-The thermoreceptor detect the temperature change in blood or skin(lower than normal)

-The heat gain centre is stimulated and send the nerve impulses to the effector

-The effector receive the nerve impulses by the heat gain centre and give response.(eg. arterioles constrict)

Child birth procedure:

-Head of fetus pushes against cervix

-Nerve impulses from cervix transmitted to brain

-Brain stimulates pituitary gland to secrete oxytocin (trigger positive feedback)

-Oxytocin carried in bloodstream to uterus is released, trigger the action of expelling the baby out

-Oxytocin stimulates uterine contractions and pushes fetus toward cervix

—>cycle repeat

If negative feedback mechanism is used in child birth:

-head of fetus pushes against cervix

-nerve impulses from cervix transmitted to brain

-the secretion of oxytocin is inhibited by brain

-less oxytocin is carried to uterus

-uterine contractions is less stimulated and fetus stop pushing towards cervix

—>baby cannot be expelled

Some consequence of hormonal secretion acts on the secretory cells to provide an arguments drive for secretion.

As example in childbirth

Oxytocin is a type of hormone which is released to stimulate the contraction of uterine muscle(effector) in order to push the baby.

The reason why Positive feedback is better than negative feedback in childbirth is that negative feedback is tend to balance the body status like homeostatic. It will stop when the body back to normal. However positive feedback can keep high concentration of hormone that lead to the contraction and the release of baby. It firms that the baby can be pregnated successfully.

Positive response: intensification and amplification of the whole mechanism to enhance the original change.

• e.g during labour, when foetus is gradually moving towards to the cervix of mother, there will be an involuntary and frequent contraction of the abdominal muscles. This action intensifies eventually. Thus it is known as a positive feedback.

Negative feedback: the mechanism to stabilise the body internal environment to reduce deviation from the set point.

• blood glucose level: when one bgl is too high after consuming meal, the pancreas will stimulate liver to secrete more insulin and less glucagon to decrease the high bgl to normal level.

When one bgl is too low after long time of fasting, the the pancreas will stimulate liver to secrete more glucagon but less insulin to decrease the high bgl to normal level.

-Thermoreceptors:

  - Located in the hypothalamus: detect internal temperature (blood temperature).

  - Located in the skin: detect external temperature (body surface temperature).

-Response to Temperature Drop:

  - When a fall in body temperature is detected:

    - Thermoreceptors send nerve impulses to the heat gain centre.

    - The heat gain centre is stimulated.

    - It sends nerve impulses to various effectors.

-Effects:

  - Produces responses that:

    - Reduce heat loss.

    - Increase heat gain.

-Outcome: Normal body temperature is restored.