Topic 7 Flashcards Preview

GCSE Edexcel Biology grade 9-1 course, topics 6-9 > Topic 7 > Flashcards

Flashcards in Topic 7 Deck (200)
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151

what is homeostasis?

maintaining a constant internal environment

152

what does MACIE stand for?

maintaining a constant internal environment.

153

why does the body have to have a constant internal environment?

to keep cells in the correct conditions in order to function properly, this includes the correct conditions for enzyme action. it can damage organs and result in unconsciousness or death if the body's conditions vary too much from normal levels.

154

what are the main processes in homeostasis?

•blood glucose regulation
•thermoregulation
•osmoregulation

155

what can the negative feedback mechanism be used for?

homeostasis (blood glucose regulation, thermoregulation and osmoregulation) and controlling the levels of hormones in the blood.

156

what is an example of when homeostasis doesn't work?

diabetes

157

what is type 1 diabetes?

a condition when the pancreas produces little to no insulin

158

how can a person with type 1 diabetes be treated?

with insulin therapy: this usually involves injecting insulin into the blood and is often done at mealtimes so the glucose is removed from the blood quickly once the food has digested.

159

where is insulin normally injected in people with type 1 diabetes?

in the subcutaneous tissue - the fatty tissue just underneath the skin

160

what does the amount of insulin someone with type 1 diabetes needs to inject depend on?

the person's diet and how active they are

161

what do people with type 1 diabetes need to consider apart from insulin therapy?

•limiting their intake of foods rich in simply carbohydrates (sugars) which cause the blood glucose level to rise rapidly.
•taking regular exercise which helps to remove excess glucose from the blood

162

what are the dangers of injecting too much insulin in insulin therapy?

it could result in a dangerously low blood glucose level

163

what is type 2 diabetes?

a condition when the pancreas doesn't produce enough insulin or when a person becomes resistant to insulin (their body's cells don't respond properly to the hormone)

164

which type of diabetes correlates with obesity?

type 2

165

when are people classed as obese?

when they have a BMI over 30

166

what does BMI stand for?

Body Mass Index

167

How is BMI worked out?

mass (kg)
—————
height² (m)

168

what is associated with an increased risk of type 2 diabetes?

a lot of fat being stored around the abdomen (tummy area)

169

how can you get an indication about how fat is stored in someone's body?

calculate their waist-to-hip ratio

170

how do you calculate waist-to-hip ratio?

waist circumference (cm)
———————————
hip circumference (cm)

171

a waist-to-hip ratio above what is associated with an increased risk of type 2 diabetes in men? why?

1.0, because it indicates that a lot of fat is being stored around the abdomen

172

a waist-to-hip ratio above what is associated with an increased risk of type 2 diabetes in women? why?

0.85, because it indicates that a lot of fat is being stored around the abdomen.

173

how can type 2 diabetes be controlled?

by eating a healthy diet, getting regular exercise and losing weight if needed. some people with type 2 diabetes also have medication or insulin injections.

174

what is the optimum temperature for enzymes in the body?

37°C

175

what happens to enzymes when above their optimum temperature?

they begin to denature and so they can't work at all and enzyme activity stops

176

what happens to enzymes below their optimum temperature?

enzyme activity decreases

177

what happens when the body temperature changes?

the thermoregulatory centre reverts the body temperature back to 37°C

178

where is the thermoregulatory centre?

in the hypothalamus

179

how does the thermoregulatory centre work?

it contains receptors that are sensitive to blood temperature in the brain and it receives impulses from nerve endings in the skin which provide information about the external temperature. these nerve endings are in the dermis and epidermis.

180

how does thermoregulation work when you are too hot?

•the erector muscles relax so the hairs on the skin lie flat so there is not an insulating layer of air

•lots of sweat (containing water and salt) is produced pub the sweat glands in the dermis. Sweat is released onto the skin and when the sweat evaporates energy is transferred from the skin to the environment, cooling the body down.

•the blood vessels near the surface of the skin dilate, resulting in more blood flow near the skin surface so more energy is transferred to the surroundings. This is vasodilation.