Lower subscapular nerves arise from the cervical
spinal nerves 5 and 6. It innervates the subscapularis
and teres major muscles. The subscapularis and
teres major are both responsible for adducting and
medially rotating the arm. A lesion of this nerve
would result in weakness in these motions. The axillary
nerve also arises from cervical spinal nerves 5
and 6 and innervates the deltoid and teres minor
muscles. The deltoid muscle is large and covers the
entire surface of the shoulder, and contributes to arm
movement in any plane. The teres minor is a lateral
rotator and a member of the rotator cuff group of
muscles. The radial nerve arises from the posterior
cord of the brachial plexus. It is the largest branch,
and it innervates the triceps brachii and anconeus in
the arm. The spinal accessory nerve is cranial nerve
XI, and it innervates the trapezius muscle, which elevates
and depresses the scapula. The ulnar nerve arises from the medial cord of the brachial plexus and
runs down the medial aspect of the arm. It innervates
muscles of the forearm and hand.

The lateral pterygoid
muscle acts on the temporomandibular joint (TMJ) to cause
protrusion (or protraction) of the mandible. During the contraction
of the lateral pterygoid muscle, the mandibular condyle
slides anterior (translation) to be located inferior to the
articular eminence of the temporal bone, which enables the
mouth to open passively due to gravity. Acting unilaterally,
the lateral pterygoid muscle produces side-to-side movements.
So, the patient has all of the signs of a paralyzed lateral
pterygoid muscle on the left side, including weakness protruding
the mandible, weakness opening the oral fi ssure (or
mouth), and the lateral deviation of the mandible during protrusion.
In this patient, herpes zoster, or shingles, is a painful
skin rash affecting the mandibular division (or motor root)
of the trigeminal nerve (CN V3). Shingles is seen in patients
who have had previous exposure to the varicella zoster virus,
which causes chickenpox in children or young adults. After
the initial exposure to chickenpox, this virus can reside latent
in ganglia of an individual for years. If this individual becomes
immunocompromised, the skin (or dermatomes supplied
by the infected ganglia) can develop shingles, a painful skin
rash, which blisters, breaks open, crusts over, and then disappears.
In this patient, the herpetic lesions were found in the
sensory distribution of the left CN V3, which means the virus
resides in the trigeminal (or semilunar) ganglion. This herpes
zoster infection also affected the motor root of CN V3, which
is why the lateral pterygoid muscle displayed weakness in this
patient. Choice A (Anterior belly of digastric) is incorrect. The
anterior belly of the digastric muscle is a suprahyoid muscle
that assists in the elevation of the hyoid bone during swallowing.
It has no role in the deviation of the mandible during
protrusion. Choice C (Masseter) is incorrect. The masseter
primarily works to close the jaw. Though its superfi cial fi bers
may play a limited role in protrusion of the mandible, it is the
deviation of the mandible to the left that signals involvement
of the left lateral pterygoid muscle. Choice D (Medial pterygoid)
is incorrect. The medial pterygoid functions to elevate
the mandible. Though it may play a limited role in protrusion
of the mandible, it is the deviation of the mandible to the left
that signals involvement of the left lateral pterygoid muscle.
Choice E (Temporalis) is incorrect. The temporalis muscle is
also involved with elevation of the mandible leading to closure
of the jaw; however, its middle and oblique fi bers are the primary
retractors of the mandible. These actions did not display
weakness in this patien

The anterior
longitudinal ligament is a vertical connective tissue band that
attaches along the anterior aspects of the vertebral bodies. Its
peripheral fi bers have strong attachments to the intervertebral
discs. The anterior longitudinal ligament resists hyperextension
of the vertebral column. However, in this patient, the
extreme forces involved with the hyperextension of the neck
overpowers the resistance of this ligament, rupturing it as well
as displacing part of the C4-5 intervertebral disc. In the given
T2-weighted MRI, the anterior longitudinal ligament is represented
by a hypointense (dark band) signal located anterior to
the vertebral column. However, the locations where the anterior
longitudinal ligament is interrupted appear as an abnormal
hyperintense (white) signal, which is evident anterior to the C5 vertebral body. Choice B (Posterior longitudinal ligament)
is incorrect. The posterior longitudinal ligament runs vertically
along the posterior aspect of the vertebral column,
mirroring the position of the anterior longitudinal ligament
located along the anterior aspect of the vertebral column. The
posterior longitudinal ligament resists fl exion of the vertebral
column. Posterolateral herniation of the gelatinous nucleus
pulposus through the anulus fi brosus of an intervertebral
disc most often projects lateral to the strong attachment sites
of the posterior longitudinal ligament. If the herniated disc
compresses spinal nerve roots, then neck, back, and/or limb
pain may be present. The T2-weighted MRI clearly shows disruption
of the anterior longitudinal ligament, evident by the
abnormal hyperintense (white) signal located anterior to the
C5 vertebral body. Choice C (Ligamentum fl avum) is incorrect.
The ligamenta fl ava (L: yellow ligament) are paired ligaments
of yellow elastic fi brous tissue, which bind together
the laminae of adjoining vertebrae and form the posterior
wall of the vertebral canal. Because these ligaments resist
fl exion of the vertebral column, it is unlikely the ligamenta
fl ava were damaged in this hyperextension injury of the neck.
Choice D (Interspinous ligament) is incorrect. The interspinous
ligament is composed of fi brous bands that connect
the spinous processes of adjacent vertebrae. Because these
ligaments resist fl exion of the vertebral column, it is unlikely
the interspinous ligaments were damaged in this hyperextension
injury of the neck. Choice E (Intertransverse ligament)
is incorrect. The intertransverse ligament is one ligament
that connects the transverse processes of adjacent vertebrae.
Because the intertransverse ligaments resist contralateral bending
(abduction; lateral fl exion) of the vertebrae, it is unlikely
the intertransverse ligaments were damaged in this hyperextension
injury of the neck.

Q10) A radiologist orders a posteroanterior (PA) plain fi lm of the
chest. This image should provide the greatest resolution of
which of the following structures?

The PA plain fi lm is the standard
radiographic view of the thorax, and probably the most
commonly obtained medical image. In basic terminology, a
PA radiograph is one in which the X-ray beam penetrates from
the patient’s posterior side to the anterior side, as shown in
the given illustration. The X-ray projector is located posterior
to the patient, and the X-ray fi lm is positioned anterior. The
part of the body under study should be as close as possible to
the X-ray fi lm in order to optimize the resolution of that part
and minimize magnifi cation artifacts. Thus, in the PA orientation,
the heart is closest to the X-ray fi lm and appears sharper
than the other structures in question. Choice A (Transverse
processes of the vertebrae) is incorrect. In the PA orientation,
the vertebral column (being in the posterior aspect of
the body) is further away from the X-ray fi lm. Also, the vertebrae
are in line with several other overlapping structures (e.g., the heart, esophagus, and aorta) that add rad

Q11) A research scientist at a pharmaceutical company discovers a
new drug that selectively blocks the release of norepinephrine
from nerve endings. At which of the following sites would this
drug have the greatest effect on normal synaptic transmission?
(A) Somatic neuron motor end plates
(B) Postsynaptic parasympathetic nerve terminals
(C) Postsynaptic sympathetic nerve terminals
(D) Synapses between presynaptic and postsynaptic parasympathetic
neurons
(E) Synapses between presynaptic and postsynaptic sympathetic
neurons

Postsynaptic sympathetic neurons typically release the neurotransmitter
norepinephrine/noradrenaline from their endings,
so the sympathetic division is described as a noradrenergic
system. Blocking the release of norepinephrine would disrupt
normal neurotransmission at these terminal sites. An
important exception to this rule is that the postsynaptic sympathetic
neurons supplying sweat glands typically release
acetylcholine from their endings. Choice A (Somatic neuron
motor end plates) is incorrect. The somatic motor neurons
that supply skeletal muscle fi bers utilize acetylcholine as their
neurotransmitter at motor end plates. Choice B (Postsynaptic
parasympathetic nerve terminals) is incorrect. Postsynaptic
parasympathetic neurons typically release acetylcholine as
the neurotransmitter at their endings, so the parasympathetic
division is described as a cholinergic system. Choice D (Synapses
between presynaptic and postsynaptic parasympathetic
neurons) is incorrect. Both sympathetic and parasympathetic
divisions utilize acetylcholine as the neurotransmitter between
their presynaptic and postsynaptic cells. Choice E (Synapses
between presynaptic and postsynaptic sympathetic neurons)
is incorrect. Both sympathetic and parasympathetic divisions
utilize acetylcholine as the neurotransmitter between their
presynaptic and postsynaptic cells.

13. A 2-year-old male patient develops progressive
generalized weakness and muscle atrophy.
The impairment first began with the muscles of
the hips, and then progressed to the pelvic area,
thigh, and shoulder muscles. The patient is
diagnosed with Duchenne’s muscular dystrophy,
a congenital disorder where the protein
dystrophin is deficient. Which of the following
describes the role of dystrophin in muscle
tissue?

Dystrophin anchors actin to the sarcolemma,
reinforcing and stabilizing the latter
during muscle contraction. Titin is a large protein
which associates with myosin filaments
and endows them with elastic recoil properties
(choice B). Desmin filaments form a supportive
network extending from Z disk to Zdisk
(choice C). Troponin I inhibits the binding of
myosin to actin (choice D). AlphaB-crystallin
protects desmin filaments from stress-induced
damage (choice E).

14)A 55-year-old man with severe coughing is admitted to the hospital. Radiographic examination reveals tuberculosis of the right lung, with extension to
the thoracic vertebral bodies of T6 and T7, producing
a “gibbus deformity.” Which of the following conditions is most likely also to be confi rmed by radiographic examination?

B Kyphosis is characterized by a “hunchback”
due to an abnormal increase in curvature of the thoracic region of the vertebral column. Lordosis, or
“swayback,” is an increase in lumbar curvature of the
spine. Lordosis can be physiologic, such as seen in a
pregnant woman. Scoliosis is a lateral curvature of
the spine with rotation of the vertebrae. Spina bifida is a neural tube defect characterized by failure of closure of the vertebral arch. Osteoarthritis is a degen-
erative disorder that affects the articular cartilage of
joints and is not specifi cally related to the thoracic
region of the spine.

15) 30-year-old female patient cones to OPDcomplains of increasing muscle weakness andfatigue during the day, requiring her to takefrequent rests. She also reports that she cannotenjoy her meals any more because her musclesof mastication quickly weaken and she has tostop chewing. When she watches television atnight for a long period of time, her visionbecomes blurry and she sees double. Her neurologistmakes a preliminary diagnosis ofmyasthenia gravis. Which of the following isthe cause of myasthenia gravis?

(C) Myasthenia gravis is an autoimmune disorder
where autoantibodies target the postsynaptic
cholinergic receptors and destroy them.
Acetylcholine released from motor neurons is
thus unable to bind and the muscle contraction
weakens due to decreased neurotransmitter
communication. Acetylcholine synthesis in
motor neurons (choice A) remains normal.
Acetylcholinesterase (choice B) is the enzyme
which degrades acetylcholine and its synthesis
is not affected in myasthenia gravis. The cholinergic
neurotransmitter release mechanism
(choice D) at the presynaptic membrane, as
well as the signal transduction mechanism
within the muscle, remain normal.