NBME 28
Exam Section 1: Item 1 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
1. A 25-year-old man was brought to the emergency department because of severe
abdominal pain, nausea, and vomiting for 1 hour. The pain originates in the left flank
and radiates to his groin. His pulse is 100/min, respirations are 18/min, and blood
pressure is
150/100 mm Hg. Physical examination shows tenderness of the left flank and the left
lower quadrant of the abdomen. Bowel sounds are mildly hypoactive. Test of the
stool for occult blood is negative. Which of the following best explains these
findings?
A) Colon neoplasm
B) Diverticulitis
C) Epididymitis
D) Renal infarction
E) Torsion of the testis
F) Ureteral calculus - ANS-F.
Ureteral calculus typically presents with colicky, unilateral flank pain radiating to the
groin, and with gross or microscopic hematuria. Pain may be significant enough to
trigger nausea, as in this case. The common types of urinary tract calculi are calcium
oxalate or
phosphate, ammonium magnesium phosphate, uric acid, and cystine. On urinalysis,
red blood cells without casts are common. Fever, dysuria, and pyuria would not be
expected unless there was a concomitant infection. Treatment for ureteral calculus is
symptomatic with pain control and nausea relief. Most ureteral calculi pass
spontaneously after a period of observation for patients with well-controlled pain and
no signs of sepsis or infection. Stone removal by shock wave lithotripsy or
endoscopic removal is an
option for patients requiring emergency therapy. It is also an option for patients with
persistent obstruction, uncontrolled symptoms, or failure of stone progression. In
general, stones smaller than 5 mm will pass without operative assistance.
Obstructing stones may
require temporary placement of a ureteral stent to prevent hydronephrosis and renal
parenchymal injury.
Incorrect Answers: A, B, C, D, and E.
Colon neoplasm (Choice A) would be unlikely in an otherwise healthy young patient
with no family history of polyposis syndromes and acute, severe, flank pain. It would
typically present with insidious weight loss, anemia, constipation, or blood per
rectum. In
addition, test for stool for occult blood is negative, making this diagnosis unlikely.
,Diverticulitis (Choice B) can present with left lower quadrant abdominal pain and
tenderness but would be less abrupt in presentation and typically present with fever,
diarrhea, and hyperactive bowel sounds. It would be unlikely to cause flank pain.
Epididymitis (Choice C) is a common cause of painful scrot
\2
Exam Section 1: Item 2 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
2. Which of the following types of sensory information is compromised by lesions of
the structure at site X in the photograph shown?
A) Conscious proprioception
B) Pain sensation
C) Two-point discrimination
D) Unconscious proprioception
E) Vibration sense - ANS-D.
The anterior lobe of the cerebellum (labeled X, pictured in cross-section as an
arborized brain area posterior to the brainstem and anterior to the primary fissure of
the cerebellum) mediates unconscious proprioception. The anterior lobe of the
cerebellum receives
information from the spinocerebellar tract about proprioception, or body position, that
is gathered from muscle stretch and tension receptors on the ipsilateral side of the
body. This proprioceptive information is transmitted outside of conscious awareness.
The deep
cerebellar nuclei use this proprioceptive information to control motor learning,
movement course changes, and balance. Damage to the anterior lobe of the
cerebellum, which commonly occurs in chronic alcoholism, may lead to broad-based
gait ataxia.
Incorrect Answers: A, B, C, and E.
Conscious proprioception (Choice A), two-point discrimination (Choice C), and
vibration sense (Choice E) are mediated by the dorsal column-medial lemniscus
pathway, which relays this sensory information up the spinal cord to the thalamus
and terminates in the
primary sensory cortex in the parietal lobe. The cortex is a high-order brain area
involved in several conscious brain functions, which reflects this pathway's mediation
of the conscious (rather than unconscious) awareness of proprioception.
Pain sensation (Choice B) is mediated by the spinothalamic pathway. The
spinothalamic pathway transmits information about pain, temperature, and crude
touch up the spinal cord to the thalamus, terminating in the primary sensory cortex.
Educational Objective: The anterior lobe of the cerebellum mediates unconscious
proprioception, whereas conscious proprioception is controlled by the dorsal
column-medial lemniscus pathway. Lesions of the anterior lobe of the cerebellum
can result in broad-
based gait ataxia.
%3D
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Next
\3
Exam Section 1: Item 3 of 50
National Board of Medical Examiners®
Comprehensive Basic Science Self-Assessment
3. Moving the forearm against resistance from palm-down to palm-up (supination)
position requires the use of which of the following muscles?
A) Biceps brachii
B) Brachialis
OC) Triceps
D) Flexor carpi radialis
E) Pronator teres - ANS-A.
The biceps brachii muscle has two main actions, flexion of the elbow joint and
supination of the forearm. The biceps brachii contains two proximal heads, with the
short head attaching to the coracoid process of the scapula and the long head
entering the shoulder
joint and attaching to the supraglenoid tubercle. The distal biceps tendon inserts on
the bicipital tuberosity of the proximal radius. Because of its orientation crossing the
elbow joint, contraction of this muscle causes elbow flexion. Its eccentric insertion on
the
proximal radius allows for it to wind around the radius during pronation and unwind
when contracted from around the proximal radius during supination.
Incorrect Answers: B, C, D and E.
The brachialis muscle (Choice B) originates on the anterior surface of the humerus
and crosses the elbow inserting on the tuberosity of the ulna. It does not wrap
around the ulna and the ulna does not rotate. Because of this, it does not contribute
to supination or
pronation.
The triceps muscle (Choice C) serves to extend the elbow joint. Proximally, it
originates from the infraglenoid tubercle of the scapula (long head), just proximal to
the radial groove (lateral head), and just distal to the radial groove (medial head).
Distally, it inserts on
the olecranon process of the ulna. Contraction of this muscle extends the elbow and
does not contribute to rotation.
Flexor carpi radialis (Choice D) originates on the medial epicondyle of the humerus
and inserts on the second and third metacarpal bones. This allows for flexion of the
wrist.
Pronator teres (Choice E) is a muscle of the proximal forearm that extends from the
medial supracondylar ridge of the humerus and inserts on the lateral aspect of the
radius. Contraction along this axis will promote pronation, not supination.
Educational Objective: The biceps brachii
\4
Exam Section 1: Item 4 of 50
, National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
4. A 35-year-old man is admitted to the hospital because of a 5-day history of fever
and dyspnea. He underwent a bone marrow transplantation 6 months ago; the
procedure was complicated by severe graft-versus-host disease. His temperature is
38°C
(100.4°F), and respirations are 30/min. Scattered crackles are heard on auscultation
of the chest. A chest x-ray shows patchy infiltrates. A transbronchial biopsy
specimen shows findings consistent with cytomegalovirus infection. Intravenous
administration of
ganciclovir is begun. This drug interferes with the function of which of the following
enzymes?
A) DNA polymerase
B) Integrase
C) Reverse transcriptase
D) RNA polymerase
E) Thymidine kinase - ANS-A.
Cytomegalovirus (CMV), also known as human herpesvirus 5 (HHV-5), is an
opportunistic infection commonly occurring in immunocompromised patients with
solid-organ or allogeneic bone marrow transplantation, severe ulcerative colitis, or
HIV/AIDS infection. It
can be transmitted through multiple modes, including sexual contact, urine,
respiratory droplets, and to a fetus via the placenta. It can cause a variety of
presentations, including mononucleosis in immunocompetent patients, and retinitis,
esophagitis, and pneumonia
in immunocompromised patients. Treatment for all human herpesvirus infections
involves drugs that inhibit viral DNA polymerase, classically by guanosine analogs
such as acyclovir, valacyclovir, and famciclovir. Prior to exerting their antiviral effects,
most
guanosine analogs must be phosphorylated by the viral enzyme thymidine kinase.
They are then able to inhibit the viral DNA polymerase by terminating the nascent
DNA chain during replication. These drugs are effective against herpes simplex virus
and varicella
zoster virus, weakly effective against Épstein-Barr virus, and not effective against
CMV, which does not have the necessary thymidine kinase needed for
phosphorylation. However, it does have the necessary phosphorylating enzyme to
activate ganciclovir, another
guanosine analog that inhibits DNA polymerase, and thus this is an effective
anti-viral treatment for CMV.
Incorrect Answers: B, C, D, and E.
Integrase inhibitors (Choice B) prevent integration of proviral DNA into the host
genome. They are a component of the highly active anti-retroviral therapy utilized in
the treatment of HIV.
Exam Section 1: Item 1 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
1. A 25-year-old man was brought to the emergency department because of severe
abdominal pain, nausea, and vomiting for 1 hour. The pain originates in the left flank
and radiates to his groin. His pulse is 100/min, respirations are 18/min, and blood
pressure is
150/100 mm Hg. Physical examination shows tenderness of the left flank and the left
lower quadrant of the abdomen. Bowel sounds are mildly hypoactive. Test of the
stool for occult blood is negative. Which of the following best explains these
findings?
A) Colon neoplasm
B) Diverticulitis
C) Epididymitis
D) Renal infarction
E) Torsion of the testis
F) Ureteral calculus - ANS-F.
Ureteral calculus typically presents with colicky, unilateral flank pain radiating to the
groin, and with gross or microscopic hematuria. Pain may be significant enough to
trigger nausea, as in this case. The common types of urinary tract calculi are calcium
oxalate or
phosphate, ammonium magnesium phosphate, uric acid, and cystine. On urinalysis,
red blood cells without casts are common. Fever, dysuria, and pyuria would not be
expected unless there was a concomitant infection. Treatment for ureteral calculus is
symptomatic with pain control and nausea relief. Most ureteral calculi pass
spontaneously after a period of observation for patients with well-controlled pain and
no signs of sepsis or infection. Stone removal by shock wave lithotripsy or
endoscopic removal is an
option for patients requiring emergency therapy. It is also an option for patients with
persistent obstruction, uncontrolled symptoms, or failure of stone progression. In
general, stones smaller than 5 mm will pass without operative assistance.
Obstructing stones may
require temporary placement of a ureteral stent to prevent hydronephrosis and renal
parenchymal injury.
Incorrect Answers: A, B, C, D, and E.
Colon neoplasm (Choice A) would be unlikely in an otherwise healthy young patient
with no family history of polyposis syndromes and acute, severe, flank pain. It would
typically present with insidious weight loss, anemia, constipation, or blood per
rectum. In
addition, test for stool for occult blood is negative, making this diagnosis unlikely.
,Diverticulitis (Choice B) can present with left lower quadrant abdominal pain and
tenderness but would be less abrupt in presentation and typically present with fever,
diarrhea, and hyperactive bowel sounds. It would be unlikely to cause flank pain.
Epididymitis (Choice C) is a common cause of painful scrot
\2
Exam Section 1: Item 2 of 50
National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
2. Which of the following types of sensory information is compromised by lesions of
the structure at site X in the photograph shown?
A) Conscious proprioception
B) Pain sensation
C) Two-point discrimination
D) Unconscious proprioception
E) Vibration sense - ANS-D.
The anterior lobe of the cerebellum (labeled X, pictured in cross-section as an
arborized brain area posterior to the brainstem and anterior to the primary fissure of
the cerebellum) mediates unconscious proprioception. The anterior lobe of the
cerebellum receives
information from the spinocerebellar tract about proprioception, or body position, that
is gathered from muscle stretch and tension receptors on the ipsilateral side of the
body. This proprioceptive information is transmitted outside of conscious awareness.
The deep
cerebellar nuclei use this proprioceptive information to control motor learning,
movement course changes, and balance. Damage to the anterior lobe of the
cerebellum, which commonly occurs in chronic alcoholism, may lead to broad-based
gait ataxia.
Incorrect Answers: A, B, C, and E.
Conscious proprioception (Choice A), two-point discrimination (Choice C), and
vibration sense (Choice E) are mediated by the dorsal column-medial lemniscus
pathway, which relays this sensory information up the spinal cord to the thalamus
and terminates in the
primary sensory cortex in the parietal lobe. The cortex is a high-order brain area
involved in several conscious brain functions, which reflects this pathway's mediation
of the conscious (rather than unconscious) awareness of proprioception.
Pain sensation (Choice B) is mediated by the spinothalamic pathway. The
spinothalamic pathway transmits information about pain, temperature, and crude
touch up the spinal cord to the thalamus, terminating in the primary sensory cortex.
Educational Objective: The anterior lobe of the cerebellum mediates unconscious
proprioception, whereas conscious proprioception is controlled by the dorsal
column-medial lemniscus pathway. Lesions of the anterior lobe of the cerebellum
can result in broad-
based gait ataxia.
%3D
,Previous
Next
\3
Exam Section 1: Item 3 of 50
National Board of Medical Examiners®
Comprehensive Basic Science Self-Assessment
3. Moving the forearm against resistance from palm-down to palm-up (supination)
position requires the use of which of the following muscles?
A) Biceps brachii
B) Brachialis
OC) Triceps
D) Flexor carpi radialis
E) Pronator teres - ANS-A.
The biceps brachii muscle has two main actions, flexion of the elbow joint and
supination of the forearm. The biceps brachii contains two proximal heads, with the
short head attaching to the coracoid process of the scapula and the long head
entering the shoulder
joint and attaching to the supraglenoid tubercle. The distal biceps tendon inserts on
the bicipital tuberosity of the proximal radius. Because of its orientation crossing the
elbow joint, contraction of this muscle causes elbow flexion. Its eccentric insertion on
the
proximal radius allows for it to wind around the radius during pronation and unwind
when contracted from around the proximal radius during supination.
Incorrect Answers: B, C, D and E.
The brachialis muscle (Choice B) originates on the anterior surface of the humerus
and crosses the elbow inserting on the tuberosity of the ulna. It does not wrap
around the ulna and the ulna does not rotate. Because of this, it does not contribute
to supination or
pronation.
The triceps muscle (Choice C) serves to extend the elbow joint. Proximally, it
originates from the infraglenoid tubercle of the scapula (long head), just proximal to
the radial groove (lateral head), and just distal to the radial groove (medial head).
Distally, it inserts on
the olecranon process of the ulna. Contraction of this muscle extends the elbow and
does not contribute to rotation.
Flexor carpi radialis (Choice D) originates on the medial epicondyle of the humerus
and inserts on the second and third metacarpal bones. This allows for flexion of the
wrist.
Pronator teres (Choice E) is a muscle of the proximal forearm that extends from the
medial supracondylar ridge of the humerus and inserts on the lateral aspect of the
radius. Contraction along this axis will promote pronation, not supination.
Educational Objective: The biceps brachii
\4
Exam Section 1: Item 4 of 50
, National Board of Medical Examiners'
Comprehensive Basic Science Self-Assessment
4. A 35-year-old man is admitted to the hospital because of a 5-day history of fever
and dyspnea. He underwent a bone marrow transplantation 6 months ago; the
procedure was complicated by severe graft-versus-host disease. His temperature is
38°C
(100.4°F), and respirations are 30/min. Scattered crackles are heard on auscultation
of the chest. A chest x-ray shows patchy infiltrates. A transbronchial biopsy
specimen shows findings consistent with cytomegalovirus infection. Intravenous
administration of
ganciclovir is begun. This drug interferes with the function of which of the following
enzymes?
A) DNA polymerase
B) Integrase
C) Reverse transcriptase
D) RNA polymerase
E) Thymidine kinase - ANS-A.
Cytomegalovirus (CMV), also known as human herpesvirus 5 (HHV-5), is an
opportunistic infection commonly occurring in immunocompromised patients with
solid-organ or allogeneic bone marrow transplantation, severe ulcerative colitis, or
HIV/AIDS infection. It
can be transmitted through multiple modes, including sexual contact, urine,
respiratory droplets, and to a fetus via the placenta. It can cause a variety of
presentations, including mononucleosis in immunocompetent patients, and retinitis,
esophagitis, and pneumonia
in immunocompromised patients. Treatment for all human herpesvirus infections
involves drugs that inhibit viral DNA polymerase, classically by guanosine analogs
such as acyclovir, valacyclovir, and famciclovir. Prior to exerting their antiviral effects,
most
guanosine analogs must be phosphorylated by the viral enzyme thymidine kinase.
They are then able to inhibit the viral DNA polymerase by terminating the nascent
DNA chain during replication. These drugs are effective against herpes simplex virus
and varicella
zoster virus, weakly effective against Épstein-Barr virus, and not effective against
CMV, which does not have the necessary thymidine kinase needed for
phosphorylation. However, it does have the necessary phosphorylating enzyme to
activate ganciclovir, another
guanosine analog that inhibits DNA polymerase, and thus this is an effective
anti-viral treatment for CMV.
Incorrect Answers: B, C, D, and E.
Integrase inhibitors (Choice B) prevent integration of proviral DNA into the host
genome. They are a component of the highly active anti-retroviral therapy utilized in
the treatment of HIV.
