This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal System, Subject name: Physiology
Secretion of which of the following is completely independent of vagal stimulation? 
Select and explain. 
A. Pancreas, B. Brunner's gland in duodenum, C. Gall bladder, D. Parotid
C: Gall bladder
Answer: C: Gall bladder 
Explanation: Gall bladder does not have any secretory activity. It stores and concentrates bile (removes water from bile). Pancreatic and duodenal glands have a parasympathetic vagal innervation. Salivary secretion is almost entirely controlled by neural influences, with the parasympathetic branch of the autonomic nervous system playing the most prominent role.