1
PHYS 261 Human Physiology Combined Quizzes
1-4 Actual Exam 2026/2027 – Complete Exam-
Style Questions with Detailed Rationales | Pass
Guaranteed – A+ Graded
[QUIZ 1: Homeostasis, Cell Physiology & Membrane Transport — Questions 1-40]
Q1: Which of the following best describes the concept of "homeostasis" as defined by Claude
Bernard and Walter Cannon?
A. The ability of the body to generate heat to maintain a constant internal temperature regardless
of the external environment.
B. The dynamic physiological process by which the body maintains a relatively stable internal
environment despite changes in external conditions.
C. The unidirectional change in physiological parameters that occurs during the aging process.
D. The complete absence of fluctuation in blood glucose and blood pressure levels under all
conditions.
Correct Answer: B
Rationale: Homeostasis refers to the body's ability to maintain dynamic stability of its internal
environment (milieu intérieur) through feedback mechanisms, allowing for survival despite
external changes. While temperature regulation is a component (A), the definition is broader.
Parameters do fluctuate within a narrow range, so (D) is incorrect. It is not unidirectional (C).
Q2: In a negative feedback loop, which component detects a change in the variable?
A. Effector
B. Stimulus
C. Receptor (Sensor)
D. Control Center
Correct Answer: C
,2
Rationale: The receptor, or sensor, is the specific structure that monitors a physiological variable
(like temperature or blood pressure) and sends input to the control center. The stimulus is the
actual change (B), the control center integrates information (D), and the effector produces the
response (A).
Q3: Which of the following is an example of a positive feedback loop in the human body?
A. Regulation of body temperature during fever.
B. Control of blood sugar levels by insulin.
C. Oxytocin release during childbirth.
D. Baroreceptor reflex to lower blood pressure.
Correct Answer: C
Rationale: Positive feedback amplifies a change rather than reversing it. During childbirth,
uterine contractions stimulate oxytocin release, which causes stronger contractions, continuing
until delivery is complete. Temperature regulation (A) and blood sugar (B) are negative
feedback. The baroreceptor reflex (D) is also negative feedback.
Q4: According to the fluid mosaic model, what is the primary function of cholesterol molecules
within the plasma membrane?
A. Forming aqueous pores for ion transport.
B. Acting as a receptor for hydrophilic signaling molecules.
C. Stabilizing membrane fluidity by preventing the fatty acid tails from packing too closely
together at low temperatures.
D. Providing energy for active transport processes.
Correct Answer: C
Rationale: Cholesterol is a "fluidity buffer"; it fits between phospholipids to prevent them from
solidifying at low temperatures and prevents them from becoming too fluid at high temperatures.
It does not form pores (A) or act as a primary receptor (B), and it is structural, not an energy
source (D).
,3
Q5: Which type of membrane transport requires the direct hydrolysis of ATP to move substances
against their concentration gradient?
A. Simple diffusion
B. Facilitated diffusion
C. Primary active transport
D. Osmosis
Correct Answer: C
Rationale: Primary active transport, such as the Sodium-Potassium pump, directly uses energy
from ATP hydrolysis to move ions against their gradients. Simple and facilitated diffusion (A, B)
are passive and do not require energy. Osmosis (D) is the passive movement of water.
Q6: The sodium-potassium pump (Na+/K+ ATPase) transports which ions and in what ratio?
A. 2 Na+ out, 3 K+ in
B. 3 Na+ out, 2 K+ in
C. 3 Na+ in, 2 K+ out
D. 2 Na+ in, 3 K+ out
Correct Answer: B
Rationale: The Na+/K+ ATPase pumps three sodium ions out of the cell and two potassium ions
into the cell against their concentration gradients, utilizing one molecule of ATP per cycle. This
contributes to the negative resting membrane potential.
Q7: During secondary active transport, the energy used to move a molecule comes from:
A. Direct breakdown of ATP by the carrier protein.
B. The movement of a specific ion (usually Na+) down its electrochemical gradient established
by primary active transport.
C. The diffusion of water through aquaporins.
D. Thermal energy generated by the mitochondria.
, 4
Correct Answer: B
Rationale: Secondary active transport relies on the potential energy stored in the electrochemical
gradient of an ion (usually sodium) that was established by the Na+/K+ pump. It does not
directly split ATP (A) and is distinct from water movement (C).
Q8: Which type of endocytosis involves the cell engulfing large solid particles, such as bacteria
or cellular debris?
A. Pinocytosis
B. Receptor-mediated endocytosis
C. Phagocytosis
D. Exocytosis
Correct Answer: C
Rationale: Phagocytosis ("cell eating") is the process by which a cell engulfs large particles by
extending pseudopods. Pinocytosis (A) involves fluids; receptor-mediated endocytosis (B)
targets specific ligands; exocytosis (D) is the process of secretion, not intake.
Q9: What is the primary determinant of the resting membrane potential (RMP) in a typical
neuron?
A. The unequal distribution of Na+ ions across the membrane.
B. The diffusion of K+ out of the cell through leak channels.
C. The active transport of Cl- ions.
D. The complete impermeability of the membrane to Na+.
Correct Answer: B
Rationale: The RMP (approx -70 mV) is largely determined by the concentration gradient of
potassium and the membrane's high permeability to K+ via leak channels. K+ diffuses out of the
cell, leaving behind large negatively charged anions (proteins), making the inside negative.
PHYS 261 Human Physiology Combined Quizzes
1-4 Actual Exam 2026/2027 – Complete Exam-
Style Questions with Detailed Rationales | Pass
Guaranteed – A+ Graded
[QUIZ 1: Homeostasis, Cell Physiology & Membrane Transport — Questions 1-40]
Q1: Which of the following best describes the concept of "homeostasis" as defined by Claude
Bernard and Walter Cannon?
A. The ability of the body to generate heat to maintain a constant internal temperature regardless
of the external environment.
B. The dynamic physiological process by which the body maintains a relatively stable internal
environment despite changes in external conditions.
C. The unidirectional change in physiological parameters that occurs during the aging process.
D. The complete absence of fluctuation in blood glucose and blood pressure levels under all
conditions.
Correct Answer: B
Rationale: Homeostasis refers to the body's ability to maintain dynamic stability of its internal
environment (milieu intérieur) through feedback mechanisms, allowing for survival despite
external changes. While temperature regulation is a component (A), the definition is broader.
Parameters do fluctuate within a narrow range, so (D) is incorrect. It is not unidirectional (C).
Q2: In a negative feedback loop, which component detects a change in the variable?
A. Effector
B. Stimulus
C. Receptor (Sensor)
D. Control Center
Correct Answer: C
,2
Rationale: The receptor, or sensor, is the specific structure that monitors a physiological variable
(like temperature or blood pressure) and sends input to the control center. The stimulus is the
actual change (B), the control center integrates information (D), and the effector produces the
response (A).
Q3: Which of the following is an example of a positive feedback loop in the human body?
A. Regulation of body temperature during fever.
B. Control of blood sugar levels by insulin.
C. Oxytocin release during childbirth.
D. Baroreceptor reflex to lower blood pressure.
Correct Answer: C
Rationale: Positive feedback amplifies a change rather than reversing it. During childbirth,
uterine contractions stimulate oxytocin release, which causes stronger contractions, continuing
until delivery is complete. Temperature regulation (A) and blood sugar (B) are negative
feedback. The baroreceptor reflex (D) is also negative feedback.
Q4: According to the fluid mosaic model, what is the primary function of cholesterol molecules
within the plasma membrane?
A. Forming aqueous pores for ion transport.
B. Acting as a receptor for hydrophilic signaling molecules.
C. Stabilizing membrane fluidity by preventing the fatty acid tails from packing too closely
together at low temperatures.
D. Providing energy for active transport processes.
Correct Answer: C
Rationale: Cholesterol is a "fluidity buffer"; it fits between phospholipids to prevent them from
solidifying at low temperatures and prevents them from becoming too fluid at high temperatures.
It does not form pores (A) or act as a primary receptor (B), and it is structural, not an energy
source (D).
,3
Q5: Which type of membrane transport requires the direct hydrolysis of ATP to move substances
against their concentration gradient?
A. Simple diffusion
B. Facilitated diffusion
C. Primary active transport
D. Osmosis
Correct Answer: C
Rationale: Primary active transport, such as the Sodium-Potassium pump, directly uses energy
from ATP hydrolysis to move ions against their gradients. Simple and facilitated diffusion (A, B)
are passive and do not require energy. Osmosis (D) is the passive movement of water.
Q6: The sodium-potassium pump (Na+/K+ ATPase) transports which ions and in what ratio?
A. 2 Na+ out, 3 K+ in
B. 3 Na+ out, 2 K+ in
C. 3 Na+ in, 2 K+ out
D. 2 Na+ in, 3 K+ out
Correct Answer: B
Rationale: The Na+/K+ ATPase pumps three sodium ions out of the cell and two potassium ions
into the cell against their concentration gradients, utilizing one molecule of ATP per cycle. This
contributes to the negative resting membrane potential.
Q7: During secondary active transport, the energy used to move a molecule comes from:
A. Direct breakdown of ATP by the carrier protein.
B. The movement of a specific ion (usually Na+) down its electrochemical gradient established
by primary active transport.
C. The diffusion of water through aquaporins.
D. Thermal energy generated by the mitochondria.
, 4
Correct Answer: B
Rationale: Secondary active transport relies on the potential energy stored in the electrochemical
gradient of an ion (usually sodium) that was established by the Na+/K+ pump. It does not
directly split ATP (A) and is distinct from water movement (C).
Q8: Which type of endocytosis involves the cell engulfing large solid particles, such as bacteria
or cellular debris?
A. Pinocytosis
B. Receptor-mediated endocytosis
C. Phagocytosis
D. Exocytosis
Correct Answer: C
Rationale: Phagocytosis ("cell eating") is the process by which a cell engulfs large particles by
extending pseudopods. Pinocytosis (A) involves fluids; receptor-mediated endocytosis (B)
targets specific ligands; exocytosis (D) is the process of secretion, not intake.
Q9: What is the primary determinant of the resting membrane potential (RMP) in a typical
neuron?
A. The unequal distribution of Na+ ions across the membrane.
B. The diffusion of K+ out of the cell through leak channels.
C. The active transport of Cl- ions.
D. The complete impermeability of the membrane to Na+.
Correct Answer: B
Rationale: The RMP (approx -70 mV) is largely determined by the concentration gradient of
potassium and the membrane's high permeability to K+ via leak channels. K+ diffuses out of the
cell, leaving behind large negatively charged anions (proteins), making the inside negative.
