Chr. 18 - The Endocrine System Flashcards
1
Q
[18.1] What is a hormone?
A
A molecule released in one part of the body regulating activity of cells in other parts of the body.
2
Q
[18.2] What is an exocrine gland?
A
A gland secreting into ducts carrying hormones to body cavities, lumen of organs, or outer surface of body.
3
Q
[18.2] What is an endocrine gland?
A
A gland secreting hormones into interstitial fluid surrounding the secretory cells, diffusing into blood stream and travelling to target cells.
4
Q
[18.3] What is down-regulation?
A
A decrease in protein receptors in cells in response to a large amount of hormone.
5
Q
[18.3] What is up-regulation?
A
An increase in protein receptors in cells in response to a deficiency in a hormone.
6
Q
[18.3] What are circulating hormones?
A
Hormones that are releasing into interstitial fluid and travel into the blood. Inactivated over a long duration due to their nature of lingering in blood.
7
Q
[18.3] What are local hormones?
A
Hormones that act on neighbouring cells, or the cell that secreted them. Inactivated quickly.
8
Q
[18.3] What are paracines?
A
Local hormones acting on neighbouring cells.
9
Q
[18.3] What are autocrines?
A
Local hormones acting on the secreting cell.
10
Q
[18.3] What are the chemical classes of hormones?
A
Lipid-soluble and water-soluble.
11
Q
[18.3] What are the classes of lipid-soluble hormones?
A
Steroid, thyroid, and nitric oxide.
12
Q
[18.3] What are steroid hormones?
A
Unique hormones each derived from cholesterol
13
Q
[18.3] What are thyroid hormones?
A
T3 and T4, synthesized from tyrosine and iodine.
14
Q
[18.3] What are the classes of water-soluble hormones?
A
Amine, peptide/protein, and eicosanoid.
15
Q
[18.3] What are amine hormones?
A
Hormones derived from amino acids.
16
Q
[18.3] What are peptide hormones?
A
Amino acid polymers acting as hormones, including protein and glycoprotein hormones.
17
Q
[18.3] What are eicosanoid hormones?
A
Hormones derived from arachidonic acid.
18
Q
[18.3] What are the classes of eicosanoid hormones?
A
Prostaglandins and leukotrienes.
19
Q
[18.3] What are transport proteins in relation to hormones?
A
Proteins synthesized in the liver transporting lipid-soluble hormones in blood.
20
Q
[18.3] List the functions of transport proteins in relation to hormones.
A
- Turning lipid-soluble hormones temporarily water-soluble for travel in blood.
- Partially inhibit hormone molecules from being filtered in kidneys.
- Provide a reserve of hormones in blood.
21
Q
[18.3] What is the free faction?
A
The percentage (0.1% - 10%) of lipid-soluble hormone not bound to transport proteins.
22
Q
[18.4] List the steps in the mechanism of action for lipid-soluble hormones.
A
- Lipid-soluble hormones diffuse from blood through lipid bilayer of cell.
- Hormone binds to receptors within cytosol or nucleus altering gene expression.
- New mRNA forms and paths to the ribosome for synthesize of proteins.
- Proteins generated from new mRNA alter activity of the cell and cause a response.
23
Q
[18.4] List the steps in the mechanism of action for water-soluble hormones.
A
- Hormone diffuses from blood to exterior receptor in target cells plasma membrane, activating adenylyl cyclase.
- Adenylyl cyclase converts ATP to cAMP within the cell.
- cAMP activates protein kinases in cytosol.
- Activated protein kinases phosphorylate proteins, activating or deactivating based on protein.
- Phosphorylated proteins cause reactions producing physiological responses.
- Phosphodiesterase inactivates cAMP, turning off cell’s response until a new hormone molecule binds.
24
Q
[18.4] What are the factors affecting the responsiveness of a target cell?
A
- Hormones concentration
- Abundance of hormone receptors
- Influence from other hormones.
25
[18.4] What is the permissive effect?
An effect produced by a hormone allowing another, primary hormone to have an effect.
26
[18.4] What is a synergistic effect as it relates to hormones?
When two hormones act together produce a response greater than the sum of their individual effect.
27
[18.4] What is an antagonistic effect as it relates to hormones?
When a hormone's effect opposes the effects of another hormone.
28
[18.5] List the ways hormone secretion is regulated.
1. Signals from nervous system
2. Chemical changes in blood
3. Other hormones
29
[18.6] What is the pituitary gland?
A pea-shaped structure on the (hypophyseal fossa of the sella turcica of the) sphenoid bone, attached to the hypothalamus, and releases hormones controlling other endocrine glands.
30
[18.6] What is the infundibulum?
The stalk attaching the pituitary gland to the hypothalamus.
31
[18.6] What are the two portions of the pituitary?
The anterior pituitary lobe and the posterior pituitary lobe.
32
[18.6] What are the two parts of the anterior pituitary lobe?
The pars distalis and pars tuberalis.
33
[18.6] What are the two parts of the posterior pituitary lobe?
The pars nervosa, and the pars intermedia.
34
[18.6] What are the types of anterior pituitary cells?
Somatotrophs, thyrotrophs, gonadotrophs, lactotrophs, and corticotrophs.
35
[18.6] Describe somatotrophs.
Cells secreting growth hormone.
36
[18.6] What is the function of growth hormone?
Stimulates general body growth and regulates aspects of metabolism.
37
[18.6] Describe thyrotrophs.
Pituitary cells secreting thyroid-stimulating hormone (TSH)
38
[18.6] What is the function of thyroid-stimulating hormone?
Controls secretions and other activities of thyroid gland.
39
[18.6] Describe gonadotrophs.
Pituitary cells secreting follicle-stimulating hormone and luteinizing hormone.
40
[18.6] What is the function of follicle-stimulating hormone and luteinizing hormone?
In men, stimulate production of sperm and secretion of testosterone.
In women, stimulate maturation of oocytes and secretion of estogen and progesterone.
41
[18.6] Describe lactotrophs.
Pituitary cells secreting prolactin.
42
[18.6] What is the function of prolactin?
Initiation of milk production in mammary glands after the glands are primed by other hormones.
43
[18.6] Describe corticotrophs.
Pituitary cells secreting adrenocorticotropic hormone and melanocyte-stimulating hormone.
44
[18.6] What is the function of adrenocorticotropic hormone?
Stimulate the adrenal cortex to secrete glucocorticoids.
45
[18.6] How does the hypothalamus control the anterior pituitary?
By secreting releasing hormones.
46
[18.6] What are the hormones released by the hypothalamus to control the anterior pituitary?
1. Growth hormone releasing hormone.
2. Thyrotropin releasing hormone
3. Corticotropin releasing hormone
4. Prolactin releasing hormone
5. Gonadotropin releasing hormone
47
[18.6] What are the inhibitng hormones released by the hypothalamus?
1. Growth hormone inhibiting hormone.
2. prolactin inhibiting hormone
48
[18.6] What is the hypophyseal portal system?
A blood flow system from capillaries in the hypothalamus into veins carrying blood to the capillaries of the anterior pituitary.
49
[18.6] List the steps of the regulation of anterior pituitary secretion.
1. Neurosecretory cells synthesize hypothalamic hormones and store in axon terminals.
2. When excited, these neurosecretory cells release vesicles containing the hormones into the blood of the hypophyseal portal system.
3. The hormones are transported to and stimulate the anterior pituitary to release the hormones of the anterior pituitary.
4. Hormones of the anterior pituitary are released into the blood stream.
50
[18.6] What are tropic hormones?
Hormones acting on other endocrine glands.
51
[18.6] What are insulin-like growth factors?
Small protein hormones secreted by the liver, skeletal muscle, cartilage, and bone when activated by growth hormone, causing growth in these tissues.
52
[18.6] What are the specific functions of insulin-like growth factors?
1.Increase growth of bone and soft tissues
2. Enhance lipolysis
3. Decrease glucose uptake
53
[18.6] How do insulin-like growth factor increase growth of bone and soft tissues?
Bone, stimulates osteoblasts, promotes cell division at epiphyseal plate, and enhances synthesis of proteins for bone matrix.
Soft tissues, increases uptake of amino acids, accelerating protein synthesis, and decrease breakdown of proteins.
54
[18.6] What is the function of the posterior pituitary?
Storing and releasing hormones. Does not produce hormones.
55
[18.6] What hormones are stored and released by the posterior pituitary?
Oxytocin and antidiuretic hormone.
56
[18.6] What are pituicytes?
Specialized supporting neuroglia associated with axon terminals of the posterior pituitary.
57
[18.6] List the steps of the release of hormones from the posterior pituitary.
1. Neurosecretory cells in the the hypothalamus synthesize and package oxytocin and ADH
2. Vesicles containing the hormones move via fast axonal transport to the posterior pituitary.
3. When appropriately stimulated, nerve impulses release oxytocin and ADH into the blood stream through the hypophyseal portal system.
4. The hormones travel to their target cells.
58
[18.6] What are the functions of oxytocin?
Enhance contractions of the smooth muscle cells in the uterus, and stimulates milk ejection in mammary glands in response to mechanical stimuli.
59
[18.6] What are the functions of antidiuretic hormone?
A hormone decreasing urine production by enhancing the kidneys ability to return water to the blood.
60
[18.7] Describe the thyroid gland.
A butterfly shaped gland inferior of the larynx, composed of right and left lobes connected by an isthmus. Thyroid follicles make up majority of the gland.
61
[18.7] What are thyroid follicles?
Spherical sacs composed of follicular cells and surrounded by a basement membrane.
62
[18.7] Describe follicular cells.
Cells composing thyroid follicles extending to the lumen of their respective follicle. Produce thyroxine and triiodothyronine (T4 and T3 respectively).
63
[18.7] What are parafollicular cells?
Cells laying between follicles producing calcitonin.
64
[18.7] List the steps of formation, storage, and release of thyroid hormones.
1. Iodide trapping
2. Synthesis of thyroglobulin
3. Oxidation of iodide
4. Iodination of tyrosine
5. Coupling of T1 and T2
6. Pinocytosis and digestion of colloid
7. Secretion of thyroid hormones
8. Transport in the blood
65
[18.7] Describe iodide trapping in relation to thyroid hormone production.
Thyroid follicular cells trap iodide by actively transporting them from blood.
66
[18.7] Describe synthesis of thyroglobulin in relation to thyroid hormone production.
Follicular cells synthesize TGB and release it into the lumen of the follicule.
67
[18.7] Describe oxidation of iodide in relation to thyroid hormone production.
Iodide is oxidized to a neutral charge as it passes into the lumen, enabling it to bind to tyrosine in TGB.
68
[18.7] Describe iodination of tyrosine in relation to thyroid hormone production.
Iodine atoms react with tyrosine, binding either 1 or 2 and forming T1/T2 on TGB. TGB with T1/T2 groups are referred to as colloid.
69
[18.7] Describe coupling of T1/T2 in relation to thyroid hormone production.
Two T2 will bind to form T4, or one T1 and one T2 will bind to for T3. These are still attached to TGB as it occurs, forming TGB with T3 or T4.
70
[18.7] Describe pinocytosis and digestion of colloid in relation to thyroid hormone production.
Molecules of colloid re-enter follicular cells through pinocytosis and merge with lysosomes where enzymes break down TGB, cleaving T3/T4 off the protein.
71
[18.7] Describe secretion of thyroid hormones in relation to thyroid hormone production.
T3/T4 diffuse through plasma membrane due to their lipid-soluble nature.
72
[18.7] Describe transport in the blood in relation to thyroid hormone production.
T3/T4 combine with transport proteins in the blood in order to travel. Mainly thyroxine-binding globulin (TBG)
73
[18.7] List the actions of thyroid hormones.
1. Increase basal metabolic rate
2. Enhance action of catecholamines
3. Regulate development and growth of nervous tissue and bones
74
[18.7] List the ways thyroid hormones increase basal metabolic rate.
1. Stimulate synthesis of Na/K ATPases, increasing the usage and need of ATP.
2. Increase concentration of enzymes involved in cellular respiration, increasing ATP production
3. Increase activity of mitochondria.
75
[18.7] How do thyroid hormones enhance action of catecholamines?
Thyroid hormones up-regulate B-adrenergic receptors promoting sympathetic response.
76
[18.7] How do thyroid hormones regulate development of nervous and bone tissue?
Promote synapse formation, myelin production, and growth of dendrites in neurons.
Promote ossification centers in developing bone, synthesis of bone proteins, and secretion of GH and IGFs.
77
[18.7] Describe the feedback loop for control of thyroid hormone secretion.
Negative feedback loop where low levels of T3/T4 induce secretion of thyrotropin-releasing hormone in the hypothalamus, which cascades to the thyroid releasing T3/T4. An increase in levels inhibits thyrotropin-releasing hormones.
78
[18.7] Describe the function of calcitonin.
Decreases levels of calcium in blood by inhibiting osteoclasts by a negative feedback loop.
79
[18.8] Describe the parathyroid gland.
Several small round masses of tissue embedded in posterior surface of lateral lobes producing parathyroid hormone.
80
[18.8] Describe parathyroid hormone.
A major regulator of calcium, magnesium, and phosphate in the blood, promoting resorption by bones through promotion of osteoclast activity and and slowing loss of minerals through urine. Also promotes calcitriol
81
[18.8] What is calcitriol?
The active form of vitamin D
82
[18.9] Describe the adrenal glands.
Flattened pyramidal shaped glands resting on the superior aspect of the kidney. Composed of an adrenal cortex and an adrenal medulla.
83
[18.9] Describe the adrenal cortex.
Peripheral structure of the adrenal glands divided into three zones: zona glomerulosa, zona fasciculata, and the zona reticularis.
84
[18.9] What is the zona golemerulosa?
The outer zone of the adrenal cortex, secreting mineralocorticoids.
85
[18.9] What are mineralocorticoids?
Hormones affecting mineral homeostasis.
86
[18.9] What is the zona fasciculata?
Widest division of the adrenal cortex, in between the zona glomerulosa and zona reticularis. Consists of cells arranged in long straight columns and secretes glucocorticoids.
87
[18.9] What are glucocorticoids?
Hormones affecting glucose homeostasis.
88
[18.9] What is the zona reticularis?
Inner zone of the adrenal cortex, arranged in branching cords and synthesize weak androgens.
89
[18.9] What are androgens?
Hormones having masculinizing affects.
90
[18.9] What is aldosterone?
The major mineralocorticoid regulating sodium and potassium.
91
[18.9] What is the RAA pathway?
The renin-angiotensin-aldosterone pathway that controls secretion of aldosterone.
92
[18.9] Describe the RAA pathway from the beginning to the point of angiotensin I
A stimuli triggers the RAA pathway through decrease in blood volume/blood pressure. This stimulates juxtaglomerular cells to secrete renin. Renin converts angiotensinogen, produced and secreted by the liver, into angiotensin I.
93
[18.9] Describe the RAA pathway from conversion of angiotensinogen to the point of aldosterone.
Angiotensin I circulates to the lungs and is converted to angiotensin II by angiotensin-converting enzyme. Angiotensin II travels in blood and stimulates the adrenal cortex to secrete aldosterone. It also has a vasoconstricting effect.
94
[18.9] Describe the RAA pathway from aldosterone being secreted to the end.
Aldosterone circulates to the kidneys and promotes reabsorption of sodium, retaining water as a result. Blood volume/pressure increases, and stimulation of the juxtaglomerular cells lowers or ceases.
95
[18.9] What are the main glucocorticoids?
Cortisol, corticosterone, and cortisone.
96
[18.9] What are the functions of glucocorticoids?
1. Protein breakdown
2. Glucose formation
3. Lipolysis
4. Resistance to stress
5. Anti-inflammatory effects
6. Depression of immune responses.
97
[18.9] What is the control system for glucocorticoid secretion?
A negative feedback loop relying on secretion of corticotropin-releasing hormone.
98
[18.9] What are chromaffin cells?
Hormone-producing cells within the adrenal medulla.
99
[18.9] What are the major hormones of the adrenal medulla?
Epinephrine and norepinephrine.
100
[18.10] What is the pancreas?
A flattened organ in the curve of the duodenum, comprised of a head, body, and tail, and acting as an endocrine and exocrine gland.
101
[18.10] What are acini?
Clusters of exocrine cells within the pancreas. Produce digestive enzymes that flow into the GI tract.
102
[18.10] What are pancreatic islets?
Endocrine tissue within the pancreas.
103
[18.10] List the types of pancreatic islet cells and the hormone they secrete.
1. Alpha cells, glucagon
2. Beta cells, insulin
3. Delta cells, somatostatin
4. F cells, pancreatic polypeptide
104
[18.10] Describe the control of secretion of glucagon and insulin.
A negative feedback loop balancing between release of glucagon mostly when blood sugar is low, and insulin mostly when blood sugar is high.
105
[18.10] What are all the stimuli for secretion of insulin?
1. Nerve impulses from Vagus X nerve
2. Increase in arginine and leucine after a meal
3. Glucose-dependent insulinotropic peptide released by small intestines in presence of glucose.
106
[18.10] What are all the stimuli for secretion of glucagon?
1. Increased activity of the sympathetic division
2. A rise in blood amino acids when blood glucose is low.
107
[18.11] What are gonads?
Organs producing hormones and gametes (sperm and oocytes).
108
[18.11] What hormones are released by the ovaries?
Estrogens, progesterone, inhibin, and relaxin.
109
[18.11] What hormones are produced by the testes?
Testosterone and androgens.
110
[18.12] What is the pineal gland?
A small endocrine gland attached to the roof of the third ventricle.
111
[18.12] What hormone is secreted from the pineal gland?
Melatonin.
112
[18.13] What are eicosanoids?
Hormones synthesized from arachidonic acid.
113
[18.13] What are the families of eicosanoids?
Prostaglandins and leukotrienes.
114
[18.13] What hormones are produced by the skin?
Cholecalciferol, aids in synthesis of calcitriol.
115
[18.13] What are the hormones produced by the GI tract? List their functions as well.
Gastrin, promotes secretion of gastric juices
Glucose-dependent insulinotropic peptide, stimulates release of insulin
Secretin, stimulates secretion of pancreatic juices and bile
Cholecystokinin, Stimulates secretion of pancreatic juice and regulates bile from gallbladder.
116
[18.13] What hormones are produced by the placenta? List their functions as well.
Human chorionic gonadotropin, stimulated corpus luteum to produce estrogens and progesterone.
Estrogens + progesterone, maintain pregnancy and prepare mammary glands.
Human chorionic somatomammotropin, stimulates development of mammary glands for lactation.
117
[18.13] What hormones are produced by the kidneys? List their function as well.
| Not the adrenal cortex
Renin, involved is RAA pathway.
Erythropoietin, increases formation of red blood cells
Calcitriol, aids in absorption of dietary calcium
118
[18.13] What hormones are produced by the heart?
Atrial natriuretic peptide, decreases blood pressure
119
[18.13] What hormones are produced by adipose tissue?
Leptin, suppresses appetite.
120
[18.13] What are growth factors?
Hormones stimulating cell and tissue growth and repair.
121
[18.14] What is the stress response?
A series of changes in response to prolonged stressful conditions.
122
[18.14] What are the stages of the stress response?
1. Fight or flight response
2. Slower resistance
3. Exhaustion
123
[18.14] What is the fight or flight response?
A response initiated by nerve impulses from the hypothalamus quickly mobilizing the body's resources for immediate physical activity.
124
[18.14] What is the slower resistance reaction?
A response initiated by the hypothalamus releasing hormones producing a longer-lasting response. Features corticotropin-releasing hormone, growth hormone-releasing hormone, and thyrotropin-releasing hormone.
125
[18.14] What is the exhaustion response?
A response incurred when resources of the body have become depleted and cannot sustain the resistance stage.
