Requirements 11.3.3 Alcohol thermometers Strip thermometers Infrared thermometer.

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Transcript of Requirements 11.3.3 Alcohol thermometers Strip thermometers Infrared thermometer.

  • Slide 1
  • Requirements 11.3.3 Alcohol thermometers Strip thermometers Infrared thermometer
  • Slide 2
  • CONTROLLING BODY TEMPERATURE p.254-5
  • Slide 3
  • Specification Sweating helps to cool the body. More water is lost when it is hot, and more water has to be taken as drink or in food to balance this loss. [B3.3.2 a)] Body temperature is monitored and controlled by the thermoregulatory centre in the brain. This centre has receptors sensitive to the temperature of the blood flowing through the brain. [B3.3.2 b)] Also temperature receptors in the skin send impulses to the thermoregulatory centre, giving information about skin temperature. [B3.3.2 c)] If the core body temperature is too high: blood vessels supplying the skin capillaries dilate so that more blood flows through the capillaries and more heat is lost sweat glands release more sweat which cools the body as it evaporates. [HT only] [B3.3.2 d)] If the core body temperature is too low: blood vessels supplying the skin capillaries constrict to reduce the flow of blood through the capillaries muscles may shiver their contraction needs respiration, which releases some energy to warm the body. [HT only] [B3.3.2 e)] Controlled Assessment: B4.3 Collect primary and secondary data. [4.3.2 c) d) f)]; B4.4 Select and process primary and secondary data. [4.4.1 a) b)], [4.4.2 a) b) c)]
  • Slide 4
  • Objectives Internal (core) temperature is kept steady by a thermoregulatory centre in the brain Control relies on sensing blood temp. in the brain, and the outside temp. through skin sensors. The skin contains effectors which increase or decrease heat loss Negative feedback and the thermostat principle explain how the core is kept steady
  • Slide 5
  • Activities Lecture/slides on temperature control Paperwork/diagrams Thermometer practical Homework
  • Slide 6
  • Why control temperature? Environmental temperature is constantly changing. One minute it can be very hot, the next very cold. Even slight changes in body temperature can have a life- threatening effect on health. If body temperature falls too low, reactions become too slow for cells to survive: too high, and the bodys enzymes are at risk of denaturing. Despite this, the body must be kept at a constant temperature of 37 C. Why? This is the optimum temperature for the bodys enzymes.
  • Slide 7
  • What is core body temperature? The vital organs located deep within the body, such as the heart, liver and kidneys, are maintained at 37 C. This is the core body temperature. Skin temperature at the body's extremities, such as the fingers and toes, is usually lower than the core body temperature. On a warm day, skin temperature may be just 1 C lower than the core body temperature, but on a very cold day it could be up to 9 C lower.
  • Slide 8
  • Finding the right balance Core temperature is maintained by balancing heat gain and heat loss. How can heat be gained? How can heat be lost? movement and exercise shivering vasoconstriction wearing extra clothing. sweating vasodilation removing extra clothing.
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  • Too hotor too cold?
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  • Finding the right balance
  • Slide 11
  • How is temperature controlled? Body temperature is monitored and controlled by temperature receptors in the skin and brain. hypothalamus These receptors detect changes in the temperature of blood flowing through those areas. The thermoregulatory centre in the brain is called the hypothalamus. If body temperature deviates from 37 C, the hypothalamus and skin receptors send out electrical signals that trigger actions or behaviours that increase or decrease heat loss.
  • Slide 12
  • Whats in skin?
  • Slide 13
  • Why do we shiver? When core body temperature drops, muscles begin to twitch. This rapid and contraction and relaxation of the muscles is called shivering. Shivering generates heat, which raises body temperature. Goose bumps involuntarily appear when a person becomes cold. Goosebumps are caused by the tiny muscles at the base of body hairs pulling the hairs erect. The upright hairs trap an insulating layer of air, which helps reduce heat loss.
  • Slide 14
  • Vasoconstriction and warming up Why do people go pale when they are cold? Vasoconstriction is caused by contraction of the muscular wall of the blood vessels. When core body temperature falls, blood vessels in the skin get narrower. This is called vasoconstriction. This reduces the volume of blood flowing near the skin surface, and reduces the amount of heat lost from the body.
  • Slide 15
  • Vasodilation and cooling down Why do people turn red when they are hot? Additional cooling occurs with the production of sweat from sweat glands. Vasodilation allows a larger volume of blood to flow near the skin surface, transferring heat to the environment. This cools the body down. When core body temperature rises, blood vessels in the skin get wider. This is called vasodilation. As the sweat evaporates it transfers heat away from the body.
  • Slide 16
  • Responding to change
  • Slide 17
  • In your notes you need 1. A labelled skin diagram 2. A picture of the regulation mechanism- fig.2 p.255 3. The ways heat is lost from the body. Include a labelled skin diagram 4. How heat is gained and conserved. Include a labelled skin diagram 5. What has to happen if you sweat a lot to balance water in the body evaporation cools 1 highlight sweat glands, hairs capillaries 2 Body temperature is monitored and controlled by the thermoregulatory centre in the brain. This centre has receptors sensitive to the temperature of the blood flowing through the brain. 2 Also temperature receptors in the skin send impulses to the thermoregulatory centre, giving information about skin temperature. 3 If the core body temperature is too high: blood vessels supplying the skin capillaries dilate so that more blood flows through the capillaries and more heat is lost sweat glands release more sweat which cools the body as it evaporates. 4 If the core body temperature is too low: blood vessels supplying the skin capillaries constrict to reduce the flow of blood through the capillaries muscles may shiver their contraction needs respiration, which releases some energy to warm the body. 5 Sweating helps to cool the body. More water is lost when it is hot, and more water has to be taken as drink or in food to balance this loss.
  • Slide 18
  • Activity Work in pairs 1.Use the infra red thermometers or the temp. probes to measure Core Temp. 2.Measure the skin Temps on upper and lower leg and arm. 3.NOW either exercise for 1 min and repeat the readings OR go outside and stand in the cold for 2 minutes and repeat 4. Show the results in a table, and explain using the ideas in fig2 p.255
  • Slide 19
  • Homework Finish the conclusions to the core and extremities activity OR page 114 in workbook
  • Slide 20
  • Slide 21