OK. First, there's the heart. Then there's the blood vessels. The arteries. Then the veins. And then there's the capillaries. <span />
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.
Answer: the answer is b
Explanation: i took the quiz
Too much nitrogen in plants is apparent both above and below the topsoil
Enzymes are biological catalysts which increase the rate of biochemical reactions without undergoing any change themselves. They bind with the substrate to form a enzyme substrate complex leding to the formation of product releasing free enzyme.
Enzymes have an optimum pH at which they show their maximum activity. Any change in the pH effects the enzyme and the enzymatic reaction. Most of the enzymes are functional at the neutral pH of 7 in the cell cytoplasm with a few exceptions. An acidic environment in the cell, changes the tertiary structure of the enzymes and the bonds of the enzymes are weakened. Thus, preventing the substrate binding to the active site of the enzyme and inhibiting catalysis. This is due to the change in the structure of the active site leading to the lack of electrostatic attraction between the enzyme and the substrate.
