there is the musculus extensor digitorum, that extends finger 2 to 5 up.
There is an extra muscle for the 2. and the 5. finger (m. extensor digiti minimi and m. extensor indicis).
But why can I than lift my middle finger (3. finger) up without lifting my ring finger (4. finger) up?
I mean, when the musculus extensor digitorum is stimulated (by the nervus radialis), shouldn't it than extend EVERY finger (2 to 5), not only one of them?
My guess was that the antagonist of the musculus extensor digitorum is pulling the other fingers back, but the musculi flexor digitorum superficialis and profundus are also just one big muscle, so this doesn't seem to be the right explanation.
Another idea was that I can activate only parts of the nervus radialis and with that only activate parts of the musculus extensor digitorum. But that doesn't seem to be very likely.
So, what is the reason behind that?