Bladder is an internal organ, which is mainly made up of smooth muscles. The contractions of the smooth muscles are not under voluntary control. The contraction of these muscles are directed by brain, without any external control.
The autonomic nervous system is a part of nervous system, which is responsible for regulation of the all the conditions, which occur involuntarily. It directs the movements of all smooth muscles. 
Hence, the movements of the bladder are controlled by the autonomic nervous system.
 
        
             
        
        
        
The sled with a rough metal bottom would take more force to move over ice, because the rough surface would increase friction and the force needed.
        
             
        
        
        
Explanation:
correlation relationships are between variables, however,it does not automatically mean that the change in one variable is the cause of the change in the values of the other variable. Causation indicates that one event is the result of the occurrence of the other event there is a causal relationship between the two events.
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