STEP1 Exam Questions and Answers | Exam-Dumps (Page: 5)

QUESTION: 21

In the brain, the amygdala plays an important role in emotional processing. Patients with lesion of the amygdala display impairment in enhanced perception of emotionally salient events. Which of the following is a major output pathway from the amygdala?

fasciculus arcuatus
fasciculus cuneatus
fasciculus of Vicq d'Azyr
fornix
stria terminalis

Answer(s): E

Explanation:

The stria terminalis or fasciculus of Foville is one of the major output pathways from the amygdala to the septal, hypothalamic, and thalamic nuclei. Another main amygdaloid output pathway is the ventral amygdalofugal pathway. The fasciculus arcuatus (choice A) or superior longitudinal fasciculus is a bundle of fibers in the cerebrum connecting ipsilateral regions of the frontal, temporal, parietal, and occipital lobes.
The fasciculus cuneatus (choice B) carries ascending sensory fibers in the dorsal funiculus of the spinal cord and terminates in the nucleus cuneatus of the medulla oblongata. The fasciculus of Vicq d'Azyr (choice C) or mammillothalamic tract connects the mammillary bodies to the anterior nuclei of the thalamus. This bundle of fibers forms part of Papez circuit, which is also involved in emotional processing.
Another part of Papez circuit is the fornix (choice D), a large efferent pathway from the hippocampus.

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QUESTION: 22

An infant is born anencephalic. He presents without both a forebrain and a cerebrum. The remaining brain tissue is exposed, not covered by bone or skin. The infant is blind, deaf, unconscious, and unable to feel pain. Because the infant has a rudimentary brainstem, reflex actions such as respiration (breathing) and responses to sound or touch occur. However, the lack of a functioning cerebrum permanently rules out the possibility of ever gaining consciousness. Anencephaly is the result of a defect in which of the following?

closure of the caudal neuropore
closure of the rostral neuropore
formation of the first branchial arch
formation of the somites
fusion of the metopon

Answer(s): B

Explanation:

Malclosure of the rostral neuropore during the fourth week of development results in anencephaly and is lethal in the affected newborn. The condition is better termed meroanencephaly because of the presence of the rudimentary brainstem with some functioning nervous tissues. Defects in the closure of the caudal neuropore (choice A) result in varying conditions of spina bifida at the lower end of the spinal cord. The first branchial arch (choice C) and the somites (choice D) do not play any role in the formation of the brain.
Fusion of the metopon or forehead (choice E) occurs after birth and also does not play a role in brain formation.

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QUESTION: 23

As the consulting physician to the US Open, you are asked to examine a golfer who complains of increased pain with right wrist flexion and pronation activities. The patient also reports discomfort even when simply shaking hands with someone. Examination reveals also decreased sensation in the territory of the ulnar nerve. Your diagnosis is golfer's elbow, affecting mostly the superficial flexor muscles of the forearm. This group of muscles has a common origin from which of the following bony landmarks?

head of the radius
lateral epicondyle of the humerus
medial epicondyle of the humerus
olecranon process of the ulna
tuberosity of the radius

Answer(s): C

Explanation:

The superficial layer of flexor muscles of the forearm all originate from the medial epicondyle of the humerus. Thus, this condition is also called medial epicondylitis and the most common finding is tenderness with palpation over the anterior aspect of the medial epicondyle. The muscles involved are most often the Pronator Teres, Flexor Carpi Radialis, and Palmaris Longus. The Flexor Digitorum Superficialis and Flexor Carpi Ulnaris may also be affected. There is no muscle attachment to the head of the radius (choice A). The lateral epicondyle of the humerus (choice B) is the attachment point of the common extensor tendon. The olecranon process of the ulna (choice D) is the attachment point for the Triceps Brachii, Flexor Carpi Ulnaris, and Anconeus. The tuberosity of the radius (choice E) receives the distal tendon of the biceps brachii.

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QUESTION: 24

A professional football player was diving for a touchdown when his face mask was grabbed and wrenched, causing neck hyperextension and rotation to the right. When brought to the sideline, the player complained of a burning sensation radiating down the right upper extremity and neurological examination revealed right lateral weakness of this limb. Movements affected were arm rotation and flexion, elbow flexion, forearm supination, and thumb flexion. The patient is diagnosed with a brachial plexus injury at the level of C6. 29. Which of the following muscles can perform arm and elbow flexion along with forearm supination?

biceps brachii
brachialis
brachioradialis
coracobrachialis
supinator

Answer(s): A

Explanation:

The biceps brachii muscle attaches proximally by its short head to the coracoid process of the scapula and by its long head to the supraglenoid tubercle. Distally it attaches by a strong tendon to the tuberosity of the radius and by an aponeurosis to the ulna. It thus can perform arm and elbow flexion along with forearm supination. The brachialis (choice B) attaches proximally to the anterior aspect of the lower half of the humerus and distally to the coronoid process of the ulna. It can only perform elbow flexion. The brachioradialis (choice C) attaches from the lateral supracondylar ridge of the humerus to the base of the styloid process of the radius. Although innervated by the nerve to the extensor compartment, the radial nerve, it performs elbow flexion and forearm pronation. The coracobrachialis (choice D) attaches from the coracoid process of the scapula to the anterior aspect of the upper half of the humerus. It performs arm flexion and weak adduction. The supinator (choice E) attaches proximally to the lateral epicondyle of the humerus and the annular ligament of the radius. Distally, it covers nearly the upper third of the radius and attaches to its lateral anterior aspect. It supinates the forearm, but is a weaker supinator than the biceps brachii.

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QUESTION: 25

In cleaning the teeth in a patient, a dental hygienist accidentally cuts the gums of the posterior two molar teeth in the lower jaw on the lateral side. The pain of this injury is registered by which of the following nerves?

anterior, middle, and posterior superior alveolar nerves
buccal nerve
greater palatine nerve
lingual nerve
nasopalatine nerve

Answer(s): B

Explanation:

The gums on the lateral side of the mandibular molar teeth are innervated by the buccal nerve (long buccal nerve). All three superior alveolar nerves (choice A) supply the gums lateral to all maxillary teeth. The greater palatine nerve (choice C) innervates the gums medial to the maxillary premolar and molar teeth.
The lingual nerve (choice D) supplies the gums medial to all mandibular teeth. The nasopalatine nerve (choice E) innervates the gums posterior to the maxillary incisors.

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USMLE STEP1 Exam (page: 5) USMLE Step1 Updated on: 12-Feb-2026

QUESTION: 21

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QUESTION: 22

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QUESTION: 23

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QUESTION: 24

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QUESTION: 25

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USMLE STEP1 Exam (page: 5)
USMLE Step1
Updated on: 12-Feb-2026