Temperature Regulation We need to regulate body temperature to provide the optimum conditions for enzyme-catalysed reactions to be carried out.

Body Temperature Normal internal body temperature is 37 0 C. Temperatures above this: denature(change)enzymes and block metabolic pathways Temperatures below this: slow down metabolism and affect the brain.

Water Bath Temperature set on thermostat Too cool? Heater kicks on and temperature goes up Too warm? Heater stays off until bath cools down Constant checking and turning on and off

Control of homeostasis through negative feedback Negative-Feedback system- cycle of events in which the status of a body condition is continually monitored, evaluated, changed, re- monitored, re-evaluated, etc.

1) receptor – sensor that responds to changes (stimuli) 2) control centre – sets range of values, evaluates input and sends output 3) effector – receives output from control centre and produces a response 3 basic components of a feedback system

Body Temperature Control The hypothalamus acts as a thermostat and receives nerve impulses from heat and cold thermoreceptors in the skin. There are also receptors in the hypothalamus- called central thermoreceptors. These detect changes in blood temperature.

Vasoconstriction and Vasodilatation

Correction of overheating 1. Detected by thermoreceptors in the hypothalamus. 2. Causes vasodilation. 3. Sweating

Cooling down When it's hot and you need to cool down, muscles at each hair relax.hair Hairs lie close to the skin. Air does not act as an insulating layer.

Sweating Heat energy in the body is used to convert the water in sweat to vapour cooling down the body.

Correction of overcooling 1. Detected by thermoreceptors in the hypothalamus. 2. Causes vasoconstriction. 3. Decreased sweating 4. Shivering

Keeping warm When it's cold, the muscle contracts pulls the hair up. A layer of warm air accumulates around the hair and insulates the organism. Heat retained

Controlling Glucose levels (another negative feedback mechanism) Your cells also need an exact level of glucose in the blood. Excess glucose gets turned into glycogen in the liver This is regulated by 2 hormones (chemicals) from the pancreas called: Insulin Glucagon

If there is too much glucose in the blood, Insulin converts some of it to glycogen Glycogen Insulin Glucose in the blood

If there is not enough glucose in the blood, Glucagon converts some glycogen into glucose. Glycogen Glucagon Glucose in the blood

Diabetes Some people do not produce enough insulin. When they eat food, the glucose levels in their blood cannot be reduced. This condition is known as DIABETES. Diabetics sometimes have to inject insulin into their blood. They have to be careful of their diet and exercise.

Time Glucose Concentration Meal eaten Insulin is produced and glucose levels fall to normal again. Glucose levels rise after a meal. Normal

Time Glucose Concentration Meal eaten Insulin is not produced so glucose levels stay high Glucose levels rise after a meal. Diabetic

The glucose in the blood increases. Glycogen Insulin Glucose in the blood But there is no insulin to convert it into glycogen. Glucose concentration rises to dangerous levels.

In summary: Temperature regulation and insulin/glucagon are examples of negative feedback occurring in the body. These are maintained within a range of normal values around a set point despite constantly changing external conditions.