0-1 Chapter 17 - Endocrine System Flashcards
1
Q
four principal mechanisms of communication between cells
A
gap junctions
neurotransmitters
paracrine (local) hormones
Hormones
2
Q
gap junctions
A
pores in cell membrane allow signaling molecules, nutrients, and electrolytes to move from cell to cell
3
Q
neurotransmitters
A
released from neurons to travel across synaptic cleft to second cell
4
Q
paracrine (local) hormones
A
secreted into tissue fluids to affect nearby cells
5
Q
hormones
A
chemical messengers that travel in the bloodstream to other tissues and organs
6
Q
endocrine system
A
glands, tissues, and cells that secrete hormones
7
Q
endocrinology
A
the study of this system and the diagnosis and treatment of its disorders
8
Q
endocrine glands
A
organs that are traditional sources of hormones
9
Q
hormones
A
chemical messengers that are transported by the bloodstream and stimulate physiological responses in cells of another tissue or organ, often a considerable distance away
10
Q
major organs of endocrine system
A
pineal gland hypothalamus pituitary gland thyroid gland thymus adrenal gland pancreas parathyroid gland gonads
11
Q
exocrine glands
A
–have ducts carry secretion to an epithelial surface or the mucosa of the digestive tract –‘external secretions’
–extracellular effects (food digestion)
12
Q
endocrine glands
A
–no ducts
–contain dense, fenestrated capillary networks which allows easy uptake of hormones into bloodstream
–‘internal secretions’
–intracellular effects such as altering target cell metabolism
13
Q
liver cells defy rigid classification
A
releases hormones, releases bile into ducts, releases albumin and blood-clotting factors into blood (not hormones)
14
Q
Comparison of Nervous and Endocrine Systems (Differences)
both serve for internal communication
A
–nervous -both electrical and chemical
–endocrine -only chemical
15
Q
Comparison of Nervous and Endocrine Systems (Differences)
speed and persistence of response
A
–nervous -reacts quickly (1 -10 msec), stops quickly
–endocrine -reacts slowly (hormone release in seconds or days), effect may continue for weeks
16
Q
Comparison of Nervous and Endocrine Systems (Differences)
adaptation to long-term stimuli
A
–nervous -response declines (adapts quickly)
–endocrine -response persists (adapts slowly)
17
Q
Comparison of Nervous and Endocrine Systems (Differences)
area of effect
A
–nervous -targeted and specific (one organ)
–endocrine -general, widespread effects (many organs)
18
Q
Nervous and Endocrine Systems (Similarities)
several chemicals function as both hormones and neurotransmitters
A
–norepinephrine, cholecystokinin, thyrotropin-releasing hormone, dopamine and antidiuretic hormone
19
Q
Nervous and Endocrine Systems (Similarities)
some hormones secreted by neuroendocrine cells
A
(neurons) that release their secretion into the bloodstream
–oxytocin and catecholamines
20
Q
Nervous and Endocrine Systems (Similarities)
both systems with overlapping effects on same target cells
A
–norepinephrine and glucagon cause glycogen hydrolysis in liver
21
Q
Nervous and Endocrine Systems (Similarities)
systems regulate each other
A
–neurons trigger hormone secretion
–hormones stimulate or inhibit neurons
22
Q
target organs or cells
A
those organs or cells that have receptorsfor a hormone and can respond to it.
23
Q
Anatomy of Hypothalamus
A
- shaped like a flattened funnel
- forms floor and walls of third ventricle of the brain
- regulates primitive functions of the body from water balance and thermoregulation to sex drive and childbirth
- many of its functions carried out by pituitary gland
24
Q
Pituitary Gland
A
(Hypophysis)
•suspended from hypothalamus by a stalk –infundibulum
•location and size
–housed in sella turcica of sphenoid bone
–size and shape of kidney bean
25
infundibulum
suspends pituitary gland from hypothalamus
26
Pituitary Gland composed of two structures
composed of two structures with independent origins and separate functions
–adenohypophysis (anterior pituitary)
–neurohypophysis(posterior pituitary)
27
adenohypophysis
(anterior pituitary)
constitutes anterior three-quarters of pituitary
–has two segments:
•anterior lobe (pars distalis)
•pars tuberalissmall mass of cells adhering to stalk
–linked to hypothalamus by hypophyseal portal system
28
hypophysealportal system
* hypothalamic releasing and inhibiting hormones travel in hypophyseal portal system from hypothalamus to anterior pituitary
* hormones secreted by anterior pituitary
29
neurohypophysis
constitutes the posterior one-quarter of the pituitary
–has 3 parts:
•median eminence, infundibulum, and the posterior lobe (pars nervosa)
30
neurohypophysis is
nerve tissue, not a true gland
•nerve cell bodies in hypothalamus pass down the stalk as hypothalamo-hypophysealtract and end in posterior lobe
•hypothalamic neurons secrete hormones that are stored in neurohypophysis until released into blood
31
eight hormones produced in hypothalamus
–six regulate the anterior pituitary
–two are released into capillaries in the posterior pituitary when hypothalamic neurons are stimulated (oxytocin and antidiuretic hormone)
32
six releasing and inhibiting hormones stimulate or inhibit the anterior pituitary
–TRH, CRH, GnRH, and GHRH are releasing hormones that affect anterior pituitary secretion of TSH, PRL, ACTH, FSH, LH, and GH
–PIH inhibits secretion of prolactin, and somatostatin inhibits secretion growth hormone & thyroid stimulating hormone by the anterior pituitary
33
Hypothalamic Hormones
two other hypothalamic hormones are
oxytocin (OT)and antidiuretic hormone (ADH)
–both stored and released by posterior pituitary
–right and left paraventricular nuclei produce oxytocin(OT)
–supraoptic nuclei produce antidiuretic hormone (ADH)
–posterior pituitary does not synthesize them
34
anterior lobe of the pituitary synthesizes and secretes six principal hormones
```
•two gonadotropin hormones that target gonads
–FSH (follicle stimulating hormone)
–LH (luteinizing hormone)
•TSH (thyroid stimulating hormone)
•ACTH (adrenocorticotropic hormone)
•PRL (prolactin)
•GH (growth hormone)
```
35
FSH
FSH (follicle stimulating hormone)
| •stimulates secretion of ovarian sex hormones, development of ovarian follicles, and sperm production
36
LH
(luteinizing hormone)
| •stimulates ovulation, stimulates corpus luteum to secrete progesterone, stimulates testes to secrete testosterone
37
TSH
(thyroid stimulating hormone)
| –stimulates secretion of thyroid hormone
38
ACTH
(adrenocorticotropic hormone)
| –stimulates adrenal cortex to secrete glucocorticoids
39
PRL
(prolactin)
| –after birth stimulates mammary glands to synthesize milk, enhances secretion of testosterone by testes
40
GH
(growth hormone)
| –stimulates mitosis and cellular differentiation
41
Posterior Pituitary Hormones
produced in hypothalamus
–transported by hypothalamo-hypophyseal tract to posterior lobe
–releases hormones when hypothalamic neurons are stimulated
•ADH(antidiuretic hormone)
•OT(oxytocin)
42
ADH
(antidiuretic hormone)
–increases water retention thus reducing urine volume and prevents dehydration
–also called vasopressin because it can cause vasoconstriction
43
OT
(oxytocin)
–surge of hormone released during sexual arousal and orgasm
•stimulate uterine contractions and propulsion of semen
–promotes feelings of sexual satisfaction and emotional bonding between partners
–stimulates labor contractions during childbirth
–stimulates flow of milk during lactation
–promotes emotional bonding between lactating mother and infant
44
Control of Pituitary Secretion
rates of secretion are not constant
| –regulated by hypothalamus, other brain centers, and feedback from target organs
45
anterior lobe control
releasing hormones and inhibiting hormones from hypothalamus
| •in cold weather, pituitary stimulated by hypothalamus to release TSH, leads to generation of body heat
46
posterior lobe control
neuroendocrine reflexes
47
neuroendocrine reflex
hormone release in response to nervous system signals
48
negative feedback
increased target organ hormone levels inhibits release of hormones
49
positive feedback
stretching of uterus increases OT release, causes contractions, causing more stretching of uterus, etc. until delivery
50
Growth Hormone
GH has widespread effects on the body tissues
–especially cartilage, bone, muscle, and fat
•induces liver to produce growth stimulants
51
insulin-like growth factors (IGF-I) or somatomedins(IGF-II)
* stimulate target cells in diverse tissues
* IGF-I prolongs the action of GH
* hormone half-life –the time required for 50% of the hormone to be cleared from the blood
52
insulin-like growth factors (IGF-I) or somatomedins(IGF-II)
causes
protein synthesis increases
lipid metabolism increased
carbohydrate metabolism
electrolyte balance
53
pineal gland
attached to roof of third ventricle beneath the posterior end of corpus callosum
•after age 7, it undergoes involution(shrinkage)
54
pineal gland
main function
may synchronize physiological function with 24-hour circadian rhythms of daylight and darkness
–synthesizes melatonin from serotonin during the night
55
seasonal affective disorder
(SAD) occurs in winter or northern climates
–symptoms -depression, sleepiness, irritability and carbohydrate craving
–2 to 3 hours of exposure to bright light each day reduces the melatonin levels and the symptoms (phototherapy)
56
Thymus
•thymus plays a role in three systems: endocrine, lymphatic, and immune
•bilobed gland in the mediastinum superior to the heart
–goes through involution after puberty
•site of maturation of T cells important in immune defense
57
Thymus secretes
secretes hormones (thymopoietin, thymosin, and thymulin) that stimulate development of other lymphatic organs and activity of T-lymphocytes
58
Thyroid Gland Anatomy
largest endocrine gland
–composed of two lobes and an isthmus below the larynx
–dark reddish brown color due to rich blood supply
59
thyroid follicles
sacs that compose most of thyroid
–contain protein rich colloid
–follicular cells –simple cuboidal epithelium that lines follicles
60
thyroid follicles secrete
```
secretes thyroxine (T4 because of 4 iodine atoms) and triiodothyronine (T3) –T4 which is converted to T3
–increases metabolic rate, O2consumption, heat production (calorigenic effect), appetite, growth hormone secretion, alertness and quicker reflexes
```
61
parafollicular (C or clear) cellssecrete
calcitonin with rising blood calcium
| –stimulates osteoblast activity and bone formation
62
thyroid follicles are filled with
colloid and lined with simple cuboidal epithelial cells (follicular cells).
63
Parathyroid Glands
usually four glands partially embedded in posterior surface of thyroid gland
–can be found from as high as hyoid bone to as low as aortic arch
64
Parathyroid Glands secrete
```
secrete parathyroid hormone (PTH)
–increases blood Ca2+ levels
•promotes synthesis of calcitriol
•increases absorption of Ca2+
•decreases urinary excretion
•increases bone resorption
```
65
Adrenal Gland
small gland that sits on top of each kidney
•they are retroperitoneal like the kidney
•adrenal cortex and medulla formed by merger of two fetal glands with different origins and functions
66
adrenal medulla
inner core, 10% to 20% of gland
| •has dual nature acting as an endocrine gland and sympathetic ganglion of sympathetic nervous system
67
adrenal medulla innervated by
innervated by sympathetic preganglionic fibers
68
when stimulated release
catecholamines(epinephrineand norepinephrine) and a trace of dopamine directly into the bloodstream
69
catecholamines
effect is longer lasting than neurotransmitters
–increases alertness and prepares body for physical activity –
•mobilize high energy fuels, lactate, fatty acids, and glucose
•glycogenolysisand gluconeogenesisboost glucose levels
•glucose-sparing effect because inhibits insulin secretion
–muscles use fatty acids saving glucose for brain
–increasesblood pressure, heart rate, blood flow to muscles, pulmonary air flow and metabolic rate
–decreasesdigestion and urine production
70
Adrenal Cortex
surrounds adrenal medulla and produces more than 25 steroid hormones called corticosteroidsor corticoids
71
Adrenal Cortex
three layers of glandular tissue
zona glomerulosa
zona fasciculate
zona reticularis
72
zona glomerulosa
(thin, outer layer)
•cells are arranged in rounded clusters
•secretes mineralocorticoid–regulate the body’s electrolyte balance
73
zona fasciculata
(thick, middle layer)
•cells arranged in fascicles separated by capillaries
•secretes glucocorticoids
74
zona reticularis
(narrow, inner layer)
•cells in branching network
•secretes sex steroids
75
mineralocorticoids
zona glomerulosa
–regulate electrolyte balance
–aldosterone stimulates Na+retention and K+excretion, water is retained with sodium by osmosis, so blood volume and blood pressure are maintained
76
glucocorticoids
–regulate metabolism of glucose and other fuels
–especially cortisol, stimulates fat and protein catabolism, gluconeogenesis(glucose from amino acids and fatty acids) and release of fatty acids and glucose into blood
–helps body adapt to stress and repair tissues
–anti-inflammatory effect becomes immune suppression with long-term use
77
sex steroids
zona reticularis
–androgens –sets libido throughout life; large role in prenatal male development (includes DHEA which other tissues convert to testosterone)
–estradiol–small quantity, but important after menopause for sustaining adult bone mass; fat converts androgens into estrogen
78
Adrenal Gland Interactions
medulla and cortex of adrenal gland are not functionally independent
•medulla atrophies without the stimulation of cortisol
•some chromaffin cells of medullary origin extend into the cortex
–they stimulate the cortex to secrete corticosteroids when stress activates the sympathetic nervous system
79
Pancreas
exocrine digestive gland and endocrine cell clusters (pancreatic islets) found retroperitoneal, inferior and posterior to stomach
80
pancreatic islets
1-2 million pancreatic islets (Islets of Langerhans) produce hormones
–other 98% of pancreas cells produces digestive enzymes
81
insulin secreted by
B or beta () cells
–secreted during and after meal when glucose and amino acid blood levels are rising
–stimulates cells to absorb these nutrients and store or metabolize them lowering blood glucose levels
82
diabetes mellitus
insufficiency or inaction is cause of diabetes mellitus
83
Pancreatic Hormones
glucagon
somatostatin
pancreatic polypeptide
gastrin
84
glucagon
secreted by A or alpha () cells
–released between meals when blood glucose concentration is falling
–in liver, stimulates gluconeogenesis, glycogenolysis, and the release of glucose into the circulation raising blood glucose level
–in adipose tissue, stimulates fat catabolism and release of free fatty acids
–glucagon also released to rising amino acid levels in blood, promotes amino acid absorption, and provides cells with raw material for gluconeogenesis
85
somatostatin
secreted by D or delta () cells
–partially suppresses secretion of glucagon and insulin
–inhibits nutrient digestion and absorption
86
pancreatic polypeptide
secreted by PP cells or F cells)
| –inhibits gallbladder contraction and secretion pancreatic digestive enzymes
87
gastrin
secreted by G cells
| –stimulates stomach acid secretion, motility and emptying
88
hyperglycemic hormones
raise blood glucose concentration
| –glucagon, growth hormone, epinephrine, norepinephrine, cortisol, and corticosterone
89
hypoglycemic hormones
blood glucose
| –insulin
90
The Gonads
ovaries and testes are both endocrine and exocrine
91
exocrine product
whole cells -eggs and sperm (cytogenic glands)
92
endocrine product
gonadal hormones –mostly steroids
93
ovarian hormones
–estradiol, progesterone, and inhibin
94
testicular hormones
testosterone, weaker androgens, estrogen and inhibin
95
functions of estradiol and progesterone
–development of female reproductive system and physique including adolescent bone growth
–regulate menstrual cycle, sustain pregnancy
–prepare mammary glands for lactation
96
inhibin suppresses
inhibin suppresses FSH secretion from anterior pituitary
97
testicular hormones
testosterone and other steroids from interstitial cells (cells of Leydig) nestled between the tubules
–inhibinfrom
98
testosterone
testosterone and other steroids from interstitial cells (cells of Leydig) nestled between the tubules
•stimulates development of male reproductive system in fetus and adolescent, and sex drive
•sustains sperm production
99
inhibin
inhibin from sustentacular (Sertoli) cells
| •limits FSH secretion in order to regulate sperm production
100
skin
keratinocytes convert a cholesterol-like steroid into cholecalciferol using UV from sun –Vitamin D is a steroid hormone
101
liver
involved in the production of at least five hormones
–converts cholecalciferol into calcidiol
–secretes angiotensinogen(a prohormone)
•precursor of angiotensin II (a regulator of blood pressure)
–secretes 15% oferythropoietin (stimulates bone marrow)
–hepcidin –promotes intestinal absorption of iron
–source of IGF-I that controls action of growth hormone
102
kidneys
plays role in production of three hormones
–converts calcidiol to calcitriol, the active form of vitamin D
•increases Ca2+ absorption by intestine and inhibits loss in the urine
–secrete renin that converts angiotensinogen to angiotensin I
•angiotensin II created by converting enzyme in lungs
–constricts blood vessels and raises blood pressure
–produces 85% of erythropoietin–
•stimulates bone marrow to produce RBCs
103
heart
–cardiac muscle secretes atrial and brain natriuretic peptides (ANP and BNP) in response to an increase in blood pressure
104
stomach and small intestine
secrete at least ten enteric hormones secreted by enteroendocrine cells
105
adipose tissue
secretes leptin
| –slows appetite
106
osseous tissue
osteocalcinsecreted by osteoblasts
–increases number of pancreatic beta cells, pancreatic output of insulin, and insulin sensitivity of other body tissues
–inhibits weight gain and onset of type II diabetes mellitus
107
placenta
secretes estrogen, progesterone and others
108
Hormone Chemistry
```
three chemical classes
–steroids
-peptides and glycoproteins
–monoamines (biogenic amines)
•all hormones are made from either cholesterol or amino acids with carbohydrate added to make glycoproteins
```
109
steroids
* derived from cholesterol
* secreted by gonads and adrenal glands
* estrogens, progesterone, testosterone, cortisol, corticosterone, aldosterone, DHEA, and calcitriol (vitamin D)
110
peptides and glycoproteins
* created from chains of amino acids
* secreted by pituitary and hypothalamus
* oxytocin, antidiuretic hormone, releasing and inhibiting hormones, and anterior pituitary hormones
111
–monoamines (biogenic amines)
* derived from amino acids
* secreted by adrenal, pineal, and thyroid glands
* epinephrine, norepinephrine, melatonin, and thyroid hormone
112
Hormone Synthesis: Steroid Hormones
synthesized from cholesterol –differs in functional groups attached to 4-ringed steroid backbone
113
Peptides
* synthesized in same way as any protein
* at first is an inactive preprohormone
* first several amino acids is a signal peptide that guides it into cisterna of rough endoplasmic reticulum
* signal peptide removed to form prohormone
* Golgi does final transformation to hormonepackaged for secretion
114
Hormone Synthesis: Insulin
begins as preproinsulin, then becomes proinsulin
| •when connecting peptideis removed, two polypeptide chains are formed that make up insulin
115
Monoamines
melatonin is synthesized from amino acid tryptophan, and other monoamines from amino acid tyrosine
–thyroid hormone is composed of 2 tyrosines
116
T3 and T4 Synthesis
follicular cells
| TSH
117
follicular cells
–absorb iodide(I-)ions from blood and store in lumen as a reactive form of iodine
–synthesize thyroglobulin and store in lumen
•forms colloid
•contains lots of tyrosine
–tyrosine and iodine combine to form thyroxine (T4) bound to thyroglobulin
–stored in follicle
118
TSH
–stimulates follicular cells to remove T4from thyroglobulin for release into plasma
–most T3is produced in liver or by target cells removing an iodine from circulating T4
–95% T4and 5% T3
119
Chemistry of Thyroid Hormone
MIT contains one iodine atom, DIT has twoT3-combination of MIT plus DITT4 -combination of two DITs
120
Hormone Transport
monoamines and peptides
most monoamines and peptides are hydrophilic
| –mix easily with blood plasma
121
Hormone Transport
steroids and thyroid hormone
steroids and thyroid hormone are hydrophobic
–bind to transport proteins (albumins and globulins synthesized by the liver)
–bound hormones have longer half-life
•protected from liver enzymes and kidney filtration
–only unbound hormone leaves capillaries to reach target cell
122
Hormone Transport
thyroid hormone
thyroid hormone binds to three transport proteins in the plasma
–albumin, thyretin and TBG (thyroxine-binding globulin)
–more than 99% of circulating TH is protein bound
123
Hormone Transport
steroid hormones
bind to globulins
| –transcortin –the transport protein for cortisol
124
Hormone Transport
aldosterone
short half-life; 85% unbound, 15% binds weakly to albumin and others
125
Hormone Receptors
hormones stimulate only those cells that have receptors for them
126
Hormone Receptors
receptors are protein or glycoprotein molecules:
–on plasma membrane, in the cytoplasm, or in the nucleus
•receptors act like switches turning on metabolic pathways when hormone binds to them
•usually each target cell has a few thousand receptors for a given hormone
127
receptor-hormone interactions exhibit
specificity and saturation
128
specificity
specific receptor for each hormone
129
saturation
saturated when all receptor molecules are occupied by hormone molecules
130
Hormone Mode of Action
hydrophobic hormones
–penetrate plasma membrane and enter nucleus
–act directly on the genes changing target cell physiology
–estrogen, progesterone, thyroid hormone act on nuclear receptors
–take several hours to days to show effect due to lag for protein synthesis
131
Hormone Mode of Action
hydrophilic hormones
–cannot penetrate into target cell
| –must stimulate physiology indirectly
132
Thyroid Hormone
thyroid hormone enters target cell by diffusion –mostly as T4with little metabolic effect
•within target cell, T4is converted to more potent T3
•T3enters target cells and binds to receptors in chromatin
•activates genes
133
Peptides and Catecholamines: Hydrophilic
```
hormone binds to cell-surface receptor
•receptor linked to second messenger system on other side of the membrane
•activates G protein which
•activates adenylate cyclase
•produces cAMP
•activates or inhibits enzymes
•metabolic reactions:
–synthesis
–secretion
–change membrane potentials
```
134
Other Second Messengers
* diacylglycerol (diglyceride) second-messenger system
* inositol triphosphate second-messenger system
* act on cell metabolism in a variety of ways
135
Enzyme Amplification
* hormones are extraordinarily potent chemicals
* one hormone molecule can trigger the synthesis of many enzyme molecules.
* very small stimulus can produce very large effect
* circulating concentrations very low
136
Modulation of Target Cell Sensitivity
target cell sensitivity adjusted by changing the number of receptors
137
up-regulation
regulation means number of receptors is increased
| –sensitivity is increased
138
down-regulation
```
regulation reduces number of receptors
–cell less sensitive to hormone
–happens with long-term exposure to high hormone concentrations
•bind to other receptors
•converted to different hormone
```
139
Hormone Interactions
most cells sensitive to more than one hormone and exhibit interactive effects
140
synergistic effects
–multiple hormones act together for greater effect
| •synergism between FSH and testosterone on sperm production
141
permissive effects
–one hormone enhances the target organ’s response to a second later hormone
•estrogen prepares uterus for action of progesterone
142
antagonistic effects
–one hormone opposes the action of another
| •insulin lowers blood glucose and glucagon raises it
143
Hormone Clearance
•hormone signals must be turned off when they have served their purpose
•most hormones are taken up and degraded by liver and kidney
–excreted in bile or urine
144
metabolic clearance rate
(MCR)
–rate of hormone removal from the blood
–half-life-time required to clear 50% of hormone from the blood
–faster the MCF, the shorter is the half-life
145
stress
caused by any situation that upsets homeostasis and threatens one’s physical or emotional well-being
•injury, surgery, infection, intense exercise, pain, grief, depression, anger, etc
146
general adaptation syndrome
(GAS)
–the consistent way body reacts to stress –typically involves elevated levels of epinephrine and glucocorticoids (especially cortisol)
147
general adaptation syndrome
occurs in three stages:
1. alarm reaction
2. stage of resistance
3. stage of exhaustion
148
Alarm Reaction
•initial response
•mediated by norepinephrine from the sympathetic nervous system and epinephrine from the adrenal medulla
–prepare body to fight or flight
–stored glycogen is consumed
–increase in aldosterone and angiotensin levels
•angiotensin helps raise blood pressure
•aldosterone promotes sodium and water conservation
149
Stage of Resistance
after a few hours, glycogen reserves gone, but brain still needs glucose
•provide alternate fuels for metabolism
•stage dominated by cortisol
•hypothalamus secretes corticotropin-releasing hormone
•pituitary secretes an increase in ACTH
150
pituitary secretes an increase in ACTH
–stimulates the adrenal cortex to secrete cortisol and other glucocorticoids
–promotes the breakdown of fat and protein into glycerol, fatty acids, and amino acids –for gluconeogenesis
151
glucose-sparing effect
cortisol has glucose-sparing effect –inhibits protein synthesis leaving free amino acids for gluconeogenesis
–adverse effects of excessive cortisol
–depresses immune function
–Increases susceptibility to infection and ulcers
–lymphoid tissues atrophy, antibody levels drop, and wounds heal poorly
152
Stage of Exhaustion
•when stress continues several months, and fat reserves are gone, homeostasis is overwhelmed
–marked by rapid decline and death
•protein breakdown and muscle wasting
•loss of glucose homeostasis because adrenal cortex stops producing glucocorticoids
•aldosterone promotes water retention and hypertension
–conserves sodium and hastens elimination of K+and H+
–hypokalemia and alkalosis leads to death
•death results from heart and kidney failure or overwhelming infection
153
paracrines
chemical messengers that diffuse short distances and stimulate nearby cells
–unlike neurotransmitters not produced in neurons
–unlike hormones not transported in blood
154
•a single chemical can act as
a hormone, paracrine, or even neurotransmitter in different locations
155
–histamine
* from mast cells in connective tissue
| * causes relaxation of blood vessel smooth muscle
156
nitric oxide
•from endothelium of blood vessels, causes vasodilation
157
somatostatin
•from gamma cells, inhibits secretion of alpha and beta cells
158
catecholamines
•diffuse from adrenal medulla to cortex
159
Eicosanoids
important family of paracrines
| –derived from fatty acid called arachidonic acid
160
lipoxygenase
converts arachidonic acid into leukotrienes
161
leukotrienes
mediates allergic and inflammatory reactions
162
cyclooxygenase
converts arachidonic acid to three other types of eicosanoids
163
prostacyclin
•inhibits blood clotting and vasoconstriction
164
thromboxanes
* produced by blood platelets after injury
* overrides prostacyclin
* stimulates vasoconstriction and clotting
165
prostaglandinsincludes
* PGE: relaxes smooth muscle in bladder, intestines, bronchioles, uterus and stimulates contraction of blood vessels
* PGF: opposite effects
166
Anti-inflammatory Drugs
* cortisol and corticosterone
| * aspirin, ibuprofen, & celecoxib (Celebrex)
167
•cortisol and corticosterone
–steroidal anti-inflammatory drugs (SAIDs)
–inhibit inflammation by blocking release of arachidonic acid from plasma membrane and inhibit synthesis of eicosanoids
•disadvantage –produce symptoms of Cushing syndrome
168
aspirin, ibuprofen, & celecoxib (Celebrex)
–nonsteroidal anti-inflammatory drugs (NSAIDs)
•COX inhibitors since block cyclooxygenase (COX)
•do not affect lipoxygenase function or leukotriene production
•useful in treatment of fever and thrombosis
–inhibit prostaglandin and thromboxane synthesis
169
Endocrine Disorders
variations in hormone concentration and target cell sensitivity have noticeable effects on body
170
hyposecretion
inadequate hormone release
| –tumor or lesion destroys gland or interferes with its ability to receive signals from another gland
171
hypersecretion
excessive hormone release
| –tumors or autoimmune disorder
172
pheochromocytoma
tumor of adrenal medulla secretes excessive epinephrine and norepinephrine
173
toxic goiter
(graves disease) –autoantibodies mimic effect of TSH on the thyroid causing thyroid hypersecretion
174
Pituitary Disorders
hypersecretion of growth hormone (GH)
175
acromegaly
thickening of bones and soft tissues in adults
•especially hands, feet and face
–problems in childhood or adolescence
176
gigantism
gigantism if hypersecretion
177
dwarfism
pituitary dwarfism if hyposecretion –rare since growth hormone is now made by genetically engineered bacteria
178
Thyroid Gland Disorders
congenital hypothyroidism
myxedema
goiter
179
congenital hypothyroidism
(decreased TH)
–hyposecretion present a birth (formerly cretinism)
–treat with oral thyroid hormone
180
myxedema
(decreased TH)
–adult hypothyroidism
–treat with oral thyroid hormone
181
goiter
any pathological enlargement of the thyroid gland
182
endemic goiter
•dietary iodine deficiency, no TH, no feedback, increased TSH stimulates hypertrophy
183
toxic goiter
(Graves disease)
•autoantibodies mimic the effect of TSH on the thyroid causing hypersecretion
•overgrown thyroid produces functional TH
184
Parathyroid Disorders
hypoparathyroidism
185
hypoparathyroidism
* surgical excision during thyroid surgery
| * fatal tetany in 3 -4 days due to rapid decline in blood calcium level
186
hyperparathyroidism
excess PTH secretion
•parathyroid tumor
•bones become soft, fragile, and deformed
•Ca2+ and phosphate blood levels increase
•promotes renal calculi formation
187
Adrenal Disorders
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Cushing syndrome
adrenogenital syndrome (AGS)
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Cushing syndrome
excess cortisol secretion
–hyperglycemia, hypertension, weakness, edema
–rapid muscle and bone loss due to protein catabolism
–abnormal fat deposition
•moon face and buffalo hump
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Diabetes Mellitus
most prevalent metabolic disease in world
| –disruption of metabolism due to hyposecretion or inaction of insulin
189
Diabetes Mellitus
symptoms
* polyuria(excess urine output), polydipsia(intense thirst) and polyphagia(hunger)
* revealed by elevated blood glucose, glucose in urine and ketones in the urine
190
polyuria
excess urine output
191
polydipsia
intense thirst
192
polyphagia
hunger
193
transport maximum
limit to how fast the glucose transporters can work to reabsorb
–excess glucose enters urine and water follows it
•causes polyuria, dehydration, and thirst
194
Types of Diabetes Mellitus
Type 1
| Type 2
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Type 1
(IDDM) –5 to 10% of cases in US
–insulin is always used to treat Type 1
•insulin injections, insulin pump, or dry insulin inhaler
•monitoring blood glucose levels and controlled diet
–hereditary susceptibility if infected with certain viruses (rubella, cytomegalovirus)
–autoantibodies attack and destroy pancreatic beta cells
196
Type 2
(NIDDM) –90 to 95% of diabetics
–problem is insulin resistance
•failure of target cells to respond to insulin
–risk factors are heredity, age (40+),obesity, and ethnicity –Native American, Hispanic, and Asian
–treated with weight loss program and exercise since:
•loss of muscle mass causes difficulty with regulation of glycemia
•adipose signals interfere with glucose uptake into most cells
–oral medications improve insulin secretion or target cell sensitivity
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pathogenesis
cells cannot absorb glucose, must rely on fat and proteins for energy needs -weight loss and weakness
–fat catabolism increases free fatty acids and ketones in blood
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ketonuria
ketonuria promotes osmotic diuresis, loss of Na+ and K+, irregular heartbeat, and neurological issues
199
ketoacidosis
ketoacidosis occurs as ketones decrease blood pH
| –deep, gasping breathing and diabetic coma are terminal result
200
chronic pathology (chronic hyperglycemia)
leads to neuropathy and cardiovascular damage from atherosclerosis and microvascular disease
•arterial damage in retina and kidneys (common in type I), atherosclerosis leads to heart failure (common in type II)
201
diabetic neuropathy
nerve damage from impoverished blood flow can lead to erectile dysfunction, incontinence, poor wound healing, and loss of sensation from area
