Homeostasis

What are examples of internal conditions that are maintained by homeostasis ?

- Body temperature - Blood sugar level - Water content

What happens when the level of glucose is too low ?

1) Effect on pancreas : Insulin not secreted into the blood 2) Effect on liver : Does not convert glucose into glycogen 3) Effect on blood glucose level : Increases

What happens when the level of glucose is too high ?

1) Effect on pancreas : Insulin secreted into the blood 2) Effect on liver : Converts glucose into glycogen 3) Effect on blood glucose level : Decreases

How is homeostatic control achieved using negative feedback mechanisms ?

1) If the level of something rises, control systems reduce it again 2) If the level of something falls, control systems raise it again

How is the body's temperature regulated ?

1) Too hot : - Sweat glands in the skin release more sweat. The sweat evaporates, removing heat energy from the skin. - Blood vessels leading to the skin capillaries become wider so more blood flows through the skin, and more heat is lost. 2) Too cold : - Muscles contract rapidly (shivering). These contractions need energy from respiration, and some of this is released as heat. - Blood vessels leading to the skin capillaries become narrower - they constrict - letting less blood flow through the skin and conserving heat in the body. - Hair rises (to trap a layer of air above the skin, which helps to insulate the skin against heat loss.)

How is the body's water content controlled ?

Controlled to protect cells by stopping too much water from entering or leaving them. Water content is controlled by water loss from: 1) the lungs - when we exhale 2) the skin - by sweating 3) the body - in urine produced by the kidneys

How and why is the body's blood sugar level controlled ?

Controlled to provide cells with a constant supply of glucose for respiration. Controlled by the release and storage of glucose, which is in turn controlled by insulin.

What is homeostasis ? What is responsible for it?

Homeostasis is the maintenance of a constant internal environment. The nervous system and hormones are

What is insulin ?

Insulin is a hormone - produced by the pancreas - that regulates glucose levels in the blood.

Why is the body's temperature controlled ?

Need to be maintained at 37 degrees (temperature where enzymes work best)

Which part of the brain monitors the body's temperature ? How does it react to negative feedback ?

The hypothalamus. Receives information from temperature-sensitive receptors in the skin and circulatory system. Sends nerve impulses to effectors to maintain body temperature.

What is vasoconstriction ?

Vasoconstriction happens when it is too cold. Arterioles get narrower. Blood flow in skin capillaries decreases Heat loss from skin decreases.

What is vasodilation ?

Vasodilation happens when it is too hot. Arterioles get wider. Blood flow in skin capillaries increases. Heat loss from skin increases.