Science 24 Tutorial – October 30th

(refer to info in last tutorial)

Does anyone know what the term “homeostasis” means?

Ans. This is a state of equilibrium or balance that our bodies maintain. Part of this process requires that the body hold a steady temperature of approximately 37 deg. C.

How does our body regulate this? What happens when you are cold?

Ans. Shiver, blood vessels near the periphery constrict so that less thermal energy is lost to the environment.

What happens if you are too hot?

Ans. Blood vessels are brought closer to the surface, perspiration….evaporation of the moisture cools the body.

Does anyone know what some of the techniques might be used by emergency response workers to treat people suffering from hypothermia or hyperthermia?

Ans. Hypothermia – remove wet clothing and get them dry. Warn them by wrapping them in blankets or putting on dry clothing and moving them to warm place. Do not warm them too quickly by immersing them in warm water. Rapid rewarming can cause heart problems. Drink something warm, hot compresses (water bottle), get out of the wind.

Hyperthermia – get out of the sun, cool drink. Rest in cool place, loosen tight clothing, remove perspiration-soaked clothing, apply cool, wet cloths to skin and fan them.

In your assignment you are asked…

List and explain four methods that an organism such as a cat uses to stay warm on cooler days.

Ans. A cat has a number of options available to stay warm. You should suggest at least three of them. For example, the cat might:

• fluff up its fur to provide greater insulation;

• constrict blood vessels so less heat is released to its surroundings;

• shiver, and give off thermal energy by these muscle contractions;

• close its mouth so it will lose less heat by evaporation from its tongue (panting); or

• move to a warmer place.

What does the term “basal metabolic rate” mean?

Ans. The energy required to keep us alive.

Every individual has a unique basal metabolic rate. This means that individual bodies use energy at different rates and at different times of day.

Daily activities increase the cells’ respiration rate. For example, both exercise and stress will increase the amount of cellular respiration. With each energy conversion involved in cellular respiration, some thermal energy is given off. This increases the body’s internal temperature slightly.

As we have already discussed, the body has many negative feedback mechanisms that offset large changes in internal temperature.

Many people go to bed warm but wake up cold, even on a relatively warm day. That is because bodies use their least amount of energy during the deepest sleep periods — and therefore give off less thermal energy from energy conversions. At this point, the internal core temperature drops slightly.

Refer to Pg. 124 in your text. For U2L7 you were required to create a line graph. (show slide)

1. At which hour or hours does the lowest temperature occur? What is this person probably doing at this time?

Ans. Hour 5 and 6. The lowest temperature usually occurs between the hours of 4:00 and 5:00 A.M. This is when individuals reach the period of their deepest sleep.

2. Examine your graph. At which point do you think this student is participating in a rigorous sport? Explain your answer.

Ans. Hour 17 and 18. This is the time the body temperature is the highest, the time when the body is producing the most thermal energy.

3. a) Assume the lowest temperatures begin at 4am. Develop a time line below the horizontal axis (x-axis) that shows at which time of day each temperature was taken.

Ans. If the lowest temperatures occur at 4am, then hour 5 must be that time. This would change the x-axis to read: midnight, 1am, 2am, 3am, 4am, 5am, 6am, 7am, 8am, 9am, 10am, 11am, noon, 1pm, 2pm, 3pm, 4pm, 5pm, 6pm, 7pm, 8pm, 9pm, 10pm, 11pm.

b) Is there a relationship between normal eating times and temperature? What do you think could account for these changes?

Ans. Yes, the temperature rises slightly as energy is being used to break down the food that is being digested.

In U2L7, you learned about our three sources of energy. What are they?

Ans. Carbohydrates, fat, protein.

What can you tell me about carbohydrates?

Ans. Preferred source of energy for the body. (should be 55-65% of our daily calorie intake). What are 5 sources of carbos – bread, oatmeal, muffins, pasta,

Fats?

Ans. Insulation, source of energy behind carbos. Saturated (from animal fats and oils) vs. non- saturated (vegetable oils). (30%)

Protein?
Ans. Builds and maintains body tissues. Necessary for growth (10%)

If your body has too little of any of these nutrients it would result in the following:

Carbohydrates – lack of energy, weight loss

Fats: lack of energy, weight loss

Proteins: lack of energy, slowed growth, weakened immune system, poor body function.

Which nutrient will the body convert into energy last? Ans protein.

When might this be an advantage? Ans. When the energy from other foods has been used up, such as in an endurance race or during high levels of stress.

Turn to the review on page 133.

Read #16.

16. Ans. The best time for her snack is the earlier time. When a body goes without food, metabolism slows. This will make it more likely that she gains weight.

Discuss with students that some schools have breakfast programs because it is wise to begin the day with a well-balanced meal. This allows for higher energy levels and more productivity.

Read #17.

17. (a) Answers should contain a balance between carbohydrates, fats, and proteins that matches what is provided in the student textbook. Students should consider using a log for daily activity, because if activity drops, so should the size of each meal.

(b) To gain weight healthily, it would be wisest to increase the carbohydrate intake.

(c) Expect the following points:

• Reduce carbohydrate and fat intake.

• Increase physical activity.