What does it mean for a membrane to be selectively permeable?
only certain molecules are allowed to pass through.
the membrane is rigid and only allows water to pass through.
all types of molecules are able to pass into the cell.
the membrane is rigid and nothing can enter or leave the cell.

Drag each tile to the correct box. the body monitors the levels of oxygen in the blood to regulate breathing. isabel is running in a marathon and is near the finish line. she feels out of breath. how will her nervous system work to generate a reaction? arrange the tiles in chronological order. isabel's breathing rate increases. sensory receptors in the arteries detect low oxygen levels. the brain sends signals through motor neurons. sensory neurons generate an impulse. the central nervous system relays an impulse to certain brain regions.