Hairs on the skin help to regulate temperature. When cold, the erector muscle of each hair forces them to stand upright. This traps a layer of warm air near the skin which provides insulation. When hot, hairs on the skin lie flat to reduce body temperature. Sweat glands also release sweat which travels to sweat ducts to sweat pores on the surface of the skin. When this sweat evaporates, it removes heat and cools the body down. Body temperature and the thermoregulatory centre Body temperature Body temperature is one of the factors controlled by homeostasis.
Too hot When we get too hot, sweat glands in the skin release more sweat. Too cold When we get too cold, skeletal muscles contract rapidly and we shiver. Too cold Too hot Process Vasoconstriction Vasodilation Arterioles Get narrower Get wider Blood flow in skin capillaries Decreases Increases Heat loss from skin Decreases Increases These diagrams show the processes that take place when vasoconstriction and vasodilation occur.
Vasoconstriction — a response to being too cold Generally, when the body temperature is too low, a variety of processes happen - vasoconstriction, sweating stops and shivering starts. Vasodilation — a response to being too hot When the temperature is too high, different processes happen - vasodilation and sweat production, which both transfer energy from skin to the environment, resulting in a cooling effect. Get narrower. If the body is too hot, glands under the skin secrete sweat onto the surface of the skin, to increase heat loss by evaporation.
Sweat secretion stops when body temperature returns to normal. Shivering is the involuntary contraction and relaxation of muscles. This occurs very quickly. It releases energy from glucose in respiration. Some of this energy is released as heat to warm us up. Blood vessels supplying blood to the skin can swell or dilate - vasodilation. This causes more heat to be carried by the blood to the skin, where it can be lost to the air.
Blood vessels can shrink down again - vasoconstriction. These diagrams show the processes that take place when vasoconstriction and vasodilation occur. The air at high altitudes contains less available oxygen. A person at high altitude will therefore experience vasodilation as their body attempts to maintain oxygen supply to its cells and tissues.
Although vasodilation decreases blood pressure in major blood vessels, it can increase blood pressure in smaller blood vessels called capillaries. This is because capillaries do not dilate in response to increased blood flow. Increased blood pressure within the capillaries of the brain can cause fluid to leak into surrounding brain tissue. This results in localized swelling, or edema. Medical professionals refer to this condition as high-altitude cerebral edema HACE.
People at high altitudes may also experience vasoconstriction within the lungs. This can cause a buildup of fluid within the lungs, which medical professionals refer to as high-altitude pulmonary edema HAPE. In some cases, a doctor may induce vasodilation as a treatment for certain conditions. In other cases, vasodilation may be what requires treatment. Vasodilators are medications that cause the blood vessels to widen. Doctors may use these drugs to reduce blood pressure and ease any strain on the heart muscle.
There are two types of vasodilator: drugs that work directly on the smooth muscle, such as that in the blood vessels and heart, and drugs that stimulate the nervous system to trigger vasodilation. The type of vasodilator a person receives will depend on the condition they have that needs treatment. Vasodilation is an important mechanism.
However, it can sometimes be problematic for people who experience hypotension or chronic inflammation. People with either of these conditions may require medications called vasoconstrictors. These drugs cause the blood vessels to narrow. For people with hypotension, vasoconstrictors help increase blood pressure. For people with chronic inflammatory conditions, vasoconstrictors reduce inflammation by restricting blood flow to certain cells and body tissues.
Vasodilation refers to the widening, or dilation, of the blood vessels. It is a natural process that increases blood flow and provides extra oxygen to the tissues that need it most. In some cases, doctors may deliberately induce vasodilation as a treatment for certain health conditions. In other cases, doctors may work to reduce vasodilation, as it can worsen conditions such as hypotension and chronic inflammatory diseases. Doctors sometimes use drugs called vasoconstrictors to help treat these conditions.
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