuroendocrine system?

A

the hypothalmo-pituitary portion of the endocrine system

87
Q

Hypothalamus + pituitary + target = an ___

A

axis

88
Q

What are the six primary hormones produced by the anterior pituitary gland?

A

FLAT PiG = FSH, LH, ACTH, TSH, PRL, GH

89
Q

What other hormones come from the anterior pituitary?

A

Beta-lipotropin and Beta-endorphin

90
Q

What are the products of proopiomelanocortin (POMC)?

A

ACTH, Beta-lipotropin and Beta-endorphin

91
Q

What is a precursor polypeptide synthesized in corticotrophs that is cleaved to yield multiple peptides with varied actions and target tissues?

A

POMC

92
Q

In addition to secreted hypophysiotropic hormones being stimulatory or inhibitory, how else can they be controlled?

A

by other hormones via feedback mechanisms

93
Q

___-loop feedback is self-regulated by product/hormone of ultimate target tissue (eg. cortisol and ACTH/CRH).

A

Long

94
Q

Short-loop negative feedback occurs when the hormone from ___(1st/2nd) gland in the axis affects the action of the ___(1st/2nd) gland (eg. LH and GNRH).

A

2nd; 1st

Human Physiology (22 decks)

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