Question 1

A 16-year-old boy has become totally deaf in his left ear after a motor vehicle accident even though hearing in his right ear is normal. A lesion at which of the following sites is the most likely cause of this finding?
A) Left dorsal and ventral cochlear nuclei
B) Left inferior colliculus
C) Left superior colliculus
D) Right medial geniculate nucleus
E) Right temporal lobe

Accepted Answer

The left dorsal and ventral cochlear nuclei are the initial processing centers for auditory information from the left ear. Damage to these nuclei would disrupt the auditory pathway, leading to deafness in the left ear, while leaving the right ear unaffected.

Question 2

A 45-year-old woman experiences blurred vision and difficulty swallowing after eating some home-canned vegetables. These symptoms are followed by respiratory distress and flaccid paralysis. The symptoms of her illness are most associated with which of the following?
A) Black widow spider toxin
B) Botulinum toxin
C) Organophosphate poisoning
D) Benzodiazepine ingestion
E) ($\alpha$)-Bungarotoxins

Accepted Answer

The symptoms described are characteristic of botulinum toxin exposure, which can occur through ingestion of improperly canned foods. Botulinum toxin causes blurred vision, difficulty swallowing, respiratory distress, and flaccid paralysis by inhibiting acetylcholine release at neuromuscular junctions.

Question 3

A 50-year-old homeless man with a 30-year history of alcoholism complains of painful lesions on the mucous membranes of his mouth and tongue and has pigmented keratotic scaling lesions on his face and hands. In addition, he is weak, forgetful, and has burning sensations in various parts of the body and diarrhea. A deficiency of which of the following is most likely to account for these findings?
A) Biotin
B) Folic acid
C) Niacin
D) Riboflavin
E) Vitamin C

Accepted Answer

The symptoms described are indicative of pellagra, which is caused by a deficiency of niacin (vitamin B3). Pellagra is characterized by the "three Ds": dermatitis, diarrhea, and dementia, which align with the patient's symptoms of keratotic scaling lesions, diarrhea, and forgetfulness, respectively.

Question 4

A healthy 16-year-old man experiences severe hemorrhaging following an automobile accident. He is conscious and aware upon arrival at the emergency department, but hypotensive, and tachypneic. Which of the following is associated with the hemodynamic response to hemorrhage?
A) Decreased coronary blood flow
B) Decreased sympathetic tone to the venous system
C) Increased blood flow to the skin, intestines, and kidneys
D) Increased cholinergic vasoconstrictor tone of skeletal muscle arterioles
E) Normal cerebral blood flow

Accepted Answer

During hemorrhage, the body prioritizes maintaining blood flow to vital organs like the brain, so cerebral blood flow remains normal despite systemic hypotension.

Question 5

An 8-year-old healthy boy is concerned about his very short stature. His growth hormone level is within normal limits despite the fact that his growth rate and bone age are below the norm for children of the same chronologic age. The level of which of the following hormones is most likely to be abnormal?
A) Fibroblast growth (FGF)
B) Insulin
C) Insulin-like growth factor I (IGF-I)
D) Somatostatin
E) Somatotropin

Accepted Answer

Insulin-like growth factor I (IGF-I) is a key hormone that mediates the effects of growth hormone (GH) on growth. If a child has normal GH levels but is experiencing reduced growth and delayed bone age, it suggests that the issue may lie in the action or production of IGF-I, rather than in the production of GH itself.

Question 6

A 5-year-old boy has a history of growth retardation, pulmonary infections, and bulky, oily, malodorous stools. Which of the following test results would be expected in this patient? A) Abnormal sweat chloride test B) Low C₃ complement level C) Abnormal nitroblue tetrazolium (NBT) dye test D) Positive wheal and flare reaction with antigen scratch testing E) Sputum with Gram-positive diplococci

Accepted Answer

The symptoms described are characteristic of cystic fibrosis, which is diagnosed with an abnormal sweat chloride test.

Question 7

The glomerular filtration rate (GFR) can be determined from: A) Urinary flow rate (V), plasma P-aminohippuric acid (PAH) concentration (P_PAH) and urinary PAH concentration (U_PAH) B) Urinary flow rate (V), plasma arginine vasopressin (AVP) concentration (P_AVP) and urinary AVP concentration (U_AVP) C) Urinary flow rate (V), plasma creatinine concentration (P_creatinine) and urinary creatinine concentration (U_creatinine) D) Urinary flow rate (V), plasma urea concentration (P_urea) and urinary urea concentration (U_urea) E) Urinary flow rate (V), plasma insulin concentration (P_insulin) and urinary insulin concentration (U_insulin)

Accepted Answer

The glomerular filtration rate (GFR) is most commonly estimated using the urinary flow rate (V), plasma creatinine concentration, and urinary creatinine concentration. Creatinine is a waste product of muscle metabolism that is filtered by the kidneys and is a standard marker used to estimate GFR.

Question 8

A 24-year-old bicyclist severely injures his right leg after colliding with an automobile. He is hemorrhaging from the wound but is stabilized, with a blood pressure of 90/40 mmHg and a heart rate of 100/min. He was not wearing protective head gear at the time of the accident, but shows no evidence of head trauma. His breathing is rapid and shallow. Blood pressure and urine flow could best be improved in this patient by:
A) Oral administration of diuretic
B) Administration of physiologic saline solution
C) Blood transfusion
D) Indirect cardiac massage
E) Intravenous injection of norepinephrine

Accepted Answer

Given the patient's severe injury and hemorrhaging, the most direct and effective way to improve blood pressure and urine flow is through a blood transfusion (C). This would address the blood loss directly, increasing the blood volume, which in turn would improve blood pressure and potentially stabilize urine flow by ensuring adequate renal perfusion.

Question 9

A 70-year-old man complains of weakness in his right leg. Physical examination is notable for hyperactive muscle stretch reflexes, a positive Babinski sign, and diffuse areas of weakness in his right leg. Although he can accurately distinguish sharp and dull pain in the right leg he is unable to distinguish these types of pain in his left leg. The most likely cause of these findings is a lesion in the:
A) Cerebellum
B) Internal capsule, left anterior limb
C) Left lateral funiculus
D) Reticular formation
E) Right frontal lobe

Accepted Answer

The symptoms suggest a lesion in the left lateral funiculus, which affects the corticospinal tract (causing weakness and hyperreflexia in the right leg) and the spinothalamic tract (causing loss of pain sensation in the left leg).

Question 10

Which of the following causes of brain hypoxia would most strongly stimulate the aortic and carotid chemoreceptors?
A) Carbon monoxide poisoning
B) Severe anemia
C) Formation of methemoglobin
D) A marked decrease in pulmonary diffusing capacity
E) Acute respiratory alkalosis

Accepted Answer

A marked decrease in pulmonary diffusing capacity would lead to a significant drop in arterial oxygen levels, which would strongly stimulate the aortic and carotid chemoreceptors to respond to the hypoxia.

Question 11

A tall, obese 14-year-old boy with long arms has bilateral gynecomastia, decreased testicular size for his age, and sparse axillary and pubic hair. A buccal smear preparation shows a single Barr body extending off the nuclear membrane of many squamous cells. Which of the following sets of laboratory studies would be expected in this patient? 
A)$\text { High} \quad \text { High } \quad \text { Low}$

B)$\text {High } \quad \text { Normal } \quad \text { Normal }$
C)$\text {Low } \quad \text {Low } \quad \text { Low }$
D)$\text {Normal } \quad \text {High } \quad \text { Low }$

E)$\text {Low } \quad \text {Low } \quad \text { High}$

Accepted Answer

The answer of A tall, obese 14-year-old boy with long...

Question 12

A 58-year-old woman has left hemiparesis and right ptosis (droopy eyelids). She cannot adduct, elevate, or depress her right eye. The most likely cause of these findings is a lesion in which of the following sites?
A) Cavernous sinus
B) Cerebral cortex
C) Left genu of the internal capsule
D) Mesencephalon
E) Right occipital lobe

Accepted Answer

The symptoms suggest a right oculomotor nerve palsy (ptosis and inability to move the eye) and left hemiparesis, which are indicative of a lesion in the right mesencephalon (midbrain), affecting the oculomotor nerve and the corticospinal tract.

Question 13

A 74-year-old comatose man, exhibits flexion of the left upper extremity with passive movement of the head to the right, and flexion of the right upper extremity when the head is moved to the left. His legs are fixed in extension during all movements. Which of the following is the most likely explanation of these findings?
A) Alternating hemiplegia syndrome
B) Brown-Séquard syndrome
C) Decerebrate rigidity
D) Decorticate rigidity
E) Transection of the spinal cord below vertebra TV

Accepted Answer

The described symptoms are indicative of decorticate rigidity, which is characterized by abnormal flexion of the upper extremities and extension of the lower extremities. This posture suggests damage to the corticospinal tract above the level of the brainstem.

Question 14

A 23-year-old woman, who complains of chronic cough, shortness of breath, and chest tightness is diagnosed with asthma. Which of the following is the best clinical indicator of significant pulmonary obstruction in patients with asthma? A) Arterial hypoxemia B) Dyspnea C) Forced expiratory volume in 1 second (FEV₁)/forced vital capacity (FVC) ratio of less than 75% D) Large anatomic dead space volume E) Rapid respirations

Accepted Answer

The forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio of less than 75% is a key indicator of significant pulmonary obstruction in patients with asthma, reflecting the degree of airflow limitation.

Question 15

A 45-year-old woman is concerned by a history of episodes of confusion and fainting over the past year that occur either on first arising in the morning or after exercising. The episodes are preceded or accompanied by shaking, sweating, and palpitations. The woman's husband has noticed that eating can prevent the onset of symptoms. Which of the following is the most likely cause of this patient's symptoms?
A) Autonomic insufficiency leading to orthostatic hypotension
B) Benign insulin-secreting tumor causing periodic hypoglycemia
C) Glucagon-secreting tumor causing periodic hypoglycemia
D) Meningioma in the region of the frontal cortex
E) Norepinephrine-secreting tumor causing periodic hyperglycemia

Accepted Answer

The symptoms described, including confusion, fainting, shaking, sweating, and palpitations, which are prevented by eating, suggest episodes of hypoglycemia. A benign insulin-secreting tumor (insulinoma) is the most likely cause of these symptoms, as it would lead to periodic hypoglycemia, especially during fasting states or after exercise when glucose levels naturally drop.

Question 16

A 30-year-old woman in her first trimester of pregnancy complains of easy fatigability, heat intolerance, and palpitations. Physical examination shows a slightly enlarged, nontender thyroid gland. Thyroid function studies show an increased total serum thyroxine (T₄) level, but normal serum thyroid-stimulating hormone (TSH) levels. Which of the following best explains the results of these studies? A) Decreased thyroid-binding globulin (TBG) B) Increased synthesis of T₄ C) Increased synthesis of triiodothyronine (T₃) D) Thyroiditis-induced release of T₄ E) Normal finding in pregnancy

Accepted Answer

The increased total serum thyroxine (T4) level with normal serum thyroid-stimulating hormone (TSH) levels in a pregnant woman is a normal finding due to the increased synthesis of thyroid-binding globulin (TBG) during pregnancy. This increases the total T4 levels while free T4 levels remain normal, hence the normal TSH.

Question 17

A 30-year-old man with a family history of sudden cardiac death has a systolic murmur that increases in intensity when he is sitting up. An echocardiogram shows abnormal movement of the anterior mitral valve leaflet against an asymmetrically thickened interventricular septum. The mechanism for sudden cardiac death in this patient's family is most closely attributed to which of the following conditions?
A) Acute myocardial infarction (MI)
B) Congenital bicuspid aortic valve
C) Conduction system defect
D) Dissecting aortic aneurysm
E) Mitral valve prolapse (MVP)

Accepted Answer

Conduction system defect

Question 18

A 32-year-old female undergoes an appendectomy without complications, but has markedly reduced bowel sounds and an absence of flatus or defecation during the immediate postoperative period. Which of the following mechanisms best explains this decrease in bowel sounds?
A) Decreased sympathetic activity to the gut
B) Increased activity of the gastrocolic reflex
C) Increased parasympathetic activity to the gut
D) Increased plasma acetylcholine concentration
E) Increased plasma norepinephrine concentration

Accepted Answer

The decrease in bowel sounds, absence of flatus, or defecation in the immediate postoperative period is due to an increase in sympathetic activity, which is mediated by norepinephrine. This leads to a decrease in gastrointestinal motility, explaining the patient's symptoms. Increased plasma norepinephrine concentration is associated with increased sympathetic activity.

Question 19

A 25-year-old woman complains of chronic constipation and progressive weight gain over the past 6 months despite maintaining a pure vegan diet. Physical examination reveals a fatigued woman with brittle hair, face and eyelid puffiness, a symmetrically enlarged, non-tender thyroid gland, prolonged relaxation phase of deep tendon reflexes, and proximal muscle weakness in her lower extremities. Which set of the following results of thyroid function studies shown below would you expect in this patient? $$\begin{array} { l l l l } 
& \begin{array} { l } 
\text { Serum } \
\text { thyroxine } \
\left( \mathrm { T } _ { 4 } \right)
\end{array} & \begin{array} { l } 
\text { Serum } \
\text { thyroid- } \
\text { stimulating } \
\text { hormone } \
\text { (TSH) }
\end{array} & \begin{array} { l } 
131 \mathrm { I } \
\text { (radioactive } \
\text { iodine) } \
\text { uptake }
\end{array} \
\hline \text { A } & \text { Low } & \text { Low } & \text { Low } \
\mathrm { B } & \text { Low } & \text { High } & \text { Nomal } \
\mathrm { C } & \text { High } & \text { Low } & \text { Low } \
\mathrm { D } & \text { High } & \text { Low } & \text { High } \
\mathrm { E } & \text { Normal } & \text { Normal } & \text { Normal }
\end{array}$$
A) $\text {Low}$ $\quad $$\quad $$\text {Low}$$\quad $ $\quad $$\text {Low}$
B) $\begin{array}{llcc}
  \text {Low   } &  \text { High } &  \text { Normal }\
\end{array}$
 
C)$\begin{array}{llcc}
  \text { High } & \text {Low  } &  \text { Low }  \
\end{array}$

D)$\text { High } \quad \text { Low } \quad \text { High }$
E)$\text { Normal } \quad \text { Normal } \quad \text { Normal }$

Accepted Answer

The patient's symptoms suggest hypothyroidism, characterized by low serum thyroxine (T4) and high thyroid-stimulating hormone (TSH) due to the thyroid gland's inability to produce sufficient hormones, prompting the pituitary gland to release more TSH in an attempt to stimulate the thyroid.

Question 20

A 56-year-old obese woman suffering from heartburn and regurgitation of acid saliva after large meals is treated with cimetidine. During cimetidine treatment, her serum creatinine concentration increases significantly. The increase in serum creatinine with cimetidine treatment is most likely due to:
A) Being reabsorbed by the nephron in exchange for creatinine
B) Blocking synthesis of creatinine by skeletal muscle
C) Causing acute renal failure
D) Competing with creatinine for renal tubular secretion
E) Inhibiting uptake of creatinine ingested with food

Accepted Answer

Cimetidine can increase serum creatinine levels by competing with creatinine for renal tubular secretion, leading to decreased renal excretion of creatinine without necessarily indicating a decline in renal function.

Quiz 2: Physiology of Cells and Molecules

A 16-year-old boy has become totally deaf in his left ear after a motor vehicle accident even though hearing in his right ear is normal. A lesion at which of the following sites is the most likely cause of this finding?

A 45-year-old woman experiences blurred vision and difficulty swallowing after eating some home-canned vegetables. These symptoms are followed by respiratory distress and flaccid paralysis. The symptoms of her illness are most associated with which of the following?

A healthy 16-year-old man experiences severe hemorrhaging following an automobile accident. He is conscious and aware upon arrival at the emergency department, but hypotensive, and tachypneic. Which of the following is associated with the hemodynamic response to hemorrhage?

A 5-year-old boy has a history of growth retardation, pulmonary infections, and bulky, oily, malodorous stools. Which of the following test results would be expected in this patient?

The glomerular filtration rate (GFR) can be determined from:

Which of the following causes of brain hypoxia would most strongly stimulate the aortic and carotid chemoreceptors?

A 58-year-old woman has left hemiparesis and right ptosis (droopy eyelids) . She cannot adduct, elevate, or depress her right eye. The most likely cause of these findings is a lesion in which of the following sites?

A 23-year-old woman, who complains of chronic cough, shortness of breath, and chest tightness is diagnosed with asthma. Which of the following is the best clinical indicator of significant pulmonary obstruction in patients with asthma?

A 32-year-old female undergoes an appendectomy without complications, but has markedly reduced bowel sounds and an absence of flatus or defecation during the immediate postoperative period. Which of the following mechanisms best explains this decrease in bowel sounds?

A 56-year-old obese woman suffering from heartburn and regurgitation of acid saliva after large meals is treated with cimetidine. During cimetidine treatment, her serum creatinine concentration increases significantly. The increase in serum creatinine with cimetidine treatment is most likely due to: