Uworld Physio 3 Flashcards
a large PO2 gradient between the alveoli (104 mm Hg) and the pulmonary venous blood (70 mm Hg) but pulmonary venous PCO2 is normal (40 mm Hg), indicating incomplete gas exchange most likely due to
diffusion impairment
propylthiouracil decrease conversion of T4 to triiodothyronine (T3), causing transient neonatal ——–
hypothyroidism (ie, low T4, high TSH)
Hypopituitarism causes central ———, which is characterized by low TSH, total T4, and free T4. Other midline defects (eg, cleft lip) or hormonal imbalances (eg, hypoglycemia due to ACTH deficiency) are often present.
hypothyroidism
Neonate with a low total thyroxine (T4) but normal free T4 and normal TSH likely has a deficiency of ——–. Congenital —- deficiency is a benign, X-linked disorder usually identified on newborn screening.
thyroxine-binding globulin (TBG)
In primary hyperaldosteronism (ie, Conn’s syndrome), an adrenal adenoma or bilateral adrenal hyperplasia causes excessive and unchecked aldosterone production that leads to —– renin levels
feedback inhibition of renin secretion (ie, low renin level).
In secondary hyperaldosteronism, overproduction of aldosterone occurs secondary to increased renin synthesis, resulting in elevated renin and aldosterone levels. Causes of secondary hyperaldosteronism include
renal artery stenosis (typically associated with fibromuscular dysplasia or atherosclerosis)
diuretic use
malignant hypertension (which leads to microvascular damage and renal ischemia)
renin-secreting tumors.
Renin-secreting tumors (reninomas) are rare, small, solitary, benign —— cell neoplasms. Reninomas should be strongly considered in patients with marked hyperreninemia and hypertension who clearly do not have renovascular disease.
juxtaglomerular
A pituitary tumor (eg, an ACTH-secreting adenoma causing Cushing’s disease) can result in secondary hypertension due to excess adrenal glucocorticoids (increases vascular sensitivity to adrenergic agents). The resulting hypertension suppresses the renin-angiotensin-aldosterone axis, leading to low levels of ——-
renin and aldosterone
LH stimulates the theca interna cells of the ovarian follicle to produce ——
androgens
Aromatase within the follicle’s ——- cells converts androgens to estradiol under —- stimulation.
granulosa
FSH
Androgens and progesterone are synthesized from ——- in the theca interna cells under the influence of —– hormone
cholesterol
luteinizing hormone (LH).
Primary hyperparathyroidism is characterized by oversecretion of parathyroid hormone despite normal (or elevated) serum calcium levels. Parathyroid hormone raises serum calcium and lowers serum phosphorus by increasing bone resorption (freeing calcium and phosphate), increasing renal reabsorption of calcium, and decreasing ——-
proximal tubular reabsorption of phosphate
Constipation is particularly common in pregnant patients and is largely due to the effects of —- hormone, which has been shown to reduce —— muscle activity
progesterone
colonic smooth
Progesterone prevents the release of ——-, a hormone responsible for stimulating the fasting migrating myoelectric complex, which normally helps propel undigested food from the small intestines into the colon.
motilin
Common gastrointestinal alterations in pregnancy include reduced —– pressure (promoting gastroesophageal reflux) and gallbladder stasis (increasing the likelihood of developing gallstones).
Hemorrhoids are also common and result from a rise in pressure within the rectal venous system due to the gravid uterus.
lower esophageal sphincter
——– occur when the rectum herniates into the vaginal canal through a thinned rectovaginal septum. They cause constipation, rectoceles typically occur in elderly individuals with a history of multiple vaginal deliveries. Patients often report needing to manually compress the vagina to induce bowel movements.
Rectoceles
A water deprivation test with desmopressin (DDAVP) administration can differentiate between central and nephrogenic DI. In patients with central DI and complete nephrogenic DI, the urine osmolality is persistently low despite an increase in serum osmolality with water deprivation. When desmopressin is administered, patients with central DI show a rapid —— in urine osmolality and reduction in urine volume, whereas those with complete nephrogenic DI do not
increase
Cystic fibrosis is an autosomal recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. The CFTR protein is a transmembrane —–gated chloride channel
ATP
Congenital long QT syndrome is caused by a mutation in a voltage-gated ——– channel
potassium
During the skeletal muscle contraction cycle, ATP binding to myosin causes release of the ————
myosin head from its binding site on the actin filament
If—– is not available, the cross-bridge between myosin and actin will persist (rigor mortis).
ATP
Calcium binding to —— shifts tropomyosin away from the myosin binding site on actin. These steps do not depend directly on ATP.
troponin C
When the endometrium is no longer exposed to ——- hormone, prostaglandin production increases, leading to vasoconstriction of the spiral arteries. —– withdrawal also causes increased secretion of metalloproteases by endometrial stromal cells (causing degradation of the extracellular matrix) and —— of the endometrial epithelium. The net effect is degeneration of the functionalis layer, which sloughs away as menstrual flow
progesterone (eg, in a progesterone withdrawal test)
apoptosis
The osmotic gradient for water reabsorption is largely established by the active cotransport of —– into the apical end of enterocytes coupled with chloride, glucose, or amino acids. Sodium is then transported out of the basolateral end of the enterocyte (sodium/potassium ATPase), which pulls water down its osmotic gradient from the gastrointestinal lumen through the tight junctions between enterocytes and into the lamina propria (and ultimately the bloodstream).
sodium
Infections that target the small intestine cause watery diarrhea by blocking the active transport of ——— into the enterocyte or by increasing chloride excretion into the gastrointestinal lumen (mediated by elevated intracellular cyclic AMP, cyclic GMP, or calcium)
sodium chloride
Children with watery diarrhea should be treated with oral rehydration solutions containing hypotonic, equimolar concentrations of —- & —- to help prevent dehydration and electrolyte abnormalities.
sodium and glucose
Following bilateral orchiectomy, extragonadal androgen sources are inadequate to replace the loss of testosterone, causing a hypogonadal state. Loss of testosterone leads to changes in body composition, including decreased ——, increased ——–, and decreased bone density. Loss of testosterone also leads to a significant decrease in prostate volume.
decreased lean body weight
increased subcutaneous fat
—– erectile dysfunction often begins abruptly following severe medical (eg, myocardial infarction) or emotional stressors. The symptoms are often situational, with normal erections at night or during masturbation but impaired with a partner. Libido is often normal.
Psychogenic
FSH from the pituitary induces the Sertoli cells to produce ——, which concentrates testosterone in the seminiferous tubules and facilitates spermatogenesis.
androgen binding protein (ABP)
Following unilateral orchiectomy, the drop in testosterone stimulates pituitary LH secretion, which stimulates increased testosterone production in the remaining testis and maintains libido, erectile function, and secondary sex characteristics. However, the loss of sperm-producing tissue (seminephrous tubule) usually causes a drop in —–
sperm counts
Regardless of the patient’s hydration status, the majority of water reabsorption in the nephron occurs in the —— passively with the reabsorption of solutes
proximal tubule
The hypothalamus controls thermoregulation by promoting alterations in the autonomic nervous system and the adrenal and thyroid axes. Physiologic adaptations in response to hypothermia include increased —– (SNS/PNS) activity and thyroid hormone release, shivering, and peripheral vasoconstriction. These actions normalize body temperature by reducing heat loss and increasing metabolic rate (promoting thermogenesis).
SNS
a normal A-a gradient is typically between—— mm Hg, with older individuals having higher normal values due to an age-related decline in O2-diffusing capacity.
4 and 15
Possible causes of hypoxemia in the setting of a normal A-a gradient include —- & —–
low partial pressure of inspired oxygen (PiO2) (ie, high altitude) & alveolar hypoventilation.
Common causes of alveolar hypoventilation include suppressed central respiratory drive (eg, sedative overdose) and diseases that decrease inspiratory capacity (eg, myasthenia gravis, obesity).
The majority of CO2 produced in the tissues is transported to the lungs as bicarbonate ion (HCO3−). Within red blood cells (RBCs), the enzyme carbonic anhydrase forms HCO3− from CO2 and water. The excess HCO3− is then transferred out of RBCs into the plasma via exchange with chloride ions (Cl−). This exchange is known as “chloride shift” and is the principal cause of high RBC chloride content in —– blood.
venous
Anovulation due to hypogonadotropic hypogonadism is a common form of infertility that can be treated by pulsatile administration of —–
GnRH
Pulsatile stimulation of pituitary gonadotrophin cells by GnRH leads to upregulation of GnRH receptors and enhanced — & —- secretion
FSH and LH
In common practice, GFR is estimated using creatinine clearance. However, creatinine is actively secreted by the proximal tubules, so uncorrected creatinine clearance overestimates the GFR by approximately —-%.
10%-20%
Vasopressin and desmopressin cause a V2 receptor-mediated increase in water and urea permeability at the inner medullary collecting duct. The resulting rise in ——- enhances the medullary osmotic gradient, allowing the production of maximally concentrated urine.
urea reabsorption (decreased urea clearance)
Defective —– hormone synthesis leads to overt hypothyroidism starting in infancy; symptoms include lethargy, hypotonia, and constipation. Laboratory evaluation shows low T3 and T4 and elevated TSH.
thyroid
Thyroid hormone resistance is characterized by decreased sensitivity of peripheral tissues to thyroid hormones due to a defect in the —- hormone receptor. Levels of T4, T3, and TSH are increased. Patients classically have goiter and frequently develop attention deficit hyperactivity disorder
thyroid
A number of changes occur in the liver with aging that can affect drug metabolism. Typical changes include ——,——,——
decreased liver mass and blood flow
decreased cytochrome P-450 expression and concentration
reduced hepatic regeneration after injury
Despite againg, what does not change in an elderlys liver compared with a younger person?
In addition to causing lytic bone lesions, multiple myeloma causes diffuse bone loss due to —— induced uncoupling of bone resorption and formation (ie, increased osteoclast activity without a restorative osteoblast action).
interleukin-1
Hyperthyroidism causes increased bone turnover with net bone loss. The bone loss in hyperthyroidism is driven by ?
— stimulates osteoclast differentiation, increased bone resorption, and release of calcium.
triiodothyronine (T3)
Ascites in cirrhosis develops from hemodynamic changes related to portal hypertension. Splanchnic vasodilation decreases the splanchnic vascular resistance and lowers the effective ——-blood volume, which causes activation of the renin-angiotensin-aldosterone system and promotes sodium and water retention. Additionally, low oncotic pressure (ie, hypoalbuminemia due to impaired hepatic function) reduces fluid resorption from the interstitium.
The capillaries remain physiologically normal, so permeability is unchanged.
arterial
The —— test compares air versus bone conduction (via the mastoid bone). As the vibration of the tuning fork fades, air-conducted sound is normally louder and heard longer than bone-conducted sound. The Rinne test is considered positive (normal) if the sound is heard best at the external auditory meatus (air conduction) and negative (abnormal) if the patient hears the vibration better at the mastoid (bone conduction)
Rinne
In conductive hearing loss, bone conduction will be greater than air conduction (abnormal Rinne test), and the Weber test will lateralize to the —— ear.
affected
In sensorineural hearing loss, air conduction will be greater than bone conduction (normal Rinne test), and the Weber test will lateralize to the —— ear.
unaffected
Adolescents typically have an immature hypothalamic-pituitary-ovarian axis for several years following menarche. During this time, they may have longer menstrual cycles and irregular bleeding patterns due to the presence of ——- cycles.
In the absence of ovulation, the ovarian follicle does not degenerate and become a corpus luteum. As a result, no progesterone is produced and estrogen levels remain persistently high, causing the endometrium to remain in the proliferative phase. Chronically proliferative endometrium becomes disorganized and fragile with unstable venous capillaries, resulting in irregular periods of stromal breakdown with variable, but often heavy, bleeding.
anovulatory
Reduced aldosterone production in primary adrenal insufficiency leads to renal sodium wasting with consequent hypovolemia, orthostasis, and potassium retention (hyperkalemia). Low cortisol stimulates increased antidiuretic hormone secretion, which leads to water retention and ——
hyponatremia
Chronic kidney disease is commonly associated with normocytic anemia due to reduced production of erythropoietin by the kidneys. Erythropoietin signal transduction is primarily mediated by the ——– pathway, which promotes erythrocyte precursor survival
Janus kinase 2/signal transducers and activators of transcription (JAK2/STAT)
Therapeutic hormones that activate a —– second messenger system include antidiuretic hormone (V1 receptor), gonadotropin-releasing hormone, and oxytocin
phosphatidylinositol
Widely used therapeutic hormones that activate a nuclear receptor include —– hormone, vitamins – & –, and the steroid hormones (eg, glucocorticoids, mineralocorticoids, sex hormones).
thyroid hormone
vitamins A & D
Physiologic changes in the respiratory system that occur with exercise include (increased/decreased) minute ventilation, ——- physiologic dead space, increased ventilation-perfusion ratio, and increased extraction of oxygen by skeletal muscle (resulting in ——– mixed venous oxygen content)
increased minute ventilation (via both an increase in respiratory rate and tidal volume)
reduced physiologic dead space
decreased mixed venous oxygen content
Physiologic renal adaptations during pregnancy include increased —— rate, greater basement membrane permeability, and decreased tubular resorption of filtered protein. As a result, trace urinary protein excretion (ie, <300 mg/24 hr) is a normal finding in pregnancy.
GFR
A drug that binds to and activates GABA-A receptors (or enhances their activity) will increase the conductance of chloride ions, leading to increased passive transport of chloride into the cell interior. This causes the membrane potential to become —-polarized by approaching or reaching the equilibrium potential for chloride
hyperpolarized (more negative than the resting membrane potential)
Individuals on a vegan diet are at increased risk for deficiencies in —- & —-. Supplementation is recommended to avoid long term consequences, including osteoporosis and bone fractures. —— deficiency can also occur.
calcium and vitamin D
Cobalamin (vitamin B12)
—— deficiency can lead to pellagra, characterized by diarrhea, dermatitis, and possible dementia. Deficiency usually occurs in severely malnourished individuals (eg, alcohol use disorder, anorexia nervosa)
Niacin
Myelin decreases membrane capacitance (reduces the amount of charge stored by the membrane) and —— membrane resistance (reduces charge leakage through the membrane) in axon segments between the nodes of Ranvier; this reduces the time constant and allows the membrane potential to change faster.
increases
demyelination decreases neuronal signaling velocity both by increasing/decreasing the length constant and increasing the time constant (ie, ↓ velocity = ↓ length / ↑ time)
decreasing
—— summation refers to the combined effect of sequential impulses from the same neuron over time, whereas —– summation refers to the combined effect of simultaneous impulses from several different neurons.
Temporal
spatial
The —— phase of the menstrual cycle occurs between ovulation and menses, from days 15-28 of the normal menstrual cycle. Progesterone released by the corpus luteum causes the uterine glands to coil and secrete glycogen-rich mucus in preparation for embryo implantation. The endometrial stroma becomes edematous and completely traversed by tortuous spiral arteries that extend from the deeper layers to the uterine lumen.
secretory phase
The —— phase is the first half of the menstrual cycle (days 1-14), beginning with the first day of menses and ending with ovulation. During this time, estrogen stimulates proliferation of the stratum functionale. Normal proliferative endometrium consists of nonbranching, nonbudding, uniform glands evenly distributed throughout a uniform stroma
proliferative
Acute lymphoblastic leukemia (ALL) is a hematologic malignancy that is generally associated with a high tumor cell burden and a rapid turnover rate. Therefore, initiation of cytotoxic chemotherapy often leads to massive lysis of tumor cells, which spills intracellular contents into the blood (tumor lysis syndrome), resulting in the following: ——–(increased or decreased) phosphate, potassium, uric acid. lactate dehydrogenous
hyperphosphatemia
hyperkalemia
hyperuricemia
elevated lactate dehydrogenase
—— chemoreceptors found in the carotid and aortic bodies are the primary sites for sensing PaO2 and are stimulated by hypoxemia.
When supplemental oxygen is administered, the rapid increase in PaO2 can reduce —– chemoreceptor stimulation and decrease the respiratory rate.
Peripheral chemoreceptors
—– chemoreceptors, located in the medulla, are more involved in the respiratory response to hypercapnia than to hypoxemia. CO2 readily diffuses through the blood-brain barrier and forms hydrogen ions in the cerebrospinal fluid; the resulting decrease in pH is detected by medullary neurons, triggering an increase in respiration. Because the blood-brain barrier is relatively impermeable to hydrogen ions, blood pH itself has little effect on central chemoreceptors.
Central chemoreceptors
In patients with chronic obstructive pulmonary disease, the response to —– is blunted and hypoxemia can contribute to respiratory drive. Peripheral chemoreceptors are primarily responsible for sensing arterial partial pressure of oxygen (PaO2) and can be suppressed with oxygen administration.
response to PaCO2 is blunted
A drop in PaCO2 due to hyperventilation causes vasoconstriction. The resulting reduction in cerebral blood volume leads to decreased ICP. Lowering PaCO2 is one of the measures employed to —— in mechanically ventilated patients with cerebral edema.
decreased ICP
reduce ICP
Induced sedation and therapeutic hypothermia can decrease brain —- demand, exerting a neuroprotective effect and improving ICP by reducing cerebral blood volume.
metabolic
On initial exposure to high altitude, the administration of a —— can accelerate the decrease in HCO3- reabsorption by the kidneys to help relieve the alkalemia and treat altitude sickness.
carbonic anhydrase inhibitor (eg, acetazolamide)
At high altitude, the low partial pressure of inspired oxygen (PiO2) leads to hypoxemia with consequent hyperventilation and respiratory alkalosis. The hypoxemia and alkalemia can cause symptoms of altitude sickness (eg, headache, fatigue, lightheadedness). The kidneys respond by creating a compensatory metabolic acidosis (——- HCO3-reabsorption and H+secretion) and by increasing erythropoietin secretion.
decrease HCO3-reabsorption and H+secretion
