Which of the following cervical nerve roots best corresponds with activation of the triceps muscle?

The correct answer is C. C7. C7 is the primary nerve root for the triceps brachii via the radial nerve; damage at C7 classically causes triceps weakness and a diminished triceps deep tendon reflex. C5 is incorrect because it primarily innervates the deltoid and is tested by the biceps reflex, not the…

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(50 responses)

A
6% (3)
B
4% (2)
C
72% (36)
D
18% (9)

Explanation

C7 is the primary nerve root for the triceps brachii via the radial nerve; damage at C7 classically causes triceps weakness and a diminished triceps deep tendon reflex. C5 is incorrect because it primarily innervates the deltoid and is tested by the biceps reflex, not the triceps. C6 is associated with the biceps and brachioradialis (the brachioradialis/"supinator" reflex), making it a plausible but wrong distractor since it neighbors C7. T2 is a thoracic root entirely outside the brachial plexus territory responsible for upper-limb musculature, so it has no role in triceps innervation.

Memory tip: Use the reflex ladder - "C5/C6 = BIceps (elBow flexion), C7 = TRIceps (elbow extension)" - and note that C7 = 7 letters in "triceps" (T-R-I-C-E-P-S).

Topics

#cervical nerve roots#triceps innervation#neuroanatomy#reflex testing

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