Answer:
Option). about 20 percent of the calcium ion required for contraction comes from outside the cell. 
Explanation:
Calcium ions play an important role in cardiac muscle physiology. Calcium ions influx is responsible for plateau phase after depolarization. Calcium ions also play role in muscle contraction with the help of troponin (regulatory protein).
For contraction, about 20 percent of calcium ions are supplied from outside of the cell, while rest of the calcium ions are released from SR (sarcoplasmic reticulum). 
Thus, the correct answer is 'forth option.'
 
        
             
        
        
        
Draw or paint your emotions
create an emotion wheel 
make a stress painting
put together a journal
making sock puppets 
paint to music 
make a scribble drawing 
finger paint 
make a mandala 
create a collage of your worries 
:)
        
                    
             
        
        
        
when your body heats up to like 100 degress thats your bodies way of fighting off the bacteria from the flu
 
        
             
        
        
        
Hyperventilation. You're freaking out when doing this.