D3.3 Homeostasis

Part of the Organ Systems unit IB Biology Sl

Homeostasis

Mechanisms that help organsims maintain a relatively constant internal environment despite changes that occur in the external environment

Aim of homeostasis

To keep the variables of the body within preset limits despite changes in environment

Types of variables in the body

Blood glucose concentration

Blood osmotic concentration

Body Temperature

Blood pH

What type of feedback is homeostasis

Negative feedback because it opposes a change in the environment (counteracts change).

Positive feedback strengthens change

Which organ maintains blood sugar levels and where is it

Pancreas (behind stomach)

What cells produce the necessary hormones to maintain blood sugar

The islets of Langerhans (in the endocrine tissue in the pancreas)

What hormones are used to maintain blood sugar levels

Insulin (too high) and glucagon (too low)

Insulin:

• Where produced

• When is it produced

• What is its target

• What does it stimulate

• Effect

1. Beta cells

2. Blood glucose levels increase

3. Targets body cells (mainly muscle and liver)

4. Stimulates transport of glucose from bloodstream into the cells

5. Decreases blood glucose level

Glucagon:

• Where produced

• When is it produced

• What is its target

• What does it stimulate

• Effect

1. Produced and secreted in alpha cells

2. Blood sugar too low

3. Targets liver cells

4. Stimulates break down of glycogen and fat into glucose and uptake into the blood

5. Increases blood sugar levels

What causes diabetes

Insufficient insulin production or when the individual is insensitive to insulin. This leads to blood glucose levels to be extremely high

Explain two early signs of diabetes

Kidneys filter excess glucose into urine and dilute the urine by drawing excessive water from the body. This leads to dehydration and excessive urination.

Type 1 diabetes

• Origin

• When does it occur

• Cure

• Treatment

1. When the immune system mistakely attacks beta cells so they cannot produce insulin leading to very high blood sugar levels

2. Occurs in adolescence

3. No cure

4. Insulin injection/patch and dietary modifications

Type 2 diabetes cause and how to reverse it

Insulin insensitivity

Reverse by moderate weight loss, heathly diet and regular excercise.

5 risk factors for diabetes

lifestyle - lack of excersise, more excersise increases insulin sensitivity

diet - high in processed foods, sugar and unhealthy fats

family history

body weight - high weight increases insulin resistance

Age - risk increases as you age

Where does temperature control occur

Hypothalamus and pituatary gland

(hypo is control centre, pituatary gland secretes hormones to regulate temperature)

What do we use to detect changes in temperature

Thermoreceptors (peripheral and central)

Peripheral is in skin and central is in body

What is the role of thyroxin

Increases metaboic rate in cells which results in more heat produced

how is thyroxin released

hypothalamus —> pituitary gland releases thyroid stimulating hormone —> thyroid gland releases thyroxin when it is cold

When hot thyroid stimulating hormone is stopped being secreted so thyroxin prodcution decreases.

what do muscles do when it is cold

involutary contractions (shivering)

hair follicle muscles contract causing them to stand up and trap a layer of air to act as a thermal insulator.

what does the skin do when it is hot

Secretes sweat and water evaporates cooling skin (latent heat of water)

what does the circulatory system do when it is hot

Vasodilation - widens arteriols - increases flow to skin surface so heat can be emitted via conduction and convection

what does the circulatory system do when it is cold

vasoconstriction - narrows arterioles - decreases blood flow rate to prevent heat loss and keep heat around vital organs

What is uncoupled respiration

Brown adipose tissue are fat storing tissues filled with mitochondria.

The mitochondria release energy without using ATP to increase body heat when cold, known as uncoupled respiration