1
WGU D312 Anatomy and Physiology I
Objective Assessment Actual Exam
2026/2027 | Questions with Verified
Answers | 100% Correct | Pass
Guaranteed
Q001: A 25-year-old runner experiences a rapid increase in heart rate at the start of
a sprint. Which membrane structure within cardiac pacemaker cells is primarily
responsible for the initial depolarization phase that propagates the action potential?
Options:
A. Rough endoplasmic reticulum
B. Sarcolemma with voltage-gated Na⁺ channels
C. Sarcolemma with specialized leak K⁺ channels
D. Golgi apparatus
ANSWER: B
Rationale: The sarcolemma of pacemaker cells contains voltage-gated Na⁺
channels that open in response to initial depolarization, allowing Na⁺ influx and
propagating the action potential throughout the heart.
Q002: During weightlifting, a 30-year-old man feels a "burn" in his biceps. Which
physiological process involving ion gradients across the sarcolemma is most
directly responsible for this sensation?
Options:
A. Na⁺/K⁺ pump failure
, 2
B. K⁺ efflux during repolarization
C. Ca²⁺ influx through L-type channels
D. Cl⁻ influx inhibiting contraction
ANSWER: B
Rationale: K⁺ efflux during repolarization increases extracellular K⁺, depolarizing
nociceptors and causing the burning sensation associated with muscle fatigue.
Q003: A 22-year-old woman receives a flu vaccine. Which organelle in antigen-
presenting cells is primarily responsible for processing viral proteins for display on
MHC class I molecules?
Options:
A. Mitochondrion
B. Rough endoplasmic reticulum
C. Lysosome
D. Peroxisome
ANSWER: B
Rationale: The rough endoplasmic reticulum processes and folds viral proteins for
loading onto MHC class I molecules, enabling cytotoxic T-cell recognition.
Q004: A 40-year-old man with psoriasis notices thickened skin plaques. Which
epidermal layer, when hyperproliferative, contributes most to this thickening?
Options:
A. Stratum corneum
B. Stratum basale
C. Stratum lucidum
D. Stratum granulosum
ANSWER: B
, 3
Rationale: The stratum basale contains mitotically active keratinocytes;
hyperproliferation here leads to increased epidermal thickness seen in psoriasis.
Q005: A 19-year-old female sprains her ankle. Which type of cartilage, rich in
collagen fibers, is most abundant in the injured joint capsule and ligaments?
Options:
A. Hyaline cartilage
B. Dense regular connective tissue
C. Elastic cartilage
D. Fibrocartilage
ANSWER: B
Rationale: Dense regular connective tissue forms ligaments and joint capsules,
providing tensile strength to stabilize joints during injury.
Q006: A 35-year-old man fractures his tibia. Which cell type, derived from
mesenchyme, is primarily responsible for laying down new bone matrix during
healing?
Options:
A. Osteoclast
B. Osteoblast
C. Chondrocyte
D. Fibroblast
ANSWER: B
Rationale: Osteoblasts synthesize and secrete osteoid, the organic matrix of bone,
which mineralizes to form new bone during fracture healing.
Q007: A 28-year-old woman undergoes resistance training. Which microscopic
structure within skeletal muscle fibers increases in number to enhance force
production?
Options:
, 4
A. Sarcoplasmic reticulum
B. Myofibril
C. Mitochondrion
D. Nucleus
ANSWER: B
Rationale: Myofibrils contain sarcomeres; hypertrophy increases myofibril
number, adding sarcomeres in parallel to boost contractile force.
Q008: A 45-year-old man experiences muscle cramps after diuretic use. Which ion,
primarily stored in the sarcoplasmic reticulum, is most critical for muscle
relaxation and preventing cramps?
Options:
A. Sodium
B. Calcium
C. Potassium
D. Chloride
ANSWER: B
Rationale: Calcium reuptake into the sarcoplasmic reticulum allows troponin-
tropomyosin to block actin-myosin binding, enabling relaxation; hypocalcemia
predisposes to cramps.
Q009: A 30-year-old female marathoner develops dark urine after a race. Which
muscle protein, when released into plasma, is most indicative of rhabdomyolysis?
Options:
A. Troponin I
B. Myoglobin
C. Creatine kinase
D. Lactate dehydrogenase
WGU D312 Anatomy and Physiology I
Objective Assessment Actual Exam
2026/2027 | Questions with Verified
Answers | 100% Correct | Pass
Guaranteed
Q001: A 25-year-old runner experiences a rapid increase in heart rate at the start of
a sprint. Which membrane structure within cardiac pacemaker cells is primarily
responsible for the initial depolarization phase that propagates the action potential?
Options:
A. Rough endoplasmic reticulum
B. Sarcolemma with voltage-gated Na⁺ channels
C. Sarcolemma with specialized leak K⁺ channels
D. Golgi apparatus
ANSWER: B
Rationale: The sarcolemma of pacemaker cells contains voltage-gated Na⁺
channels that open in response to initial depolarization, allowing Na⁺ influx and
propagating the action potential throughout the heart.
Q002: During weightlifting, a 30-year-old man feels a "burn" in his biceps. Which
physiological process involving ion gradients across the sarcolemma is most
directly responsible for this sensation?
Options:
A. Na⁺/K⁺ pump failure
, 2
B. K⁺ efflux during repolarization
C. Ca²⁺ influx through L-type channels
D. Cl⁻ influx inhibiting contraction
ANSWER: B
Rationale: K⁺ efflux during repolarization increases extracellular K⁺, depolarizing
nociceptors and causing the burning sensation associated with muscle fatigue.
Q003: A 22-year-old woman receives a flu vaccine. Which organelle in antigen-
presenting cells is primarily responsible for processing viral proteins for display on
MHC class I molecules?
Options:
A. Mitochondrion
B. Rough endoplasmic reticulum
C. Lysosome
D. Peroxisome
ANSWER: B
Rationale: The rough endoplasmic reticulum processes and folds viral proteins for
loading onto MHC class I molecules, enabling cytotoxic T-cell recognition.
Q004: A 40-year-old man with psoriasis notices thickened skin plaques. Which
epidermal layer, when hyperproliferative, contributes most to this thickening?
Options:
A. Stratum corneum
B. Stratum basale
C. Stratum lucidum
D. Stratum granulosum
ANSWER: B
, 3
Rationale: The stratum basale contains mitotically active keratinocytes;
hyperproliferation here leads to increased epidermal thickness seen in psoriasis.
Q005: A 19-year-old female sprains her ankle. Which type of cartilage, rich in
collagen fibers, is most abundant in the injured joint capsule and ligaments?
Options:
A. Hyaline cartilage
B. Dense regular connective tissue
C. Elastic cartilage
D. Fibrocartilage
ANSWER: B
Rationale: Dense regular connective tissue forms ligaments and joint capsules,
providing tensile strength to stabilize joints during injury.
Q006: A 35-year-old man fractures his tibia. Which cell type, derived from
mesenchyme, is primarily responsible for laying down new bone matrix during
healing?
Options:
A. Osteoclast
B. Osteoblast
C. Chondrocyte
D. Fibroblast
ANSWER: B
Rationale: Osteoblasts synthesize and secrete osteoid, the organic matrix of bone,
which mineralizes to form new bone during fracture healing.
Q007: A 28-year-old woman undergoes resistance training. Which microscopic
structure within skeletal muscle fibers increases in number to enhance force
production?
Options:
, 4
A. Sarcoplasmic reticulum
B. Myofibril
C. Mitochondrion
D. Nucleus
ANSWER: B
Rationale: Myofibrils contain sarcomeres; hypertrophy increases myofibril
number, adding sarcomeres in parallel to boost contractile force.
Q008: A 45-year-old man experiences muscle cramps after diuretic use. Which ion,
primarily stored in the sarcoplasmic reticulum, is most critical for muscle
relaxation and preventing cramps?
Options:
A. Sodium
B. Calcium
C. Potassium
D. Chloride
ANSWER: B
Rationale: Calcium reuptake into the sarcoplasmic reticulum allows troponin-
tropomyosin to block actin-myosin binding, enabling relaxation; hypocalcemia
predisposes to cramps.
Q009: A 30-year-old female marathoner develops dark urine after a race. Which
muscle protein, when released into plasma, is most indicative of rhabdomyolysis?
Options:
A. Troponin I
B. Myoglobin
C. Creatine kinase
D. Lactate dehydrogenase
