In the name of ALLAH, the Compassionate, the Merciful the Merciful.

Physiology, a Beauty and a Philosophy of Basic Medical sciences Physiology, a Beauty and a Philosophy of Basic Medical sciences

Cells Are Basic Units Of Life  Obtain food from environment  Perform chemical reactions to provide energy  Eliminate by- products to the environment  Synthesis material for growth and function  Control exchange of materials between cell and environment  Moving material from one part of the cell to other to carry out cellular activities.  Being sensitive and responsive to changes in the environment.  Most cells – reproducing

Modes of intercellular signaling

 Composition of the body the body  Organization of the body fluid - the body fluid - compartments compartments  Measurements of body fluid volume body fluid volume Major Body Fluid Compartments

Components Of Extra Cellular Fluids

Prof. M Amjad Hameed7 Water: largest constituent of body; 55-65% of body weight Intracellular Fluid Intracellular Fluid –66.6% –Within cells –High potassium Extracellular Fluid Extracellular Fluid –33% –Interstitial, space surrounding cells –Intravascular; 7-8% of total body water, % of ECF –High sodium Osmotic pressure (concentrations of all solutes in a fluid compartment) is equivalent between ECF and ICF compartments

Prof. M Amjad Hameed8 What is Homeostasis? The maintenance of a constant environment in the body is called Homeostasis

Cells – Body system and Homeostasis

OVERVIEW The term HOMEOSTASIS is defined as constancy of internal environmental & most often used in biological sense. Multicellular organisms requires a homeostatic internal environment to survive & live. Many environmentalists believe that this principle also applies to the external environment. Many ecological and social systems are homeostatic.

TYPES OF HOMEOSTASIS  Strong homeostasis: In it the structure and reserve do not change in composition. Since the amount of reserve and structure can vary, still a particular change is allowed in the composition of the whole body.  Weak homeostasis: It is the constancy of the ratio in the amounts of body reserve and structure, as long as food availability is constant. It is also true when the organism grows.  Structural homeostasis: means that the sub-individual structures grow in harmony with the whole individual.

Factors Homeostatically Maintained Are  Concentration of nutrient molecule  Concentration of oxygen and carbon dioxide  Concentration of waste product / toxic substances  Concentration of water, salt and electrolytes  pH maintenance  Temperature regulation  Volume and pressure

How Homeostatic Systems Work?  These homeostatic system oppose change to maintain equilibrium.  If the system does not succeed in re- establishing its balance, it may ultimately lead the system to stop functioning. Body cells work best if they have the correct Body cells work best if they have the correct Temperature Temperature Water levels Water levels Glucose concentration Glucose concentration

FLUCTUATIONS When organisms exhibit equilibrium, their physiological state is not necessarily static. Many organisms exhibit endogenous fluctuations Circadian (period 20 to 28 hours) Ultra-dian (period < 20 hours) and Infra-dian (period > 28 hours) rhythms. Thus even in homeostasis, body temperature, blood pressure, heart rate and most metabolic indicators are predictably with time.

Control Systems Of The Body Homeostasis Control Systems Of The Body Homeostasis  Within cell (genetic control system)  Within organ  Operate through the body Regulation of gases Regulation of gases Regulation of endocrine Regulation of endocrine Regulation of BP Regulation of BP Regulation of NS Regulation of NS

Mechanism of Homeostasis through Feed Back When a change in variable occurs in a body system, two types of feedback are used to avert this change towards normal: Negative feed back Positive feed back

Prof. M Amjad Hameed17 Characteristic Of Control System  Negative feed back Gain of control system is measured of quality of regulation of quality of regulation Gain = Correction applied Residual Change OR Correction OR Correction error error Higher the gain, higher the accuracy of regulation  Positive feed back

Indices of Quality of Regulation Variabl Set Point Dist. Change without Regul. Regul. Residual -change with Regul. Regul.CorrectRegul.Regul. Factor (R) Gain B.P 120 mm Hg 120 mm HgHge 60 mm Hg 20 mm Hg 40 1/32 Body Temp. 37 o C Cold 17 o C 0.5 o C 16.5 o C 1/3433

Homeostasis- through Negative Feed Back Negative feed back is a reaction in which the system responds to reverse the direction of change.  Carbon dioxide concentration in the human body.  Thermoregulation.  Blood Pressure Regulation.

Negative Feedback Control

Operation Of Feedback System Basic components  Stimulus  Receptors  Control center  Effectors

Feed Back of Home Heating System

Prof. M Amjad Hameed23 Controlling body temperature Volume : Surface area ratio = 1:6 Volume : Surface area ratio = 1:5 The bigger the Volume : Surface Area ratio is, the faster heat will be lost.

Prof. M Amjad Hameed24 Two Kinds of Thirst

Prof. M Amjad Hameed25 Volume homeostasis Thirst is triggered by increased plasma osmolality Thirst is inhibited by decreased plasma osmolality (OVLT receptors) and by increased blood pressure (hypervolemia )

Prof. M Amjad Hameed26 Volume homeostasis Hypovolemia triggers not only thirst, but also salt appetite Blood volume is corrected only by replacing both water and salt Drinking water alleviates thirst (by reducing plasma osmolality), but triggers salt appetite, whereas consuming salt triggers subsequent thirst (by increasing plasma osmolality)

Prof. M Amjad Hameed27 A loss of blood volume (hypovolemia) leads to compensatory mechanisms, which include thirst and increased salt consumption Volume homeostasis Baroreceptors sense hypovolemia and cause kidney to secret renin Renin interacts with angiotensinogen to produce angiotensin I, which is converted to angiotensin II (AII) AII is a vasoconstrictor and promotes aldosterone secretion from adrenal cortex and AVP secretion)

Prof. M Amjad Hameed28 Controlling Glucose levels Your cells also need an exact level of glucose in the blood. Your cells also need an exact level of glucose in the blood. Excess glucose gets turned into glycogen in the liver Excess glucose gets turned into glycogen in the liver This is regulated by 2 hormones (chemicals) from the pancreas called: This is regulated by 2 hormones (chemicals) from the pancreas called:InsulinGlucagon

Prof. M Amjad Hameed29 If there is too much glucose in the blood, Insulin converts some of it to glycogen Glycogen Insulin Glucose in the blood

Prof. M Amjad Hameed30 If there is not enough glucose in the blood, Glucagon converts some glycogen into glucose. Glycogen Glucagon Glucose in the blood

Negative Feed Back

Feed Back Control Of B.P.

Prof. M Amjad Hameed33 Starling equilibrium: Distribution of fluid between intravascular and interstitial space is determined by balance between hydrostatic pressure of the blood and osmotic pressure from plasma proteins Also compliance and glomerular filtration rate help regulate fluid balance Blood volume and blood pressure are partially regulated by hydrostatic and osmotic pressure gradients Interstitial Intravascular

Homeostatic Regulation of BP Disturbance:- Disturbance:-  Increase/decrease B.P. B.P.  Receptors (BR)  Control center (VMC)  Effectors (Heart/BV)

Positive Feed Back In positive feedback mechanism the change occurred is further amplified as its response. This has destabilizing effect, so does not result in homeostasis. It is less common in naturally occurring systems then negative feedback. e.g. Blood clotting, childbirth,nerve action potential are other types of positive feedback.

Positive feedback control of labor contractions Disturbance:- Increase-contraction of wall of uterus Increase-contraction of wall of uterus Receptors- Stretch- sensitive nerve cell Receptors- Stretch- sensitive nerve cell Control center- Control center- Brain interprets and releases oxytocin Brain interprets and releases oxytocin Effectors- Muscle of uterus contract Effectors- Muscle of uterus contract

Positive Feed Back

Compliment System

Intrinsic Pathway For Clotting

Application to human body  Complex systems, such as human body, must have homeostasis to maintain stability and to survive.  These systems not only give tolerance to body for survival; but they also adapt themselves and evolve to modifications of the environment.

Characteristics of best Homeostasis  Sustainable systems require combinations of both kinds of feedback.  Generally with the recognition of divergence from the homeostatic condition positive feedbacks are called into play, whereas:  Once the homeostatic condition is approached, negative feedback is used for “fine tuning” responses.

Homeostatic Centre Most of these organs are controlled by hormones secreted from the pituitary gland, one of the important homeostatic centre, which in turn is directed by the hypothalamus.

Role of body System in homeostasis 1)Nervous System: Act control of rapid of responses of body 2)Respiratory system: Regulate o,co2 &Ph 3)Circulatory system: Transport material and nutrient 4)Unary system: Regulate fluid volume, electrolytes and pH 5)Digestive system: Obtain nutrients water and electrolytes 6)Immune system: Defends against foreign invaders 7)Endocrine system: Release of hormones to blood 8)Reproduction system: Perpetuation of species 9)Muscular Skelton system: Protect body parts and allows movement of the body 10) Integumentary system: protective barrier between external environment