Chapter 18: Endocrine System Flashcards
1
Q
Which substance acts as a neurotransmitter and a hormone?
A
Norepinephrine. Released as a NT from sympathetic postganglionic neurons. Released as a hormone from chromatin cells of adrenal medullae.
2
Q
Exocrine glands.
A
Secrete their products into ducts that carry the secretions into body cavities, the lumen of an organ, or to the outer surface of the body. Sudoriferous (sweat), sebaceous (oil), mucous and digestive glands.
3
Q
Endocrine glands.
A
Secrete their products into the interstitial fluid surrounding the secretory cells and then into blood capillaries which carries the hormones to target cells throughout the body. Pituitary, thyroid, parathyroid, adrenal and pineal glands.
4
Q
Functions of hormones.
A
Regulate chemical composition, volume of internal environment, metabolism, energy balance, contraction of smooth and cardiac muscle fibres, glandular secretions, immune system, growth, development, reproductive system, circadian rhythms.
5
Q
A target cell has how many receptors for a specific hormone?
A
2000-100000.
6
Q
Down regulation.
A
If a hormone is present in excess, then the number of target cell receptors will decrease to make the cell less sensitive to the hormone.
7
Q
Up regulation.
A
If a hormone is deficient, then the number of target cell receptors will increase to make the cell more sensitive to the hormone.
8
Q
Circulating hormones.
A
Most endocrine hormones. Pass from secretory cells to interstitial fluid to blood. Linger in blood and have longer-lasting effects. Inactivated by liver and excreted by kidneys.
9
Q
What might happen in kidney or liver failure?
A
Build-up of hormones in the blood.
10
Q
Local hormones.
A
Act locally on neighbouring cells or on the same cell that secreted them without entering the blood. Paracrines and autocrines. Inactivated quickly.
11
Q
Lipid-soluble hormones.
A
Steroid hormones, thyroid hormones, nitric oxide.
12
Q
Water-soluble hormones.
A
Amine hormones, peptide and protein hormones, eicosanoid hormones.
13
Q
Steroid hormones.
A
Derived from cholesterol.
14
Q
Thyroid hormones.
A
Synthesized by attaching iodine to tyrosine.
15
Q
Nitric oxide.
A
A hormone and a NT. Synthesis is catalyzed by nitric oxide synthase.
16
Q
Amine hormones.
A
Synthesized by decarboxylating certain amino acids. Catecholamines are made by modifying tyrosine. Histamine is made by modifying histidine. Serotonin and melatonin are made by modifying tryptophan.
17
Q
Peptide and protein hormones.
A
Amino acid polymers. Small: 3-49 amino acids. Large: 50-200 amino acids.
18
Q
Eicosanoid hormones.
A
Derived from arachidonic acid. Prostaglandins. Leukotrienes.
19
Q
How do water-soluble hormones circulate in the blood?
A
Circulate freely in the watery blood plasma.
20
Q
How do lipid-soluble hormones circulate in the blood?
A
Transport proteins.
21
Q
Functions of transport proteins.
A
Transport lipid soluble hormones in blood. Retard passage of small hormones through the filtering mechanism in the kidneys to slow the rate of hormone loss in the urine. Provide a ready reserve of hormone in the bloodstream.
22
Q
What happens to the 0.1-10% of lipid-soluble hormones not bound to transport proteins?
A
The free fraction diffuse out of capillaries, bind to receptors and trigger responses.
23
Q
Where are the receptors for lipid-soluble hormones?
A
Inside the target cell.
24
Q
Where are the receptors for water-soluble hormones?
A
Plasma membrane of the target cell.
25
Describe the action of a lipid-soluble hormone.
Hormone diffuses from blood --> interstitial fluid --> lipid bilayer of PM --> target cell --> binds and activates receptors --> alters gene expression --> DNA transcribes --> mRNA forms --> mRNA leave nucleus --> mRNA enters cytosol --> direct synthesis of a new protein on the ribosomes --> new proteins alter cell activity.
26
Describe the action of a water-soluble hormone.
Hormones diffuses from blood --> interstitial fluid --> binds to integral transmembrane protein receptor on PM --> activates G-protein --> activates adenylyl cyclase --> converts ATP to cAMP in cytosol --> activates protein kinases to phosphorylate cellular proteins --> reactions --> physiological responses --> phosphodiesterase eventually inactivates cAMP --> response is turned off.
27
What does the responsiveness of a target cell to a hormone depend on?
The hormone concentration in the blood, the abundance of the target cell's hormone receptors, and influences exerted by other hormones.
28
The actions of some hormones on target cells require:
A simultaneous or recent exposure to a second hormone, which has a permissive effect. Sometimes the permissive hormone increases the number of receptors for the other hormone, and sometimes it promotes the synthesis of an enzyme required for the expression of the other hormone's effects.
29
Synergistic effect.
When the effect of two hormones acting together is greater than the sum of their individual effects. The hormones activate pathways that lead to the formation of the same types of second messengers to amplify the cellular response.
30
Antagonistic effect.
When one hormone opposes the actions of another by activating the opposite cellular responses, or decreasing the number of receptors for the other hormone.
31
Hormone secretion is regulated by signals from:
Nervous system, chemical changes in the blood, and other hormones. Most hormone regulatory systems work via negative feedback, but some work via positive feedback.
32
Hypothalamus.
Major link between nervous and endocrine systems. Hypothalamus cells synthesize at least 9 different hormones.
33
Pituitary gland.
Controlled by hypothalamus. Secretes 7 different hormones. Pea-shaped. Lies in hypophyseal fossa of sella turcica of sphenoid bone. Attaches to hypothalamus by infundibulum.
34
Pars intermedia.
Third region of the pituitary gland. Atrophies during human fetal development. Ceases to exist as a separate lobe in adults.
35
Anterior pituitary.
Adenohypophysis. Larger region of the pituitary gland. Composed of epithelial tissue. Pars distalis (larger part). Pars tuberalis (forms a sheath around the infundibulum).
36
What are the anterior pituitary cells, and what do they secrete?
Somatotrophs (growth hormone), thryotrophs (TSH), gonadotrophs (FSH and LH), lactotrophs (prolactin), corticotrophs (ACTH, MSH).
37
What is MSH?
Melanocyte-stimulating hormone. Increases skin pigmentation in amphibians by stimulating the dispersion of melanin granules in melanocytes. Its exact role in humans is unknown, but the presence of MSH receptors in the brain suggests it may influence brain activity. Continued administration of MSH for days produces skin darkening.
38
Hypothalamic hormones reach the anterior pituitary through:
A portal system. Blood will flow from a capillary network --> portal vein --> second capillary network --> return to heart.
39
The name of the portal system indicates:
The location of the second capillary network in the system.
40
Hypophyseal portal system.
Blood flows from capillaries in the hypothalamus --> portal veins --> capillaries of anterior pituitary.
41
Which arteries bring blood to the hypothalamus?
Superior hypophyseal arteries, which are branches of internal carotid arteries.
42
Primary plexus.
First capillary network in portal system.
43
Secondary plexus.
Second capillary network in portal system.
44
Control of anterior pituitary secretions.
Neurosecretory cells synthesize hypothalamic releasing and inhibiting hormones --> package into vesicles --> exocytosis when stimulated --> diffuse into blood of primary plexus of hypophyseal portal system --> hypophyseal portal veins --> secondary plexus --> diffuse out of blood --> anterior pituitary cells secrete hormones into secondary plexus --> hormones drain into hypophyseal veins --> general circulation --> target tissues.
45
Which anterior pituitary cells work via negative feedback?
Thyrotrophs, corticotrophs, gonadotrophs.
46
Growth hormone.
Most abundant anterior pituitary hormone. Regulates growth (indirectly) and metabolism (directly). Exerts its effects indirectly through insulin-like growth factors (IGFs), which are secreted by liver, skeletal muscle, cartilage and bone cells.
47
Describe the difference between IGFs synthesized by the liver, and IGFs synthesized by skeletal muscle, cartilage and bone.
Liver: enter blood as hormones that circulate to target cells. Other: act locally as autocrines or paracrines.
48
Three functions of IGFs.
Increase growth of bones and soft tissues, enhance lipolysis, and decrease glucose uptake.
49
How do IGFs increase growth of bones and soft tissues?
Bones: IGFs stimulate osteoblasts, promote cell division at epiphyseal plate, and enhance synthesis of the proteins needed to build bone matrix. Soft tissue: IGFs cause cells to grow by increasing uptake of amino acids into cells, accelerating protein synthesis, and decreasing the breakdown of proteins and the use of amino acids for ATP production.
50
How do IGFs influence CHO metabolism?
By decreasing glucose uptake, which decreases the use of glucose for ATP production by most body cells. This allows for the availability of glucose for ATP production in neurons when glucose levels are low. Liver cells are also stimulated to release glucose into the blood.
51
How is growth hormone released?
Somatotrophs release bursts of GH every few hours.
52
Describe the release of GH.
GHRH is secreted from hypothalamus --> enters hypophyseal portal system --> anterior pituitary --> somatotrophs secrete GH --> GH acts directly on cells to promote metabolic reactions --> elevated levels of GH and IGFs inhibit release of GHRH and GH --> GHIH is secreted from hypothalamus --> enters hypophyseal portal system --> anterior pituitary --> prevents somatotrophs from secreting GH.
53
Thyroid stimulating hormone.
Stimulates T3 and T4 synthesis and secretion. Is stimulated by thyroid releasing hormone from the hypothalamus.
54
Follicle stimulating hormone.
Females: FSH initiates development of ovarian follicles, and stimulates follicular cells to secrete estrogens. Males: FSH stimulates sperm production in testes. Is stimulated by gonadotropin releasing hormone from the hypothalamus.
55
What suppresses GnRH and FSH release?
Estrogens (females) and testosterone (males) through negative feedback.
56
Luteinizing hormone.
Females: LH triggers ovulation, formation of corpus luteum in ovary, and the secretion of progesterone by the corpus luteum. Males: LH stimulates testes cells to secrete testosterone. Is stimulated by gonadotropin releasing hormone from the hypothalamus.
57
How do FSH and LH work together?
Stimulate secretion of estrogens by ovarian cells. Estrogens and progesterone prepare uterus for implantation, and prepare the mammary glands for milk secretion.
58
Prolactin.
Initiates milk production by mammary glands after the glands have been primed by estrogens, progesterone, glucocorticoids, GH, T4, and insulin.
59
Which substance regulates the ejection of milk from the mammary glands?
Oxytocin.
60
Prolactin inhibitory hormone.
Dopamine. In females, PH inhibits the release of prolactin from the anterior pituitary. Each month before menstruation, the secretion of PIH decreases and the blood level of prolactin increases, but not enough to stimulate milk production. As menstruation begins, PIH is again secreted and prolactin decreases.
61
Does prolactin increase or decrease during pregnancy?
Increase. Stimulated by PRH from hypothalamus.
62
Sucking action of an infant causes:
A reduction in hypothalamic secretion of PIH.
63
Hypersecretion of prolactin causes:
Females: galactorrhea and amenorrhea. Males: erectile dysfunction.
64
ACTH.
Controls the production and secretion of cortisol and other glucocorticoids by adrenal gland cortex.
65
What causes the release of ACTH?
Corticotropin releasing hormone from hypothalamus. Stress-related stimuli.
66
What stimulates and inhibits MSH?
Stimulates: excessive levels of CRH. Inhibits: dopamine.
67
Posterior pituitary.
Neurohypophysis. Composed of neural tissue. Pars nervosa (large bulbar part). Infundibulum (stalk). Does not synthesize hormones; it stores and releases hormones. Consists of axons and axon terminals of more than 10000 hypothalamic neurosecretory cells, which form the hypothalamic-hypophyseal tract.
68
Describe the release of oxytocin and vasopressin.
Neuronal cell bodies of paraventricular and supraoptic nuclei synthesize oxytocin and ADH --> packaged into vesicles --> move by fast axonal transport along hypothalamic-hypophyseal tract --> axon terminals in posterior pituitary --> stored --> nerve impulses trigger exocytosis and release of oxytocin or ADH into blood --> target tissues.
69
Oxytocin in delivery and post-delivery.
Delivery: stretching of cervix stimulates oxytocin release to enhance contraction of uterine walls. Post-delivery: oxytocin stimulates milk ejection from mammary glands in response to mechanical stimulus of suckling infant.
70
Oxytocin in males and non pregnant females.
Unclear. Oxytocin may influence parental behaviour toward offspring and sexual pleasure during and after intercourse.
71
Vasopressin.
ADH. Decreases urine production by causing the kidneys to return more water to the blood. Also decreases the water lost through sweating, and constricts arterioles to increase BP.
72
What happens in the absence of ADH?
Urine output increases from 1-2 L / day to 20 L / day.
73
How does alcohol cause more urination?
Alcohol inhibits ADH secretion.
74
What stimulates and inhibits ADH secretion?
Stimulates: Increased blood osmolarity detected by osmoreceptors. Inhibits: Decreased blood volume detected by volume receptors in atria and baroreceptors in walls of blood vessels. Other stimulators: pain, stress, trauma, anxiety, ACh, nicotine, morphine, anesthetics, tranquillizers.
75
Thyroid gland.
Right and left lateral lobes connected by an isthmus. The only endocrine gland that stores its secretory product in large quantities.
76
Pyramidal lobe of thyroid gland.
Half of thyroid glands have a small third lobe that extends superiorly from isthmus.
77
Thyroid follicles.
Microscopic spherical sacs that make up most of the thyroid gland. Inactive shape: cuboidal, squamous. Active shape: cuboidal, columnar.
77
Thyroid follicles.
Microscopic spherical sacs that make up most of the thyroid gland. Inactive shape: low cuboidal, squamous. Active shape: cuboidal, low columnar.
78
Follicular cells.
In walls of thyroid follicles. Extend to lumen of follicle. Produce T3 and T4.
79
Parafollicular cells.
C cells. Between follicles. Produce calcitonin.
80
Step 1: Iodide trapping.
Thyroid follicular cells trap I- ions by actively transporting them from the blood into the cytosol.
81
Step 2: Synthesis of thyroglobulin.
Produced in RER --> modified in Golgi complex --> packaged into vesicles --> exocytosis --> TGB is released into follicle lumen.
82
Step 3: Iodine oxidation.
Negatively charged I- ions cannot bind to tyrosine until they undergo oxidation to iodine. Tyrosine amino acids in TGB become iodinated after I- ions are oxidized.
83
Step 4: Tyrosine iodination.
Iodine reacts with tyrosine. Monoiodotyrosine (T1). Diiodotyrosine (T2). TGB with attached iodine atoms is a colloid, and is a sticky material that accumulates and is stored in the lumen.
84
Step 5: T1 and T2 coupling.
T2 + T2 = T4. T1 + T2 = T3.
85
Step 6: Colloid pinocytosis and digestion.
Colloid droplets re-enter follicular cells by pinocytosis and merge with lysosomes. Digestive enzymes break down TGB to cleave T3 and T4.
86
Step 7: Thyroid hormone secretion.
T3 and T4 diffuse through PM into interstitial fluid and blood. After T4 enters a body cell, most of it is converted to T3 by removal of one iodine.
87
Step 8: Transport in blood.
Most of T3 and T4 combine with transport proteins in blood, mainly TGB.
88
Thyroid hormone functions.
Increase basal metabolic rate, enhance actions of catecholamines, and regulate development and growth of nervous tissue and bone.
89
How do thyroid hormones increase basal metabolic rate?
Stimulate synthesis of additional Na+/K+ ATPases to increase the concentrations of enzymes involved in cellular respiration and increase the number and activity of mitochondria in cells. As cells produce and use more ATP, BMR increases --> more heat is given off --> body temperature rises.
90
How to thyroid hormones enhance catecholamine actions?
They upregulate beta-adrenergic receptors. This is why excessive thyroid hormone = increased HR, BP, force of contraction.
91
How do thyroid hormones regulate the development and growth of nervous tissue and bone?
Promote synapse function, myelin production, growth of dendrites, formation of ossification centres, synthesis of bone proteins, secretion of GH and IGFs.
92
How are thyroid hormones released?
Low blood levels of T3 and T4 or low metabolic rate --> hypothalamus secretes TRH --> enters hypothalamic-hypophyseal portal system --> anterior pituitary --> thyrotrophs secrete TSH --> stimulates thyroid follicular cells to release T3 and T4 --> blood --> elevated T3 inhibits TRH and TSH release.
93
What increases secretion of thyroid hormones?
Conditions that increase ATP demand. Cold environment, hypoglycaemia, high altitude, pregnancy.
94
Calcitonin.
Decrease Ca2+ blood levels by inhibiting osteoclasts and accelerating Ca2+ uptake into bone ECM.
95
Miacalcin.
Calcitonin extract derived from salmon. 10x more potent than calcitonin. Prescribed to treat osteoporosis.
96
Parathyroid glands.
One superior and one inferior parathyroid gland are attached to each lateral thyroid lobe. Contain two kinds of epithelial cells: chief cells and oxyphil cells.
97
Chief cells of parathyroid glands.
Produce PTH.
98
Oxyphil cells of parathyroid glands.
Secrete excess PTH in parathyroid gland cancer.
99
PTH.
Major regulator of Ca2+, Mg and P. Increases osteoclasts. Works on kidneys to slow the rate at which Ca2+ and Mg are lost in urine, increase loss of HPO in urine, and promote formation of calcitriol in kidney.
100
Calcitriol.
Active form of vitamin D. Increases rate of Ca2+, HPO and Mg absorption from GI into blood.
101
Describe the release of calcitonin and calcitriol.
High Ca2+ in blood --> parafollicular cells of thyroid gland release calcitonin --> inhibits osteoclasts --> low Ca2+ in blood --> chief cells of parathyroid gland release PTH --> promotes resorption of bone ECM and stimulates kidneys to synthesize calcitriol --> stimulates increased absorption of Ca2+ from food in GI --> high Ca2+ in blood.
102
Adrenal cortex.
Large region of adrenal glands (80-90%). Produces steroid hormones essential for life. Subdivided into 3 zones.
103
Zona glomerulosa of adrenal cortex.
Outer zone. Deep to connective tissue capsule. Cells are closely packed and arranged in spherical clusters and arched columns. Secrete mineralocorticoids that affect mineral homeostasis.
104
Zona fasciculata of adrenal cortex.
Middle zone. Widest. Cells are arranged in long straight columns. Secrete glucocorticoids and cortisol to affect glucose homeostasis.
105
Zona reticularis of adrenal cortex.
Inner zone. Cells are rrranged in branching cords. Synthesized small amounts of weak androgens.
106
Aldosterone.
Major mineralocorticoid. Regulates homeostasis of Na2+ and K+ ions, helps adjust BP and blood volume, and promotes excretion of H+ in urine to prevent acidosis. Secretion is controlled by renin-angiotensin-aldosterone (RAA) pathway.
107
Describe aldosterone release.
Dehydration, Na+ deficiency, hemorrhage --> decreased blood volume --> decreased BP --> juxtaglomerular cells of kidneys secrete renin enzyme --> converts angiotensinogen to angiotensin I --> ACE converts angiotensin I to angiotensin II hormone --> stimulates adrenal cortex to secrete aldosterone --> kidneys --> increase reabsorption of Na+ which increases reabsorption of water by osmosis --> kidneys also increase K+ and H+ secretion into urine --> blood volume increases --> blood pressure increases to normal --> angiotensin II stimulates arterioles to contract to further increase BP --> K+ in blood also increases aldosterone secretion.
108
Glucocorticoids.
Regulate metabolism and resistance to stress. Cortisol, corticosterone, cortisone. Low blood cortisol --> neurosecretory cells of hypothalamus secrete CRH --> ACTH is released from anterior pituitary --> blood --> adrenal cortex --> glucocorticoid secretion.
109
Which are the functions of glucocorticoids?
Protein breakdown: increase rate of protein breakdown in muscle fibres and increase liberation of amino acids in bloodstream. Glucose formation: liver cells convert certain amino acids or lactic acid into glucose. Lipolysis: breakdown of triglycerides and release of FAs from adipose tissue into blood. Resistance to stress: additional glucose supplied by liver cells provides tissues with a ready source of ATP to combat stresses. Anti-inflammatory: inhibit WBCs that participate in inflammatory responses. Depression of immune responses: prescribe for organ transplant.
110
Androgens.
Stimulate growth of axillary and pubic hair in males and females. Contribute to prepubertal growth spurt. Stimulated by ACTH. Males: testosterone is released by testes after puberty. Females: adrenal androgens are important for libido, and can be converted to estrogens.
111
How do post-menopausal women create estrogens?
From conversion of adrenal androgens.
112
Adrenal medulla.
Small region of adrenal glands. Produces catecholamines. Chromaffin cells are innervated by sympathetic preganglionic neurons of ANS. Releases hormone very quickly. Chromaffin cells secrete 80% EP and 20% NE. Very important for fight-or-flight.
113
Describe EP and NE release from adrenal medulla.
Stress or exercise --> hypothalamus impulses stimulate sympathetic preganglionic neurons --> chromaffin cells --> EP and NE release.
114
Pancreatic islets.
Islets of Langerhans. Millions of tiny clusters of endocrine tissue scattered among acini.
115
What type of gland is the pancreas?
Endocrine and exocrine. Located in curve of duodenum.
116
Acini.
99% of exocrine cells of pancreas are arranged in acini, which are clusters that produce digestive enzymes that flow into GI tract through a network of ducts.
117
Alpha cells.
17% of pancreatic islet cells. Secrete glucagon.
118
Glucagon.
Raises blood glucose level. Directly stimulates insulin release. Controlled via negative feedback. Stimulated by sympathetic division of ANS, and a rise in blood amino acids if blood glucose is low (after protein meal).
119
Beta cells.
70% of pancreatic islet cells. Secrete insulin.
120
Insulin.
Lowers blood glucose level. Directly suppresses glucagon secretion. Controlled via negative feedback. Indirectly stimulated by GH and ACTH. Stimulated by ACh. Stimulated by arginine and leucine (after protein meal). Stimulated by glucose dependent insulinotropic peptide (GIP).
121
Delta cells.
7% of pancreatic islet cells. Secrete somatostatin, which inhibits insulin and glucagon release from neighbouring beta and alpha cells. It also acts as a circulating hormone to slow absorption of nutrients from GI tract. It also inhibits GH secretion.
122
F-cells.
6% of pancreatic islet cells. Secrete pancreatic polypeptide, which inhibits somatostatin release, gallbladder contraction, and secretion of digestive enzymes by pancreas.
123
Describe the hormone release from pancreatic islets.
Low blood glucose --> alpha cells secrete glucagon --> acts on hepatocytes to accelerate conversion of glycogen to glucose and promote formation of glucose from lactic acid and amino acids --> hepatocytes release glucose into blood more rapidly --> blood glucose increases (if blood glucose continues to rise, glucagon release will be inhibited) --> beta cells secrete insulin --> acts on cells to accelerate facilitated diffusion of glucose into cells, to speed conversion of glucose to glycogen, to increase uptake of amino acids by cells, to increase protein synthesis, to increase FA synthesis, to slow the conversion fo glycogen to glucose, to slow the formation of glucose from lactic acid and amino acids --> blood glucose decreases (if blood glucose continues to drop, insulin release will be inhibited and glucagon release will be stimulated).
124
Ovaries.
Paired oval bodies. Produce steroid hormones, estrogens (estradiol, estrone), and progesterone. Regulate menstrual cycle, maintain pregnancy, prepare mammary glands, promote breast enlargement, promote widening of hips, maintain female secondary sex characteristics, produce inhibin (inhibits FSH).
125
Relaxin.
Released during pregnancy by ovaries and placenta. Increases the flexibility of the pubic symphysis and helps dilate the uterine cervix during labour and delivery.
126
Testes.
Oval glands in scrotum. Produces testosterone. Stimulates descent of testes before birth, regulates production of sperm, stimulates development and maintenance of male secondary sex characteristics, produce inhibin.
127
Pineal gland.
Endocrine gland attached to roof of third ventricle at midline. Part of epithalamus. Consists of masses of neuroglia and pinealocytes. Produces melanin.
128
Melanin.
Amine hormone derived from serotonin. Contributes to biological clock by promoting sleepiness. Increased in children, darkness and sleep. Decreased before awakening. Antioxidant.
129
Describe the release of melanin.
Suprachiasmatic nucleus of hypothalamus stimulates sympathetic postganglionic neurons of superior cervical ganglion to stimulate pinealocytes of pineal gland to secrete melatonin in a rhythmic pattern.
130
Thymus.
Located behind sternum and between the lungs. Role in immunity. Produces thymosin, thymic humoral factor, thymic factor and thymopoietin. Promote maturation of T-cells. May retard aging process.
131
Eicosanoids.
Prostaglandins and leukotrienes. Found in all body cells except RBCs where they act as local hormones in response to chemical or mechanical stimuli. Synthesized from arachidonic acid. Have rapid inactivation. Bind to PM receptors and stimulate or inhibit second messenger synthesis. Promote inflammation, fever and pain.
132
Prostaglandins.
Alter smooth muscle contraction, glandular secretions, blood flow, reproductive processes, platelet function, respiration, nerve impulse transmissions, lipid metabolism, and immune responses.
133
Leukotrienes.
Stimulate chemotaxis of WBCs to mediate inflammation.
134
Thromboxane.
Modified prostaglandin. Constricts blood vessels and promotes platelet activation.
135
Cholecalciferol.
Secreted from skin. Contributes to calcitriol synthesis.
136
Gastrin.
Secreted from GI tract. Promotes gastric juice secretion to increase stomach movements.
137
GIP.
Secreted from GI tract. Stimulates insulin release.
138
Secretin.
Secreted from GI tract. Stimulates secretion of pancreatic juice and bile.
139
CCK.
Secreted from GI tract. Stimulates secretion of pancreatic juice, regulates release of bile from gallbladder, and causes fullness feeling.
140
hCG.
Secreted from placenta. Stimulates corpus luteum to continue production of estrogens and progesterone to maintain pregnancy.
141
hCS.
Secreted from placenta. Stimulates development of mammary glands for lactation.
142
Renin.
Secreted from kidneys. Raises BP by inducing vasoconstriction and secretion of aldosterone.
143
EPO.
Secreted from kidneys. Increases rate of RBC function.
144
Atrial natriuretic peptide (ANP).
Secreted from heart. Decreases BP.
145
Leptin.
Secreted from adipose tissue. Suppresses appetite, and increases FSH and LH activity.
146
Growth factors.
Mitogenic substances. Cause growth by stimulating cell division.
147
Eustress.
Helpful stress that prepares us to meet certain challenges.
148
Distress.
Harmful stress.
149
What controls the stress response, and what is the stress response?
Hypothalamus. General adaptation syndrome (GAS).
150
Fight or flight response.
Initiated by nerve impulses from hypothalamus to sympathetic division of ANS. Reduction of blood flow to kidneys promotes release of renin, which sets into motion the RAS pathway. Aldosterone causes kidneys to retain Na+, leading to water retention and elevated BP. Water retention also helps preserve the fluid volume in case of severe bleeding.
151
Resistance reaction.
Initiated by hypothalamic releasing hormones. Longer lasting reaction. Helps the body continue to fight a stressor long after the fight or flight response dissipates. This is why our heart continues to pound for several minutes after stressor is removed.
152
How is CRH involved in resistance reaction?
CRH stimulates anterior pituitary to secrete ACTH --> stimulates adrenal cortex to increase release of cortisol --> stimulates gluconeogenesis by liver cells, breakdown of triglycerides into FAs, catabolism of proteins into amino acids, reduced inflammation --> tissues throughout the body can use the resulting glucose, FA and amino acids to produce ATP or to repair damaged cells.
153
How is GnRH involved in resistance reaction?
GnRH causes anterior pituitary to secrete GH --> stimulates lipolysis and glycogenolysis in liver.
154
How is TRH involved in resistance reaction?
TRH stimulates anterior pituitary to secrete TSH --> promotes secretion of thyroid hormones --> stimulates increased use of glucose for ATP production.
155
What happens if the resistance stage fails to combat the stressor?
The body moves into exhaustion.
156
Exhaustion.
When the resources of the body eventually becomes so depleted that they cannot sustain the resistance stage. Prolonged exposure to high levels of cortisol and other hormones involved in the resistance reaction causes muscle wasting, immune system suppression, GI tract ulceration, and failure of pancreatic beta cells.
157
Stress-related disorders.
Gastritis, ulcerative colitis, IBS, hypertension, asthma, rheumatoid arthritis, migraines, headaches, anxiety, depression.
158
IL-1.
Secreted by macrophages. Important link between stress and immunity. Stimulates secretion of ACTH --> cortisol --> provides resistance to stress and inflammation --> suppresses further production of IL-1.
