Homeostasis is a self-regulating process that biological systems use to maintain stability while adapting to changing conditions, essential for survival. The document explains the concepts of feedback control systems, highlighting the differences between negative and positive feedback loops, with examples from both mechanical and biological contexts. It also discusses ecological homeostasis and the Gaia hypothesis, linking biodiversity and ecological interactions to ecosystem stability.

1. HOMEOSTASIS
what is the homeostasis and its definition…&
feedback control system –
a brief medical study
PREPARED BY | MARTIN SHAJI | PHARM D

2. HOMEOSTASIS:(homo>same)staisis>condition)
• Homeostasis, any self-regulating process by which biological
systems tend to maintain stability while adjusting to
conditions that are optimal for survival. If homeostasis is
successful, life continues; if unsuccessful, disaster or death
ensues. The stability attained is actually a dynamic
equilibrium, in which continuous change occurs yet relatively
uniform conditions prevail.

3. • Any system in dynamic equilibrium tends to reach a steady
state, a balance that resists outside forces of change. When
such a system is disturbed, built-in regulatory devices
respond to the departures to establish a new balance; such a
process is one of feedback control. All processes of
integration and coordination of function, whether mediated
by electrical circuits or by nervous and hormonal systems,
are examples of homeostatic regulation.

4. • A familiar example of homeostatic regulation in a mechanical
system is the action of a room-temperature regulator, or
thermostat. The heart of the thermostat is a bimetallic strip
that responds to temperature changes by completing or
disrupting an electric circuit. When the room cools, the circuit
is completed, the furnace operates, and the temperature rises.
At a preset level the circuit breaks, the furnace stops, and the
temperature drops. Biological systems, of greater complexity,
however, have regulators only very roughly comparable to
such mechanical devices. The two types of systems are alike,
however, in their goals—to sustain activity within prescribed
ranges, whether to control the thickness of rolled steel or the
pressure within the circulatory system.

5. THERMOSTAT:
• Adjusting a residential thermostat. A bimetallic strip inside the device
responds to temperature changes by completing or disrupting an
electric circuit. In a cold room the circuit is completed, the furnace
switches on, and the room's air temperature rises. At a preset level
the circuit breaks, causing the furnace to switch off and thereby
allowing the temperature to fall.

6. The concept of homeostasis
• The concept of homeostasis has also been applied to ecological settings. First
proposed by Canadian-born American ecologist Robert MacArthur in 1955,
homeostasis in ecosystems is a product of the combination of biodiversity and
large numbers of ecological interactions that occur between species. It was
thought of as a concept that could help to explain an ecosystem’s stability—that
is, its persistence as a particular ecosystem type over time (see ecological
resilience). Since then, the concept has changed slightly to incorporate the
ecosystem’s abiotic (nonliving) parts; the term has been used by many ecologists
to describe the reciprocation that occurs between an ecosystem’s living and
nonliving parts to maintain the status quo. The Gaia hypothesis—the model of
Earth posited by English scientist James Lovelock that considers its various living
and nonliving parts as components of a larger system or single organism—makes
the assumption that the collective effort of individual organisms contributes to
homeostasis at the planetary level. The single-organism aspect of the Gaia
hypothesis is considered controversial because it posits that living things, at
some level, are driven to work on behalf of the biosphere rather than toward the
goal of their own survival.

7. FEEDBACK CONTROL SYSTEM:
Feedback control system has two types
1:POSITIVE FEEDBACK
2:NEGATIVE FEEDBACK
First of all we need to understand feedback control system.

8. FEEDBACK CONTROL SYSTEM:
• Control system, means by which a variable quantity or set of
variable quantities is made to conform to a prescribed norm.
It either holds the values of the controlled quantities
constant or causes them to vary in a prescribed way. A
control system may be operated by electricity, by mechanical
means, by fluid pressure (liquid or gas), or by a combination
of means. When a computer is involved in the control circuit,
it is usually more convenient to operate all of the control
systems electrically, although intermixtures are fairly
common.

9. 1:POSITIVE FEEDBACK:
• Homeostatic circuits usually involve negative feedback loops. The hallmark of a
negative feedback loop is that it counteracts a change, bringing the value of a
parameter—such as temperature or blood sugar—back towards it set point.
• Some biological systems, however, use positive feedback loops. Unlike negative
feedback loops, positive feedback loops amplify the starting signal. Positive
feedback loops are usually found in processes that need to be pushed to
completion, not when the status quo needs to be maintained.
• A positive feedback loop comes into play during childbirth. In childbirth, the
baby's head presses on the cervix—the bottom of the uterus, through which the
baby must emerge—and activates neurons to the brain. The neurons send a
signal that leads to release of the hormone oxytocin from the pituitary gland.
• Oxytocin increases uterine contractions, and thus pressure on the cervix. This
causes the release of even more oxytocin and produces even stronger
contractions. This positive feedback loop continues until the baby is born.

10. 2:NEGATIVE FEEDBACK:
• Definition(1)
• A feedback in which the system responds to the
perturbation in the opposite direction as the perturbation
• (2) A feedback mechanism resulting in the inhibition or the
slowing down of a process

11. Supplement
• A feedback mechanism is a loop system wherein the system responds to a
perturbation. The response may be in the same direction (as in positive
feedback) or in the opposite direction (as in negative feedback).A negative
feedback is one that which responds to the perturbation in the opposite
direction as the perturbation, as opposed to a positive feedback that responds
in the same direction. While the mechanism involved in positive feedback
tends to initiate or accelerate a process, the mechanism involved in negative
feedback tends to inhibit it or slow down.
• A negative feedback is a self-regulatory system in which it feeds back to the
input a part of a system’s output so as to reverse the direction of change of
the output. The process reduces the output of a system in order to stabilize or
re-establish internal equilibrium.
• There are several negative feedback in biological system to regulate and
maintain homeostasis. Some of them are the regulation of hormone synthesis,
blood glucose levels, body temperature, and baroflex in blood pressure.

12. For a detailed study on acid base homeostasis
• https://www.slideshare.net/martinshaji/acid-base-homeostasis-a-
brief-study