PHYS 261 HUMAN PHYSIOLOGY
MIDTERM EXAM QUESTIONS AND 100%
VERIFIED ANSWERS WITH RATIONALES
GRADED A+ LATEST
WEST COAST UNIVERSITY
1. A patient presents with decreased blood calcium levels. Which hormone is
primarily responsible for increasing calcium in the blood?
A. Calcitonin
B. Parathyroid hormone
C. Thyroxine
D. Aldosterone
Answer: B. Parathyroid hormone
Rationale: Parathyroid hormone (PTH) increases blood calcium levels by
stimulating osteoclast activity, increasing calcium absorption in the intestines, and
reducing calcium excretion by the kidneys.
2. During an action potential, which ion is primarily responsible for the
depolarization phase of a neuron?
A. Sodium
B. Potassium
C. Calcium
D. Chloride
Answer: A. Sodium
Rationale: Depolarization occurs when voltage-gated sodium channels open,
allowing Na⁺ to flow into the neuron, making the inside more positive.
,3. Which of the following best describes the Frank-Starling law of the heart?
A. Heart rate increases in response to sympathetic stimulation
B. Stroke volume increases with increased venous return
C. Blood pressure remains constant regardless of cardiac output
D. Contractility decreases as end-diastolic volume increases
Answer: B. Stroke volume increases with increased venous return
Rationale: The Frank-Starling law states that the heart pumps more forcefully
when more blood fills the ventricles, optimizing stroke volume.
4. A patient with a high fever is likely to have which effect on hemoglobin's
oxygen affinity?
A. Increased affinity (left shift)
B. Decreased affinity (right shift)
C. No change
D. Complete saturation of hemoglobin
Answer: B. Decreased affinity (right shift)
Rationale: Higher temperatures cause hemoglobin to release oxygen more easily
(Bohr effect), producing a rightward shift in the oxygen-hemoglobin dissociation
curve.
5. Which structure in the nephron is primarily responsible for the reabsorption of
glucose?
A. Loop of Henle
B. Distal convoluted tubule
C. Proximal convoluted tubule
D. Collecting duct
Answer: C. Proximal convoluted tubule
Rationale: The proximal convoluted tubule reabsorbs most nutrients, including
glucose, amino acids, and electrolytes, back into the bloodstream.
,6. Which type of muscle contraction occurs when muscle tension increases but the
muscle length does not change?
A. Isotonic
B. Isometric
C. Eccentric
D. Concentric
Answer: B. Isometric
Rationale: Isometric contraction generates tension without changing muscle
length. This is typical when holding a static position.
7. Which of the following is true regarding the primary pacemaker of the heart?
A. The AV node has the fastest intrinsic firing rate
B. The SA node initiates action potentials under normal conditions
C. Purkinje fibers control heart rate under normal conditions
D. Bundle of His initiates contraction before the SA node
Answer: B. The SA node initiates action potentials under normal conditions
Rationale: The sinoatrial (SA) node generates spontaneous depolarizations, setting
the normal heart rhythm.
8. A patient exhibits hyperventilation. Which of the following blood changes is
most likely?
A. Increased CO₂ and decreased pH
B. Decreased CO₂ and increased pH
C. Increased CO₂ and increased pH
D. Decreased CO₂ and decreased pH
Answer: B. Decreased CO₂ and increased pH
Rationale: Hyperventilation expels CO₂, reducing carbonic acid levels in the
blood and increasing pH, leading to respiratory alkalosis.
, 9. Which neurotransmitter is primarily excitatory in the central nervous system?
A. GABA
B. Glycine
C. Glutamate
D. Serotonin
Answer: C. Glutamate
Rationale: Glutamate is the main excitatory neurotransmitter in the CNS,
increasing the likelihood of postsynaptic neuron depolarization.
10. A decrease in baroreceptor firing would lead to:
A. Increased parasympathetic activity
B. Decreased heart rate
C. Increased sympathetic activity
D. Decreased cardiac output
Answer: C. Increased sympathetic activity
Rationale: Baroreceptors detect low blood pressure; decreased firing triggers
sympathetic activation, increasing heart rate and vascular resistance to restore BP.
11. Which organ produces erythropoietin in response to hypoxia?
A. Liver
B. Kidney
C. Spleen
D. Bone marrow
Answer: B. Kidney
Rationale: The kidney detects low oxygen levels and releases erythropoietin,
stimulating red blood cell production in the bone marrow.
MIDTERM EXAM QUESTIONS AND 100%
VERIFIED ANSWERS WITH RATIONALES
GRADED A+ LATEST
WEST COAST UNIVERSITY
1. A patient presents with decreased blood calcium levels. Which hormone is
primarily responsible for increasing calcium in the blood?
A. Calcitonin
B. Parathyroid hormone
C. Thyroxine
D. Aldosterone
Answer: B. Parathyroid hormone
Rationale: Parathyroid hormone (PTH) increases blood calcium levels by
stimulating osteoclast activity, increasing calcium absorption in the intestines, and
reducing calcium excretion by the kidneys.
2. During an action potential, which ion is primarily responsible for the
depolarization phase of a neuron?
A. Sodium
B. Potassium
C. Calcium
D. Chloride
Answer: A. Sodium
Rationale: Depolarization occurs when voltage-gated sodium channels open,
allowing Na⁺ to flow into the neuron, making the inside more positive.
,3. Which of the following best describes the Frank-Starling law of the heart?
A. Heart rate increases in response to sympathetic stimulation
B. Stroke volume increases with increased venous return
C. Blood pressure remains constant regardless of cardiac output
D. Contractility decreases as end-diastolic volume increases
Answer: B. Stroke volume increases with increased venous return
Rationale: The Frank-Starling law states that the heart pumps more forcefully
when more blood fills the ventricles, optimizing stroke volume.
4. A patient with a high fever is likely to have which effect on hemoglobin's
oxygen affinity?
A. Increased affinity (left shift)
B. Decreased affinity (right shift)
C. No change
D. Complete saturation of hemoglobin
Answer: B. Decreased affinity (right shift)
Rationale: Higher temperatures cause hemoglobin to release oxygen more easily
(Bohr effect), producing a rightward shift in the oxygen-hemoglobin dissociation
curve.
5. Which structure in the nephron is primarily responsible for the reabsorption of
glucose?
A. Loop of Henle
B. Distal convoluted tubule
C. Proximal convoluted tubule
D. Collecting duct
Answer: C. Proximal convoluted tubule
Rationale: The proximal convoluted tubule reabsorbs most nutrients, including
glucose, amino acids, and electrolytes, back into the bloodstream.
,6. Which type of muscle contraction occurs when muscle tension increases but the
muscle length does not change?
A. Isotonic
B. Isometric
C. Eccentric
D. Concentric
Answer: B. Isometric
Rationale: Isometric contraction generates tension without changing muscle
length. This is typical when holding a static position.
7. Which of the following is true regarding the primary pacemaker of the heart?
A. The AV node has the fastest intrinsic firing rate
B. The SA node initiates action potentials under normal conditions
C. Purkinje fibers control heart rate under normal conditions
D. Bundle of His initiates contraction before the SA node
Answer: B. The SA node initiates action potentials under normal conditions
Rationale: The sinoatrial (SA) node generates spontaneous depolarizations, setting
the normal heart rhythm.
8. A patient exhibits hyperventilation. Which of the following blood changes is
most likely?
A. Increased CO₂ and decreased pH
B. Decreased CO₂ and increased pH
C. Increased CO₂ and increased pH
D. Decreased CO₂ and decreased pH
Answer: B. Decreased CO₂ and increased pH
Rationale: Hyperventilation expels CO₂, reducing carbonic acid levels in the
blood and increasing pH, leading to respiratory alkalosis.
, 9. Which neurotransmitter is primarily excitatory in the central nervous system?
A. GABA
B. Glycine
C. Glutamate
D. Serotonin
Answer: C. Glutamate
Rationale: Glutamate is the main excitatory neurotransmitter in the CNS,
increasing the likelihood of postsynaptic neuron depolarization.
10. A decrease in baroreceptor firing would lead to:
A. Increased parasympathetic activity
B. Decreased heart rate
C. Increased sympathetic activity
D. Decreased cardiac output
Answer: C. Increased sympathetic activity
Rationale: Baroreceptors detect low blood pressure; decreased firing triggers
sympathetic activation, increasing heart rate and vascular resistance to restore BP.
11. Which organ produces erythropoietin in response to hypoxia?
A. Liver
B. Kidney
C. Spleen
D. Bone marrow
Answer: B. Kidney
Rationale: The kidney detects low oxygen levels and releases erythropoietin,
stimulating red blood cell production in the bone marrow.
