This document provides a summary of a department of physiology presentation on homeostasis, cell structure, and functions. It was presented by three students and covered homeostasis, including homeostatic regulation and feedback mechanisms. It also discussed the main components of cells - the cell membrane, nucleus, and cytoplasm and organelles. It described the structure and functions of the cell membrane, nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, and cytoskeleton.

1. DEPARTMENT OF
PHYSIOLOGY
 PRESENTED BY:
• AARYASH RAJ SHUKLA(01)
• ABHINANDAN JAISWAL(02)
• ABHISHEK KUMAR(03)
 TOPIC- HOMEOSTASIS,CELL STRUCTURE &
FUNCTIONS

2. TOPIC COVERED:
HOMEOSTASIS
1.Homeoststic Regulation
2.Types of control System
Cell Structure & Functions of Cell
1.Cell Membrane
2.Nucleus
3.Cytoplasm & Cell Organelles

3. Homeostasis
• Homeostasis means the maintenance of nearly constant internal
environment of body.
• Claude Bernard introduce a term Milieu interieur means the
extracellular fluid is called the internal environment of the body.
• W.B. Cannon coined the term Homeostasis.
• The Cell maintains its internal environment nearly constant which
depend on the immediate external environment (Interstitial fluid ISF).

4. COMPONENTS OF HOMEOSTATIC SYSTEM
It includes 4 components
1. Sensors or detectors : recognise the deviation
2. Transmission of message : control centre
3. Transmission of information from control centre to effectors ( for
correcting deviation )
4. Effectors : which corrects the deviation

5. Homeostatic Regulation
• Homeostatic Regulation is done by various Control Systems or Mechanisms
known as Homeostatic Mechanism
Feedback
positive negative
Homeostatic
mechanism

6. Negative Feedback Mechanism
Rise in BP
(a stimulus )
Decrease in BP to
normal range
Negative
feedback
Major contribution to homeostasis
Examples:
1.Regulation of Hormone in blood
2.Regulation of BP
3.Regulation of Body Temperature..
In this , system reacts in such a way to arrests the change or reverse the direction of
change in order to maintain homeostasis

7. NEGATIVE FEEDBACK MECHANISM – SECRETION OF THYROXINE

8. Positive Feedback Mechanism
• In this the system reacts in such a way to increase the intensity of the change in the same
direction
• It is less common than negative feedback – but has its own significance during
emergency conditions
Uterine Contraction:
Stretch in
muscle
Release of
oxytocin
Contraction of
muscle
• Examples :
1.Blood Clotting
2.Parturition

9. COAGULATION OF BLOOD : blood clotting is necessary to stop bleeding
during injury and occurs in three stages
1. Formation of prothrombin activators
2. Conversion of prothrombin into thrombin
3. Conversion of fibrinogen into fibrin

10. Cell Structure & Functions of Cell
Cell is the structural and functional unit of life
• The three principle constituents of a cell are :
1.Cell Membrane
2.Nucleus
3.Cytoplasm and cell Organelles

11. Cell Membrane
• Thin elastic outermost structure which envelops
the cell
• It consists of bilipid layer with embedded
proteins that are-
1. integral proteins
2. peripheral proteins

12.  Functions of Cell Membrane
• Protective: Forms outermost boundary of the cell organelles.
• Digestive : takes in food and excretes waste products.
• Selective permeability :
a. Non polar Molecules : gases (like O2,CO2,N2),Lipids Steroids Hormones Alcohols can
dissolve in non-polar regions of the membrane and move rapidly across the membrane.
b polar molecules : H2O soluble ions, glucose, urea etc . Have much lower solubility therefore
penetrate the membrane much more slowly.
• Chemical and physical properties of membrane control the free passage of ions in and out of cell. This
property helps in maintaining components in ICF and ECF.

13.  The Nucleus
 Structure:
• It is Spherical Structure surrounded by nuclear membrane.
• It have two unit membranes with nuclear pores.
 It contain Chromatin ,RNAs , nuclear proteins
 It contains a nucleolus which synthesize the RNA for the ribosomes.
 Functions:
• control house of the cell.
• It is concerned with cellular reproduction and multiplication
• It contains genetic information of the cell

14.  Cytoplasm
 Thick ,gel-like semitransparent fluid that is found in all type of cell.
 Bounded by the plasma membrane and many organelles.
 The constituent part of cytoplasm are:
1. Cytosol(aqueous part)
2.Cell organelles
3.cytoplasmic inclusions.

15.  Cell Organelles
Following organelles are present in the cytoplasm:
1.Mitochondria
2.Endoplasmic Reticulum
3.Golgi Apparatus
4.Lysosomes
5.Peroxisomes
6.Cytoskeleton

16.  Mitochondria
 Structure :
• Length :5-12micron diameter : 0.5-1micron
• Made up outer and inner membrane , inner membrane folded to form cristae
• Outer membrane –covered with enzymes concerned with biological oxidation
• Interior of mitochondrion contains enzymes concerned with citric acid cycle.
 Functions:
• Power generating unit of cell
• Contains DNA and can synthesize proteins

17.  Endoplasmic Reticulum(ER)
• Network of Tubular and flat vesicular structures in the cytoplasm.
• An extensive network of closed, flattened membrane-bounded sacs called cisternae.
• Spaces insides the tubules is filled with endoplasmic matrix.
• Two Types:

18. • Functions:
1.Synthesis of Proteins
2.proteins segregations
3.unsaturation of fatty acid
4.Muscle contraction , ER is commonly known as Sarcoplasmic Reticulum in muscle fibers

19.  Golgi Complex/Golgi Bodies
• It is the collection of membrane enclosed sacs composed of four or more stacked layers of thin, flat
enclosed vessels lying near the side of the nucleus.
• Functions:
1.Wrapping and packaging department of the cell
2.Produces secretion granules(packages proteins..)
3.Transport proteins received from ER.
4.Site of formation of Lysosomes.
5.Its adds certain carbohydrates to proteins to form
glycoproteins.

20.  Lysosomes
• These are the irregular structures surrounded by unit membrane .
• Diameters : 250-750nm
• The interior is kept acidic by the action of proton pump
• Functions:
1.Acts as a form of digestive system for the cell.
2.Engulf bacteria (exogenous substances)
3.When cell died, lysosomal enzymes cause autolysis of the remnant that is why
lysosomes are called as Suicidal bags.

21.  Peroxisomes
• Diameter: 0.5micron
• Its structure is similar to that of lysosomes but with a different chemical composition.
• Its contains oxidases that remove hydrogen to produce h2o2.
• Functions:
1.h2o2 metabolism and detoxification
2.biosynthesis of lipids
3.synthesis of bile acids in liver.

22.  Cytoskeleton
• System of fibers that not only maintains the structure of the cell but also permit it to change shape
and move.
• The cytoskeleton is made up primarily of :
1.Microtubules
2.Intermediate filaments
3.Microfilaments
along with protein that anchor tie them together
25nm
8-12nm
4-6nm

23. • Functions:
1. Movement of the chromosomes
2. cell movement
3. Movement of proteins within the cell membrane.
4.Processes that move secretion granules in the cell.

24. Thank You