Endocrine System Flashcards
(108 cards)
1
Q
What is paracrine communication?
A
the use of chemical messengers (paracrine factors) to transfer information from cell to cell within a single tissue
2
Q
What is a hormone?
A
chemical messengers that are released in one tissue and transported in the bloodstream to reach specific cells in other tissues (target cells)
3
Q
What is endocrine communication?
A
The use of hormones to coordinate cellular activities in tissues in distant portions of the body
4
Q
What is in the endocrine system?
A
includes all the endocrine cells and tissues of the body which release hormones
5
Q
What are endocrine glands?
A
- are ductless glands
- many are made of glandular epithelium whose cells manufacture and secrete hormones
- a few are made of neurosecretory tissue
6
Q
Where are endocrine glands?
A
widely scattered throughout the body
7
Q
Where are some of the locations of endocrine glands?
A
hypothalamus, pineal gland, heart, kidney, digestive tract, pancreatic islets, gonads, adrenal glands, thymus, thyroid gland
8
Q
What are the three groups of hormones?
A
- amino acid derivatives
- peptide hormones
- lipid derivatives
9
Q
Describe amino acid derivatives (amine)
A
- small molecules structurally related to amino acids
- synthesized from the amino acids tyrosine and tryptophan
10
Q
What the tyrosine derivatives?
A
thyroid hormones, catecholamines, epinephrine (E), norepinephrine (NE), dopamine
11
Q
What is the tryptophan derivative?
A
melatonin, serotonin
12
Q
Describe peptide/protein hormones
A
- chains of amino acids
- all hormones secreted by hypothalamus, heart, thymus, digestive tract, pancrease and some by pituitary gland
13
Q
What are the two types of peptide/protein hormones?
A
glycoproteins: > 200aa and short polypeptides <200 aa
14
Q
What are the three main glycoproteins?
A
- thyroid-stimulating hormone (TSH)
- luteinizing hormones (LH)
- follicle-stimulating hormone (FSH)
15
Q
What are the two classes of lipid derivatives?
A
eicosanoids and steroid hormones
16
Q
What are the characteristics of eicosanoids?
A
- derived from arachidonic acid
- include prostaglandins
17
Q
What are the characteristics of steroid hormones?
A
- derived from cholesterol
- released by: reproductive organs (androgens by testes, estrogens, and progestins by ovaries), adrenal glands (corticosteroids), kidneys (calcitriol)
18
Q
How are hormones distributed and transported?
A
within the blood, hormones may circulate freely or bound to transport proteins. The bloodstream contains substantial reserve of bound hormones. There is an equilibrium, free <–> bound
19
Q
How do steroid and thyroid hormones react with water?
A
they are hydrophobic
20
Q
How long are fre hormones active for?
A
< 1 hr, theu diffuse out of bloodstream and bind to receptors in raget tissues. enzymes?
21
Q
Which hormone transport protein is not selective?
A
albumin
22
Q
Which transport hormones are selective?
A
- sex hormone binding globulin (SHBG)
- corticosteroid binding globulin (CBG)
- thyroid binding globulin (TBG) and transthyretin (TTR)
23
Q
What do the disrupting compounds do?
A
prevent hormones from reaching its target cels
24
Q
What determines hormonal sensitivity?
A
the presence or absence of specific receptors for target cells, there is a lock and key mechanism
25
What are the actions of hormones on target cells?
- receptor activation
- conversion
- response of the cell
26
What do some of the response of the cells include?
- synthesis
- transport
- secretion
- contraction
- breakdown
27
What is synergism and who is involved?
epinephrine and norepinephrine. Hormones act in concert
28
What is permissiveness and who is involved?
estrogen and progesterone. Estrogen stimulates initial thickening of endometrium, progesterone further increases thickness. Without estrogen, progesterone's effect would not be as effective
29
What is antagonism and who is involved?
insulin and glucagon? Insulin decreases blood glucose levels, glucagon increases it
30
Where are the hormone receptors for catecholamines and peptide hormones?
- are water soluble (hydrophilic)
- unable to penetrate cell membrane
- receptors in cell surface membrane
31
What are eicosanoids and steroid hormones?
are lipid soluble (hydrophobic)
32
Where are thyroid hormones receptors?
enter cell by diffusion or transport proteins and receptors are in organelles, hydrophobic
33
What are the mechanisms of membrane receptors?
- binds to receptors
- G-protein activation (2nd messenger)
- amplification
- cAMP, cGMP, calcium ions
34
What are the mechanisms of intracellular receptors?
- steroid and thyroid
- binds to cytoplasm or nucleus (DNA)
- metabolic activity
35
How are endocrine organs controlled?
hormonal regulation (hypothalamus, pituitary gland), neural regulation, humoral regulation, negative feedback
36
Describe the control the hypothalamus has in hormone secretion
- the highest level of endocrine control
- controls more-complex endocrine reflexes
- integrates activities in three ways
37
What are the three characterstics of the hypothalamus?
1. secrete regulatory hormones (control endocrine cells in pituitary gland which in turn controls activities of other endocrine organs)
2. acts as an endocrine organ (release of ADH and oxytocin)
3. conrains autonomic centers (exert direct enural control over endocrine cells of adrenal medullae)
38
What is the structure of the pituitary gland (hypophysis)?
small, oval gland located on the ventral surface of the brain, under the hypothalamus.
39
What does the infundibulum do?
connects pituitary to the hypothalamus
40
What are the two seperate glands of the pituitary glands?
anterior pituitary glands (adenohypophysis) and the posterior pituitary gland (neurohypophysis)
41
What are the 7 hormones of the anterior pituitary?
1. thyroid stimulating hormone (TSH)
2. adrenocorticotropic hormone (ACTH)
3. gonadotropin
4. luteinizing hormone (LH)
5. prolactin (PRL)
6. growth hormone (GH)
7. melanocyte-stimulating hormone (MSH)
42
What does thyroid stimulating hormone (TSH) do?
also called thyrotropin, triggers the release of thyroid hormones
43
What does adrenocorticotropic hormone (ACTH) do?
stimulates release of glucocorticoids by adrenal cortex
44
What does gonadotropin do?
Is a follicle stimulating hormone (FSH) and stimulate follicle development and estrogen secretion in females
45
What doe the luteinizing hormone (LH) do?
causes ovulation and progestin production in females. Causes androgen production in males
46
What does prolactin do?
stimulates development of mammary glands and milk production
47
What does growth hormone do?
stimulates growth and replication
48
What does melanocyte stimulating hormone do?
stimulates melanocytes to produce melanin
49
What does the posterior pituitary contain?
Unmyelinated axons of hypothalamic neurons
50
What does the posterior pituitary gland store and release?
- antidiuretic hormone (ADH)
- oxytocin (OT)
51
Where is the thyroid gland?
lies near the thyroid cartilage of the larynx and has two lobes
52
What is the histology of the thyroid gland?
- thyroid follicles: thyroid hormones
- c (clear) cells: calcitonin
53
What do follicular cells produce?
thyroxin converted to T3 and T4
54
What do parafollicular cells produce?
calcitonin
55
What are the two different thyroid hormones?
T4 (tetraiodothyronine or thyroxine) and T3 (triiodothyronine)
56
What are the functions of the thyroid hormones?
enter target cells by diffusion or transport system, have a general target, and bind to receptors in the cytoplasm, surfaces of mitochondria, and nucleus.
57
What do thyroid hormones control?
the metabolic rate of all cells
58
What is goiter the result of?
result of iodine deficiency. There is a lack of thyroid hormones that removes negative feedback at the pituitary and TSH stimulates gland hyperplasia
59
What is calcitonin?
Synthesized and secreted by the parafollicular cells (C cells) of the thyroid gland
60
What does calcitonin do?
antagonist to parathyroid hormones, acts to decrease plasma Ca2+ levels
61
What is the action of calcitonin?
to inhibit osteoclast motility and cell shape and inactivates them. Ca2+ depletion (reduced bone resorption). In the kidney, calcitonin increases Ca2+ by inhibiting renal tubular Ca2+ absorption
62
What is the target cell for calcitonin?
osteoclase
63
What is the major stimulus of calcitonin?
a rise in plasma Ca2+ levels
64
What is the structure of the parathyroid glands?
4-5 glands embedded in the posterior surface of the thyroid's lateral lobes
65
What produce the parathyroid hormone?
chief cells
66
What is the function of parathyroid hormone?
increase Ca2+ concentration in body fluids
67
What is PTH antagonist to?
calcitonin
68
What does parathyroid hormone do?
1. stimulate osteoclasts
2. inhibits osteoblasts
3. enhances the reabsorption of Ca2+ at the kidneys
4. stimulating active vitamin D production in kidney --> a rise in Ca2+ absorption in intestines
69
What is the regulation of the parathyroid hormone?
direct negative feedback by blood Ca2+ levels
70
What are the hormones involved in the regulation of calcium homeostasis?
PTH, Vitamin D (calcitriol), calcitonin
71
What is hypocalcemia?
milk fever in cattle and eclampsia in other species. This is due to a loss of calcium in milk and disturbance in skeletal muscle function.
72
Where are the adrenal glands located?
on top of the kidnets, fitting like caps
73
What are the two parts of the adrenal glands?
adrenal cortex and adrenal medulla
74
What is the adrenal cortex compose of?
endocrine tissue
75
What are the hormones in the adrenal cortex?
cortical hormones are steroids known as corticosteroids
76
What is the adrenal medulla composed of?
neurosecretory tissue
77
What are the 3 categories of hormones produced by the adrenal cortex?
mineralocorticoids, glucocorticoids, androgens
78
What are the hormones of the adrenal cortex derived from?
cholesterol (adrenocorticosteroids)
79
What are the characteristics of mineralocorticoids?
- Essential to maintain sodium and potassium balance
- include aldosterone + deoxycorticosterone (DOC)
80
What are the characteristics of glucocorticoids?
- include cortisol and corticosterone
- maintain CHO reserves
81
What do androgens effect?
puberty and fetal life
82
What is the action of aldosterone?
- it promotes Na+ reabsoprtion at the distal convuluted tubules and collecting ducst of kidney
- Na+ retention is accompanied by corresponding water retention and excretion of K+, H+, and NH4+ ions.
83
What is the major role of glucocorticoids?
maintaining carbohydrate reserves
84
What regulates adrenal cortical hormone synthesis?
cortisol and androgens: primarily regulated by ACTH
aldosterone: renin-angiotensin II-aldosterone axis, humoral regulation
85
What are the main secretory products of the adrenal medulla?
catecholamines
86
What are the types of catecholamines?
epinephrine (80%), norepinephrine, dopamine
87
What is the structure of the pancrease?
elongated gland composed of endocrine and exocrine tissues
88
What do the pancreatic islets contaim?
also known as the islets of Langerhans (1%): endocrine portion, contain four cell types (alpha, beta, delta, and F cells)
89
What is the acini of the pancreas?
the exocrine portion (99%): digestive enzymes into ducts draining into the small intestine
90
What are the major target tissues of insulin?
liver, skeletal muscle, adipose
91
What is the major role of insulin?
increase uptake of glucose, fatty acid, and amino acids
92
What are the major target tissues of glucagon?
the liver: inhibits glycolysis and also increases lipolysis, to free fatty acids for metabolism
93
What is the main role of glucagon?
maintenance of blood glucose levels during fasting
94
What is polyuria/polydipsia?
unexplained weight alteration, usually in middle-aged dogs (spayed females are somewhat more susceptible)
95
What are the parts of the gonads?
the testes and ovary
96
What are the testes?
paired organs within the scrotum in males
97
What are the testes composed of?
mainly of coils of sperm producing seminiferous tubules and a scattering of endocrine interstitial cells between the tubules
98
What does LH do with the testes?
interstitial cells produce testosterone
99
What does the FSH do with the testes?
seminiferous tubules produce sperm plus inhibition
100
What is the function of estrogen?
regulate the menstrual cycle
101
What does estrogen do structurally?
promotes formation of female secondary sex characteristics; stimulate endometrial growth, increase uterine and mammary growth, maintenance of vessel and skin, reduce bone resorption, increase bone formation
102
What is considered the hormone of pregnancy?
progestin
103
What are the main roles of progestin?
converts the endometrium to secretory stage to prepare the uterus for implantation, affects the vaginal epithelium and cervical mucus, stimulate mammary development
104
What happens when pregnancy does not ocue?
progestin levels decrease, leading to menstruation. Normal menstrual bleeding is progesterone withdrawal bleeding
105
What does the epiphysis (pineal gland) do?
produces melatonin
106
What is melatonin secretion controlled by?
under the control of the endogenous circadian clock in the hypothalamus
107
When is melatonin secreted?
during the night
108
What is melatonin's role?
seasonal hormonal fluctuations -- seasonal breeding
