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PHGY 216 mod 1 > Section 6 > Flashcards

Section 6 Flashcards

1
Q

What are the two main periods of rapid growth?

A

The first two years of life and during puberty.

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2
Q

When does the second period of rapid growth occur?

A

During puberty.

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3
Q

Is there a significant difference in male and female height or weight before puberty?

A

No, there is little difference in male and female height or weight prior to puberty.

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4
Q

What experiences a large acceleration during puberty?

A

The lengthening of long bones.

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5
Q

What supports pubertal growth in both males and females?

A

Growth hormone and androgens.

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6
Q

What is the primary androgen responsible for stimulating growth in females?

A

DHEA, released from the adrenal cortex.

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7
Q

What is the primary androgen responsible for stimulating growth in males?

A

Testosterone, which is much more potent than DHEA.

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8
Q

Among the hormones produced by the anterior pituitary, which is the most abundant?

A

Growth hormone.

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9
Q

What are the three primary metabolic actions of growth hormone?

A
  1. Increased rate of protein synthesis
  2. Increased fatty acid mobilization and use
  3. Decreased rate of glucose use by body tissues
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10
Q

How does growth hormone affect protein synthesis?

A

It increases the rate of protein synthesis.

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11
Q

What impact does growth hormone have on fatty acid metabolism?

A

It increases fatty acid mobilization and use.

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12
Q

How does growth hormone affect glucose utilization by body tissues?

A

It decreases the rate of glucose use by body tissues.

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13
Q

During prolonged fasting, why is the shift in metabolic effects of growth hormone important?

A

It preserves glucose for the brain by primarily using fat stores for metabolism.

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14
Q

What soft tissue actions can growth hormone have on tissues sensitive to its stimulation?

A

Growth hormone can induce hyperplasia (increase in the number of cells) and hypertrophy (increase in cell size) in sensitive soft tissues.

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15
Q

True or false: Bone is an inert tissue

A

FALSE: it is an active and dynamic tissue.

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16
Q

What are the two cell types responsible for the dynamic nature of bone?

A

1) Osteoblasts - responsible for depositing new bone.

2) Osteoclasts - responsible for dissolving bone.

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17
Q

What is the term for the process by which bone is almost constantly being remodeled?

A

Remodeling.

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18
Q

How is bone characterized in terms of vascularity?

A

Bone is highly vascularized.

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19
Q

What are osteoblasts responsible for?

A

Osteoblasts deposit new bone.

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20
Q

What is the role of osteoclasts in bone activity?

A

Osteoclasts dissolve bone.

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21
Q

Can bone growth lead to both an increase in thickness and length?

A

Yes, bone growth can lead to either an increase in thickness or length.

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22
Q

How is bone growth in thickness achieved?

A

By adding new bone to the outer layer of existing bone.

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23
Q

What is the role of osteoblasts in bone growth in thickness?

A

Osteoblasts deposit new bone on the outer surface of the existing bone

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24
Q

What is the role of osteoclasts in bone growth in thickness?

A

Osteoclasts on the inside of the bone remove bone during the process of growth in thickness.

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25
Q

What is the Marrow Cavity, also known as the medullary cavity?

A

The central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored.

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26
Q

What increases as a result of bone growth in thickness?

A

Both the diameter of the bone and the marrow cavity increase.

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27
Q

Where does the lengthening of long bones occur?

A

At the ends of long bones, between the epiphysis and the diaphysis, in the epiphyseal plate.

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28
Q

What are the cartilage-forming cells in the region of bone growth in length called?

A

Chondrocytes.

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29
Q

How do chondrocytes divide in the epiphyseal plate during bone growth in length? What side are the new cells towards, and what side are the older cells towards?

A

Chondrocytes divide and stack themselves in columns, with newer cells towards the epiphysis and older cells near the diaphysis.

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30
Q

What causes long bones to elongate during bone growth in length?

A

The division and increase in the number of chondrocytes.

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31
Q

What happens as chondrocytes mature during bone growth in length?

A

They hypertrophy, pushing the epiphysis away from the diaphysis, and the matrix around them calcifies.

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32
Q

Why do older chondrocytes eventually die during bone growth in length?

A

Cartilage itself is not highly vascularized, and older chondrocytes become too far away from the nutrient supply.

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33
Q

What happens after the removal of dead chondrocytes and calcified matrix during bone growth in length?

A

Osteoclasts remove the dead chondrocytes and calcified matrix, allowing osteoblasts and their capillary supply to invade the space and start depositing bone through ossification.

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34
Q

What marks the end of linear bone growth in length?

A

At the end of adolescence, sex hormones cause the epiphyseal plates to completely ossify, and linear bone growth ceases. Thickening of bone can occur throughout life.

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35
Q

What aspects of bone does growth hormone promote?

A

Growth hormone promotes both the thickness and length of bone.

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36
Q

Is there controversy regarding the direct effect of growth hormone on chondrocytes in cell culture?

A

Yes, there is controversy; chondrocytes in cell culture do not respond to growth hormone application experimentally.

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37
Q

How are the effects of growth hormone on bone growth mediated?

A

The effects of growth hormone on bone growth are mediated through other peptides known as somatomedins, also called insulin-like growth factors (IGFs).

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38
Q

What are the two types of IGFs?

A

IGF-I and IGF-II.

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39
Q

Where is IGF-I primarily synthesized and released?

A

IGF-I is primarily synthesized and released in the liver, stimulated by growth hormone.

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40
Q

Can other tissues produce IGF-I?

A

Yes, most other tissues can produce IGF-I when stimulated by growth hormone, but they do not release it into the blood; it may have paracrine actions.

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41
Q

Which type of IGF mediates most of the growth-promoting actions of growth hormone?

A

IGF-I mediates most of the growth-promoting actions of growth hormone.

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42
Q

Does growth hormone stimulate the production of IGF-II?

A

No, growth hormone does not stimulate the production of IGF-II.

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43
Q

What is an important role of IGF-II?

A

IGF-II is important during fetal development.

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44
Q

What is the definition of paracrine?

A

Paracrine is a type of hormone that has effects only in the vicinity of the gland secreting it.

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45
Q

What are the two regulatory hormones for growth hormone from the hypothalamus?

A
  • Growth hormone-releasing hormone (GHRH) stimulates its release.
  • Growth hormone-inhibiting hormone (GHIH; aka somatostatin) inhibits its release.
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46
Q

How can growth hormone secretion be increased?

A

To increase growth hormone secretion, you can either increase GHRH or decrease GHIH.

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47
Q

When does growth hormone reach peak levels?

A

Growth hormone reaches peak levels about an hour after entering deep sleep.

48
Q

Name some factors that can increase the release of growth hormone.

A

Exercise, stress, low blood glucose, and high blood amino acids can increase the release of growth hormone.

49
Q

What is the diurnal pattern of growth hormone secretion?

A

Similar to cortisol, growth hormone has a diurnal pattern of secretion.

50
Q

Besides sleep, what other factors influence the release of growth hormone?

A

Exercise, stress, low blood glucose, and high blood amino acids influence the release of growth hormone.

51
Q

What is the role of negative-feedback loops in the regulation of growth hormone secretion?

A

Negative-feedback loops participate in the regulation of growth hormone secretion.

52
Q

What can cause growth hormone deficiency?

A

Growth hormone deficiency can result from dysfunction at the level of the hypothalamus, the pituitary, or at the tissue level.

53
Q

What is the consequence of growth hormone deficiency during childhood?

A

The consequence of growth hormone deficiency during childhood is dwarfism, as growth hormone is necessary for full growth potential.

54
Q

How can dwarfism caused by growth hormone deficiency during childhood be treated?

A

Dwarfism caused by growth hormone deficiency during childhood can be successfully treated with growth hormone if recognized early enough.

55
Q

What is Laron dwarfism, and what causes it?

A

Laron dwarfism is another form of dwarfism caused by the lack of response from tissues to growth hormone.

56
Q

How does Laron dwarfism respond to treatment?

A

Laron dwarfism responds to IGF-I treatment.

57
Q

What symptoms may adults with growth hormone deficiency experience?

A

Adults with growth hormone deficiency may experience reduced skeletal muscle mass and strength, decreased bone density, and an increased risk of developing heart failure.

58
Q

What is the significance of the timing of growth hormone deficiency?

A

The timing of growth hormone deficiency is crucial; if it occurs during childhood, it can result in dwarfism, but if recognized early, it can be successfully treated with growth hormone.

59
Q

What is the typical cause of growth hormone excess?

A

Growth hormone excess is typically caused by a tumor in the anterior pituitary.

60
Q

How does the timing of growth hormone excess affect its effects?

A

The effects of growth hormone excess depend on when it occurs.

61
Q

What is the result of growth hormone excess in childhood?

A

In childhood, growth hormone excess causes pronounced effects on the epiphyseal plates, leading to rapid growth and producing gigantism.

62
Q

What happens if growth hormone excess occurs after epiphyseal plate closure?

A

If growth hormone excess occurs after epiphyseal plate closure, height is not affected, but bones can still thicken, leading to the condition of acromegaly.

63
Q

How is gigantism characterized?

A

Gigantism is characterized by rapid growth, particularly affecting the epiphyseal plates.

64
Q

What characterizes acromegaly?

A

Acromegaly is characterized by a marked coarsening of the jaw and cheekbones, enlargement of the hands and feet, and thickening of the fingers and toes.

65
Q

What part of the body is particularly affected by acromegaly?

A

Acromegaly particularly affects the jaw, cheekbones, hands, feet, fingers, and toes.

66
Q

What is the most abundant mineral in the human body?

A

Calcium

67
Q

Why is calcium highly regulated in the body?

A

Calcium is highly regulated because it acts as an electrolyte and is vital to the health of the muscular, circulatory, and digestive systems.

68
Q

What role does calcium play in bone health?

A

Calcium is indispensable to the building of bone.

69
Q

Does calcium support the synthesis and function of blood cells?

A

Yasss

70
Q

What are the three pools into which calcium within the human body is divided?

A

Extracellular calcium (0.1%)

Intracellular calcium (0.9%)

Calcium in the bone matrix (99%)

71
Q

How is calcium (Ca2+) regulated in the body, in comparison to sodium (Na+) and potassium (K+)?

A

Calcium (Ca2+) is under hormonal control to ensure the proper concentration is maintained, unlike sodium (Na+) and potassium (K+), which are regulated by renal function and urinary excretion.

72
Q

What happens during periods of high dietary intake of calcium (Ca2+)?

A

During periods of high dietary intake of calcium (Ca2+), excess Ca2+ is avoided by decreasing absorption.

73
Q

Where is excess calcium (Ca2+) generally stored?

A

Excess calcium (Ca2+) is generally stored in the bones.

74
Q

What happens when there is a need for increased Ca2+ in the plasma?

A

When there is a need for increased Ca2+ in the plasma, Ca2+ can readily be removed from the bones.

75
Q

Name three hormones that regulate the plasma concentrations of Ca2+.

A
  1. Parathyroid hormone (PTH)
  2. Calcitonin
  3. Vitamin D
76
Q

Why is it important to consider the regulation of PO43- when discussing calcium (Ca2+) regulation?

A

It is important to consider the regulation of PO43- as it is part of how Ca2+ is stored in the bone.

77
Q

Select the following statements that DO(ES) NOT involve calcium.

o Neuromuscular excitability
o Secretion of vesicles
o Immune system activation
o Excitation-contraction coupling in cardiac and smooth muscles
o Release of neurotransmitters
o Gas exchange
o Role as a second messenger

A

o Immune system activation
o Gas exchange

78
Q

Where is Parathyroid hormone (PTH) secreted from?

A

Parathyroid hormone (PTH) is secreted by the parathyroid glands.

79
Q

Where are the parathyroid glands located?

A

The parathyroid glands are four very small glands located on the back of the thyroid gland.

80
Q

Why is PTH considered essential for life?

A

PTH is considered essential for life because removing the parathyroid glands causes death due to hypocalcemia within a few days.

81
Q

What is the primary action of PTH?

A

The primary action of PTH is to raise plasma Ca2+ levels by its effects on bone, the kidneys, and intestines.

82
Q

How does PTH affect bone remodeling?

A

Under the influence of PTH, osteoclast activity is slightly enhanced, and osteoblast activity is slightly inhibited, leading to more breakdown of bone than build-up, resulting in the release of Ca2+ and PO43- into the plasma.

83
Q

What is the primary storage of Ca2+ in the body?

A

The primary storage of Ca2+ in the body is within the bones, where it is stored as hydroxyapatite crystals (precipitated Ca3(PO4)2).

84
Q

How does PTH affect the reabsorption of Ca2+ in the kidneys?

A

PTH stimulates the reabsorption of Ca2+ in the kidneys.

85
Q

What process does PTH stimulate in the kidneys?

A

PTH stimulates the kidneys to remove PO43-.

86
Q

Why is the stimulation of vitamin D activation in the kidneys important?

A

PTH stimulates the kidneys to activate vitamin D, which is important for calcium regulation.

87
Q

How is the release of Parathyroid Hormone (PTH) regulated?

A

The release of PTH increases in response to decreasing plasma Ca2+ concentrations and decreases as Ca2+ levels rise.

88
Q

What is the primary stimulus for the release of PTH?

A

The primary stimulus for the release of PTH is a decrease in plasma Ca2+ concentrations.

89
Q

How does the release of PTH respond to increasing plasma Ca2+ concentrations?

A

PTH secretion decreases as plasma Ca2+ levels rise.

90
Q

What is the cascade of events that occur to decrease PTH secretion?

A

The cascade of events involves an increase in plasma Ca2+ concentrations, leading to a decrease in PTH secretion.

91
Q

Where was Calcitonin originally thought to be produced?

A

Calcitonin was originally thought to be a hormone of the parathyroid gland.

92
Q

Where is Calcitonin actually secreted from?

A

Calcitonin is secreted from the thyroid gland.

93
Q

What type of cells in the thyroid gland secrete calcitonin?

A

C cells of the thyroid gland secrete calcitonin.

94
Q

What are the actions of calcitonin?

A

The actions of calcitonin are opposite to those of parathyroid hormone. Calcitonin is secreted in response to increased plasma Ca2+ levels and acts on osteoclasts to decrease their activity, preventing the release of Ca2+ and PO43- from the bone.

95
Q

How does calcitonin respond to changes in plasma Ca2+ levels?

A

Calcitonin is secreted in response to increased plasma Ca2+ levels.

96
Q

What is the primary effect of calcitonin on osteoclasts?

A

Calcitonin decreases the activity of osteoclasts.

97
Q

What is the proper name for Vitamin D?

A

Vitamin D is properly called cholecalciferol.

98
Q

What is the biologically active form of Vitamin D?

A

The biologically active form of Vitamin D is calcitriol.

99
Q

How is calcitriol formed?

A

Calcitriol is formed by the hydroxylation of cholecalciferol in the kidneys.

100
Q

Does Vitamin D function as a hormone or a vitamin?

A

Although classified as a vitamin, Vitamin D functions as a hormone as it can be produced by the skin.

101
Q

What precursor is used to produce Vitamin D in the skin?

A

Using cholesterol as a precursor, UV light on the skin causes the formation of 7-dehydrocholesterol.

102
Q

How does the lack of daily skin exposure to sunlight affect Vitamin D production in colder climates?

A

In colder climates like Canada, where there is not daily skin exposure to sunlight, the majority of Vitamin D comes from dietary supplements.

103
Q

What is the main function of Vitamin D?

A

The main function of Vitamin D is to increase the intestinal absorption of Ca2+.

104
Q

What happens to dietary Ca2+ without Vitamin D?

A

Without Vitamin D, dietary Ca2+ is not freely absorbed and is excreted in the feces.

105
Q

Does Vitamin D affect the responsiveness of bone cells to PTH?

A

Yes, Vitamin D increases the responsiveness of bone cells to PTH.

106
Q

Where do the two steps of Vitamin D activation occur?

A

The first step of Vitamin D activation occurs in the liver.

The second step of Vitamin D activation occurs in the kidneys.

107
Q

What is added in each step of Vitamin D activation?

A

In each step of Vitamin D activation, a hydroxyl group is added to the compound.

108
Q

What role does PTH play in the formation of activated Vitamin D?

A

PTH plays a role in the formation of activated Vitamin D by stimulating the enzymes in the kidney.

109
Q

What is the end result of the activation of Vitamin D?

A

The end result of the activation of Vitamin D is the formation of 1,25-(OH)2-vitamin D3, also called calcitriol, which is the active form.

110
Q

How do PTH and Vitamin D work together in Ca2+ homeostasis?

A

PTH and Vitamin D work together in Ca2+ homeostasis, with PTH playing the primary role.

111
Q

What is the most dramatic effect of activated vitamin D in Ca2+ regulation?

A

The most dramatic effect of activated vitamin D is to increase Ca2+ absorption in the intestine.

112
Q

Is dietary Ca2+ indiscriminately absorbed by the digestive system?

A

No, dietary Ca2+ is not indiscriminately absorbed by the digestive system. In fact, the majority of ingested Ca2+ is typically not absorbed but is lost in the feces.

113
Q

Under what influence is more dietary Ca2+ absorbed into the plasma?

A

More dietary Ca2+ is absorbed into the plasma under the influence of vitamin D when needed.

114
Q

Besides increasing Ca2+ absorption, what else does the active form of vitamin D do?

A

Besides increasing Ca2+ absorption, the active form of vitamin D also increases the responsiveness of bone to PTH.

115
Q

Are vitamin D and PTH interdependent in Ca2+ regulation?

A

Yes, Vitamin D and PTH are closely interdependent in Ca2+ regulation.

116
Q
A

PHGY 216 mod 1 (7 decks)

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