Leia o trecho de livro-texto a seguir.
Why do we sometimes feel dizzy when we stand up?
When a person moves from lying down to standing, gravity pulls roughly 500 to 800 mL of blood into the veins of the legs and abdomen. As a result, less blood returns to the heart, and cardiac output and blood pressure fall briefly. Stretch receptors called baroreceptors, located in the carotid sinus and the aortic arch, detect this drop within seconds. They send fewer signals to the brainstem, which then increases sympathetic activity: the heart beats faster and the blood vessels constrict. In most healthy young people, this reflex corrects the pressure so quickly that nothing is noticed. In older adults or in people who are dehydrated, however, the response may be slower, and they may feel lightheaded, see dark spots, or even faint for a few seconds.
(Adapted from a physiology textbook)
A palavra 'lightheaded', na última frase, pode ser inferida pelo contexto. Considerando a explicação fisiológica do texto, ela descreve uma pessoa que se sente: