In healthy adults, the normal plantar flexion causes a:

Combined AIIMS - 2020 (Jodhpur, Bhopal, Patna, Raipur)

Applied Physiology

Easy

Appeared in: Combined AIIMS - 2020 (Jodhpur, Bhopal, Patna, Raipur)

Explanation

In healthy adults, stimulating the sole of the foot elicits the plantar reflex.
The normal response, also known as a negative Babinski sign, is the downward movement or flexion of the great toe (hallux) and the other toes.
This flexor response indicates the proper functioning of the corticospinal tract, a major motor pathway in the central nervous system.
The question correctly identifies this downward movement as the normal finding.

Option B: Dorsiflexion (upward movement) of the hallux upon plantar stimulation is known as the Babinski sign.
Option C: The normal (flexion) and abnormal (dorsiflexion) responses are mutually exclusive; they cannot both occur at the same time in response to a single stimulus.
Option D: This option is incorrect because a correct answer exists.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Assessment of the plantar reflex (Babinski sign) in adults as background academic context rather than a clinical decision trigger.
The plantar reflex is a fundamental component of the neurological exam. A nurse's ability to correctly perform and interpret this test is vital for detecting serious neurological conditions.
An abnormal Babinski sign in an adult is a red flag that requires immediate reporting and further investigation, as it can indicate conditions like a stroke, brain tumor, spinal cord injury, or amyotrophic lateral sclerosis (ALS).
What if? If this same test was performed on a 9-month-old infant and showed dorsiflexion of the hallux, the finding would be considered normal. The Babinski sign is expected in infants because their corticospinal tracts are not yet fully myelinated.

How to Approach the Question

First, identify the core concept being tested. The question mentions 'plantar flexion' and 'hallux response', which points to the plantar reflex or Babinski test.
Recall the procedure for the plantar reflex test: stroking the sole of the foot.
Differentiate between the normal and abnormal responses in the target population, which is 'healthy adults'.
Remember that in adults, the normal response is flexion (downward curling) of the toes.
Remember that the abnormal response (Babinski sign) is extension/dorsiflexion (upward movement) of the big toe.
Evaluate the options based on this knowledge. Option A correctly describes the normal flexor response. Option B describes the abnormal response. Options C and D are therefore incorrect.

Concept Tested & Keywords

Concept Tested: Assessment of the plantar reflex (Babinski sign) in adults.
Stem keywords: healthy adults, normal plantar flexion, hallux
Lead-in keywords: causes a
Clinical cues: The term 'plantar flexion' in the stem is used to refer to the plantar reflex test, a standard neurological assessment.

Q6A3cSYlRqU5Khg4SV9k6Q

E6 Medicine Harrison 22e Part 2 p. 1285-1287

E6 Nursing Brunner Adult Health 3SA Vol 2 Part 2 p. 12-14

E6 Medicine Macleod Clinical Examination 15e p. 350-352