Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: DrN on 01/11/2004 14:30:20
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what is the funny bone? why is it called that and why does it hurt so much when you just knock it? got mine on the taps yesterday when i was reaching for the shampoo in the bath! it didn't make me laugh I can tell you!
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I think it hurts so much because there is not much flesh protecting the joint, so like when someone kicks you in the shin it really hurts...
Oh wait google turns up a much more in depth and KLEVAR answer:
quote:
Funny bone, highly sensitive area at the back of the elbow where the ulnar nerve passes close to the surface of the skin in a groove between end prominences of the humerus (the upper arm bone) and the ulna (the large forearm bone). A blow to the area causes the nerve to compress against bone, producing a characteristic tingling in the forearm and the last two fingers.
wOw the world spins?
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The anatomical term for the funny bone is the olecranon. It's the end of the ulna, the forearm-partner to the radius, and it forms a hinge joint at the elbow with the end of the humerus (that's the bone from the shoulder to the elbow !).
The ulnar nerve (one of the 3 main nerves supplying the arm and hand - the other two are called the median and radial nerves) winds around the medial side of the olecranon (i.e. the side closest to the body) and is therefore exposed and prone to compression whenever the elbow is knocked or bashed.
On each side the ulnar nerve supplies the bottom half of your hand including the palm, your little finger, and the bottom half of the ring (4'th) finger. When the nerve is compressed by elbow trauma, or laying on your arm for too long, it temporarily stops transmitting information and you experience numbness, pins and needles, and weakness in the palm and the 4 and 5th digits.
Because the sensation, and the distribution, feels 'funny' the name stuck !
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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aha! thanks both of you! I didn't realise it was the same thing when my fingers go numb in the night.
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An interesting condition affecting the arm is called 'Saturday Night Palsy' - this is a form of neuropathy affecting people after a big night out.
Classically the sufferer complains of a drooping wrist (put very politically correctly, their hand naturally occupies the position that malicious people use to imply that someone is gay), an inability to extend the fingers and thumb, and loss of sensation over the wrist, back of the hand, thumb and first 2 fingers :
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.ncemi.org%2Fcse%2Fcse0918.gif&hash=11a339a89c9aee454301b05744af071e)
The patient usually gives a history of falling asleep, drunk (hence Saturday night palsy) with their arm draped over the back of an armchair. In this position the radial nerve is damaged by compression against the humerus (the upper arm bone). The nerve can also be damaged by those old fashioned wooden crutches that lodge in your arm pits (this is why this type of crutch has been switched in favour of the ones which lock around the forearms instead).
In terms of recovery, luckily, unlike the central nervous system (the brain and spinal cord), the peripheral nervous system is better adapted to repair itself and the damaged nerve fibres do eventually regrow. But the rate of regrowth is very slow (as little as 5 mm a day) and hence it may be weeks before someone's apparent switch in sexual orientation recovers. In the interim it's important to maintain mobility and provide support for the affected joints to maximise the prospects of full recovery.
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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The elbow is one of the areas we are sure to pad in surgery as prolonged pressure on the elbow against the armboard during surgery can cause ulnar nerve damage. Got to pad it, and document it for the lawyers. Always got to protect against malpractice.
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I teach a fun pratical where we put recording electrodes over the abductor digiti minimi and then stimulate the ulna nerve at various positions along the arm in order to calculate speed of conduction. It doesn't half make people squeak when you zap their "funny bone"!!
Simon
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That's a great practical. I demonstrated it for National Science Week a few years back. It went down a storm.
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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I think we did a similar experiment using a nerve from a frogs leg or something. can't really remember, but I'm sure I'd have remembered my funny bone being zapped a lot more!
I do remember attaching electrodes to peoples legs for some reason too. yes, it was definately in class too.
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Yes we also measure the Hoffman reflex by stimulating the achilles tendon with a tendon hammer linked to a microswitch, and then do the same again using direct stimulation of the popliteal nerve whilst measuring voltage change across the gastrocnemius.
Personally I think these are some of the best undergrad practical classes we do, although making lie detectors is also fun.
Simon
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we had a good lecture on the gene pool involving a large bag of m&ms! that was good! we were allowed 4 or 5 'alleles' each.