BIOD 152 AP2 LAB 2 ACTUAL EXAM 2026/2027 | Portage Learning |
25 Questions with Rationales | Complete Answer Key | Updated Lab
Edition | Pass Guaranteed - A+ Graded
Q1 (Diagram Labeling): Identify structures 1-6 on the brachial plexus diagram below:
plainCopy
[Diagram Description: Right brachial plexus with numbered structures:
1 - Five spinal nerve roots emerging from intervertebral foramina
2 - Three large trunks superior to clavicle
3 - Six divisions passing posterior to clavicle
4 - Three cords in axilla relative to axillary artery
5 - Terminal nerve descending to flexor compartment
6 - Terminal nerve wrapping posterior to humerus]
1.
2.
3.
4.
5.
6.
Correct Answer:
1. Roots (C5, C6, C7, C8, T1) [CORRECT]
2. Trunks (Upper, Middle, Lower) [CORRECT]
3. Divisions (Anterior and Posterior divisions of each trunk) [CORRECT]
4. Cords (Lateral, Posterior, Medial) [CORRECT]
5. Median Nerve [CORRECT]
6. Radial Nerve [CORRECT]
Rationale: The brachial plexus innervates the upper limb and is organized by the
mnemonic "5 Roots, 3 Trunks, 6 Divisions, 3 Cords, 5 Terminal Branches" or "Randy
Travis Drinks Cold Beer" (Roots, Trunks, Divisions, Cords, Branches). Roots (1) are the
anterior rami of C5-T1 spinal nerves. Trunks (2) form in the posterior triangle: Upper
(C5-C6), Middle (C7), Lower (C8-T1). Divisions (3) occur behind the clavicle where each
,trunk splits into anterior and posterior divisions. Cords (4) form around the axillary
artery: Lateral cord (anterior divisions of upper/middle trunks), Posterior cord (all three
posterior divisions), Medial cord (anterior division of lower trunk). Terminal nerves (5, 6)
emerge from cords: The median nerve (5) arises from lateral and medial cord
contributions (lateral/medial heads) and innervates most flexor forearm muscles and
thenar muscles. The radial nerve (6) is the largest terminal branch from the posterior
cord, wrapping posterior to the humerus in the radial groove to innervate the posterior
arm and forearm extensors. Distractor identification: Students often confuse the cords'
positions—the lateral cord is lateral to the axillary artery, medial cord is medial, and
posterior cord is posterior to the artery.
Q2 (Matching): Match each peripheral nerve to its plexus of origin and primary motor
function:
TableCopy
Nerve Plexus of Origin Primary Motor Function
1. Phrenic A. Lumbar A. Flexes knee; plantarflexes foot
2. Musculocutaneous B. Brachial B. Flexes elbow; supinates forearm
3. Obturator C. Cervical C. Flexes hip; adducts thigh
4. Tibial D. Sacral D. Flexes elbow; flexes supinated forearm
5. Common Fibular (Peroneal) E. Sacral E. Extends knee; dorsiflexes foot
, 6. Femoral F. Lumbar F. Controls diaphragm
Correct Answer:
1. C-F (Cervical plexus; controls diaphragm) [CORRECT]
2. B-D (Brachial plexus; flexes elbow and supinated forearm) [CORRECT]
3. A-C (Lumbar plexus; flexes hip and adducts thigh) [CORRECT]
4. D-A (Sacral plexus; flexes knee and plantarflexes foot) [CORRECT]
5. E-E (Sacral plexus; extends knee and dorsiflexes foot - Correction: Common
fibular enables dorsiflexion/eversion) [CORRECT]
6. F-F (Lumbar plexus; extends knee via quadriceps) [CORRECT]
Note: For #5, correct pairing is E-E (Sacral; dorsiflexes and everts foot)
Rationale:
● Phrenic nerve (C3-C5) arises from the cervical plexus (not brachial), descends
through thorax to innervate the diaphragm—the sole motor nerve for breathing.
Distractor confusion: Students often think phrenic is brachial because C5 is
involved, but it leaves the cervical plexus medially.
● Musculocutaneous nerve (brachial plexus, lateral cord) innervates anterior arm
muscles (biceps brachii, brachialis, coracobrachialis) for elbow flexion and
forearm supination; continues as lateral cutaneous nerve of forearm.
● Obturator nerve (lumbar plexus, L2-L4) exits pelvis via obturator foramen to
innervate medial thigh adductors (adductor longus, brevis, magnus, gracilis,
obturator externus).
● Tibial nerve (sciatic branch, sacral plexus L4-S3) innervates posterior thigh
(hamstrings except short head biceps femoris), posterior leg (gastrocnemius,
soleus, tibialis posterior), and plantar foot muscles; enables knee flexion and
plantarflexion.
● Common fibular (peroneal) nerve (sciatic branch, sacral plexus L4-S2) wraps
around fibular neck, divides into superficial fibular (everts foot) and deep fibular
(dorsiflexes foot and extends toes); injury causes foot drop.
● Femoral nerve (lumbar plexus, L2-L4) is the largest branch, innervating
quadriceps femoris (knee extension), sartorius (hip flexion), and iliopsoas (hip
flexion); provides sensation to anterior thigh and medial leg.
, Q3 (Diagram Labeling): Identify the components of the reflex arc labeled A-E:
plainCopy
[Diagram Description: Patellar reflex pathway with numbered components:
A - Structure in quadriceps tendon
B - Neuron with cell body in dorsal root ganglion entering spinal cord
C - Synapse region in spinal cord gray matter
D - Neuron exiting spinal cord ventral root to muscle
E - Quadriceps femoris muscle]
A. _____________
B. _____________
C. _____________
D. _____________
E. _____________
Correct Answer:
A. Muscle Spindle (Stretch Receptor) [CORRECT]
B. Sensory (Afferent) Neuron / 1a Afferent Fiber [CORRECT]
C. Integration Center / Synapse in Spinal Cord (L2-L4) [CORRECT]
D. Motor (Efferent) Neuron / Alpha Motor Neuron [CORRECT]
E. Effector (Quadriceps Femoris Muscle) [CORRECT]
Rationale: The patellar (knee-jerk) reflex is a monosynaptic stretch reflex with five
essential components: A (Receptor) - Muscle spindles (intrafusal fibers) in the
quadriceps tendon detect sudden stretch from patellar tap; they are encapsulated
sensory receptors that respond to length changes. B (Sensory neuron) - Large,
25 Questions with Rationales | Complete Answer Key | Updated Lab
Edition | Pass Guaranteed - A+ Graded
Q1 (Diagram Labeling): Identify structures 1-6 on the brachial plexus diagram below:
plainCopy
[Diagram Description: Right brachial plexus with numbered structures:
1 - Five spinal nerve roots emerging from intervertebral foramina
2 - Three large trunks superior to clavicle
3 - Six divisions passing posterior to clavicle
4 - Three cords in axilla relative to axillary artery
5 - Terminal nerve descending to flexor compartment
6 - Terminal nerve wrapping posterior to humerus]
1.
2.
3.
4.
5.
6.
Correct Answer:
1. Roots (C5, C6, C7, C8, T1) [CORRECT]
2. Trunks (Upper, Middle, Lower) [CORRECT]
3. Divisions (Anterior and Posterior divisions of each trunk) [CORRECT]
4. Cords (Lateral, Posterior, Medial) [CORRECT]
5. Median Nerve [CORRECT]
6. Radial Nerve [CORRECT]
Rationale: The brachial plexus innervates the upper limb and is organized by the
mnemonic "5 Roots, 3 Trunks, 6 Divisions, 3 Cords, 5 Terminal Branches" or "Randy
Travis Drinks Cold Beer" (Roots, Trunks, Divisions, Cords, Branches). Roots (1) are the
anterior rami of C5-T1 spinal nerves. Trunks (2) form in the posterior triangle: Upper
(C5-C6), Middle (C7), Lower (C8-T1). Divisions (3) occur behind the clavicle where each
,trunk splits into anterior and posterior divisions. Cords (4) form around the axillary
artery: Lateral cord (anterior divisions of upper/middle trunks), Posterior cord (all three
posterior divisions), Medial cord (anterior division of lower trunk). Terminal nerves (5, 6)
emerge from cords: The median nerve (5) arises from lateral and medial cord
contributions (lateral/medial heads) and innervates most flexor forearm muscles and
thenar muscles. The radial nerve (6) is the largest terminal branch from the posterior
cord, wrapping posterior to the humerus in the radial groove to innervate the posterior
arm and forearm extensors. Distractor identification: Students often confuse the cords'
positions—the lateral cord is lateral to the axillary artery, medial cord is medial, and
posterior cord is posterior to the artery.
Q2 (Matching): Match each peripheral nerve to its plexus of origin and primary motor
function:
TableCopy
Nerve Plexus of Origin Primary Motor Function
1. Phrenic A. Lumbar A. Flexes knee; plantarflexes foot
2. Musculocutaneous B. Brachial B. Flexes elbow; supinates forearm
3. Obturator C. Cervical C. Flexes hip; adducts thigh
4. Tibial D. Sacral D. Flexes elbow; flexes supinated forearm
5. Common Fibular (Peroneal) E. Sacral E. Extends knee; dorsiflexes foot
, 6. Femoral F. Lumbar F. Controls diaphragm
Correct Answer:
1. C-F (Cervical plexus; controls diaphragm) [CORRECT]
2. B-D (Brachial plexus; flexes elbow and supinated forearm) [CORRECT]
3. A-C (Lumbar plexus; flexes hip and adducts thigh) [CORRECT]
4. D-A (Sacral plexus; flexes knee and plantarflexes foot) [CORRECT]
5. E-E (Sacral plexus; extends knee and dorsiflexes foot - Correction: Common
fibular enables dorsiflexion/eversion) [CORRECT]
6. F-F (Lumbar plexus; extends knee via quadriceps) [CORRECT]
Note: For #5, correct pairing is E-E (Sacral; dorsiflexes and everts foot)
Rationale:
● Phrenic nerve (C3-C5) arises from the cervical plexus (not brachial), descends
through thorax to innervate the diaphragm—the sole motor nerve for breathing.
Distractor confusion: Students often think phrenic is brachial because C5 is
involved, but it leaves the cervical plexus medially.
● Musculocutaneous nerve (brachial plexus, lateral cord) innervates anterior arm
muscles (biceps brachii, brachialis, coracobrachialis) for elbow flexion and
forearm supination; continues as lateral cutaneous nerve of forearm.
● Obturator nerve (lumbar plexus, L2-L4) exits pelvis via obturator foramen to
innervate medial thigh adductors (adductor longus, brevis, magnus, gracilis,
obturator externus).
● Tibial nerve (sciatic branch, sacral plexus L4-S3) innervates posterior thigh
(hamstrings except short head biceps femoris), posterior leg (gastrocnemius,
soleus, tibialis posterior), and plantar foot muscles; enables knee flexion and
plantarflexion.
● Common fibular (peroneal) nerve (sciatic branch, sacral plexus L4-S2) wraps
around fibular neck, divides into superficial fibular (everts foot) and deep fibular
(dorsiflexes foot and extends toes); injury causes foot drop.
● Femoral nerve (lumbar plexus, L2-L4) is the largest branch, innervating
quadriceps femoris (knee extension), sartorius (hip flexion), and iliopsoas (hip
flexion); provides sensation to anterior thigh and medial leg.
, Q3 (Diagram Labeling): Identify the components of the reflex arc labeled A-E:
plainCopy
[Diagram Description: Patellar reflex pathway with numbered components:
A - Structure in quadriceps tendon
B - Neuron with cell body in dorsal root ganglion entering spinal cord
C - Synapse region in spinal cord gray matter
D - Neuron exiting spinal cord ventral root to muscle
E - Quadriceps femoris muscle]
A. _____________
B. _____________
C. _____________
D. _____________
E. _____________
Correct Answer:
A. Muscle Spindle (Stretch Receptor) [CORRECT]
B. Sensory (Afferent) Neuron / 1a Afferent Fiber [CORRECT]
C. Integration Center / Synapse in Spinal Cord (L2-L4) [CORRECT]
D. Motor (Efferent) Neuron / Alpha Motor Neuron [CORRECT]
E. Effector (Quadriceps Femoris Muscle) [CORRECT]
Rationale: The patellar (knee-jerk) reflex is a monosynaptic stretch reflex with five
essential components: A (Receptor) - Muscle spindles (intrafusal fibers) in the
quadriceps tendon detect sudden stretch from patellar tap; they are encapsulated
sensory receptors that respond to length changes. B (Sensory neuron) - Large,
