Tag: coordination in human beings- chemical control

• A feedback mechanism for multistep reactions is a biological occurrence wherein the output of a system amplifies the system (positive feedback) or inhibits the system (negative feedback).
• For example, a positive feedback system is childbirth. During labour, a hormone called oxytocin is released that intensifies and speeds up contractions and facilitates childbirth.
• Hence A major regulatory mechanism for multistep reactions is the feedback mechanism.
• So, the correct answer is 'Feed-back mechanism'.

• The prostaglandins are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals.
• Prostaglandins have been found in almost every tissue in humans and other animals. 
• They are derived enzymatically from the fatty acid arachidonic acid. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring. 
• They are a subclass of eicosanoids and of the prostanoid class of fatty acid derivatives. Hence, Prostaglandins are complex fatty acids that function as intercellular messengers.

Negative feedback, a self-regulated process occurs when some function of the output of a system process, or mechanism is fed back in a manner that tends to reduce the fluctuation in the output whether caused by the changes in the input or by other disturbance.

Endocrine glands----> hormones-----> blood----> organs / tissues----> biochemical / physiological activity.

In feed back inhibition product of a reaction inhibits the enzyme catalysing that reaction. It is a type of control mechanism at the enzyme level. If the product is produced in sufficient amount, it inhibits the enzyme to stop the further production. So, the correct answer is 'End product'.

Accumulation of end products triggers an inhibiting action as a feedback inhibition of the metabolic pathway causing its inhibition. as a result, the metabolic pathway is switched off or halted. For example, the absence of the suckling stimulus leads to inhibition of the milk secretion.

Most hormones are regulated by feedback mechanisms. A feedback mechanism is a loop in which a product feeds back to control its own productions. Most negative feedback loops get involved from hormone feedback mechanisms. Here the time delay occurs and hormones are released.

There are two sets of nerve cells in the hypothalamus that produce hormones.

The feedback mechanism is the process wherein the upregulation and downregulation of genes, hormones, homoeostasis and other factors are controlled. For example, if the level of sugar concentration in blood has increased feedback mechanism upregulates the hormone insulin which helps to stabilise the sugar in the blood. 

One distinctive feature of hormones whose secretion is regulated through the hypothalamus and pituitary is that they regulate their own secretion through negative feedback inhibition. CRH (corticotropin releasing hormone) and ACTH (adrenocorticotropic hormone). Less tropic hormone secretion leads to less stimulation of cortisol secretion by cells of the zona fasciculata of the adrenal cortex. The usefulness of negative feedback inhibition is that it works to keep hormone levels within a particular appropriate physiological range.  The reduced negative feedback inhibition means that more CRH and ACTH will be secreted. More ACTH will stimulate the remaining adrenal tissue to grow and to secrete more cortisol. This will have the effect of bringing cortisol back up towards its normal daily level of secretion.