1
Q
hormone
A
a mediator molecule that is released in one part of the body but regulates the activity of cells in other parts of the body; most enter the bloodstream; bind to receptors on or in the target cells
2
Q
exocrine gland
A
secrete products into ducts that carry the secretions into body cavities, into the lumen of an organ, or to the outer surface of the body; i.e. sudoriferous (sweat), sebaceous (oil), mucous and digestive glands
3
Q
endocrine glands
A
secrete their products (hormones) into interstitial fluid surrounding the secretory cells rather than into ducts, from the interstitial fluid, hormones diffuse into the blood which carries the hormones to the target cells
4
Q
receptors
A
protein that only specifically recognize and bind to one hormone
5
Q
down regulation
A
if a hormone is present in excess, the number of target cell receptors may decrease; makes target cell less sensitive to the hormone
6
Q
up regulation
A
when a hormone is deficient, the number of target cell receptors may increase; makes target cell more sensitive to a hormone
7
Q
circulating hormones
A
most endocrine hormones; pass from secretory cells that make them into interstitial fluid and into the blood
8
Q
local hormone
A
act locally on neighbouring cells or on the same cell that secreted them without first entering the blood stream
9
Q
paracrine
A
local hormones that act on neighbouring cells
10
Q
autocrine
A
local hormones that act on the same cell that secreted them
11
Q
lipid soluble hormones
A
soluble in lipids; include steroid hormones, thyroid hormones and nitric oxide
12
Q
steroid hormone
A
derived from cholesterol; each is unique due to the presence of different chemical groups attached at various sites on the four rings at the core of its structure (allows for different function)
13
Q
thyroid hormones
A
synthesized by attaching iodine to the amino acid tyrosine
14
Q
nitric oxide
A
gas; both a hormone and a neurotransmitter
15
Q
water soluble hormones
A
soluble in water; include amine hormones, peptide and protein hormones and eicosanoid hormones
16
Q
amine hormones
A
synthesized by removing a molecule of CO2
17
Q
peptide and protein hormones
A
amino acid polymers
18
Q
glycoprotein hormones
A
protein hormones with attached carbohydrate groups ; i.e. thyroid stimulating hormone
19
Q
eicosanoid hormones
A
derived from arachidonic acid (20 C fatty acid)
20
Q
prostaglandins and leukotrienes
A
two types of eicosanoid hormones
21
Q
3 functions of transport proteins
A
- make lipid soluble hormones temporarily water soluble (increasing solubility in blood)
- they retard passage of small hormone molecules through the filtering mechanism in the kidneys (slowing the rate of hormone loss in the urine)
- provide a ready reserve of hormone (already ready in the bloodstream)
22
Q
free fraction
A
0.1-10% of the molecules of a lipid soluble hormone are not bound to a transport protein
23
Q
Action of Lipid-Soluble Hormones
A
- A free lipid-soluble hormone molecule diffuses from the blood, through interstitial fluid, and through the lipid bilayer of the plasma membrane into a cell.
- If the cell is a target cell, the hormone binds to and activates receptors located within the cytosol or nucleus. The activated receptor–hormone complex then alters gene expression: It turns specific genes of the nuclear DNA on or off.
- As the DNA is transcribed, new messenger RNA (mRNA) forms, leaves the nucleus, and enters the cytosol. There, it directs synthesis of a new protein, often an enzyme, on the ribosomes.
- The new proteins alter the cell’s activity and cause the responses typical of that hormone.
24
Q
Action of Water Soluble Hormones
A
- A water-soluble hormone (the first messenger) diffuses from the blood through interstitial fluid and then binds to its receptor at the exterior surface of a target cell’s plasma membrane. The hormone–receptor complex activates a membrane protein called a G protein. The activated G protein in turn activates adenylate cyclase.
- Adenylate cyclase converts ATP into cyclic AMP (cAMP). Because the enzyme’s active site is on the inner surface of the plasma membrane, this reaction occurs in the cytosol of the cell.
- Cyclic AMP (the second messenger) activates one or more protein kinases, which may be free in the cytosol or bound to the plasma membrane. A protein kinase is an enzyme that phosphorylates (adds a phosphate group to) other cellular proteins (such as enzymes). The donor of the phosphate group is ATP, which is converted to ADP.
- Activated protein kinases phosphorylate one or more cellular proteins. Phosphorylation activates some of these proteins and inactivates others, rather like turning a switch on or off.
- Phosphorylated proteins in turn cause reactions that produce physiological responses. Different protein kinases exist within different target cells and within different organelles of the same target cell. Thus, one protein kinase might trigger glycogen synthesis, a second might cause the breakdown of triglyceride, a third may promote protein synthesis, and so forth. As noted in step 4 , phosphorylation by a protein kinase can also inhibit certain proteins. For example, some of the kinases unleashed when epinephrine binds to liver cells inactivate an enzyme needed for glycogen synthesis.
- After a brief period, an enzyme called phosphodiesterase inactivates cAMP. Thus, the cell’s re- sponse is turned off unless new hormone molecules continue to bind to their receptors in the plasma membrane
25
first messenger
when a water soluble hormone binds to its receptor at the outer surface of the plasma membrane, it acts as the first messenger
26
second messenger
the first messenger (the hormone) then causes the production of a second messenger inside the cell, where hormone specific stimulated responses take place
27
cyclic AMP (cAMP)
common second messenger
28
G protein
a membrane protein that activates edentate cyclase
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adenylate cyclase
converts ATP into cyclic AMP
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permissive effect
the actions of some hormones on target cells require a simultaneous or recent exposure to a second hormone (second hormone is said to have a permissive effect)
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synergistic effect
when the effect f two hormones acting together is greater or more extensive than the effect of each hormone acting alone, the two hormones are said to have a synergistic effect
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antagonistic effect
when one hormone opposes the actions of another hormone, the two hormones are said to have antagonistic effects
33
3 factors that affect responsiveness of a target cell to a hormone
1. the hormone's concentration in the blood
2. the abundance of target cell's hormone receptors
3. influences exerted by other hormones
34
control of hormone secretion (3 factors)
1. signals from the nervous system
2. chemical changes in the blood
3. other hormones
35
pituitary gland (hypophysis)
"master" endocrine gland since it secretes several hormones that control other endocrine glands
36
hypothalamus
master of the pituitary gland
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infundibulum
a stalk that attaches the hypothalamus to the pituitary gland
38
anterior pituitary or anterior lobe or adenohypophysis
composed of epitelial tissue; consists of 2 parts: the pars distalis (larger portion) and the pars tuberalis (forms a sheath around the infundibulum)
39
releasing hormones
stimulates release of anterior pituitary hormones
40
inhibiting hormones
suppresses release of anterior pituitary hormones; from the hypothalamus
41
hypophyseal portal system
blood flows from capillaries int he hypothalamus into portal veins that carry blood to capillaries of the anterior pituitary
42
neurosecretory cells
clusters of specialized neurons above the optic chiasm
43
human growth hormone (hGH) or somatotropin
stimulates several tissues to secrete insulinlike growth factors (hormones that stimulate general body growth and regulate aspects of the metabolism
44
thyroid-stimulating hormone (TSH) or thyrotropin
controls the secretions and other activities of the thyroid gland
45
follicle-stimulating hormone (FSH)
secreted by gonadotrophs; stimulate secretion of estrogens and progesterone and the maturation of oocytes in the ovaries and they stimulate sperm production and secretion of testosterone in the testes
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Luteinizing hormone (LH)
secreted by gonadotrophs; stimulate secretion of estrogens and progesterone and the maturation of oocytes in the ovaries and they stimulate sperm production and secretion of testosterone in the testes
47
Growth Hormone Releasing Hormone (GHRH)
promotes secretion of human growth hormone
48
Growth Hormone Inhibiting Hormone (GHIH)
suppresses secretion of human growth hormone
49
Thyrotropin Releasing Hormone (TRH)
from the hypothalamus; controls TSH secretion
50
gonadotropins
secreted by gonadotrophs; FSH and LH
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Gonadotropin Releasing Hormone (GnRH)
controls secretion of LH and FSH
52
Prolactin (PRL)
initiates and maintains milk production by the mammary glands; by itself only has a weak effect
53
Prolactin Inhibiting Hormone (PIH)
dopamine in females; inhibits the release of prolactin from the anterior pituitary most of the time
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Prolactin Releasing Hormone (PRH)
promotes release of prolactin
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adrenocorticotropic hormone (ACTH) or corticotropin
controls production and secretion of cortisol and other glucocorticoids by the cortex of the adrenal glands
56
Corticotropin Releasing Hormone (CRH)
stimulates secretion of ACTH by corticotrophs
57
Melanocyte Stimulating Hormone (MSH)
increases skin pigmentation in amphibians by stimulating the dispersion of melanin granules in melanocytes; Exact role in humans is unknown but may influence brain activity; when present in excess, can cause darkening of skin.
58
posterior pituitary or neurohypophysis
does not synthesize hormones; it does store and release 2 hormones
59
pituicytes
specialized neuroglia that are associated with the axon terminals in the posterior pituitary
60
hypothalamohypophyseal tract
this tract begins in the hypothalamus and ends near blood capillaries in the posterior pituitary
61
oxytocin (OT)
two target tissues: mother's uterus and breasts; stretching of cervix of uterus stimulates the release of OT which enhances contraction of smooth muscle cells in the wall of the uterus; after delivery: stimulates mammary glands to release milk in response to the sucking by an infant
62
Antidiuretic (ADH)
substance that decreases urine production; causes kidneys to return more water to the blood, decreasing urine volume
63
thyroid gland
butterfly shaped
64
lateral lobes
2 sides of the thyroid gland (either side of the trachea)
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isthmus
narrow passage anterior to the trachea that connects the lateral lobes
66
thyroid follicles
microscopic spherical sacs that make up most of the thyroid gland
67
follicular cells
secrete thyroid hormones;
68
thyroxine or tetraiodothyronine or T4 and Triiodothyronine T3
secretion is increased by TRH which stimulates TSH; high iodine levels suppresses T4; Increase basal metabolic rate; stimulate synthesis of proteins; increase use of glucose and fatty acids for ATP production; increase lipolysis; enhance cholesterol excretion; accelerate body growth; contribute to development of nervous system
69
parafollicular cells or C cells
produce calcitonin (CT)
70
Calcitonin
decrease the calcium level in the blood by inhibiting the action of osteoclasts (the cells that break down bone EM); controlled by negative feedback system
71
thyroglobulin (TGB)
T3 and T4 combine with transport proteins in the blood (mainly TGB)
72
Basal Metabolic Rate (BMR)
increased by thyroid hormone; the rate of oxygen consumption under standard (basal) conditions by stimulating the use of cellular oxygen to produce ATP
73
calorigenic effect
As cells produce and use more ATP, more heat is given off and body temperature rises
74
Control of Thyroid Hormone Secretion
1. Low blood levels of T3 and T4 or low metabolic rate stimulates the hypothalamus to secrete TRH.
2. TRH enters the hypophyseal portal veins and flows to the ante- rior pituitary, where it stimulates thyrotrophs to secrete TSH.
3. TSH stimulates virtually all aspects of thyroid follicular cell activity, including iodide trapping (1 in Figure 18.11), hormone synthesis and secretion (2 and 7 in Figure 18.11), and growth of the follicular cells.
4. The thyroid follicular cells release T3 and T4 into the blood until the metabolic rate returns to normal.
5. An elevated level of T3 inhibits release of TRH and TSH (negative feedback inhibition).
75
parathyroid glands
round masses of tissue partially embedded in the posterior surface of the lateral lobes of the thyroid gland
76
chief (principal) cells
most numerous cells in the parathyroid hormones; produce PTH
77
parathyroid hormone (PTH) or parathormone
major regulator of levels of calcium, magnesium and phosphate; increase the number and activity of osteoclasts; result: elevated bone resorption which releases ionic calcium and phosphates
78
calcitrol
stimulates increased absorption of Ca2+ from foods in the GI tract which helps increase the blood level of Ca2+
79
adrenal glands or suprarenal glands
superior to each kidney
80
adrenal cortex (3 zones)
zona glomerulosa, zona fasciculata and zona reticularis
81
mineralocorticoids
hormone that affects bone homeostasis; secreted by the zone glomerulosa
82
aldosterone
major mineralcorticoid; regulates homeostasis of 2 mineral ions (sodium and potassium ions); helps adjust blood pressure and volume; promotes excretion of H+ in urine and removal of acids from the body
83
renin-angiotensin-aldosterone (RAA) pathway
controls secretion of aldosterone
84
renin
enzyme that is secreted by certain cells of the kidneys when stimulated by lowered BP
85
angiotensinogen
plasma protein produced by the liver; renin converts angiotensinogen into angiotensin I
86
glucocorticoids
regulate metabolism and resistance to stress: includes cortisol, corticosterone and cortisone; control of glucocorticoid secretion involves corticotropin releasing hormone (CRH)
87
androgens
secreted by adrenal cortex; includes DHEA, testosterone and estrogen
88
adrenal medulla
the inner region of the adrenal gland; modified sympathetic ganglion of the autonomic nervous system
89
chrommaffin cells
hormone producing cells int he adrenal medulla
90
epinephrine and norepinephrine (NE)
synthesized by adrenal medulla; adrenaline and noradrenaline; fight or flight response
91
pancreas
both an endocrine and exocrine gland
92
acini
clusters of exocrine cells of the pancreas
93
pancreatic islets or islets of Langerhans
clusters of endocrine tissue; 4 types: A cells, B cells, D cells and F cells
94
alpha or A cells
17% of pancreatic islet cells and secrete glucagon
95
Beta or B cells
constitue 70% of pancreatic islet cells; secrete insulin
96
Delta or D cells
constitute about 7% of pancreatic islet cells; secrete somatostatin
97
F cells
remainder of pancreatic islet cells; secrete pancreatic polypeptide
98
regulation of insulin and glucagon secretion
The principal action of glucagon is to increase blood glucose level when it falls below normal. Insulin, on the other hand, helps lower blood glucose level when it is too high. The level of blood glucose controls secretion of glucagon and insulin via negative feedback
99
ovaries
paired oval bodies located int he female pelvic cavity; produce steroid hormones: estrogens and progesterone
100
estrogen and progesterone
Together with gonadotropic hormones of anterior pituitary, regulate female reproductive cycle and oogenesis, maintain pregnancy, prepare mammary glands for lactation, and promote development and maintenance of female secondary sex characteristics
101
inhibin
Inhibits secretion of FSH from anterior pituitary.
102
relaxin
Increases flexibility of pubic symphysis during pregnancy; helps dilate uterine cervix during labor and delivery.
103
testosterone
Stimulates descent of testes before birth; regulates spermatogenesis; promotes development and maintenance of male secondary sex characteristics
104
inhibin
Inhibits secretion of FSH from anterior pituitary.
105
pineal gland
small endocrine gland attached to the roof of the third ventricle of the brain at the midline; consists of neuroglia and secretory cells called pinealocytes
106
pinealocytes
secretory cells of the pineal gland; secretes melatonin
107
thymus
located behind the sternum between the lungs
108
thymosin, thymic humoral factor, thymic factor and thymopoietin
hormones produced by the thymus; promote maturation of T cells (a type of white blood cell that destroys microbes and foreign substances) and may retard the aging process
109
eicosanoids
2 families: prostaglandins (PG) and leukotrienes (LT); found in virtually all body cells except RBC, where they act as local hormones
110
growth factors
play important roles in tissue development, growth and repair
111
stress and the general adaptation syndrome
sequence of bodily changes resulting from a variety of stressful situations
112
resistance reaction
second stage of stress response
113
exhaustion
Prolonged exposure to high levels of cortisol and other hormones involved in the resistance reaction causes wasting of muscle, suppression of the immune system, ulceration of the gas- trointestinal tract, and failure of pancreatic beta cells.
114
stress and disease
Although the exact role of stress in human diseases is not known, it is clear that stress can lead to particular diseases by temporarily inhibiting certain components of the immune system. Stress related disorders include gastritis, ulcerative colitis, irritable bowel syndrome, hypertension, asthma, rheumatoid arthritis (RA), migraine headaches, anxiety, and depression. People under stress are at a greater risk of developing chronic disease or dying prematurely.
115
pituitary dwarfism
hypo secretion of hGH during growth years slows bone growth and the epiphyseal plate close before normal height is reached
116
giantism
hyper secretion of hGH during childhood; an abnormal increase in the length of long bones
117
acromegaly
hyper secretion of hGH during adulthood; Although hGH cannot produce further lengthening of the long bones because the epiphyseal plates are already closed, the bones of the hands, feet, cheeks, and jaws thicken and other tissues enlarge. In addition, the eyelids, lips, tongue, and nose enlarge, and the skin thickens and develops furrows, especially on the forehead and soles
118
diabetes insipidus
disfunction of posterior pituitary; due to defects in ADH receptors or an inability to secrete ADH
119
congenital hypothyroidism
hypo secretion of the thyroid hormones that is present at birth; causes severe mental retardation and stunted bone growth
120
myxedema
hypothyroidism during the adult years; symptom: is edema (accumulation of interstitial fluid) that makes the facial tissues swell and look puffy
121
graves disease
most common hyperthyroidism; occurs more in females than males; autoimmune disorder in which the person produces antibodies that mimic the action of TSH, so the antibodies continually stimulate the thyroid; symptom: enlarged thyroid
122
goiter
an enlarged thyroid; associated with hyperothyrodism, hypothyroidism and eurothyroidism (normal secretion of thyroid hormone)
123
cushing's syndrome
hyper secretion of cortisol by the adrenal cortex; can be caused a tutor; causes breakdown of muscle proteins and redistribution of body fat resulting in spindly arms and legs, a round face and a hump on the back
124
Addison's disease
cause: hypo secretion of glucocorticoid and aldosterone
symptoms: mental lethargy, anorexia, nausea and vomiting, weight loss
125
diabetes mellitus
most common endocrine disorder
cause: an inability to produce or use insulin
symptom: excessive urine production, excessive thirst and excessive eating
126
hypoglycemia
decreased blood glucose level because the excess insulin stimulates too much uptake of glucose by body cells (symptom of hyperinsulism- too much insulin injected)
127
hyperglycemia
increased blood glucose levels
