Which muscle is innervated by C7–C8 rather than C5–C6?

Which muscle is innervated by C7–C8 rather than C5–C6?

• A. Biceps Brachii
• B. Deltoid
• C. Triceps
• D. Brachioradialis

Answer: (C)

Elbow extension relies on input from nerve roots C7–C8 via the radial nerve. The triceps brachii is the muscle among these choices that is primarily innervated by those roots, with C7–C8 providing the dominant supply (C6 may contribute but is not the main driver). In contrast, the biceps brachii is mainly innervated by C5–C6 through the musculocutaneous nerve; the deltoid by C5–C6 through the axillary nerve; and the brachioradialis by C5–C6 through the radial nerve. So the triceps stands out as the muscle whose primary innervation is from C7–C8.

Elbow extension relies on input from nerve roots C7–C8 via the radial nerve. The triceps brachii is the muscle among these choices that is primarily innervated by those roots, with C7–C8 providing the dominant supply (C6 may contribute but is not the main driver). In contrast, the biceps brachii is mainly innervated by C5–C6 through the musculocutaneous nerve; the deltoid by C5–C6 through the axillary nerve; and the brachioradialis by C5–C6 through the radial nerve. So the triceps stands out as the muscle whose primary innervation is from C7–C8.