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Systems test 4
test 4
82
Physiology
Professional
04/15/2008

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Term
What is the Henderson-Hasselbach equation?
Definition
pH=pKa + log [A-]/[HA]
Term
When does pH = pK?
Definition
when [A-] = [HA]
Term
Does acid strength increase or decrease with lower pK?
Definition
increase
Term
How does alkalosis lower the free concentration of Ca2+?
Definition
when pH rises, additional anionic sites on plasma proteins are exposed, some of these sites bind Ca2+ lowering the free concentration
Term

What is the pH range necessary for survival?

 

For health? 

Definition

survival: 6.8-7.8

 

health: 7.35-7.45 

Term
What is the most important of the non bicarbonate buffers and how does it act as a buffer?
Definition

hemoglobin

 

protonates and deprotonates histidine

 

other plasma proteins and phosphate also act as a buffer 

Term
What are the concentrations of extracellular HCO3- and CO2 in health?
Definition

HCO3- = 25mM

CO2 = 1.2 mM 

Term
What is the most important intracellular buffer?
Definition
protein
Term
What is the isohydric principle?
Definition
all buffers in a homogenous solution are in equilibrium with the same [H+], any change in [H+] will be redistributed among all buffers in the body so for a given pH all buffers have apporpriate ratio of acid and base depending on their pK; thus total acid-base status determined by measuring one
Term
What is a volatile acid?
Definition
one that is blown out as CO2
Term
How are non-volatile acids produced and dealt with?
Definition
protein and amino acid oxidation, they are buffered with bicarbonate, the kidney must excrete acid salts and replenish bicarbonate
Term
What happens for every HCO3- lost in the stool?
Definition
one H+ retained in the extracellular fluid
Term
For each NH4+ excreted in the urine, what happens?
Definition
an HCO3- is returned to the extracellular fluid
Term
What happens in the collecting duct with a decrease in pH?
Definition

the intercalated cells insert more H+-ATPases into the apical membrane allowing more H+ to be pumped into the tubular fluid. also there is an increase in Na/H antiporters and Na/3HCO3- symporters in the basolateral membrane

 

H+ is excreted with a non-bicarbonate buffer 

Term
When the acid-base disorder results from a primary change in bicarbonate, what type of disorder is it?
Definition
metabolic
Term
When the acid-base disorder results from a primary change in PCO2, what type of disorder is it?
Definition
respiratory
Term

For each 10 mmHg increase in PCO2, how much does [HCO3-] increase?

 

For each 10mmHg decrease in PCO2, how much does [HCO3-] decrease? 

Definition

1 meq/L

 

2 meq/L 

Term
What is the compensatory response to respiratory acidosis?
Definition
an increase in plasma HCO3-
Term
What is the compensatory response to metabolic acidosis?
Definition
decreased PCO2
Term
What are some causes of metabolic acidosis?
Definition

increased H+ from endogenous sources (lactic acidosis or ketoacidosis)

 

increased H+ from exogenous sources (ingestion of methanol or salicylates)

 

decreased H+ excretion

 

loss of bicarbonate from the GI tract (diarrhea) 

Term
What is the anion gap? What is the normal range and what does an increase in the anion gap indicate?
Definition

the difference between [Na+] and [HCO3-]  + [Cl-]

 

10-12 meq/L

 

metabolic acidosis 

Term
In a fully compensated metabolic alkalosis, what is the change in PCO2?
Definition
an increase of around 0.7 mmHg/1mM increase in [HCO3-]
Term
What are some causes of metabolic alkalosis?
Definition

severe vomiting

 

antacids

 

diuretics 

Term
What is neuroendocrine communication?
Definition
a neuronal cell, innervated by another neuron, responds by secreting a hormone into the circulatory system. the hormone travels through the circulatory system until it encounters a target cell expressing the appropriate receptor
Term
What are the three categories of hormones?
Definition
peptides, tyrosine derivatives, steroids
Term
When is the influence of a hormone the greatest?
Definition
when receptors are undersaturated
Term
What does the supraoptic nuclei of the posterior pituitary synthesize?
Definition
ADH, vasopressin
Term
What hormone is synthesized by the paraventricular nuclei of the posterior pituitary?
Definition
oxytocin
Term
WHat type of hormone is GH and what does it do?
Definition

peptide hormone

 

regulates longitudinal bone growth and the metabolism of glucose, amino acids and fatty acids 

Term
What stimulates GH secretion? What inhibits it?
Definition

GHRH

 

somatostatin 

Term
What stimulates GH receptor synthesis?
Definition
low concentrations of circulating GH, insulin, and estrogen
Term
What pathology is caused by excess GH secretion? What are symptoms?
Definition

gigantism/acromegaly

 

accelerated growth, insulin resistance, mild carb intolerance 

Term
What pathology is caused by GH deficiency? What are symptoms?
Definition

dwarfism

 

short stature, delayed bone maturation, mild obesity, delayed puberty 

Term
What does cortisol do?
Definition
increases the flucose concentration in plasma by stimulating hepatic gluconeogenesis using amino acids derived from protein breakdown in muscle and other tissues
Term
What class are most of the enzymes responsible for cholesterol conversion?
Definition
cytochrome P450 oxidases
Term
What is the rate limiting step of steroid biosynthesis?
Definition
C27 cholesterol cleaved to C21 pregnenolone by the cholesterol side chain cleavage complex
Term
Which enzyme is not present in significant quantitiy in the zona glomerulosa causing cortisol to only be synthesized int he fasciculata and reticularis layers of the adrenal cortex?
Definition
17 alpha-hydroxylase
Term
What does cortisol bind when it reaches the cytoplasm?
Definition

90% to corticosteroid-binding globulin

6% albumin

4% unbound   

Term
What does aldosterone do?
Definition
regulates Na+ transport by increasing the expression of the Na/K pump, Na channels and the NA/K/Cl cotransporter; thse will sustain increased Na reabsorption and increased K secretion
Term
What are 3 mediators of aldosterone production by the glmerulosa cells?
Definition

angiotensin II

 increased concentrations of extracelular K

ACTH 

Term
What is Addison's disease?
Definition

primary adrenal cortical insufficiency - complete destruction of the adrenal cortex due to autoimmune disease, infection, cancer

 

slow, progressive loss of cortisol and aldosterone secretion, produces a chronic, steadily worsening fatigue, low Na, high K and low BP 

Term
What is Cushing's syndrome?
Definition
cronic glucocorticoid excess, overproduction of cortisol, thin arms and legs and a redistribution of fat from the extremities to the thrunk, face, shoulder blades and base of neck, thinning of skin, blood vessels closer to surface, characteristic stretch marks
Term
What protein is colloid made of? What does it do?
Definition
thyroglobulin which is synthesized and secreted by the follicular cells, serves as the protein backbone for the thyroid hormones which are iodinated derviatives of tyrosines
Term
How much iodide is in the thyroid and how much is taken up daily? How is the iodide which is taken up utilized?
Definition

8000 ug

80 ug

most goes into thyroid hormone, the rest released as free iodide 

Term

What is the Wolf-Chaikoff effect?

     

Definition
if iodide intake exceeds 2 mg/day, the excess iodide in the thyroid gland inhibites the iodide trap and hormone synthesis
Term
How does the thyroid gland retain iodine?
Definition
by conjugating it to tyrosine on thyroglobulin
Term
How is iodine transported across the basal plasma membrane of the thyroid follicular cell?
Definition
actively by the Na/I symporter through the use of the Na/K ATPase
Term
What is the iodide trap?
Definition
the coupling of the transported iodide to thyroglobulin in the lumen of the thyroid gland traps the iodide within the gland
Term
How does iodide exit the thyroid follicular cell?
Definition
at the apical surface through an anion exchanger called pendrin, entering the lumen of the follicle
Term
What does the thyroid follicular cell package into secretory vesicles?
Definition
thyroglobulin and thyroid peroxidase
Term
What does thyroid peroxidase do?
Definition
in the presence of H2O2 converts iodide to iodine, completes iodination where iodine is coupled to certain tyrosines on the secreted thyroglobulin; couples the iodotyrosyl residues on thyroglobulin to form MIT and DIT which form T3 and T4
Term
How is iodinated thyroglobulin stored?
Definition
as colloid in the lumen formed by the follicular cells
Term
How is T3 or T4 released?
Definition
colloid is endocytosed by the follicle cell, the colloid droplet fuses with lysosomes and the thyroglobulin is cleaved by lysosomal proteases, releasing T3 and T$ which transit the basal plasma membrane and are taken up into the circulatory system by the adjacent capillaries
Term
In what form is thyroid hormone in circulation?
Definition

bound to thyroxine-binding globulin

 

some also bound to transthyretin and albumin 

Term
Which form of thyroid hormone is most active?
Definition
T3
Term
What type of receptor is the thyroid hormone receptor?  
Definition
nuclear
Term
What happens to the cortex and medulla of the gonad in the male?
Definition
Term
What do androgens formed by the testes do during development?
Definition
cause the mesonepthros to differentiate into the epididymis and the wolffian duct into the vas defernes, the seminal vesicles and the ejaculatory duct
Term
What do androgens formed by the testes do during development?
Definition
cuase the mesonephros to differentiate into the epidiymis and the wolffian duct into the vas deferens, the seminal vesicles, and the ejaculatory duct
Term
What does antim ullerian hormone do?
Definition
cuases regression of the mullerian duct
Term
What must testosterone be transformed into before it can act on the external genital structures? What enzyme is needed to make this transformation?
Definition

HGT

5 alpha-reductase 

Term
What enzyme present within the brain tissues converts testosterone to estrone and estradiol?
Definition
aromatase
Term
WHat are the Sertoli cell's response to stimulation by FSH?
Definition
the production of inhibins, activins, and follistatins
Term
What are activins?
Definition
polypeptide hormones that are produced by the sertoli cells that stimulate FSH release by the anterior pituitary gland
Term
What is antimullerian homrone?
Definition
a glycoprotein that causes atrophy of the mullerian ducts in the male during the period of fetal differentiation
Term
What is a gonadotrophic hormone released by the anterior pituitary gland that stimulates Sertoli cells, thereby fostering spermatogenesis. it stimulates the synthesis of androgen-binding protein P450 aromatase, growth factors, inhinins, activins and follistatin
Definition
FSH
Term
What is a family of glycoproteins that bind to activin and inhibit its ability to stimulate FSH by the pituitary gland?
Definition
follistatins
Term
What is a decapeptide hormone that is synthesized by neurons in the hypothalamus, released into the capillary system of the median eminence and transported via a portal venous system to the anterior pituitary?
Definition
gonadotropin releasing hormone
Term
What is a polypeptide hormone that is released from the sertoli cells which signals back to the pituitary gland and reduces the release of FSH?
Definition
inhibin
Term
A gonadotrophic hormone released by the anterior pituitary gland that primarily affects the Leydig cells within the testes. It stimulates the development and functional activity of the Leydig cells. The primary effect is the stimulation of testosteron synthesis and release
Definition
luteinizing hormone
Term
What is the principal androgenic hormone, primarily produced by the Leydig cells in response to LH released by the pituitary gland. responsible for the regulation of gonadotropin secretion, spermatogenesis, differentiation of the wolffian duct and development of male secondary sexual characteristics
Definition
testosterone
Term
androgen formed within systemic tissues as the result of 5 alpha reductase enzyme activity. has the same spectrum of activites as testosterone but is 30 to 50 times more potent on a molar basis
Definition
dihydrotestosterone
Term
a hormone synthesized from testosterone in peripheral tissue by a p450 aromatase enzyme. plays a role in sperm production, bone formation and masculinization of the male sexual centers of the brain
Definition
estradiol
Term
Where are FSH receptors expressed?
Definition
granulosa cells in the ovary
Term
Where are LH receptors expressed?
Definition
on thec interna and stromal cells
Term
What does estradiol do?
Definition
stimulates granulosa celland theca interna cell proliferation. it increases granulosa cell responsiveness to FSH by increasing the expression of FSH receoptors
Term
What does LH do in the thecal cells?
Definition
stimulates the synthesis of androstenedione and testosterone
Term
What does FSH do in the granulosa cells?
Definition
stimulates the synthesis of the aromatase complex which converts the androgens produced by thecal cells into estrogens
Term
A surge of which hormone signals ovulation?
Definition

LH

 

a modest increase in FSH also occurs 

Term
What does estrogen do during the late follicular stage that enhances the probability of fertilization?
Definition

- the cervical epithelial cells produce more watery secretions, which decreases the viscosity of the mucous in the cervix

- the pH of the cervical mucous increases, which supports increased sperm motility

- contractions of hte myometrium and the smooth muscle around the oviducts propel the sperm towards the ampulla 

Term
What is RU486?
Definition
a progesterone antagonist that prevents implantation by causing the shedding of the uterine lining
Term
What is oxytocin secreted in response to?
Definition
stretching of the uterine cervix, not the trigger for parturition
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