COMSAE Phase 1 Form 113 Practice Exam
Questions And Correct ANSWERs (Verified
ANSWERs) Plus Rationales 2025/2026 Q&A
ALREADY GRADED A+!!!!
1. The motor cortex responsible for voluntary movement is located in which gyrus?
A. Superior temporal gyrus
B. Precentral gyrus
C. Postcentral gyrus
D. Inferior frontal gyrus
Correct ANSWER: B. Precentral gyrus
Rationale: The primary motor cortex is located in the precentral gyrus of the frontal lobe and
controls voluntary movement. The superior temporal gyrus is involved in auditory processing,
the postcentral gyrus is the primary somatosensory cortex, and the inferior frontal gyrus
contains Broca's area for speech production.
2. Which amino acid is essential and a precursor for nitric oxide synthesis?
A. Lysine
B. Arginine
C. Glycine
D. Glutamine
,Correct ANSWER: B. Arginine
Rationale: Arginine is the substrate for nitric oxide synthase (NOS), which produces nitric oxide
(NO), a potent vasodilator. Lysine is involved in protein synthesis, glycine is an inhibitory
neurotransmitter, and glutamine is involved in nitrogen transport.
3. Which heart valve prevents backflow from the left ventricle into the left atrium?
A. Aortic valve
B. Pulmonary valve
C. Mitral valve
D. Tricuspid valve
Correct ANSWER: C. Mitral valve
Rationale: The mitral (bicuspid) valve is located between the left atrium and left ventricle,
preventing backflow during ventricular systole. The aortic valve prevents backflow from the
aorta, the pulmonary valve prevents backflow from the pulmonary artery, and the tricuspid
valve prevents backflow from the right ventricle to the right atrium.
4. Which of the following hormones is produced by the adrenal medulla?
A. Cortisol
B. Aldosterone
C. Epinephrine
D. Androstenedione
Correct ANSWER: C. Epinephrine
,Rationale: The adrenal medulla produces catecholamines including epinephrine and
norepinephrine. Cortisol and aldosterone are produced by the adrenal cortex, and
androstenedione is also produced by the adrenal cortex as a sex hormone precursor.
5. The primary function of the loop of Henle is which of the following?
A. Filtration of blood
B. Reabsorption of glucose
C. Concentration of urine
D. Secretion of renin
Correct ANSWER: C. Concentration of urine
Rationale: The loop of Henle establishes a concentration gradient in the renal medulla through
countercurrent multiplication, allowing for urine concentration. Filtration occurs in the
glomerulus, glucose reabsorption occurs in the proximal convoluted tubule, and renin is
secreted by juxtaglomerular cells.
6. Which immunoglobulin is primarily involved in allergic reactions?
A. IgA
B. IgM
C. IgE
D. IgG
Correct ANSWER: C. IgE
Rationale: IgE binds to mast cells and basophils, triggering histamine release during allergic
reactions. IgA is found in mucosal secretions, IgM is the first antibody produced during
infection, and IgG is the most abundant antibody in serum.
, 7. The pacemaker of the heart is located in which structure?
A. Atrioventricular node
B. Sinoatrial node
C. Bundle of His
D. Purkinje fibers
Correct ANSWER: B. Sinoatrial node
Rationale: The sinoatrial (SA) node is the primary pacemaker of the heart, located in the right
atrium. The AV node serves as the secondary pacemaker, the Bundle of His conducts impulses
to ventricles, and Purkinje fibers distribute impulses through the ventricular myocardium.
8. Which vitamin is required for calcium absorption in the gastrointestinal tract?
A. Vitamin A
B. Vitamin B12
C. Vitamin C
D. Vitamin D
Correct ANSWER: D. Vitamin D
Rationale: Vitamin D (calcitriol) promotes calcium absorption from the intestine. Vitamin A is
important for vision, Vitamin B12 is essential for red blood cell formation, and Vitamin C is
important for collagen synthesis and antioxidant function.
9. Which neurotransmitter is deficient in Parkinson's disease?
A. Serotonin
B. Acetylcholine
Questions And Correct ANSWERs (Verified
ANSWERs) Plus Rationales 2025/2026 Q&A
ALREADY GRADED A+!!!!
1. The motor cortex responsible for voluntary movement is located in which gyrus?
A. Superior temporal gyrus
B. Precentral gyrus
C. Postcentral gyrus
D. Inferior frontal gyrus
Correct ANSWER: B. Precentral gyrus
Rationale: The primary motor cortex is located in the precentral gyrus of the frontal lobe and
controls voluntary movement. The superior temporal gyrus is involved in auditory processing,
the postcentral gyrus is the primary somatosensory cortex, and the inferior frontal gyrus
contains Broca's area for speech production.
2. Which amino acid is essential and a precursor for nitric oxide synthesis?
A. Lysine
B. Arginine
C. Glycine
D. Glutamine
,Correct ANSWER: B. Arginine
Rationale: Arginine is the substrate for nitric oxide synthase (NOS), which produces nitric oxide
(NO), a potent vasodilator. Lysine is involved in protein synthesis, glycine is an inhibitory
neurotransmitter, and glutamine is involved in nitrogen transport.
3. Which heart valve prevents backflow from the left ventricle into the left atrium?
A. Aortic valve
B. Pulmonary valve
C. Mitral valve
D. Tricuspid valve
Correct ANSWER: C. Mitral valve
Rationale: The mitral (bicuspid) valve is located between the left atrium and left ventricle,
preventing backflow during ventricular systole. The aortic valve prevents backflow from the
aorta, the pulmonary valve prevents backflow from the pulmonary artery, and the tricuspid
valve prevents backflow from the right ventricle to the right atrium.
4. Which of the following hormones is produced by the adrenal medulla?
A. Cortisol
B. Aldosterone
C. Epinephrine
D. Androstenedione
Correct ANSWER: C. Epinephrine
,Rationale: The adrenal medulla produces catecholamines including epinephrine and
norepinephrine. Cortisol and aldosterone are produced by the adrenal cortex, and
androstenedione is also produced by the adrenal cortex as a sex hormone precursor.
5. The primary function of the loop of Henle is which of the following?
A. Filtration of blood
B. Reabsorption of glucose
C. Concentration of urine
D. Secretion of renin
Correct ANSWER: C. Concentration of urine
Rationale: The loop of Henle establishes a concentration gradient in the renal medulla through
countercurrent multiplication, allowing for urine concentration. Filtration occurs in the
glomerulus, glucose reabsorption occurs in the proximal convoluted tubule, and renin is
secreted by juxtaglomerular cells.
6. Which immunoglobulin is primarily involved in allergic reactions?
A. IgA
B. IgM
C. IgE
D. IgG
Correct ANSWER: C. IgE
Rationale: IgE binds to mast cells and basophils, triggering histamine release during allergic
reactions. IgA is found in mucosal secretions, IgM is the first antibody produced during
infection, and IgG is the most abundant antibody in serum.
, 7. The pacemaker of the heart is located in which structure?
A. Atrioventricular node
B. Sinoatrial node
C. Bundle of His
D. Purkinje fibers
Correct ANSWER: B. Sinoatrial node
Rationale: The sinoatrial (SA) node is the primary pacemaker of the heart, located in the right
atrium. The AV node serves as the secondary pacemaker, the Bundle of His conducts impulses
to ventricles, and Purkinje fibers distribute impulses through the ventricular myocardium.
8. Which vitamin is required for calcium absorption in the gastrointestinal tract?
A. Vitamin A
B. Vitamin B12
C. Vitamin C
D. Vitamin D
Correct ANSWER: D. Vitamin D
Rationale: Vitamin D (calcitriol) promotes calcium absorption from the intestine. Vitamin A is
important for vision, Vitamin B12 is essential for red blood cell formation, and Vitamin C is
important for collagen synthesis and antioxidant function.
9. Which neurotransmitter is deficient in Parkinson's disease?
A. Serotonin
B. Acetylcholine
