Homeostasis PART 2

Skin (Last Lesson)Summary of Skin Structure Epidermis - New cells form by mitosis. New cells move to surface and die forming Cornified Layer. Protects living cells below. Contains Melanin to protect from UV rays Hair follicles form when epidermis folds inwards Dermis – Formed from connective tissue. Contains Sweat Glands, blood vessels and nerve endings. Adipose Tissue – Fatty tissue containing oil. Insulates against the cold. Energy storage.

How we keep our body temperature constant• What is the Hypothalamus?

• The Hypothalamus is a part of the brain which helps regulate body temperature

How we keep our body temperature constant • How?• The hypothalamus co-ordinates the activities of the parts of the body

that can effect temperature changes.

• Thermostat (in your house) - Contains temperature receptors (senses blood running through it)- 37 degrees!!!- Hypothalamus then sends electrical impulses to appropriate parts of the body (along nerves)

How we keep our body temperature constant  

• Below 37 degrees• Muscles relax and contract very quickly (SHIVERING). - This causes heat to generate, which then warms the blood, and spreads the heat around the body.

• Metabolism may increase – speed of respiration increases to release more heat.• Hair stands up – erector muscles contract. Acts as an insulator in furry animals

by trapping warm air next to the skin. Humans (not useful)• Vasoconstriction – causes surface capillaries to become narrower. (constricted).- Less blood runs through, forcing blood to run through deeper cap. beneath fatty tissue (insulation)

How we keep our body temperature constant   

• Above 37 degrees • Hair lies flat – erector muscles relax. • Vasodilation – surface capillaries widen (dilate). More blood can flow through.- Blood is near the surface so heat is lost easily into the air.• Sweat glands secrete sweat. Sweat on hot skin evaporates taking heat from the

skin with it.

• More blood is supplied to sweat glands to produce more sweat.

How we keep our body temperature constant Hypothalamus senses

blood temperature (receptors)

Sends electrical impulses to necessary parts of the

body(nervous system)

Muscles (shivering)Erector muscles (hairs)

Capillaries constrict

Sweat glands (sweating)Erector muscles (hairs)

Capillaries dilate

The role of negative feedback in homeostasis• What is negative feedback?• "A mechanism in which a change in parameter brings about actions

that push it back to normal"

• A stimulus causes an opposite effect to maintain the normal level

• If we are too hot mechanisms occur to cool us down, until we are back to normal levels. Then mechanisms are stopped. And vice versa.• Hypothalamus is constantly monitoring any small changes in the

blood temp.

Experiment• Write how we could test this hypothesis: A large body cools more slowly than a small one.

Next time?

How the pancreas and liver help to keep blood glucose concentration steady• Why is glucose concentration important?• Cells need a steady supply of glucose for respiration (especially brain

cells)

• However• Too much glucose can cause water to move out of cells through

osmosis. Effecting metabolic processes.

How the pancreas and liver help to keep blood glucose concentration steady• How is the glucose level controlled?• By the pancreas and the liver.

• Negative feedback

• Glucose too high = Islets of Langerhans (pancreas) release Insulin- Liver uses some of the glucose in resp. & stores some as glycogen. • Glucose too low = Islets of Langerhans release Glucagon• - Liver breaks down glycogen into glucose

How the pancreas and liver help to keep blood glucose concentration steady • Insulin hormone secreted by the pancreas to reduce glucose level• Glucagon hormone secreted by the pancreas to raise glucose level

• IMPORTANT

• Glycogen is glucose stored in the liver.

How the pancreas and liver help to keep blood glucose concentration steady • What is Diabetes?• A condition where a persons blood glucose concentration isn't

controlled properly.

• Type 1 Diabetes is an auto-immune disease, where the body's own immune system attacks and destroys insulin producing cells(in pancreas)

How the pancreas and liver help to keep blood glucose concentration steady • Person without Type 1 Diabetes:-• Eating carbohydrates causes rise of glucose level, triggers pancreas to

release Insulin, return level to normal.

• Person with Type 1 Diabetes:-• Glucose level rises and stays up (HYPERGLYCAEMIA)

• Signs – dry mouth, blurred vision, thirst, increased heart rate/breathing

How the pancreas and liver help to keep blood glucose concentration steady 

• And vice versa• Person without Type 1 Diabetes:-• Not eating carbohydrates causes drop of glucose level, triggers pancreas to release

glucagon which breaks down stored glycogen, level returns to normal.

• Person with Type 1 Diabetes:-• Glucose level drops and stay low (HYPOGLYCAEMIA) the person doesn't have the

stored glycogen levels in liver

• Signs – tired (no glucose for resp.), confusion/irrational. Eventually unconsciousness• People can eat something sweet when these signs start to occur.

How the pancreas and liver help to keep blood glucose concentration steady 

• Prolonged fluctuations of high and low glucose levels can have longterm harmful effects on bodily organs.

• Therefore• People check their blood regularly (blood sugar monitoring device)• Or • People can check their urine (dipsticks)• Glucose should be reabsorbed by the kidneys (nephron) so urine shouldn't

contain any.• If it does, levels are too high for the kidney to function properly.

How the pancreas and liver help to keep blood glucose concentration steady 

• What else doe people with type 1 Diabetes need to do?

• They need to inject themselves with Insulin• They need to eat little and often• They need to avoid large amounts of carbohydrates