Xylem are tubes in the stem that transport water and minerals upward, from the roots to the leaves. Phloem are tubes in the stem that move food made in the leaves to other parts of the plant. ... Chlorophyll is a pigment that helps plants use energy from the sun to produce sugars.
In the center of the centrosome
2.) occasionally beneficial
3.) omission of information
4.) addition of information
5.) mistakes in copying
Think of a stroke as a "brain attack"— it is an emergency! When symptoms appear call 911 immediately; every minute counts. A stroke occurs when the brain is deprived of blood supply. Without oxygen brain cells die. Depending on the area affected, a person may have problems speaking, walking, seeing, or thinking. It may result in permanent brain damage, disability or death. If the stroke is caused by a blood clot, a clot-busting drug may be given to restore blood supply.To understand stroke, it is helpful to understand the circulatory system of the brain (see Anatomy of the Brain). Blood is carried to the brain by two paired arteries, the internal carotid arteries and the vertebral arteries (Fig. 1). The internal carotid arteries supply the anterior (front) areas and the vertebral arteries supply the posterior (back) areas of the brain. After passing through the skull, the right and left vertebral arteries join together to form a single basilar artery.
The basilar artery and the internal carotid arteries “communicate” with each other in a ring at the base of the brain called the Circle of Willis by the anterior communicating (Acom) and posterior communicating (Pcom) arteries. The middle cerebral artery is the artery most often occluded in stroke.
