homeostasis- principles of homeostasis and negative feedback

Question 1

define homeostasis

Answer 1

involves physiological control systems that maintain the internal environment within restricted limits.

Question 2

how does the endocrine system carry out homeostasis

Answer 2

1. communication through hormones
2. hormones carried through the circulator system
3. stimulate target cells that have specific receptors
4. the effect is slow, long lasting and widespread

Question 3

what affect does the endorine system have on target cells ?

Answer 3

1. affests the permiability of the cell-surface membrane
2. causes the release of a ‘second’ messenger inside cell
3. diffuse into cells and promote/inhibit transcription

Question 4

define negative feedback

Answer 4

a series of changes that restore the condition to the set point when it moves away from this point

Question 5

define positive feedback

Answer 5

a series of changes that enhance a condition from the set point when i moves away from this point, when a small change is detected

Question 6

why is negative feedback important

Answer 6

ensures conditions remain within the tolerance range

Question 7

why is positive feedback important

Answer 7

useful when a stimuli needs to be amplified to produce the desired effect, amplifies change from the normal level

Question 8

why can positive feedback be unhelpful

Answer 8

when the increase in response cannot be controlled

eg. leading to hyper/hypo thermia

Question 9

what are the 3 conditions for negative feedback to occur?

Answer 9

1. detected a change in the internal environment
2. siganlled to other cells
3. response is to reverse the change

Question 10

how is heat lost?

Answer 10

1. some lost when:
   - breathing, urinating, defecating
2. mostly from skin:
   - evapourating (heat energy evapourating liquid)
   - radiation (infrared)

Question 11

how do endothermers regulate body heat

Answer 11

1. maintain body heat at a set point
2. generate heat energy through respiration
3. change celluar energy and physiological processes
4. hypothalamus monitors blood temperature
5. also receives nerve impulses from peripheral receptors
6. impulses sent to the thermoregulatory centre within hypothalamus if change is detected

Question 12

how do exotherms regulate body heat

Answer 12

1. mostly rely on external heat energy

2. warm/cool their bodies by changing behaviour

Question 13

why is maintaining a stable core temperature important?

Answer 13

1. enzymes work at optimum
2. Too low- not enough KE; fewer ES complexes form
3. Too high- enzymes denature as H bonds in tertiary structure break; shape of active site changes; substrate no longer complementory to active site; fewer ES complexes form

Question 14

why is it important to maintain a stable blood pH?

Answer 14

1. enzymes work at optimum pH
2. Too low/high- enzymes dentaure as ionic bonds in tertiary structure break; shape of active site changes; substrate no longer complementory to active site; fewer ES complexes form

Question 15

what is the importance of maintaining stable blood glucose concentration?

Answer 15

1. Too low
   - not enough glucose for respiration; less ATP produced
   - active transport cannot occur
2. Too High
   - blood has low water potential
   - water lost from tissue to blood via osmosis
   - kidneys cannot absorb all glucose; more water lost in urine causing dehydration