Organs.
if you're having trouble remembering them they are
cell
tissue
organ
organ systems
organism
One of the factor is the Sun's elevation where the UV reaches us at a much lower frequency when the sun is more distant. Next is our ozone, with our ozone depleting as time goes by, the amount of solar energy it can diffuse is much lesser thus the heat is much more than the previous decades.
Blood clots will do this. Cutting off blood flow while also increasing blood pressure. Also, if the viscosity (thickness of the blood) is thick which will slow down the flow and cause the body to use more effort to pump blood.
Okay what u want me to help you with