Physical structures..........
        
             
        
        
        
Answer:
depolarization leading to action potentials
Explanation:
The voltage-gated Na+ channels are responsible for rapid depolarization phase of the action potential. Action potential generation require depolarization of neuronal membrane which is acquired by influx of sodium ions through voltage gated sodium ion channels. If the Na+ channels are blocked, there will be no influx of sodium ions to cause depolarization hence action potential will not be generated.
 
        
             
        
        
        
Valves, they are like flaps of muscle that keeps the blood in its place util its ready to be pumped along.
        
                    
             
        
        
        
For an organism to function properly all the physiological factors should be favorable. These physiological factors include water level, pH, temperature etc. To perform the basic function of the life, it is important to maintain the physiological parameter in a particular range.  
In case, these physiological parameters are not balanced, then the body of the organism does not perform well and causes illness.  
So, the first blank can be filled with temperature and the second blank can be filled with range.  
 
        
             
        
        
        
Explanation:
 When there is DNA shape mutation, one of the main things that could happend in the change of shape of the proteins, this creates a different pattern to arrange the nucleotids in the nuclei of the cells