25. Homeostasis

Question 1

Homeostasis definition

Answer 1

Homeostasis is the maintenance of a constant internal environment within the body

Question 2

What needs to be kept constant in our internal environment

Answer 2

Temperature-37'C
pH-7.4
Sufficient levels of oxygen
Prevention of toxins building up (urea, CO2) and infection
Blood glucose levels
Water balance

Question 3

Importance of Homeostasis

Answer 3

1. For metabolism to function efficiently (respiration and digestion-optimum environment for enzymes)
2. Needed for organism to be independent of its surroundings for survival (endotherm)
3. Needed to adapt to slight fluctuations and stay efficient (sleep, puberty, menopause, menstrual cycle)

Question 4

Examples of Homeostasis:

Temperature

Answer 4

If Hot: vasodilation, hair follicles lie down, sweat

If Cold: shiver, piloerection, vasoconstriction

Question 5

Examples of Homeostasis:

Pathogens

Answer 5

Immune system
Skin
Circulatory system (WBC and platelets)
Lymphatic system (mature lymphocytes)
Stomach (HCL)
Tears, Saliva, Sweat (lysozome)
Liver (toxin removal)

Question 6

Examples of Homeostasis:

Blood glucose levels

Answer 6

Islets of Langerhans produce insulin

Question 7

Examples of Homeostasis:

CO2

Answer 7

Medulla oblongata in brain sends a signal to the lungs to breathe faster.

Question 8

Examples of Homeostasis:

pH and Water

Answer 8

Kidneys and excretory system

Hormone ADH

Question 9

What are endotherms

Answer 9

Warm blooded- fairly constant temperature
Independent of their environment
Keep rate of enzyme activity optimum regardless of environment
eg. Mammals and birds
Generate heat by metabolism

Question 10

What are ectotherms

Answer 10

Cold blooded-body temperature varies with the external environment.
They gain or lose heat based on environment
eg. fish and frogs

Question 11

Importance of diffusion and exchange in homeostasis

Answer 11

Most homeostatic processes involve the exchange of materials. eg. Oxygen and CO2
Therefore diffusion and exchange must be efficient

Question 12

Mechanisms to make diffusion and exchange efficient

Answer 12

Have developed systems that specialize in exchange (respiratory and excretory)
Plants have flat leaves to aid in exchange, and have lenticels and stomata
Large surface area in respiratory system for gaseous exchange
Alveoli with large supply of capillaries, moist thin walls.

Question 13

Homeostasis for temperature process

Elevated

Answer 13

Elevated because of exercise or environment.
Sensed by hypothalamus and nerves.
Capillaries dilate, sweat evaporates, hairs flatten. Behaviour- move into shade, less clothes.
Heat lost from body and temp drops.

Question 14

Homeostasis for temperature process

Low

Answer 14

Low because of environment.
Sensed by hypothalamus and nerves.
Hairs upright, capillaries dilate, erector muscle contracts.
Seek heat source, exercise, shiver, warmer clothes.
Heat increases to normal levels.