1. Keystone Anchor
BIO.A.4.2 Explain mechanisms that permit organisms to maintain biological balance between their internal and external environments.
In other words - _______________________________________________ ______________________________________________________________ ______________________________________________________________
BIO.A Explain how organisms maintain homeostasis (e.g., thermoregulation, water regulation, oxygen regulation).

2. KEY CONCEPT Homeostasis - regulation and maintenance of a CONSTANT environment in the body
The term ‘homeostasis’ is derived from two Greek words; Homeo which means ‘unchanging’ and Stasis which means ‘standing’
It is an organism’s internal environment which ‘stays the same’

3. Type 1
Think about this person’s body, describe the factors that need to remain in homeostasis.

4. Sensors -gather data and detect changes
Control systems in the body.
pore
sweat
glands
hair
follicle
muscle
goose
bump
Sensors -gather data and detect changes
Control center - receives data, sends messages, usually the brain
-Communication system - delivers messages in form of nerve impulses and hormones to target organs, tissues
Targets – organ, tissue or cell that responds to change

5. Negative feedback loops are necessary for homeostasis.
Feedback compares current conditions to set ranges.
Negative feedback- counteracts change.
Reverses any change and returns body to set point
Negative Feedback Loop *
O2 / CO2 level returns to normal
Holding breath, CO2 levels rise,
Control system forces exhale, inhale
Keep athlete running

6. KEY CONCEPT Systems interact to maintain homeostasis.

7. Each organ system affects other organ systems.
Organ systems must also work together to keep the organism healthy.
There is no specific organ which controls homeostasis.
The skin, kidneys, liver, endocrine system, nervous system and sensory system all play a part in maintaining the internal environment within narrow limits.
The hypothalamus is involved
to a degree in each of these regulations

8. Type I Describe how this picture of an automotive race team is similar to the systems of a body.

9. Body cells work best if they have the correct
Temperature
Glucose concentration, (sugar)
Water levels
Homeostasis involves keeping the internal environment within set ranges

10. Organs and involved: skin regulate water & mineral salts concentration
Water - kidneys :
regulate water & mineral salts concentration
Thermoregulation –skin and muscles :
regulate body temperature
Glucose - liver & pancreas :
regulate blood glucose level
skin
tissue cells
kidney
blood
liver +
pancreas

11. Thermoregulation – process of maintaining a steady body temperature
Sweating
When your body is hot, sweat glands are stimulated to release sweat.
The liquid sweat turns into a gas (it evaporates)
To do this, it needs heat.
It gets that heat from your skin.
As your skin loses heat, it cools down.

12. Thermoregulation – process of maintaining a steady body temperature
Shivering
Hypothalamus signals skin and muscular, respiratory, and circulatory systems
Blood vessels constrict to reduce blood flow to prevent loss of heat
Muscles contract around pores
Muscles contract causing shivering
Thyroid releases hormones that increase
metabolism

13. Controlling Glucose levels
Your cells also need an exact level of glucose in the blood.
Excess glucose gets turned into glycogen in the liver
This is regulated by 2 hormones (chemicals) from the pancreas called Insulin and Glucagon
In this way, the concentration of glucose in the blood is kept within narrow limits

14. The glucose concentration in the blood is controlled by the pancreas12
The glucose concentration in the blood is controlled by the pancreas
The pancreas contains cells which produce digestive enzymes but it also produces the hormones insulin and glucagon
If the glucose concentration rises, the pancreas releases insulin
If the glucose concentration falls, the pancreas releases glucagon

15. Insulin stimulates the liver and muscles to remove excess glucose from the blood and store it as glycogen
Glucagon stimulates the liver to convert its stored glycogen into glucose which is then released into the bloodstream
In this way, the concentration of glucose in the blood is kept within narrow limits

16. Water Regulation
After having a very salty meal
produce concentrated urine to remove excess salts in solution form
extra water is needed to be excreted along with the excess salts
sensation of thirst (drink more water to compensate for the water loss)

17. Water Regulation
The amount of water in the blood must be kept more or less the same all the time to avoid cell damage as a result of osmosis.
There has to be a balance between the amount of water gained (from your diet though drinks and food and the water produced by cellular respiration) and the amount of water lost by the body (in sweating, evaporation, feces and urine).
This is achieved by the action of the hormone ADH (anti-diuretic hormone).

18. Water Regulation
Part of the brain, the hypothalamus, detects that there is not enough water in the blood. The hypothalamus sends a message to the pituitary gland which releases ADH.
This travels in the blood to your kidneys and as a result you make a smaller volume of more concentrated urine. The level of water in your blood increases until it is back to normal.
If the level of water in your blood goes up the hypothalamus detects the change and sends a message to the pituitary. The release of ADH into the blood is slowed down or even stopped. Without ADH the kidneys will not save as much water and you produce large volumes of dilute urine.
This is an example of negative feedback.

19. There are 11 major organ systems in the human body.

20. TYPE I
Name 3 systems that help maintain homeostasis and describe how they work to maintain homeostasis. 1. 2. 3.