B9.4 and B9.5 - Homeostasis and Tropic Responses Flashcards
What is homeostasis?
The maintenance of a constant internal environment.
What is negative feedback?
The mechanism for how homeostasis works.
A change that sets of a response that cancels the change.
Why does body temperature need to be controlled?
To maintain optimum enzyme activity.
Why does our blood glucose concentration need to be controlled?
To keep the blood/tissue fluid isotonic to the cells to prevent osmosis and the bursting or shrinking of our cells.
Why does our water concentration need to be controlled?
To keep the blood/tissue fluid isotonic to the cells to prevent osmosis and the bursting or shrinking of our cells.
What are the steps of negative feedback. [4]
- Deviation from the norm (above or below)
- Detected by receptors
- Effectors stimulated and initiate corrective mechanisms
- Restoration of the norm
Where does blood glucose come from?
Starch/carbs that you’ve eaten and digested.
When is the hormone insulin released?
When the level of blood glucose is too high.
Where is insulin released from?
Pancreas.
What does insulin do?
It allows the liver to turn excess glucose into glycogen.
What happens if the blood glucose level drops too low?
Glucagon is released.
What does glucagon do?
Makes the liver turn glycogen back into glucose.
What are the three mechanisms to reduce body temperature?
- Hairs lie flat.
- Sweating.
- Vasodilation.
What are the four mechanisms to increase body temperature?
- Hairs stand up
- Much less sweat
- Shivering
- Vasoconstriction
What happens in vasodilation?
- Shunt vessel narrows
- Arterioles widen/dilate
- Capillaries widen/dilate
-More blood flows through the capillaries in the surface of the skin - More heat is lost by radiation and conduction
What happens in vasoconstriction?
- Arterioles constrict
- Shunt vessel widens
- Less blood to capillaries near surface of skin so less heat loss
Where is sweat produced and what does it do?
- Sweat gland
- Is secreted onto surface of skin where it evaporates and cools the skin
What is the role of the fatty tissue?
Insulation.
What is the muscle that makes the hair stand up called?
Hair erector muscle.
What is a tropism?
A growth response of a plant to a directional stimulus.
What is phototropism?
A response in which parts of a plant grow towards or away from the direction from which light is coming.
Where is positive phototropism found and why?
Shoots because light is needed for photosynthesis.
Where is negative phototropism found and why?
Roots because roots need to be anchored in the ground and also access minerals and water.
What is gravitropism?
A response in which parts of a plant frow towards or away from gravity.
Where are positive and negative gravitropism found?
Positive = roots
Negative = shoots
What is the plant hormone that chemically controls growth near the tips of shoots?
Auxin.
