27.2 the principles of feedback mechanisms

Question 1

why is feedback loop important

Answer 1

• informs receptor that effector has corrected the deviation from the set point
• if not, receptor will continue to stimulate the effector
• leading to over correction and further deviation in the opposite directions

Question 2

two types of feedback

Answer 2

1) negative feedback

2) positive feedback

Question 3

negative feedback occurs when…

Answer 3

• when the feedback causes the corrective measures to be turned off
• it returns the system to its set point

Question 4

control mechanism when blood temperature rises excluding feedback loop (e.g. during heavy exercise)

Answer 4

1) thermoreceptors (receptors) in the hypothalamus send nerve impulses to heat loss centre (controller) in the hypothalamus
2) this sends impulses to the skin (effector); vasodilation, sweating, and lowering of body hair leads to a reduction in blood temperature - it reaches the set point again

Question 5

control mechanism when blood temperature rises including feedback loop (e.g. during heavy exercise)

Answer 5

1) cooler blood returning from skin passes through the hypothalamus
2) thermoreceptors detect that blood temperature has returned to normal and stops sending nerve impulses to heat loss centre
3) impulses sent to skin to vasodilate and sweat stop
4) blood temperature remains constant at set point

Question 6

what is vasodilation

Answer 6

• relaxation of smooth muscle

- which leads to blood vessel to dilate

Question 7

how does vasodilation help with reducing blood temperature

Answer 7

• it helps to direct a higher flow of blood toward your skin

- heat is able to escape to external environment

Question 8

what would happen if there is no negative feedback to stop the skin from lowering blood temperature

Answer 8

• hypothermia occurs
• body temperature decreases much below the normal internal temperature
• reducing biochemical reactions and metabolic processes

Question 9

control mechanism when blood temperature falls excluding feedback loop

Answer 9

1) thermoreceptors (receptors) in the hypothalamus send nerve impulses to heat gain centre (controller) in the hypothalamus
2) this sends impulses to the skin (effector); vasoconstriction, reduced sweating, and raising of body hair leads to a rise in blood temperature - it reaches the set point again

Question 10

control mechanism when blood temperature falls including feedback loop

Answer 10

1) warmer blood returning from skin passes through the hypothalamus
2) thermoreceptors detect that blood temperature has returned to normal and stops sending nerve impulses to heat gain centre
3) impulses sent to skin to vasoconstrict and reduce sweat stop
4) blood temperature remains constant at set point

Question 11

what gives negative feedback a greater degree of homeostatic control

Answer 11

• is having many separate negative feedback mechanisms that control departues from norm in either direction

Question 12

positive feedback occurs when…

Answer 12

• when feedback causes the corrective measures to remain turned on
• it causes system to deviate away from the set point

Question 13

examples of positive feedback

Answer 13

• muscle contractions of the wall of the uterus during birth giving
• hypothermia (temperaature < normal)
• hyperthermia (temperature > normal)

Question 14

why does positive feedback occur

Answer 14

• when there is a breakdown of control systems

- usually in extreme conditions