When you accidentally bump your elbow and a peculiar sensation shoots down your arm, you’ve likely encountered what is commonly known as your “funny bone.” This experience often involves a tingling, sometimes painful, feeling. It leaves many wondering about this seemingly humorous anatomical spot.
Unmasking the “Funny Bone”
Despite its name, the “funny bone” is not a bone; it is a nerve. This nerve is the ulnar nerve, one of the three main nerves in the arm. It originates from the C8 and T1 spinal nerve roots, traveling from the neck down to the hand. As it descends, a segment of this nerve becomes exposed at the elbow.
At the elbow, the ulnar nerve passes through a narrow groove behind a bony prominence on the inner side of your upper arm bone (humerus), called the medial epicondyle. This area, sometimes referred to as the cubital tunnel, offers minimal protection. Its superficial position makes the ulnar nerve vulnerable to direct impact, leading to the familiar sensation when bumped.
The Sensation Explained
Hitting the ulnar nerve produces a distinctive sensation because it is temporarily compressed against the underlying bone. This compression irritates the nerve, sending mixed signals to the brain. The resulting feeling is often described as an electric shock, tingling, or numbness that radiates down the forearm and into the little finger and half of the ring finger.
This temporary disruption of nerve function causes the “funny” feeling. Normally, nerves transmit clear signals for sensation or movement, but a direct impact on the ulnar nerve creates an overload or confusion of these signals. The term “funny bone” is also a play on words, as the nerve passes near the “humerus” bone, which sounds similar to “humorous.”
Beyond the Bump: The Ulnar Nerve’s Purpose
Beyond the sensation it causes when bumped, the ulnar nerve plays a role in arm and hand function. It provides both motor control and sensory perception. The nerve innervates several muscles in the forearm and hand, which are important for fine motor movements.
These muscles enable actions such as gripping objects, spreading fingers, and controlling pinky finger movement. The ulnar nerve also provides sensation to the skin of the little finger, the adjacent half of the ring finger, and parts of the palm. This dual function highlights its contribution to hand dexterity and feeling.