homeostasis PART 2

homeostasis

maintaining a stable internal environment despite changes in the internal or external environment

importance of homeostasis (2)

-ensures cells function properly and avoid damage

-allows enzymes to work at their optimum temperature, ensuring efficient metabolic reactions.

factors that need to be kept constant (4)

-body temperature

-blood glucose concentration

-water potential of blood

-pH of blood

What conditions need to be maintained within cells? (5)

-pH

-temperature

-glucose concentration

-oxygen level

-carbon dioxide level

stimuli

change in environment

role of receptor

detects stimuli [and sends a signal to an effector]

examples of receptors (3)

-eyes

-skin

-ear

role of effector

makes a response to restore conditions to normal.

examples of effectors 

-muscles

-glands

negative feedback

reverses the change in internal environment to restore the normal/optimum level

con of negative feedback

only works within certain limits→If a change is too large, the system may not be able to restore normal conditions.

positive feedback

amplifies a change from the normal level.

positive feedback examples (2)

-blood clotting [platelets release a chemical which attract more platelets]

-childbirth [oxytocin stimulates uterine contractions]

why is positive feedback rare? (2)

-makes the internal environment unstable→ destabilises the system which is harmful for cells

-can cause harm if uncontrolled

pro of positive feedback

rapidly activates processes in the body

positive vs negative feedback

-change

-maintains homeostasis (yes or no)

positive feedback

-amplifies a change from normal level

-does not maintain homeostasis (as it doesn’t maintain a constant internal environment.)

negative feedback

-reverses change to restore normal level

-maintains homeostasis