A pressure point refers to an area on the human body that may produce significant pain or other effects when manipulated in a specific manner. There are several types of pressure points — each is applied differently and each creates a different effect. Types of pressure points include "Pain points", which use tendons, ligaments, and muscles, and "Reflex points", which produce involuntary movements. Most pressure points are located on pathways on the nervous system. Some pressure points produce pain when struck, pressed, or rubbed, depending on the point itself, and are also referred to as nerve centers. Pressure points can be used to cause a variety of effects, including pain, blood pressure changes, breaks, and concussions. The baroreceptors in the carotid artery are pressure-sensitive, supplying the brain with information to control systemic blood pressure. Certain areas, such as the "floating ribs", the philtrum, and the side of the knee, are likely to lead to a break if struck effectively. The brain is a sensitive organ which floats in cerebrospinal fluid and can be affected by certain pressure points, such as a strike just below the occipital ridge or the chin or lower jaw.