An over view of Homeostasis.

1. Mr. Sayantan Dutta
Assistant professor
Faculty of Pharmaceutical Sciences,
Rama University, Mandhana, Kanpur,
Uttar Pradesh.

2. Homeostasis
 A condition of equilibrium (balance) in the
body’s internal environment due to the
constant interaction of body’s many
regulatory process.
It is a dynamic condition meant to keep body
functions in the narrow range compatible
with maintaining life.
The meaning of this term is ‘unchanging’,
but in practice it describes a dynamic, ever-
changing situation
Where a multitude of physiological
mechanisms and measurements are kept
within the limits.
Homeostasis

3. Some important physiological variables which are
maintained within narrow limits by homeostatic control
mechanisms they are
• Core temperature
• Water and electrolyte concentrations
• pH (acidity or alkalinity) of body fluids
• Blood glucose levels
• Blood and tissue oxygen and carbon dioxide levels
• Blood pressure

4.  An important aspect of homeostasis is maintaining the volume and composition of body
fluids, dilute, watery solutions containing dissolved chemicals that are found inside cells as
well as surrounding them.
 The fluid within cells is intracellular fluid (intra- = inside), abbreviated ICF.
 The fluid outside body cells is extracellular fluid (ECF) (extra = outside).
 The ECF that fills the narrow spaces between cells of tissues is known as interstitial fluid
(inter = between).
 Blood Plasma is the ECF within blood vessels.
 Lymph is the ECF within lymphatic vessels.
 Cerebrospinal fluid (CSF) is the ECF in the brain and spinal cord.
 Synovial fluid is the ECF in joints.
 Aqueous humour is the ECF in eyes.

5.  Control systems
• Homeostasis is maintained by the body’s responses to adverse stimuli, ensuring
maintenance of an optimal physiological environment which is maintained by control
systems that detect and respond to changes in the internal environment
• A control system has three basic components: detector, control center and effector.
• The control center determines the limits within which the variable factor should be
maintained.
• It receives an input from the detector, or sensor, and integrates the incoming information.
• Example of this type of receptor is peripheral chemoreceptor which indicate the change of
pH.
• When the incoming signal indicates that an adjustment is needed, the control center
responds and its output to the effector is changed.
• Most important example is hypothalamus which control various thing like body
temperature, heart rate, blood pressure , etc.
• And effector is an any organ or tissues which receive information from integrating center
and acts to bring about the changes needed to maintain homeostasis.
• Example is kidney which retains water if blood pressure is two low.
• It is a dynamic process that allows constant readjustment of many physiological variables.

7.  The body can regulates its internal environment system
through many feedback system.
 A feedback system is a cycle of a events in which the
status of a body condition is monitored, evaluated,
changed , re monitored, re evaluate and change and so
on.
 A process that uses one component to regulate another,
either through positive or negative feedback.
 Each monitored variable, like blood pressure,
temperature, pH or blood glucose levelled is termed on
a controlled condition.
 Any disruption which can changes the controlled
condition is known as stimulus.
 A feedback system composed on three basic
component like a receptor, a controlled centre and an
effector.
Feedback system

9.  Feedback System
 Negative Feedback systems:
 Reverses a change in a controlled condition
 Regulation of blood pressure
 Positive Feedback systems:
 Strengthens or reinforces a change in one of the body’s
controlled conditions
 Normal child birth

10.  Negative feedback mechanisms
 Negative feedback means that any movement of
such a control system away from its normal set
point is negated (reversed).
 If a variable rises, negative feedback brings it
down again and if it falls, negative feedback
brings it back up to its normal level.
 The response to a stimulus therefore reverses the
effect of that stimulus, keeping the system in a
steady state and maintaining homeostasis
Negative feedback occurs when a change in
a variable triggers a response which
reverses the initial change

11.  Positive feedback mechanisms
 There are only a few of these cascade or amplifier
systems in the body. In positive feedback mechanisms,
the stimulus progressively increases the response, so
that as long as the stimulus is continued the response is
progressively amplified.
 Examples include blood clotting and uterine
contractions during labour.
 During labour, contractions of the uterus are
stimulated by the hormone oxytocin.
 These force the baby’s head into the uterine cervix
stimulating stretch receptors there.
 In response to this, more oxytocin is released, further
strengthening the contractions and maintaining labour.
 After the baby is born the stimulus (stretching of the
cervix) is no longer present so the release of oxytocin
stops.
Positive feedback occurs when
a change in a variable triggers
a response which causes more
change in the same direction

12.  Homeostatic imbalance
• This arises when the fine control of a variable factor in the internal environment is
inadequate and its level falls outside the normal range.
• If the control system cannot maintain homeostasis, an abnormal state develops that may
threaten health, or even life itself.
• Disorder is a general term for any abnormality of structure or function
• A diseases is an illness with a definite set of sign and symptoms.
• Diseases alter body structures and functions in characteristic ways. A person with a disease
may experience symptoms and sign.
• Symptoms are subjective changes of a body function that are not apparent to an observer.
• Examples of symptoms are headache, nausea, and anxiety.
• Signs are objective change that can be observed and measured.
• Signs of disease can be either anatomical, such as swelling or a rash,or physiological, such
as fever, high blood pressure, or paralysis.

14. Anatomical position
 When describing any orientation, location, movement, and direction, the reference is
the anatomical position.
 In this universally accepted reference, the person is considered to be standing upright, with the
arms hanging by the side, palms facing forward, and thumbs pointing away from the body. The
feet are slightly parallel, and toes oriented to the front.
 The anatomical position has no real meaning on its own since it is a reference for position. It
has to be placed in the same context as other anatomical terms, such as body planes, directions,
and relations. Regarding anatomical planes, these are imaginary planes that intersect the body,
creating various cuts or slices of various organs and structures.

16. Midsagittal plane

17.  Planes of the Body
 Coronal Plane (Frontal Plane) - A vertical plane
running from side to side; divides the body or any of
its parts into anterior and posterior portions.
 Sagittal Plane (Lateral Plane) - A vertical plane
running from front to back; divides the body or any of
its parts into right and left sides.
 Axial Plane (Transverse Plane) - A horizontal plane;
divides the body or any of its parts into upper and
lower parts.
 Median plane - Sagittal plane through the midline of
the body; divides the body or any of its parts into right
and left halves.

18.  A sagittal plane (SAJ-i-tal; sagitt- = arrow) is a vertical plane that
divides the body or an organ into right and left sides.
 More specifically, when such a plane passes through the midline of the
body or an organ and divides it into equal right and left sides, it is
called a midsagittal plane or a median plane.
 The midline is an imaginary vertical line that divides the body into
equal left and right sides. If the sagittal plane does not pass through the
midline but instead divides the body or an organ into unequal right and
left sides, it is called a para sagittal plane (para- = near).
 A frontal or coronal plane (koˉ-RO– -nal; corona =crown) divides the
body or an organ into anterior (front) and poste-rior (back) portions. A
transverse plane divides the body or an organ into superior (upper) and
inferior (lower) portions.
 Other names for a transverse plane are a cross-sectional or horizontal
plane. Sagittal, frontal, and transverse planes are all at right angles to
one another.
 An oblique plane (oˉ-BLE–K), by contrast, passes through the body or
an organ at an oblique angle (any angle other than a 90-degree angle).

19. Body Cavities
 Body cavities are spaces that enclose internal organs. Bones, muscles, ligaments, and
other structures separate the various body cavities from one another.
 The cavities, or spaces, of the body contain the internal organs, or viscera.
 The two main cavities are called the ventral and dorsal cavities.
 The ventral is the larger cavity and is subdivided into two parts (thoracic and
abdominopelvic cavities) by the diaphragm, a dome-shaped respiratory muscle.
 Thoracic cavity
 The upper ventral, thoracic, or chest cavity contains the heart, lungs, trachea, esophagus,
large blood vessels, and nerves. The thoracic cavity is bound laterally by the ribs (covered
by costal pleura) and the diaphragm caudally (covered by diaphragmatic pleura).

20.  Abdominal and pelvic cavity
 The lower part of the ventral (abdominopelvic) cavity can be further
divided into two portions: abdominal portion and pelvic portion.
 The abdominal cavity contains most of the gastrointestinal tract as
well as the kidneys and adrenal glands.
 The abdominal cavity is bound cranially by the diaphragm, laterally
by the body wall, and caudally by the pelvic cavity.
 The pelvic cavity contains most of the urogenital system as well as
the rectum.
 The pelvic cavity is bounded cranially by the abdominal cavity,
dorsally by the sacrum, and laterally by the pelvis.
 Dorsal cavity
 The smaller of the two main cavities is called the dorsal cavity.
 As its name implies, it contains organs lying more posterior in the
body.
 The dorsal cavity, again, can be divided into two portions.
 The upper portion, or the cranial cavity, houses the brain, and the
lower portion, or vertebral canal houses the spinal cord.