Endocrine System (ch.28): pt.2 Flashcards
1
Q
What is the shape and structure of the thyroid gland?
A
The thyroid gland is butterfly-shaped, consisting of a central isthmus connecting two lateral lobes (right and left).
2
Q
Where is the thyroid gland located?
A
It is located inferior to the larynx and anterior to the trachea, centrally within the neck.
3
Q
What is a pyramidal lobe?
A
A pyramidal lobe is an extra lobe projecting from the isthmus, which is a normal anatomical variant.
4
Q
What are follicular cells?
A
Follicular cells are the endocrine workhorses of the thyroid gland, producing hormones T4 and T3.
5
Q
What stimulates follicular cells?
A
Follicular cells are stimulated by thyroid-stimulating hormone (TSH) secreted by the pituitary gland.
6
Q
What role does iodine play in thyroid hormone synthesis?
A
Iodine is essential for the synthesis of T3 and T4; without adequate iodine, these hormones cannot be synthesized properly.
7
Q
What are parafollicular cells?
A
Parafollicular cells (C cells) are found in the spaces between thyroid follicles and secrete calcitonin.
8
Q
What is the function of calcitonin?
A
Calcitonin lowers blood calcium levels and inhibits bone resorption, maintaining calcium homeostasis.
9
Q
What is iodide trapping?
A
Iodide trapping is the uptake of iodine into follicular cells, the first step in thyroid hormone production.
10
Q
How does TSH regulate thyroid hormone production?
A
TSH binds to receptors on follicular cells, triggering pathways that increase hormone production and secretion.
11
Q
What is the negative feedback loop involving T3 and T4?
A
Elevated levels of T3 and T4 inhibit TSH production by the pituitary, ensuring hormone levels remain balanced.
12
Q
What physiological processes do thyroid hormones influence?
A
Thyroid hormones (T3 and T4) influence metabolic rate, growth, development, and cardiovascular function.
13
Q
What is the significance of calcitonin in the body?
A
Calcitonin assists in regulating blood calcium levels and contributes to skeletal stability by inhibiting calcium release from bone.
14
Q
What are thyroid follicles?
A
Thyroid follicles are tiny, round structures inside the thyroid gland that hold the beginning of thyroid hormones.
15
Q
What are follicular cells?
A
Follicular cells are special cells that line the thyroid follicles and produce thyroid hormones when signaled by the brain (TSH).
16
Q
What is the function of thyroid hormones?
A
Thyroid hormones help control many body functions, including energy use and growth.
17
Q
What is the basement membrane?
A
The basement membrane is a thin, supportive layer surrounding each group of follicular cells that helps keep the cells organized and supports their function.
18
Q
What are parafollicular cells?
A
Parafollicular cells are cells in the thyroid gland that produce calcitonin, a hormone that helps manage calcium levels in the blood.
19
Q
What is the role of calcitonin?
A
Calcitonin helps regulate calcium levels in the blood.
20
Q
Why is the thyroid gland important?
A
The thyroid gland is essential for both metabolism and bone health due to its production of thyroid hormones and calcitonin.
21
Q
What shape does the thyroid gland have?
A
The thyroid gland is butterfly-shaped.
22
Q
Where is the thyroid gland located?
A
It is located below the larynx and in front of the trachea.
23
Q
What are thyroid follicles?
A
They are small, round structures in the thyroid gland where hormones are made and stored.
24
Q
Which cells surround thyroid follicles?
A
Follicular cells surround the follicles.
25
What do follicular cells make?
Follicular cells make T₃ (triiodothyronine) and T₄ (thyroxine) hormones.
26
Why is iodine important for the thyroid?
Iodine is essential for making T₃ and T₄ hormones.
27
What is thyroglobulin (TGB)?
TGB is a protein made by follicular cells that holds iodine to make T₃ and T₄.
28
What is the first step in thyroid hormone production?
Iodine trapping, where iodine is taken from the blood into thyroid cells.
29
What process makes iodine ready for hormone production?
Iodine is oxidized to make it chemically active.
30
What happens when iodine binds to tyrosine in the follicles?
It forms parts of thyroid hormones within thyroglobulin, like MIT and DIT.
31
How are T₃ and T₄ formed?
MIT and DIT molecules combine to form T₃; two DIT molecules combine to form T₄.
32
Where are T₃ and T₄ stored before being released?
They are stored in the colloid inside the follicles.
33
What happens when the body needs thyroid hormones?
The colloid is taken back into follicular cells, and T₃ and T₄ are released into the bloodstream.
34
Which cells produce calcitonin?
Parafollicular cells produce calcitonin.
35
What does calcitonin do?
Calcitonin helps regulate calcium levels by lowering excess calcium in the blood.
36
How do T₃ and T₄ travel in the body?
They are carried by transport proteins in the blood, such as thyroxine-binding globulin.
37
What do thyroid hormones increase?
Thyroid hormones increase basal metabolic rate (BMR).
38
How do thyroid hormones help in maintaining body temperature?
Thyroid hormones help maintain normal body temperature.
39
What do thyroid hormones stimulate?
Thyroid hormones stimulate protein synthesis.
40
What do thyroid hormones increase the use of for ATP production?
Thyroid hormones increase the use of glucose and fatty acids for ATP production.
41
What do thyroid hormones upregulate?
Thyroid hormones upregulate beta (β) receptors that attach to catecholamines.
42
With which hormones do thyroid hormones work to accelerate body growth?
Thyroid hormones work with hGH and IGFs to accelerate body growth.
43
What hormone is released from the anterior pituitary?
Thyroid-stimulating hormone (TSH)
44
What do TRH and TSH stimulate?
Synthesis and release of thyroid hormones
45
What mechanism regulates the synthesis and release of thyroid hormones?
Negative feedback mechanism
46
Where are T₃ and T₄ hormones produced?
In the follicular cells of the thyroid gland.
47
What stimulates the secretion of T₃ and T₄?
Thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH), in response to low thyroid hormone levels, low metabolic rate, cold, pregnancy, or high altitudes.
48
What inhibits the secretion of T₃ and T₄?
High levels of T₃ and T₄ through negative feedback; high levels of iodine also suppress their secretion.
49
What are the principal actions of T₃ and T₄?
Increase basal metabolic rate (BMR).
Stimulate protein synthesis.
Increase the use of glucose and fatty acids for ATP production.
Enhance cholesterol excretion.
Promote body growth.
Aid in the development of the nervous system.
50
Where is calcitonin produced?
In the parafollicular cells of the thyroid gland.
51
What stimulates the secretion of calcitonin?
High blood calcium (Ca²⁺) levels.
52
What inhibits the secretion of calcitonin?
Low blood calcium (Ca²⁺) levels.
53
What are the principal actions of calcitonin?
Lowers blood calcium (Ca²⁺) and phosphate levels.
Inhibits bone resorption by osteoclasts.
Accelerates the uptake of calcium and phosphate into the bone extracellular matrix.
54
What are the two types of cells in the parathyroid glands?
Chief cells and Oxyphil cells.
55
What do Chief cells produce?
Chief cells produce parathyroid hormone (PTH, parathormone).
56
What is the function of Oxyphil cells in normal parathyroid glands?
The function of Oxyphil cells is not known in normal parathyroid glands.
57
What do Oxyphil cells secrete in cases of parathyroid cancer?
Oxyphil cells secrete excess parathyroid hormone (PTH) in cases of parathyroid cancer.
58
What hormone is released when blood calcium levels are too high?
Calcitonin is released from the thyroid gland.
## Footnote
Calcitonin signals bones to store more calcium by stopping osteoclasts.
59
What effect does calcitonin have on blood calcium levels?
Calcitonin reduces the amount of calcium in the blood by promoting storage in bones.
60
What hormone is released when blood calcium levels are too low?
Parathyroid hormone (PTH) is released by the parathyroid glands.
## Footnote
PTH encourages bones to release stored calcium into the blood.
61
What are the effects of PTH on bones and kidneys?
PTH encourages bones to release calcium and tells kidneys to save calcium instead of excreting it.
62
What is the role of calcitriol in calcium regulation?
Calcitriol helps absorb more calcium from food and works with PTH to increase calcium levels.
## Footnote
Calcitriol is the active form of Vitamin D.
63
How does calcitriol assist PTH?
Calcitriol ensures more calcium is absorbed into the bloodstream from food.
64
How do calcitonin and PTH interact?
Calcitonin lowers blood calcium, while PTH raises it.
65
What happens when calcium levels are high?
Calcitonin lowers blood calcium by storing it in bones.
66
What happens when calcium levels are low?
PTH and calcitriol increase blood calcium by releasing it from bones and enhancing absorption from the diet.
67
Why is calcium balance important?
Calcium is vital for strong bones, muscle contraction, nerve function, and heart health.
68
Where are the adrenal glands located?
On top of each kidney.
69
What covers the adrenal glands?
A connective tissue capsule.
70
What are the two main regions of the adrenal glands?
The outer cortex and the inner medulla.
71
What percentage of the adrenal gland is made up by the cortex?
Approximately 80-90%.
72
What hormones are produced by the adrenal cortex?
Cortisol, aldosterone, and androgens.
73
Why are hormones from the adrenal cortex essential for survival?
They prevent dehydration and maintain electrolyte balance.
74
What hormones are produced by the adrenal medulla?
Adrenaline (epinephrine), noradrenaline (norepinephrine), and dopamine.
75
What is the function of adrenaline?
It prepares the body for emergencies by increasing heart rate and energy.
76
What is the function of noradrenaline?
It helps maintain blood pressure during stress.
77
Are the adrenal glands highly vascularized?
Yes, they receive a lot of blood flow to distribute hormones efficiently.
78
What is the location of the Zona Glomerulosa?
This is the outermost layer of the cortex, right below the capsule.
79
What does the Zona Glomerulosa produce?
It produces mineralocorticoids, the most important of which is aldosterone.
80
What is aldosterone’s job?
Controls your body's water and salt balance by signaling the kidneys to retain sodium (Na⁺) and water.
Helps regulate blood pressure by managing fluid levels in your body.
81
What is the location of the Zona Fasciculata?
This is the middle and largest layer of the adrenal cortex, making up the bulk of the gland.
82
What does the Zona Fasciculata produce?
It produces glucocorticoids, mainly cortisol.
83
What is cortisol’s job?
Helps the body respond to stress (e.g., during illness or emergency).
Regulates metabolism by breaking down fats, proteins, and glucose for energy.
Suppresses inflammation and reduces overactive immune responses.
84
What is the location of the Zona Reticularis?
This is the innermost layer of the adrenal cortex, closest to the adrenal medulla.
85
What does the Zona Reticularis produce?
It produces androgens, which are weak sex hormones.
86
What are androgens’ jobs?
Contribute to puberty and development of secondary sexual characteristics.
In women, androgens are converted into estrogen, especially after menopause.
87
What does the Zona Glomerulosa regulate?
The zona glomerulosa regulates water and salt balance with aldosterone.
88
What does the Zona Fasciculata regulate?
The zona fasciculata regulates stress and metabolism with cortisol.
89
What does the Zona Reticularis produce?
The zona reticularis produces sex-related hormones, like androgens, which influence growth and sex characteristics.
90
What is the primary mineralocorticoid hormone secreted by the adrenal gland?
Aldosterone.
91
What are the main roles of aldosterone?
It regulates sodium and potassium balance, adjusts blood pressure, and helps control blood volume.
92
What pathway controls the secretion of aldosterone?
The Renin-Angiotensin-Aldosterone (RAA) pathway.
93
What conditions trigger the RAA pathway?
Dehydration, sodium deficiency, or blood loss (which decrease blood volume).
94
Which cells release renin in response to low blood pressure?
Juxtaglomerular cells in the kidneys.
95
What does renin do in the RAA pathway?
Renin converts angiotensinogen (from the liver) into angiotensin I.
96
How is angiotensin I converted to angiotensin II?
An enzyme in the lungs converts angiotensin I into angiotensin II.
97
What does angiotensin II do?
It stimulates the adrenal cortex to release aldosterone and narrows blood vessels to increase blood pressure.
98
What effect does aldosterone have on the kidneys?
It tells the kidneys to retain sodium and water and excrete potassium.
99
How does aldosterone help increase blood pressure?
By increasing blood volume through sodium and water retention.
100
What are the main glucocorticoids produced?
Cortisol (hydrocortisone), cortisone, and corticosterone.
101
How is the secretion of glucocorticoids regulated?
By negative feedback.
102
What role do glucocorticoids play in protein metabolism?
They help control protein breakdown for new proteins or ATP production.
103
What effect do glucocorticoids have on glucose formation?
They stimulate gluconeogenesis.
104
How do glucocorticoids affect lipolysis?
They promote the release of fatty acids into the blood.
105
What is the impact of glucocorticoids on stress resistance?
They increase resistance to stress due to increased ATP.
106
How do glucocorticoids influence inflammation?
They inhibit inflammation and slow repair.
107
What effect do glucocorticoids have on immune responses?
They depress immune responses.
108
What is the major androgen secreted by the adrenal cortex?
The major androgen secreted by the adrenal cortex is dehydroepiandrosterone (DHEA).
109
What happens to DHEA levels in males after puberty?
In males, after puberty, testosterone is secreted in much larger quantities, so DHEA has virtually no effect.
110
What role does DHEA play in females?
In females, DHEA and other adrenal androgens play a major role in promoting libido and are converted to estrogens.
111
Where do all female estrogens come from in menopausal women?
In menopausal women, all female estrogens come from adrenal androgens.
112
What is the adrenal medulla?
The adrenal medulla is the inner part of the adrenal gland, playing a key role in the 'fight-or-flight' response during stressful situations.
113
How does the adrenal medulla get activated?
It is controlled by the autonomic nervous system (ANS), specifically the sympathetic division, which prepares the body to respond to stress.
114
What are chromaffin cells?
Chromaffin cells are special cells inside the adrenal medulla that release epinephrine and norepinephrine into the bloodstream.
115
What hormones do chromaffin cells release?
They release epinephrine (adrenaline) and norepinephrine (noradrenaline), which act as messengers for the 'fight-or-flight' response.
116
What is the amount of hormones secreted by the adrenal medulla?
The medulla releases 80% epinephrine and 20% norepinephrine.
117
What happens during the fight-or-flight response?
Epinephrine and norepinephrine are released, intensifying the actions of the sympathetic nervous system to help respond to danger.
118
What effects do epinephrine and norepinephrine have on heart rate?
They increase heart rate and cardiac output to deliver oxygen and nutrients quickly.
119
How does blood pressure change during stress?
Blood pressure rises to ensure adequate blood flow during stress.
120
How is blood flow redirected during the fight-or-flight response?
Blood flow increases to critical areas like the liver, heart, and skeletal muscles while decreasing in non-essential areas.
121
What happens to the airways during the fight-or-flight response?
Airways in the lungs widen to allow more oxygen to enter the body.
122
What metabolic adjustments occur during stress?
Increased blood glucose and increased fatty acids are released to provide energy.
123
What role does the hypothalamus play in this process?
The hypothalamus detects stress and activates sympathetic preganglionic neurons, stimulating chromaffin cells.
124
What are the key takeaways about the adrenal medulla?
The adrenal medulla acts as a rapid-response system, releasing hormones to prepare the body for immediate action.
125
What are the clusters of exocrine cells in the pancreas called?
Almost all of the exocrine cells of the pancreas are arranged in clusters called acini.
126
What do acini produce?
Acini produce digestive enzymes that are delivered to the gastrointestinal tract through ducts.
127
What are the clusters of endocrine tissue in the pancreas called?
Scattered among the acini are clusters of endocrine tissue called pancreatic islets (islets of Langerhans).
128
What do the pancreatic islets contain?
The islets contain secretin cells.
129
What are pancreatic islets?
Small groups of cells in the pancreas responsible for producing hormones that help regulate blood sugar and digestion.
130
What do Alpha (A) cells produce?
Glucagon, a hormone that raises blood sugar levels by telling the liver to release stored glucose into the bloodstream.
131
What do Beta (B) cells produce?
Insulin, a hormone that lowers blood sugar levels by helping sugar move from the blood into the cells for energy.
132
What do Delta (D) cells produce?
Somatostatin, which regulates the activity of other cells in the islets and stops the release of insulin, glucagon, and growth hormone.
133
What do F cells produce?
Pancreatic polypeptide, which regulates the pancreas and digestion by reducing somatostatin secretion and slowing gallbladder contraction.
134
What is the role of somatostatin?
Acts as a 'traffic control' hormone that slows down the release of glucagon and insulin, ensuring balance.
135
What does pancreatic polypeptide do?
Helps regulate digestion by reducing gallbladder movement and controlling the release of digestive enzymes.
136
What are the primary regulators of blood sugar?
Alpha and Beta cells: Glucagon increases blood sugar, while insulin decreases blood sugar.
137
How does somatostatin function in hormone regulation?
It moderates the activity of other hormones in a balancing act.
138
What is the overall function of pancreatic islets?
They work together to keep blood sugar levels steady and support proper digestion, ensuring the body has energy and nutrients when needed.
139
Where is the pineal gland located?
The pineal gland is attached to the roof of the third ventricle of the brain.
140
What hormone does the pineal gland secrete?
The pineal gland secretes melatonin.
141
What is the function of melatonin?
Melatonin helps to regulate the body’s biological clock – more is secreted during periods of darkness.
142
Where is the thymus located?
The thymus is located behind the sternum between the lungs.
143
What hormones does the thymus produce?
The thymus produces thymosin, thymic humoral factor (THF), thymic factor (TF), and thymopoietin.
144
What is the role of the hormones produced by the thymus?
These hormones promote maturation of the immune system’s T cells (a type of white blood cell that destroys microbes and foreign substances).
145
What are eicosanoids?
Eicosanoids are locally-acting hormones derived from the 20-carbon fatty acid arachidonic acid.
146
What are the two families of eicosanoids?
The two families of eicosanoids are prostaglandins and leukotrienes.
147
What is the role of eicosanoids?
Both classes of eicosanoids mediate or promote inflammatory responses.
148
How do eicosanoids appear in the blood?
Eicosanoids appear in the blood in very small quantities and are inactivated quickly.
149
How do eicosanoids act on target cells?
Eicosanoids act by binding to receptors on target cells to stimulate or inhibit synthesis of second messengers.
150
What is eustress?
Eustress is helpful, everyday stress that prepares us to meet challenges.
151
What is distress?
Distress is any type of harmful stress that may be damaging.
152
What is the fight-or-flight response?
The fight-or-flight response is the first stage of the stress response that stimulates the body’s resources to prepare for immediate activity.
153
What is the resistance reaction?
The resistance reaction is the second stage in the stress response and lasts longer than the fight-or-flight response.
154
What happens if the resistance reaction lasts too long?
If the resistance reaction lasts too long, exhaustion will result.
155
What does the body do to counteract stress?
The body works to maintain homeostasis to counteract stress.
