Answer:
Sadness has sad feeling. for example, if a friend dies, you will cry. that is what sadness is. 
Explanation:
 
        
                    
             
        
        
        
Answer:
it's curve1000 for this question 
 
        
             
        
        
        
The correct answer is microglia. 
<span>Microglia is glial cells found in the central nervous system with the protective role. Because they are the resident macrophage cells, they act as the first and main form of active immune defense. Microglia is constantly cleaning the CNS for plaques, damaged or unnecessary neurons, and infectious agents, like viruses or other microorganisms.</span>
        
             
        
        
        
Explanation:
Un estimulo es cualquier cambio que es capaz de producir una respuesta por parte del organismo. Los receptores son estructuras muy especializadas capaces de percibir los estímulos y convertirlos en impulsos nerviosos