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!

http://www.e-learningforkids.org/Courses/Liquid_Animation/Body_Parts/Endocrine_System/

Negative Feedback control

http://www.distance.mun.ca/media/samples/homeostasis/04_audio.swf

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.

http://bcs.whfreeman.com/thelifewire/content/chp41/4101s.swf

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 level

1. Detected by β cells in regions of pancreas called Islets of Langerhans

2. 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

http://www.medmovie.com/mmdatabase/

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