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Physiology > BIOL 0800 Reading- Chapter 11 > Flashcards

BIOL 0800 Reading- Chapter 11 Flashcards

1
Q

What are hormones?

A

Chemical messengers that enter the blood, which carries them, from their site of secretion to the cells upon which they act

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2
Q

What is the difference between exocrine and endocrine?

A

Exocrine glands secret products into ducts to exit the body; whereas endocrine glands are ductless and release their secretory products into the interstitial fluid to diffuse into the blood

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3
Q

What are amine hormones?

A

Derivatives of the amino acid tyrosine

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4
Q

What are the two classes of hormones encompassed by “amine hormones?”

A

Thyroid hormones and catecholamines

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5
Q

What are the three catecholamines?

A

Epinephrine, norepinephrine, and dopamine

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6
Q

What are the two parts of the adrenal gland?

A

Inner adrenal medulla and outer adrenal cortex

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7
Q

What does the adrenal medulla secret more of, epinephrine or norepinephrine?

A

Epinephrine

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8
Q

Where is dopamine synthesized?

A

In thy hypothalamus, and released by a portal system to inhibit pituitary gland activity

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9
Q

What are prohormones?

A

The precursor to peptide hormones, which are cleaved from preprohormone by proteolytic enzymes in the RER, to be packaged in the Golgi to yield the active peptide hormones

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10
Q

Does a single prohormone create one kind of peptide hormone?

A

Nope, can create a whole bunch that are all released together

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11
Q

What are the three classes of hormones?

A

Amine hormones, peptide hormones, and steroid hormones

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12
Q

What are steroid hormones?

A

Primarily produced in the adrenal cortex and gonads

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13
Q

What is the general process of steroid hormones synthesis?

A

Anterior pituitary gland hormone binds to receptors in adrenal cortex/gonads, which are linked to G proteins for cAMP production, activating protein kinase A to facilitate the process through phosphorylation

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14
Q

What is the precursor to all steroid hormones?

A

Cholesterol

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15
Q

How is cholesterol introduced into and used by cells?

A

Enters as LDLs, which centers cells by receptor-mediated endocytosis and is stored in a liquid droplet until released by the enzyme cholesterol esterase, activated by a protein kinase; then carried to the mitochondria and processed into steroid hormones by cytochrome P450s

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16
Q

What are cytochrome P450s?

A

Attach hydroxyl groups to carbon atoms and cleave carbon-carbon bonds, to modify cholesterol into steroid hormones

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17
Q

What happens to steroid hormones after synthesis? Where are they stored?

A

Diffuse across plasma membrane into interstitial fluid and into circulation; not highly soluble in the blood, so primarily transported in plasma bound to carrier proteins like albumin

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18
Q

What are the five major hormones secreted by the adrenal cortex?

A

Aldosterone, cortisol, corticosterone, DHEA, and androstenedione

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19
Q

What is aldosterone?

A

A mineralocorticoid, since it affects kidneys’ mineral balances (potassium, sodium, hydrogen)

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20
Q

What hormone controls aldosterone production?

A

Angiotensin II

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21
Q

What steroid hormones are glucocorticoids?

A

Cortisol and corticosterone

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22
Q

What steroid hormone is a mineralcorticoid?

A

Aldosterone

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23
Q

What are cortisol and corticosterone?

A

Glucocorticoids because they affect glucose metabolism

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24
Q

What steroid hormones are androgens?

A

DHEA and androstenedione

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25
Q

What are DHEA and androstenedione?

A

Androgens, which includes testosterone

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26
Q

What are the three layers of the adrenal cortex?

A

Zona glomerulosa, zona fasciculata, and zona reticularis

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27
Q

What is the zona glomerulosa?

A

Outer layer of the adrenal cortex; only synthesizes/secretes aldosterone; coverts corticosterone to aldosterone, but do NOT code for genes that form cortisol and androgens

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28
Q

What is the zona fasciculata?

A

Middle layer of the adrenal cortex; secretes cortisol, primarily

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29
Q

What is the zona reticularis?

A

Inner layer of the adrenal cortex; secretes primarily androgens

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30
Q

What are the two hormones that make up the category “estrogens?”

A

Estradiol and estrone

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31
Q

Which estrogen is the major hormone secreted by the ovaries?

A

Estradiol

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32
Q

What gonadal hormone is secreted by the corpus luteum (ovarian structure after ovulation)?

A

Progesterone

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33
Q

How are most hormones transported in the blood?

A

Dissolved in plasma

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34
Q

How are steroid and thyroid hormones transported in the blood?

A

Bound to large proteins in the plasma, but a small concentration exists dissolved in the plasma as well

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35
Q

Why is the concentration of free hormone in the plasma more important than the total concentration of hormone-protein complex?

A

Because only the free hormones can diffuse out of capillaries to target cells

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36
Q

What are the two major organs that metabolize or excrete hormones?

A

Liver and kidneys

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37
Q

What kinds of hormone are removed from the bloodstream quickest? Why?

A

Peptide and catecholamine hormones are removed quickly because there are enzymes in the bloodstream that break them down quickly; steroid and thyroid hormones take longer because enzymes won’t break them down if they’re bound to proteins

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38
Q

What are the receptors for peptide and catecholamine hormones?

A

In the plasma membranes of target cells

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39
Q

Where are the receptors for thyroid and steroid hormones?

A

Inside the target cells

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40
Q

What is up-regulation?

A

An increase in the number of a hormone’s receptors in a cell, resulting from prolonged exposure to a low concentration of the hormone; temporarily increases target-cell responsiveness

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41
Q

What is down-regulation?

A

A decrease in receptor number, often from exposure to high concentrations of the hormone; temporarily decreases target-cell responsiveness and prevents overstimulation

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42
Q

How do up and down regulation affect responsiveness to hormones?

A

Up regulation increases, down regulation decreases

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43
Q

What is permissiveness?

A

When hormone A must be present for the full strength of hormone B’s effect

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44
Q

What are the three main controls of inputs to endocrine cells?

A

Changes in plasma concentrations of mineral ions or organic nutrients; neurotransmitters released from the neurons ending on the endocrine cells; or another hormone or paracrine substance on the endocrine cell

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45
Q

What is an example of input to endocrine cell controlled by plasma concentrations of mineral ions of organic nutrients?

A

Insulin secretion stimulated by high plasma glucose levels; PTH secretion stimulated by low plasma calcium ion levels

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46
Q

What is an example of input to endocrine cell controlled by neurons?

A

Insulin and gastrointestinal hormone secretion, stimulated by neurons of the parasympathetic nervous system and inhibited by sympathetic nervous system

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47
Q

How does the adrenal medulla relate to the sympathetic nervous system?

A

It’s a modified sympathetic ganglion, so it’s stimulated by sympathetic preganglionic fibers

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48
Q

Which group of hormones is under direct control of brain neurons themselves, rather than autonomic neurons?

A

Those secreted by the hypothalamus and co.

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49
Q

What is an example of input to endocrine cells controlled by other hormones?

A

Tropic hormone, which often stimulates secretion of other hormones as well as the growth of the gland itself

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50
Q

What are three causes of primary hyposecretion?

A

Partial gland destruction, enzyme deficiency, and dietary iodine deficiency

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51
Q

What is secondary hyposecretion?

A

Endocrine gland isn’t damaged, but is receiving too little of its topic hormone

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52
Q

What is primary hyposecretion?

A

When the endocrine gland can’t function normally

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53
Q

How does one diagnose primary or secondary hyposecretion?

A

Measure the level of tropic hormone in the blood; if elevated, then primary; if lowere, then secondary

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54
Q

What is the difference between primary and secondary hypersecretion?

A

Primary is when the gland is secreting too much hormone, and secondary is when the tropic hormone excessively stimulates the gland

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55
Q

How does one diagnose primary vs secondary hypersecretion?

A

Primary if decreased concentration of the tropic hormone because of negative feedback trying to turn off excessive hormone secretion; Secondary if both concentrations of hormone and tropic hormone are elevated.

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56
Q

What is an important example of hyporesponsiveness?

A

Diabetes mellitus, when target cells of insulin are hyporesponsive

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57
Q

What is one cause of hyporesponsiveness?

A

Lack of receptors, or defective receptor behavior, or deficiency in enzymes needed to catalyze the steps of the reaction

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58
Q

What is an example of hyperresponsiveness?

A

Hypersecretion of thyroid hormones causes hyperresponsiveness of epinephrine, which results in elevated heart rate

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59
Q

What is the infundibulum?

A

The pituitary stalk that connects the pituitary gland to the hypothalamus

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60
Q

Is the posterior pituitary actually a gland?

A

Nope, it’s technically an extension of the neural components of the hypothalamus

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61
Q

What happens to the axons in the infundibulum? Where do their terminals end up?

A

Directly on capillaries to release hormones into circulation

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62
Q

What is the median eminence?

A

The junction of the hypothalamus and infundibulum, where capillaries recombine to form the hypothalamo-pituitary portal vessels

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63
Q

What is a portal vessel?

A

A vessel that connects two capillary beds

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64
Q

Where are posterior pituitary hormones synthesized?

A

In the hypothalamus itself

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65
Q

What are the two posterior pituitary gland hormones?

A

Oxytocin and vasopressin (ADH)

66
Q

What are hypophysiotropic hormones?

A

The hypothalamic hormones that regulate anterior pituitary gland function

67
Q

What is the standard three-hormone sequence of the hypophysiotropic hormones? Which hormones doesn’t follow that route?

A

Dopamine doesn’t follow: 1) hypophysiotropic hormone controls secretion of 2) anterior pituitary gland hormone to control secretion of 3) other endocrine gland hormone to act on target cells

68
Q

What are the six most common anterior pituitary hormones?

A

FSH, LH, GH, TSH, prolactin, ACTH

69
Q

What is the main function of the TSH and ACTH?

A

To stimulate target cells to synthesize and secret other hormones

70
Q

What does growth hormone do?

A

Stimulates the liver to secret a growth-promoting peptide hormones known as IGF-1 (insulin like growth factor 1)

71
Q

What controls anterior pituitary hormone activity?

A

Hypothalamus hormones, or hypophysiotropic hormones

72
Q

How do hypophysiotropic hormones work?

A

Secreted by neurons originating in the hypothalamus, terminate in the median eminence around the capillaries of the hypothalamo-pituitary portal vessels to release the hormones into the capillaries

73
Q

What is the difference in the secretion of posterior pituitary hormones and hypophysiotropic hormones?

A

For posterior pituitary hormones, the hypothalamic neurons end in the posterior pituitary gland and enter the general bloodstream; For hypophysiotropic hormones, the hypothalamic neurons stay in the hypothalamus and end in the median eminence and enter median eminence capillaries and hypothalamo-pituitary portal vessels to the cells of the anterior pituitary gland

74
Q

What is the primary function of the hypothalamo-pituitary portal vessels?

A

To ensure that the hypophysiotropic hormones can reach the anterior pituitary glands quickly

75
Q

What are the two hypophysiotropic hormones that inhibit the secretion of anterior pituitary gland hormones?

A

Somatostatin and dopamine

76
Q

What does somatostatin inhibit?

A

Secretion of growth hormone

77
Q

What does dopamine inhibit?

A

Secretion of prolactin

78
Q

What anterior pituitary hormone is controlled by two hypophysiotropic hormones?

A

Growth hormones, inhibited by somatostatin and stimulated by GHRH

79
Q

What are the two mechanisms by which secretion of hypophysiotropic hormones are released?

A

Neural and hormonal controls

80
Q

How do neurons control secretion of hypophysiotropic hormones?

A

Neurotransmitters (like catecholamines and serotonin) are at the synapses of hormone-secreting hypothalamic neurons

81
Q

What is one example of neuronal control of hypophysiotropic hormone secretion?

A

CRH from the hypothalamus stimulates ACTH in the anterior pituitary which stimulates the adrenal cortex to secrete cortisol; BUT release of CRH is regulated by complex neural pathways based on stress levels, circadian rhythms, etc.

82
Q

What is one example of hormonal control of hypophysiotropic hormone secretion?

A

When the CRH-ACTH pathway stimulates the adrenal cortex to produce cortisol, the cortisol itself acts as negative feedback for secretion of CRH; also acts on anterior pituitary to reduce response to CRH

83
Q

What is a long-loop negative feedback?

A

When the third hormone in the three-hormone sequence acts as negative feedback effect over the other two steps

84
Q

What is short-loop negative feedback?

A

When the prolactin hormone acts on the hypothalamus to stimulate dopamine to inhibit secretion of prolactin; influence of an anterior pituitary gland hormone on the hypothalamus

85
Q

What are the two iodine-containing thyroid hormones?

A

Thryoxine, and triiodothyrozxine (T4 and T3)

86
Q

What is the “main” iodine-containing thyroid hormone?

A

T3, because T4 is generally converted into T3 by deiodinase enzymes

87
Q

What is iodide trapping?

A

When the iodide ion is trapped into the follicular cell in the thyroid, after being cotransported in with sodium ions

88
Q

What does thyroid peroxidase do?

A

Oxidizes iodides and attaches them to tyrosines on thyroglobulin in the colloid

89
Q

What is unique about the thyroid gland?

A

Large storage capacity of iodinated thyroglobulin stored in the follicles to provide enough thyroid hormone for several weeks

90
Q

Essentially all follicular cell actions are stimulated by what hormone?

A

TSH, which is stimulated by TRH

91
Q

What is the basic control mechanism of TSH production?

A

Negative feedback action of T3 and T4 on the anterior pituitary gland and sometimes hypothalamus

92
Q

What does TSH do in the follicular cells?

A

Stimulates T3 and T4 production, increases protein synthesis, increases DNA replication and cell division, increases amount of RER

93
Q

What is different about receptor location for thyroid hormones from other hormones?

A

Located in the nuceli of most cells in the body, whereas others are usually more limited

94
Q

Thyroid hormones have a greater affinity for which compound, T3 or T4?

A

T3 (but this is okay because T4 is usually deiodinized to T3 anyway)

95
Q

How do T3 and T4 act?

A

By inducing gene transcription and protein synthesis

96
Q

How do T3 and T4 affect carbohydrate and lipid metabolism?

A

Increase carb absorption from the small intestine; increase fatty acid release from adipocytes

97
Q

What pump’s activity is highly dependent on thyroid hormones?

A

The Na/K pump

98
Q

What effect does a decrease in cellular ATP (used up by the Na/K pump stimulated by thyroid hormones) stores have on glycolysis?

A

Increase in glycolysis: burns additional glucose that restores ATP levels, which requires heat and increased metabolism of fuels: calorigenic action of T3 and T4

99
Q

How do thyroid hormones contribute a significant fraction of body heat?

A

Stimulate use of ATP to fuel Na/K-ATPase pump; increases use of glycolysis to provide more ATP for cellular function, which generates heat

100
Q

What does it mean that T3 and T4 are permissive on catecholamines?

A

Up-regulate beta-adrenergic receptors in many tissues (esp. heart and nervous)

101
Q

Excess thyroid hormone symptoms look like excess of what other hormones? Why?

A

Epi/norepi because they upregulate beta-adrenergic receptors for catecholamines

102
Q

Epi and norepi are associated with which nervous system?

A

Sympathetic

103
Q

Why are T3 and T4 crucial for nervous system development?

A

Forms axon terminals and production of synapses, growth of dendrites and dendritic extensions, formation of myelin

104
Q

What disorder is a result of T3/4 deficit in infancy?

A

Congenital hypothyroidism: poorly developed nervous system and compromised intellectual function

105
Q

What happens during hypothyroidism?

A

Increase in TRH and TSH levels (lack of negative feedback to hypothalamus and pituitary due to lack of T3/4); increase thyroid gland, goiters

106
Q

What is the most common cause of hypothyroidism in the US?

A

Autoimmune thryoiditis, often Hashimoto’s disease when the immune system T cells attack thyroid tissue

107
Q

Why are two symptoms of hypothyroidism weight gain and sensitivity to cold?

A

Lack of T3/4 stimulation of Na/K pump leads to decreased calorigenic actions

108
Q

What is Graves’ disease?

A

Hyperthyroid disorder: autoimmune disease, overstimulation and growth and activity of the thyroid gland

109
Q

What are some symptoms of thyrotoxicosis?

A

Heat intolerance, weight loss, increased appetite, increased sympathetic nervous system activity

110
Q

What hormone is released during stress?

A

Cortisol (glucocorticoid hormone); and sometimes epi from the adrenal medulla

111
Q

Where is cortisol secreted from, and what kind of hormone is it?

A

Glucocorticoid hormone secreted from the adrenal cortex

112
Q

What system mediates increased cortisol secretion during stress?

A

Hypothalamo-anterior pituitary gland system

113
Q

How does the HPA axis increase cortisol secretion?

A

Neural input to H induces CRH secretion, through HP portal vessels to anterior P to stimulate ACTH secretion, which circulates in the blood to reach the adrenal cortex and stimulate cortisol release

114
Q

What biological molecule helps stimulate ACTH secretion directly and by stimulating secretion of CRH as a way to elicit endocrine stress response?

A

Cytokines: secretions from immune system cells

115
Q

Why do basal levels of cortisol help maintain normal blood pressure?

A

Because even under nonstressed conditions, they’re permissive for epi/norepi that controls smooth muscle cells around arterioles

116
Q

What are the two important main systemic actions of cortisol?

A

Anti-inflammatory and anti-immune functions

117
Q

How does cortisol inhibit the immune system?

A

Inhibits leukotrine and prostaglandin production (involved in inflammation); stabilizes lysosomal membranes in damaged cells tp prevent release of contents; reduces capillary permeability in injured areas (reduces fluid leakage)

118
Q

What are the five main effects of increased cortisol?

A

1) effects on organic metabolism (protein catabolism up, liver gluconeogenesis up, plasma glucose maintenance, triglyceride catabolism up), 2) enhanced vascular reactivity; 3) unidentified protective effects against damaging stress, 4) inhibits inflammation and specific immune responses; 5) inhibition of nonessential functions

119
Q

What is a summary of cortisol’s effect on organic metabolism?

A

Increases plasma concentrations of amino acids, glucose, glycerol, and free fatty acids

120
Q

Why do certain cytokines stimulate secretion of ACTH and thus cortisol?

A

To dampen the body’s immune response and protect against damage from excessive inflammation during infection or trauma

121
Q

What is primary adrenal insufficiency?

A

Due to loss of adrenal cortical function as in TB or tumors, but most often an autoimmune attack of the adrenal cells as foreign

122
Q

What indicates primary adrenal insufficiency?

A

Low levels of cortisol and aldosterone, but increased ACTH levels (no negative feedback)

123
Q

What is the effect of low levels of aldosterone, as caused by primary adrenal insufficiency?

A

Imbalance in Na/K/water, leading to hypotension

124
Q

What is Addison’s disease?

A

Primary adrenal insufficiency

125
Q

What is secondary adrenal insufficiency?

A

Due to ACTH deficiency, as with pituitary disease

126
Q

Which has more drastic symptoms, primary or secondary adrenal insufficiency?

A

Primary, because secondary doesn’t affect aldosterone levels

127
Q

What is Cushing’s syndrome?

A

Excess cortisol in the blood even when unstressed

128
Q

What are five other hormones besides cortisol that are released during stress?

A

Aldosterone, vasopression (ADH), GH, glucagon, and beta-endorphin (coreleased with ACTH from anterior pituitary)

129
Q

What are five actions of the sympathetic NC during stress?

A

1) increased hepatic and muscle gluconeogenesis; 2) increased adipose triglyceride breakdown; 3) increased cardiac function; 4) diversion of blood to skeletal muscles (vasocon in visceral, vasodil in skeletal); 5) increased lung ventilation

130
Q

What is epiphyses vs shaft?

A

The ends vs rest of bones

131
Q

What is the epiphyseal growth plate?

A

The portion of each epiphysis in contact with the shaft; plate of actively proliferating cartilage

132
Q

What are osteoblasts?

A

Bone-forming cells at the shaft edge of epiphyseal growth plates

133
Q

What are chondrocytes?

A

Cells that lay down new cartilage in the interior of the epiphyseal growth plate

134
Q

What is a mitogen?

A

A chemical that stimulates cell division

135
Q

How does GH affect epiphyseal growth plates?

A

Stimulates maturation and cell division of chondrocytes in epiphyseal plates

136
Q

How does GH accomplish its mitogenic effects?

A

Indirectly through mediation of mitogenic hormone IGF-1

137
Q

How do GH and IGF-1 interact on epiphyseal plates?

A

GH stimulates prechondrocytes, which begin to differentiate and secrete and become response to IGF-1, which acts as a paracrine/autocrine substance to stimulate differentiating chondrocytes to undergo cell division

138
Q

How does IGF-1 directly stimulate protein synthesis, especially in muscle?

A

Increases amino acid uptake and synthesis/activity of ribosomes

139
Q

What hormones stimulate and inhibit GH?

A

GHRH and somatostatin

140
Q

What is IGF-2?

A

Secreted independent of GH, crucial mitogen during prenatal period

141
Q

Why are thyroid hormones necessary for growth?

A

Required for synthesis and growth-promoting effects of GH

142
Q

What is insulin?

A

Anabolic hormone that promotes glucose and AA transport from ECF into adipose/skeletal/cardiac cells; stimulates fat storage, inhibits protein degradation

143
Q

What effect do sex hormones have on growth?

A

Stimulate bone growth AND stop it by inducing epiphyseal closure

144
Q

What hormone has antigrowth effects?

A

Cortisol: inhibits DNA synthesis and stimulates protein catabolism and inhibits bone growth, in high concentrations

145
Q

What three areas does Ca homeostasis depend on?

A

Bones, kidneys, and GI tract

146
Q

What is the osteoid?

A

Collagen matrix in bones upon which minerals and calcium/phosphate/hydroxyapatite are deposited

147
Q

What are the three types of bone cells?

A

Osteoblasts, osteocytes, osteoclasts

148
Q

What are osteoblasts?

A

Bone-forming cells; secret collagen into the matrix, which becomes calcified during mineralization

149
Q

What are osteocytes

A

Osteoblasts that have been surrounded by a calcified matric: long cytoplasmic processes through the bone, form tight junctions

150
Q

What are osteoclasts?

A

Large multinucleated cells that break down previously formed bone by secreting hydrogen ions to dissolve the crystals and hydrolytic enzymes to digest the osteoid

151
Q

Of the hormones that affect bone calcium, which is the only one regulated by plasma calcium concentration?

A

Parathyroid hormone

152
Q

How do kidneys affect plasma calcium concentration?

A

Control Ca excretion and reabsorption; also regulates phosphate ion balance

153
Q

How does the GI tract affect plasma calcium concentration?

A

Controls large regulated increases or decreases of amount of Ca absorbed from the diet, since the GI tract usually doesn’t absorb much calcium

154
Q

What are the two major hormones that regulate plasma calcium concentration?

A

PTH and 1,25 dihydroxyvitamin D

155
Q

How does plasma calcium concentration affect PTH secretion?

A

Decreased concentration stimulates PTH secretion

156
Q

How does PTH increase extracellular calcium?

A

Directly increases osteoclast bone resorption to move calcium ions from bone to Ecf; directly stimulates 1,25dhv D formation to increase intestinal absorption of Ca and phosphate; directly increases Ca reabsorption in kidneys; reduces absorption of phosphate ions in kidneys (increases urinary excretion) which keeps plasma phosphate from increasing, since the Gi tract and bone are increasing phosphate concentration

157
Q

What is 1,25- (OH)2D?

A

Calcitriol: active form of vitamin D

158
Q

What is the major action of calcitriol?

A

Stimulate intestinal absorption of calcium ions

159
Q

What is calcitonin?

A

Peptide hormone secreted by parafollicular cells in the thyroid gland

160
Q

What does calcitonin do?

A

Decreases plasma calcium concentration by inhibit osteoclasts

161
Q

What is the most common cause of hypercalcemia?

A

Primary hyperparathyroidism

162
Q

What is the most common cause of hypocalcemia?

A

Primary hypoparathyroidism

Physiology (13 decks)

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