NU110 Exam 2 Actual Exam Style V3
1. Which layer of the epidermis is responsible for the continuous production of new skin cells
through mitosis?
A. Stratum basale
B. Stratum corneum
C. Stratum lucidum
D. Stratum spinosum
Correct Answer: A
Expert Explanation: The stratum basale is the deepest layer of the epidermis and contains
stem cells that undergo rapid cell division. As new cells are produced, they are pushed
upward toward the surface to replace older cells. This layer is crucial for skin regeneration
and maintaining the integrity of the integumentary system.
2. During an action potential, what occurs immediately after the threshold potential is
reached?
A. Potassium channels open, causing repolarization
B. Sodium-potassium pumps stop working
C. Voltage-gated sodium channels open, causing depolarization
D. Calcium ions are sequestered into the sarcoplasmic reticulum
Correct Answer: C
,Expert Explanation: Once the threshold potential is reached, voltage-gated sodium
channels open rapidly, allowing an influx of sodium ions into the cell. This influx causes the
membrane potential to become more positive, a process known as depolarization. This step
is essential for the propagation of the electrical signal along the axon.
3. What is the primary role of the sarcoplasmic reticulum in skeletal muscle contraction?
A. Synthesizing ATP for cross-bridge cycling
B. Binding to troponin to expose myosin-binding sites
C. Transmitting action potentials into the cell interior
D. Storing and releasing calcium ions
Correct Answer: D
Expert Explanation: The sarcoplasmic reticulum acts as a specialized calcium storage
organelle within muscle fibers. When an action potential reaches the muscle cell, calcium is
released from this structure into the sarcoplasm to initiate contraction. This release is a
critical step in the excitation-contraction coupling mechanism.
4. In the process of bone remodeling, which cells are primarily responsible for the resorption
of bone matrix?
A. Osteoblasts
B. Osteocytes
C. Osteoclasts
, D. Osteoprogenitor cells
Correct Answer: C
Expert Explanation: Osteoclasts are large, multinucleated cells that break down bone
tissue by secreting acid and enzymes. This process releases stored minerals like calcium
into the blood to maintain homeostasis. Bone resorption must be balanced with bone
formation to ensure skeletal strength and health.
5. Which neurotransmitter is released at the neuromuscular junction to stimulate skeletal
muscle contraction?
A. Dopamine
B. Acetylcholine
C. Serotonin
D. Norepinephrine
Correct Answer: B
Expert Explanation: Acetylcholine is the specific neurotransmitter that bridges the gap
between the motor neuron and the muscle fiber. It binds to nicotinic receptors on the
motor end plate, leading to a localized depolarization. This depolarization eventually
triggers the action potential necessary for muscle contraction.
6. Which type of burn is characterized by damage to the epidermis and dermis, resulting in
blisters and severe pain?
A. First-degree burn
1. Which layer of the epidermis is responsible for the continuous production of new skin cells
through mitosis?
A. Stratum basale
B. Stratum corneum
C. Stratum lucidum
D. Stratum spinosum
Correct Answer: A
Expert Explanation: The stratum basale is the deepest layer of the epidermis and contains
stem cells that undergo rapid cell division. As new cells are produced, they are pushed
upward toward the surface to replace older cells. This layer is crucial for skin regeneration
and maintaining the integrity of the integumentary system.
2. During an action potential, what occurs immediately after the threshold potential is
reached?
A. Potassium channels open, causing repolarization
B. Sodium-potassium pumps stop working
C. Voltage-gated sodium channels open, causing depolarization
D. Calcium ions are sequestered into the sarcoplasmic reticulum
Correct Answer: C
,Expert Explanation: Once the threshold potential is reached, voltage-gated sodium
channels open rapidly, allowing an influx of sodium ions into the cell. This influx causes the
membrane potential to become more positive, a process known as depolarization. This step
is essential for the propagation of the electrical signal along the axon.
3. What is the primary role of the sarcoplasmic reticulum in skeletal muscle contraction?
A. Synthesizing ATP for cross-bridge cycling
B. Binding to troponin to expose myosin-binding sites
C. Transmitting action potentials into the cell interior
D. Storing and releasing calcium ions
Correct Answer: D
Expert Explanation: The sarcoplasmic reticulum acts as a specialized calcium storage
organelle within muscle fibers. When an action potential reaches the muscle cell, calcium is
released from this structure into the sarcoplasm to initiate contraction. This release is a
critical step in the excitation-contraction coupling mechanism.
4. In the process of bone remodeling, which cells are primarily responsible for the resorption
of bone matrix?
A. Osteoblasts
B. Osteocytes
C. Osteoclasts
, D. Osteoprogenitor cells
Correct Answer: C
Expert Explanation: Osteoclasts are large, multinucleated cells that break down bone
tissue by secreting acid and enzymes. This process releases stored minerals like calcium
into the blood to maintain homeostasis. Bone resorption must be balanced with bone
formation to ensure skeletal strength and health.
5. Which neurotransmitter is released at the neuromuscular junction to stimulate skeletal
muscle contraction?
A. Dopamine
B. Acetylcholine
C. Serotonin
D. Norepinephrine
Correct Answer: B
Expert Explanation: Acetylcholine is the specific neurotransmitter that bridges the gap
between the motor neuron and the muscle fiber. It binds to nicotinic receptors on the
motor end plate, leading to a localized depolarization. This depolarization eventually
triggers the action potential necessary for muscle contraction.
6. Which type of burn is characterized by damage to the epidermis and dermis, resulting in
blisters and severe pain?
A. First-degree burn
