Hormones and Homeostasis
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Hormones and Homeostasis IB Biology Topic 6
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Hormones and Homeostasis. IB Biology Topic 6. Group Activity. Which group can come up with the biggest list of hormones you have already come across in biology? You have 2 min!. Negative Feedback control. Involuntary responses. Mechanisms of temperature regulation are involuntary - PowerPoint PPT Presentation
Transcript of Hormones and Homeostasis
Hormones and HomeostasisIB Biology
Topic 6
Group Activity
• Which group can come up with the biggest list of hormones you have already come across in biology?
• You have 2 min!
Negative Feedback control
Involuntary responses
• Mechanisms of temperature regulation are involuntary
• Controlled at a subconscious level by the hypothalamus
Vasodilation
• Skin becomes dilated
• Large volume of blood flows through capillaries near skin surface
• Blood able to lose heat by radiation
Increase in rate of sweating• Heat energy from body• Convert sweat into water vapour• Lowers body temperature
Vasoconstriction• Arterioles leading to skin become
constricted• Small volume of blood flow to surface
capillaries• Little heat lost by radiation
If the temperature falls, the blood vessel constricts (gets shut off).
This means less heat is lost from the surface of the skin
Decreased rate of sweating• Sweating reduced to a minimum• Heat conserved
Contraction of erector muscles• Wide layer of air trapped between
body and external environment• Air poor conductor of heat• Layer of insulation reduces heat
loss
Voluntary responses• Body temperature drops below
normal• Nerve impulses transmit this
information to cerebrum• Person ‘feels cold’• Takes appropriate action to correct
problem-puts on a jacket-has a cup of tea etc.
EVERYONE (except Alonso!)• Write down as a group EVERYTHING you know or heard about diabetes
under these three headings
1. The science of the disease
2. The lifestyle change for the individual
3. The cure/medication
Then Alonso or I will check it!
Not This Cure!!
Control of blood sugar level• Living cells need a continuous supply
of energy
• Most of this energy released by oxidation of glucose
• Cells using up glucose present in bloodstream (blood sugar)
Homeostatic Mechanism• Body only obtains supplies of glucose
when food is eaten
• Need to guarantee regular supply of glucose regardless of how often food is consumed
• Body employs a homeostatic mechanism
The Liver• 100g of glucose stored as glycogen
in the liver
• Glucose can be added or removed from this reservoir of stored carbohydrate
Rise in blood sugar level1. Detected by β cells in regions of
pancreas called Islets of Langerhans2. Receptor cells produce insulin3. Hormone transported in bloodstream to
the liver4. Insulin activates an enzyme which
catalyses glucose glycogen5. Blood sugar concentration brought down
to normal
Drop in blood sugar level• Detected in α cells by Islets of
Langerhans• Release the hormone glucagon• Glucagon transported to the liver and
activates a different enzyme which catalyses the reaction
• glycogen glucose
Diabetes mellitus• 2 types of diabetes
• Type I diabetes
• Type II diabetes
Type I diabetes
• Insufficient insulin produced
Causesbody produces antibodies against insulin and/or
β cells in Islets of LangerhansTreatment Inject insulin (why can´t you just take a tablet?)Transplant pancreas or β cells
Type II diabetes• Insufficient insulin produced• Body cells become less sensitive to insulin
CausesObesity, age, familiy history
Treatment Eat less carbsExercise and lose weightMedication (lower blood glucose and increase insulin production)
Absence of insulin• Cells unable to use glucose efficiently• Fat stores become depleted• Weight loss• Tissue wastage
