Section 6 Flashcards
1
Q
What are the two main periods of rapid growth?
A
The first two years of life and during puberty.
2
Q
When does the second period of rapid growth occur?
A
During puberty.
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.
4
Q
What experiences a large acceleration during puberty?
A
The lengthening of long bones.
5
Q
What supports pubertal growth in both males and females?
A
Growth hormone and androgens.
6
Q
What is the primary androgen responsible for stimulating growth in females?
A
DHEA, released from the adrenal cortex.
7
Q
What is the primary androgen responsible for stimulating growth in males?
A
Testosterone, which is much more potent than DHEA.
8
Q
Among the hormones produced by the anterior pituitary, which is the most abundant?
A
Growth hormone.
9
Q
What are the three primary metabolic actions of growth hormone?
A
- Increased rate of protein synthesis
- Increased fatty acid mobilization and use
- Decreased rate of glucose use by body tissues
10
Q
How does growth hormone affect protein synthesis?
A
It increases the rate of protein synthesis.
11
Q
What impact does growth hormone have on fatty acid metabolism?
A
It increases fatty acid mobilization and use.
12
Q
How does growth hormone affect glucose utilization by body tissues?
A
It decreases the rate of glucose use by body tissues.
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.
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.
15
Q
True or false: Bone is an inert tissue
A
FALSE: it is an active and dynamic tissue.
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.
17
Q
What is the term for the process by which bone is almost constantly being remodeled?
A
Remodeling.
18
Q
How is bone characterized in terms of vascularity?
A
Bone is highly vascularized.
19
Q
What are osteoblasts responsible for?
A
Osteoblasts deposit new bone.
20
Q
What is the role of osteoclasts in bone activity?
A
Osteoclasts dissolve bone.
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.
22
Q
How is bone growth in thickness achieved?
A
By adding new bone to the outer layer of existing bone.
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
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.
25
What is the Marrow Cavity, also known as the medullary cavity?
The central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored.
26
What increases as a result of bone growth in thickness?
Both the diameter of the bone and the marrow cavity increase.
27
Where does the lengthening of long bones occur?
At the ends of long bones, between the epiphysis and the diaphysis, in the epiphyseal plate.
28
What are the cartilage-forming cells in the region of bone growth in length called?
Chondrocytes.
29
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?
Chondrocytes divide and stack themselves in columns, with newer cells towards the epiphysis and older cells near the diaphysis.
30
What causes long bones to elongate during bone growth in length?
The division and increase in the number of chondrocytes.
31
What happens as chondrocytes mature during bone growth in length?
They hypertrophy, pushing the epiphysis away from the diaphysis, and the matrix around them calcifies.
32
Why do older chondrocytes eventually die during bone growth in length?
Cartilage itself is not highly vascularized, and older chondrocytes become too far away from the nutrient supply.
33
What happens after the removal of dead chondrocytes and calcified matrix during bone growth in length?
Osteoclasts remove the dead chondrocytes and calcified matrix, allowing osteoblasts and their capillary supply to invade the space and start depositing bone through ossification.
34
What marks the end of linear bone growth in length?
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.
35
What aspects of bone does growth hormone promote?
Growth hormone promotes both the thickness and length of bone.
36
Is there controversy regarding the direct effect of growth hormone on chondrocytes in cell culture?
Yes, there is controversy; chondrocytes in cell culture do not respond to growth hormone application experimentally.
37
How are the effects of growth hormone on bone growth mediated?
The effects of growth hormone on bone growth are mediated through other peptides known as somatomedins, also called insulin-like growth factors (IGFs).
38
What are the two types of IGFs?
IGF-I and IGF-II.
39
Where is IGF-I primarily synthesized and released?
IGF-I is primarily synthesized and released in the liver, stimulated by growth hormone.
40
Can other tissues produce IGF-I?
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.
41
Which type of IGF mediates most of the growth-promoting actions of growth hormone?
IGF-I mediates most of the growth-promoting actions of growth hormone.
42
Does growth hormone stimulate the production of IGF-II?
No, growth hormone does not stimulate the production of IGF-II.
43
What is an important role of IGF-II?
IGF-II is important during fetal development.
44
What is the definition of paracrine?
Paracrine is a type of hormone that has effects only in the vicinity of the gland secreting it.
45
What are the two regulatory hormones for growth hormone from the hypothalamus?
- Growth hormone-releasing hormone (GHRH) stimulates its release.
- Growth hormone-inhibiting hormone (GHIH; aka somatostatin) inhibits its release.
46
How can growth hormone secretion be increased?
To increase growth hormone secretion, you can either increase GHRH or decrease GHIH.
47
When does growth hormone reach peak levels?
Growth hormone reaches peak levels about an hour after entering deep sleep.
48
Name some factors that can increase the release of growth hormone.
Exercise, stress, low blood glucose, and high blood amino acids can increase the release of growth hormone.
49
What is the diurnal pattern of growth hormone secretion?
Similar to cortisol, growth hormone has a diurnal pattern of secretion.
50
Besides sleep, what other factors influence the release of growth hormone?
Exercise, stress, low blood glucose, and high blood amino acids influence the release of growth hormone.
51
What is the role of negative-feedback loops in the regulation of growth hormone secretion?
Negative-feedback loops participate in the regulation of growth hormone secretion.
52
What can cause growth hormone deficiency?
Growth hormone deficiency can result from dysfunction at the level of the hypothalamus, the pituitary, or at the tissue level.
53
What is the consequence of growth hormone deficiency during childhood?
The consequence of growth hormone deficiency during childhood is dwarfism, as growth hormone is necessary for full growth potential.
54
How can dwarfism caused by growth hormone deficiency during childhood be treated?
Dwarfism caused by growth hormone deficiency during childhood can be successfully treated with growth hormone if recognized early enough.
55
What is Laron dwarfism, and what causes it?
Laron dwarfism is another form of dwarfism caused by the lack of response from tissues to growth hormone.
56
How does Laron dwarfism respond to treatment?
Laron dwarfism responds to IGF-I treatment.
57
What symptoms may adults with growth hormone deficiency experience?
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
What is the significance of the timing of growth hormone deficiency?
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
What is the typical cause of growth hormone excess?
Growth hormone excess is typically caused by a tumor in the anterior pituitary.
60
How does the timing of growth hormone excess affect its effects?
The effects of growth hormone excess depend on when it occurs.
61
What is the result of growth hormone excess in childhood?
In childhood, growth hormone excess causes pronounced effects on the epiphyseal plates, leading to rapid growth and producing gigantism.
62
What happens if growth hormone excess occurs after epiphyseal plate closure?
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
How is gigantism characterized?
Gigantism is characterized by rapid growth, particularly affecting the epiphyseal plates.
64
What characterizes acromegaly?
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
What part of the body is particularly affected by acromegaly?
Acromegaly particularly affects the jaw, cheekbones, hands, feet, fingers, and toes.
66
What is the most abundant mineral in the human body?
Calcium
67
Why is calcium highly regulated in the body?
Calcium is highly regulated because it acts as an electrolyte and is vital to the health of the muscular, circulatory, and digestive systems.
68
What role does calcium play in bone health?
Calcium is indispensable to the building of bone.
69
Does calcium support the synthesis and function of blood cells?
Yasss
70
What are the three pools into which calcium within the human body is divided?
Extracellular calcium (0.1%)
Intracellular calcium (0.9%)
Calcium in the bone matrix (99%)
71
How is calcium (Ca2+) regulated in the body, in comparison to sodium (Na+) and potassium (K+)?
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
What happens during periods of high dietary intake of calcium (Ca2+)?
During periods of high dietary intake of calcium (Ca2+), excess Ca2+ is avoided by decreasing absorption.
73
Where is excess calcium (Ca2+) generally stored?
Excess calcium (Ca2+) is generally stored in the bones.
74
What happens when there is a need for increased Ca2+ in the plasma?
When there is a need for increased Ca2+ in the plasma, Ca2+ can readily be removed from the bones.
75
Name three hormones that regulate the plasma concentrations of Ca2+.
1. Parathyroid hormone (PTH)
2. Calcitonin
3. Vitamin D
76
Why is it important to consider the regulation of PO43- when discussing calcium (Ca2+) regulation?
It is important to consider the regulation of PO43- as it is part of how Ca2+ is stored in the bone.
77
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
o Immune system activation
o Gas exchange
78
Where is Parathyroid hormone (PTH) secreted from?
Parathyroid hormone (PTH) is secreted by the parathyroid glands.
79
Where are the parathyroid glands located?
The parathyroid glands are four very small glands located on the back of the thyroid gland.
80
Why is PTH considered essential for life?
PTH is considered essential for life because removing the parathyroid glands causes death due to hypocalcemia within a few days.
81
What is the primary action of PTH?
The primary action of PTH is to raise plasma Ca2+ levels by its effects on bone, the kidneys, and intestines.
82
How does PTH affect bone remodeling?
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
What is the primary storage of Ca2+ in the body?
The primary storage of Ca2+ in the body is within the bones, where it is stored as hydroxyapatite crystals (precipitated Ca3(PO4)2).
84
How does PTH affect the reabsorption of Ca2+ in the kidneys?
PTH stimulates the reabsorption of Ca2+ in the kidneys.
85
What process does PTH stimulate in the kidneys?
PTH stimulates the kidneys to remove PO43-.
86
Why is the stimulation of vitamin D activation in the kidneys important?
PTH stimulates the kidneys to activate vitamin D, which is important for calcium regulation.
87
How is the release of Parathyroid Hormone (PTH) regulated?
The release of PTH increases in response to decreasing plasma Ca2+ concentrations and decreases as Ca2+ levels rise.
88
What is the primary stimulus for the release of PTH?
The primary stimulus for the release of PTH is a decrease in plasma Ca2+ concentrations.
89
How does the release of PTH respond to increasing plasma Ca2+ concentrations?
PTH secretion decreases as plasma Ca2+ levels rise.
90
What is the cascade of events that occur to decrease PTH secretion?
The cascade of events involves an increase in plasma Ca2+ concentrations, leading to a decrease in PTH secretion.
91
Where was Calcitonin originally thought to be produced?
Calcitonin was originally thought to be a hormone of the parathyroid gland.
92
Where is Calcitonin actually secreted from?
Calcitonin is secreted from the thyroid gland.
93
What type of cells in the thyroid gland secrete calcitonin?
C cells of the thyroid gland secrete calcitonin.
94
What are the actions of calcitonin?
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
How does calcitonin respond to changes in plasma Ca2+ levels?
Calcitonin is secreted in response to increased plasma Ca2+ levels.
96
What is the primary effect of calcitonin on osteoclasts?
Calcitonin decreases the activity of osteoclasts.
97
What is the proper name for Vitamin D?
Vitamin D is properly called cholecalciferol.
98
What is the biologically active form of Vitamin D?
The biologically active form of Vitamin D is calcitriol.
99
How is calcitriol formed?
Calcitriol is formed by the hydroxylation of cholecalciferol in the kidneys.
100
Does Vitamin D function as a hormone or a vitamin?
Although classified as a vitamin, Vitamin D functions as a hormone as it can be produced by the skin.
101
What precursor is used to produce Vitamin D in the skin?
Using cholesterol as a precursor, UV light on the skin causes the formation of 7-dehydrocholesterol.
102
How does the lack of daily skin exposure to sunlight affect Vitamin D production in colder climates?
In colder climates like Canada, where there is not daily skin exposure to sunlight, the majority of Vitamin D comes from dietary supplements.
103
What is the main function of Vitamin D?
The main function of Vitamin D is to increase the intestinal absorption of Ca2+.
104
What happens to dietary Ca2+ without Vitamin D?
Without Vitamin D, dietary Ca2+ is not freely absorbed and is excreted in the feces.
105
Does Vitamin D affect the responsiveness of bone cells to PTH?
Yes, Vitamin D increases the responsiveness of bone cells to PTH.
106
Where do the two steps of Vitamin D activation occur?
The first step of Vitamin D activation occurs in the liver.
The second step of Vitamin D activation occurs in the kidneys.
107
What is added in each step of Vitamin D activation?
In each step of Vitamin D activation, a hydroxyl group is added to the compound.
108
What role does PTH play in the formation of activated Vitamin D?
PTH plays a role in the formation of activated Vitamin D by stimulating the enzymes in the kidney.
109
What is the end result of the activation of Vitamin D?
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
How do PTH and Vitamin D work together in Ca2+ homeostasis?
PTH and Vitamin D work together in Ca2+ homeostasis, with PTH playing the primary role.
111
What is the most dramatic effect of activated vitamin D in Ca2+ regulation?
The most dramatic effect of activated vitamin D is to increase Ca2+ absorption in the intestine.
112
Is dietary Ca2+ indiscriminately absorbed by the digestive system?
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
Under what influence is more dietary Ca2+ absorbed into the plasma?
More dietary Ca2+ is absorbed into the plasma under the influence of vitamin D when needed.
114
Besides increasing Ca2+ absorption, what else does the active form of vitamin D do?
Besides increasing Ca2+ absorption, the active form of vitamin D also increases the responsiveness of bone to PTH.
115
Are vitamin D and PTH interdependent in Ca2+ regulation?
Yes, Vitamin D and PTH are closely interdependent in Ca2+ regulation.
116
