Uworld Physio 3

Question 1

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

Answer 1

diffusion impairment

Question 2

propylthiouracil decrease conversion of T4 to triiodothyronine (T3), causing transient neonatal ——–

Answer 2

hypothyroidism (ie, low T4, high TSH)

Question 3

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.

Answer 3

hypothyroidism

Question 4

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.

Answer 4

thyroxine-binding globulin (TBG)

Question 5

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

Answer 5

feedback inhibition of renin secretion (ie, low renin level).

Question 6

In secondary hyperaldosteronism, overproduction of aldosterone occurs secondary to increased renin synthesis, resulting in elevated renin and aldosterone levels. Causes of secondary hyperaldosteronism include

Answer 6

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.

Question 7

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.

Answer 7

juxtaglomerular

Question 8

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 ——-

Answer 8

renin and aldosterone

Question 9

LH stimulates the theca interna cells of the ovarian follicle to produce ——

Answer 9

androgens

Question 10

Aromatase within the follicle’s ——- cells converts androgens to estradiol under —- stimulation.

Answer 10

granulosa

FSH

Question 11

Androgens and progesterone are synthesized from ——- in the theca interna cells under the influence of —– hormone

Answer 11

cholesterol

luteinizing hormone (LH).

Question 12

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 ——-

Answer 12

proximal tubular reabsorption of phosphate

Question 13

Constipation is particularly common in pregnant patients and is largely due to the effects of —- hormone, which has been shown to reduce —— muscle activity

Answer 13

progesterone

colonic smooth

Question 14

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.

Answer 14

motilin

Question 15

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.

Answer 15

lower esophageal sphincter

Question 16

——– 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.

Answer 16

Rectoceles

Question 17

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

Answer 17

increase

Question 18

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

Answer 18

ATP

Question 19

Congenital long QT syndrome is caused by a mutation in a voltage-gated ——– channel

Answer 19

potassium

Question 20

During the skeletal muscle contraction cycle, ATP binding to myosin causes release of the ————

Answer 20

myosin head from its binding site on the actin filament

Question 21

If—– is not available, the cross-bridge between myosin and actin will persist (rigor mortis).

Answer 21

ATP

Question 22

Calcium binding to —— shifts tropomyosin away from the myosin binding site on actin. These steps do not depend directly on ATP.

Answer 22

troponin C

Question 23

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

Answer 23

progesterone (eg, in a progesterone withdrawal test)

apoptosis

Question 24

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).

Answer 24

sodium

Question 25

**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**)

Answer 25

**sodium chloride**

Question 26

**_Children with watery diarrhea_** should be treated with oral rehydration solutions containing **hypotonic, equimolar concentrations of ---- & ----** to help **prevent dehydration** and electrolyte abnormalities.

Answer 26

**sodium and glucose**

Question 27

**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.**

Answer 27

decreased lean body weight increased subcutaneous fat

Question 28

**----- erectile dysfunction** often begins abruptly **following severe medical (eg, myocardial infarction) or emotional stressors.** The symptoms are often situational, with n**ormal erections at night or during masturbation** but impaired with a partner. **Libido is often normal.**

Answer 28

**Psychogenic**

Question 29

**FSH** from the pituitary induces the **Sertoli cells to produce ------**, which **concentrates testosterone in the seminiferous tubules** and facilitates **spermatogenesis.**

Answer 29

**androgen binding protein (ABP)**

Question 30

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 -----

Answer 30

sperm counts

Question 31

**Regardless of the patient's hydration status**, the **majority of water reabsorption** in the nephron occurs in the ------ passively with the reabsorption of solutes

Answer 31

proximal tubule

Question 32

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).

Answer 32

SNS

Question 33

**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.

Answer 33

4 and 15

Question 34

Possible causes of **hypoxemia in the setting of a normal A-a gradient** include **---- & -----**

Answer 34

**low partial pressure of inspired oxygen (PiO2) (ie, high altitude) & alveolar hypoventilation.** Common causes of alveolar hypoventilation include suppressed central respiratory drive (eg, s**edative overdose)** and diseases that decrease inspiratory capacity (eg, **myasthenia gravis, obesity**).

Question 35

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.

Answer 35

venous

Question 36

**Anovulation** due to **hypogonadotropic hypogonadism** is a common form of **infertility** that can be treated by **pulsatile** administration of -----

Answer 36

GnRH

Question 37

**Pulsatile** stimulation of **pituitary gonadotrophin** cells by **GnRH** leads to upregulation of GnRH receptors and enhanced --- & ---- secretion

Answer 37

FSH and LH

Question 38

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 ----%.

Answer 38

10%-20%

Question 39

**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**.

Answer 39

**urea reabsorption (decreased urea clearance)**

Question 40

**Defective ----- hormone synthesis** leads to overt **hypothyroidism** starting in **infancy;** symptoms include **lethargy, hypotonia, and constipation.** Laboratory evaluation shows l**ow T3 and T4** and **elevated TSH.**

Answer 40

**thyroid**

Question 41

**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**

Answer 41

**thyroid**

Question 42

A number of **_changes occur in the liver with aging_** that can **affect drug metabolism**. Typical changes include **------,------,------**

Answer 42

**decreased liver mass and blood flow** **decreased cytochrome P-450 expression and concentration** **reduced hepatic regeneration after injury**

Question 43

Despite againg, what does not change in an elderlys liver compared with a younger person?

Question 44

In addition to causing **lytic bone lesions**, **_multiple myeloma_** causes diffuse bone loss due to ------ induced **uncoupling of bone resorption and formation** (ie, i**ncreased osteoclast activity without a restorative osteoblast action).**

Answer 44

interleukin-1

Question 45

**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.

Answer 45

**triiodothyronine (T3)**

Question 46

**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**.

Answer 46

**arterial**

Question 47

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)**

Answer 47

**Rinne**

Question 48

In **_conductive hearing loss_**, **bone conduction will be greater than air conduction** (abnormal Rinne test), and the Weber test will lateralize to the **------** ear.

Answer 48

affected

Question 49

In **_sensorineural hearing loss_**, **air conduction will be greater than bone conduction** (normal Rinne test), and the **Weber test** will lateralize to the **------** ear.

Answer 49

**unaffected**

Question 50

**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.**

Answer 50

anovulatory

Question 51

**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 ------

Answer 51

hyponatremia

Question 52

**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

Answer 52

Janus kinase 2/signal transducers and activators of transcription **(JAK2/STAT)**

Question 53

Therapeutic hormones that activate a **-----** second messenger system include **antidiuretic hormone** (V1 receptor), **gonadotropin-releasing hormone, and oxytocin**

Answer 53

**phosphatidylinositol**

Question 54

Widely used therapeutic hormones that activate a **nuclear receptor** include ----- hormone, **vitamins -- & --**, and the **steroid hormones** (eg, glucocorticoids, mineralocorticoids, sex hormones).

Answer 54

**thyroid hormone** **vitamins A & D**

Question 55

**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**)

Answer 55

**increased minute ventilation** (via both an increase in respiratory rate and tidal volume) **reduced physiologic dead space** **decreased mixed venous oxygen content**

Question 56

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.

Answer 56

GFR

Question 57

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

Answer 57

**hyperpolarized (more negative than the resting membrane potential)**

Question 58

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.

Answer 58

calcium and vitamin D Cobalamin (vitamin B12)

Question 59

------ 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**)

Answer 59

Niacin

Question 60

**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.**

Answer 60

**increases**

Question 61

**demyelination** decreases neuronal signaling velocity both by **increasing**/**decreasing the length constant** and **increasing the time constant** (ie, ↓ velocity = ↓ length / ↑ time)

Answer 61

**decreasing**

Question 62

**------ 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.**

Answer 62

**Temporal** **spatial**

Question 63

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 e**ndometrial stroma becomes edematous** and completely traversed by **_tortuous spiral arteries_** that extend from the deeper layers to the uterine lumen.

Answer 63

**secretory phase**

Question 64

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**

Answer 64

**proliferative**

Question 65

**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**

Answer 65

**hyperphosphatemia** **hyperkalemia** **hyperuricemia** **elevated lactate dehydrogenase**

Question 66

**------ 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.**

Answer 66

**Peripheral chemoreceptors**

Question 67

**----- 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.

Answer 67

**Central chemoreceptors**

Question 68

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.**

Answer 68

**response to PaCO2 is blunted**

Question 69

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_**.

Answer 69

**decreased ICP** **reduce ICP**

Question 70

**Induced sedation and therapeutic hypothermia** can **decrease brain ---- demand**, exerting a neuroprotective effect and **improving ICP by reducing cerebral blood volume.**

Answer 70

**metabolic**

Question 71

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.**

Answer 71

**carbonic anhydrase inhibitor (eg, acetazolamide)**

Question 72

**_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.**

Answer 72

decrease HCO3-reabsorption and H+secretion