Red blood cells sense low oxygen in the brain
![images of blood cells in capillaries](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2016/08/080416_LS_bloodcells_feat.jpg?fit=860%2C460&ssl=1)
TO THE RESCUE When oxygen levels are low (bottom), red blood cells become more flexible and squeeze through an artificial capillary quickly. When oxygen levels are high (top), the cells move slower.
H. Wei et al.