Which knob-like process on the second cervical vertebra in human beings is responsible for rotational movements of the head?
Prezygapophysis
Postzygapophysis
Olecranon process
Odontoid process
The odontoid process is located on the second cervical vertebra and acts as a knob-like projection that enables rotational movements of the head. It serves as a pivotal point for the rotation between the first cervical vertebra (atlas) and the head. Essentially, the odontoid process allows for the turning and twisting motions of the head. Hence, the correct answer is option 4.