Homeostasis

Question 1

Homeostasis

Answer 1

It is the maintenance of a constant internal environment
(to help an organism be independent to changes in its external environment)

Question 2

Principles of homeostasis

Answer 2

1. Negative feedback
   - Occurs when the body reacts to bring an opposite effect to the changes detected
2. Stimulus
   - It is a change from the normal conditions in the internal environment
3. Receptor
   - Detects the stimulus
4. Corrective mechanism
   - Brings about a reverse effect from the stimulus

Question 3

Hormones

Answer 3

Hormones are chemical substances produced in minute quantities by endocrine glands

Question 4

Types of glands

Answer 4

1. Endocrine gland
2. Exocrine gland

Question 5

Endocrine gland

Answer 5

Endocrine glands are ductless glands that transport their secretions through the bloodstream

Example:
1. Pituitary gland
- Secretes Anti-diuretic hormones (ADH)
2. Pancreas
- Islets of langerhans in pancreas secrete insulin and glucagon to control blood glucose concentration

Question 6

Exocrine gland

Answer 6

Exocrine glands are glands with ducts that transport their secretions to target organs

Example:
1. Pancreas
- Secretes pancreatic juice through pancreatic duct

Question 7

When the water potential rises above normal

Answer 7

1. The hypothalamus in the brain detects this rise in water potential
2. The pituitary gland secretes less ADH into the bloodstream
3. Decreasing the permeability of the kidney tubules and collecting duct for less water to be selectively reabsorbed , causing more water to be excreted and urine to be less concentrated
4. Water potential decreases

Question 8

Effects of insulin

Answer 8

Insulin decreases blood glucose concentration:
- Stimulating the liver to convert glucose into glycogen for storage

Question 9

Effects of glucagon

Answer 9

Glucagon increases blood glucose concentration:
- Stimulating the liver to convert store glycogen into glucose for use

Question 10

When the blood glucose concentration rise above normal

Answer 10

1. The islets of langerhans in the pancreas detect the rise in blood glucose concentration
2. The islets of langerhans in the pancreas secrete more insulin into the bloodstream
3. The insulin stimulates the liver to absorb more and convert excess glucose into glycogen for storage
4. Blood glucose concentration decreases

Question 11

Diabetes mellitus

Answer 11

A condition where blood glucose concentration cannot be regulated

Cause:
- Insufficient insulin secretion

Question 12

Type 2 diabetes

Answer 12

The features of type 2 diabetes:
1. Late onset
2. Insulin is secreted but target cells do not respond well
3. Treatment through exercise and control over dietary intake

Question 13

Vasodilation

Answer 13

When arterioles dilate, more blood flows to the skin surface causing the skin to turn red

Question 14

Vasoconstriction

Answer 14

When arterioles contrict, less blood flows to the skin surface, causing the blood to turn pale

Question 15

Sweating

Answer 15

• Sweat is secreted by sweat glands and are carried to the skin surface via the sweat duct and sweat pore
• When sweat evaporates from the skin surface, heat is loss

Question 16

When body temperature rises above normal

Answer 16

1. The thermoreceptors in the skin detect this rise in temperature
2. Corrective mechanism:
   - Vasodilation of arterioles cause the arterioles to dilate and for more blood to flow to the capillaries near skin surface, allowing more heat to be loss through the skin

• Sweat glands secrete more sweat, as more water from sweat evaporates from the skin surface, more latent heat of vapourisation is loss through the skin surface
• Metabolic rate decreased, reducing the amount of heat produced

3. Body temperature drops

Question 17

When body temperature falls below normal

Answer 17

1. The thermoreceptors in the skin detect this drop in the temperature
2. Corrective mechanism:
   - Vasoconstriction of artetioles cause less blood to flow to the skin surface, causing less heat to be loss through the skin surface

• Less sweat is secreted by the sweat glands, as less sweat evaporates from the skin surface, less heat is loss through the skin surface
• Shivering occurs, the rapid contraction and relaxation of muscles increase the amount of heat released