Heat causes responses in the body that may result in an increase in stress hormone levels and brain temperature. Furthermore, high heat may depress dopamine and serotonin levels (these neuromediators are important for the feeling of happiness). The human body can only withstand relatively low temperatures for a certain period of time, after which time serious damage may occur. The brain is particularly vulnerable to heat because it cannot sweat like other parts of the body and lacks any significant blood flow of its own; it depends entirely on the rest of the body for cooling it through the blood stream. The brain and spinal cord contain many nerve cells that communicate with each other to control muscles, sense pain, see, hear, and smell. These nerve cells are very sensitive to heat; if the brain reaches 42 degrees Fahrenheit or higher, severe injury may occur. Even if the brain does not reach this degree, high heat can still cause problems by interfering with how it functions. High heat can lead to irrational behavior, altered senses, confusion, coma, and death. It goes without saying that avoiding heat exposure is the best way to protect yourself from excessive brain temperature. When you do need to work in hot conditions, such as when building houses in Texas, be sure to take regular breaks in the shade or indoors where it's cool.