Homeostasis mechanism

Homeostasis mechanism By Tanoj Patidar, 1st year M.sc Nursing, D.Y. patil university.

1. HOMEOSTASIS MECHANISM BY-TANOJ PATIDAR

2. INTRODUCTION Homeostasis refers to the maintenance of the constant internal environment of the body. homeo = same; Stasis = standing. The word ‘homeostasis’ was introduced by Walter B Canon in 1930. Biologist Bernard enlightened the fact that multicellular organisms including man live in a perfectly organized and controlled internal environment, which he called ‘milieu interieur ’. Internal environment in the body is ECF in which the cell live, it is the fluid outside the cell and it constantly moves throughout the body. Human beings depends upon the the constant maintenance of internal environment within the physiological limits.

3. CONT… The concept of homeostasis forms basis of physiology because it explain why various physiological functions are able to maintained by or within normal range and in case if any function deviates from this range how it is brought back to normal. For the functioning of homeostatic mechanism, the body must recognize the deviation of any physiological activity from the normal limits. In the body sensors sense the deviation and alert the integrating centre, this centre sends the information to the concern effectors to either accelerate or inhibit the activity so that the normalcy is restored.

4. DEFINITION Homeostasis is the physiological process by which the internal systems of the body ( Eg . Blood pressure, Body temperature, Acid base balance) are maintained at equilibrium despite variations in the external conditions.

5. NEED AND IMPORTANCE IMPORTANCE: A stable internal environment allows on organism to be independent of changes in the external environment. To maintain internal environment of organisms especially higher vertebrates in a steady and balanced state. To establish optimum condition of organisms. NEEDS: conditions outside our body are changing all the time, but condition within our body must be kept constant. Eg . pH and body temperature .WHY? Ensure that enzymes do not do not get inactivated or denatured since enzymes only work within a certain temperature range.

6. CONT… Change in pH affects enzyme reactions in the cells. Change in water potential affects the cells ( cells can be crenate or burst)

7. COMPONENTS OF HOMEOSTATIC SYSTEM Homeostatic system in the body acts through self-regulating device, which operate in a cyclic manner. This cycle includes four components. Sensors or detectors , which recognize the deviation . Transmission of this message to a control centre. Transmission of information from the control centre to the effectors for correcting the deviation. Effectors , w hich correct the deviation.

8. ROLE OF VARIOUS SYSTEMS IN THE BODY Each body system contributes to the homeostasis of other systems. No system of the body works in isolation. Well being of the person depends upon the well being of all the interacting body systems. NERVOUS SYSTEM: Since the nervous system does not store nutrients, it must receive a continuous supply from blood, any interruption to the flow of blood may bring brain damage or death. The nervous system maintains homeostasis by controlling and regulating the other parts of the body. A deviation from a normal set point act as a stimulus to a receptor, which sends nerve impulses to a regulating centre in the brain.

9. CONT… The brain directs an effector to act in such a way that an adaptive response takes place. For example the deviation was a lowering of blood temperature. The adaptive response returns the body to a state of normalcy and the receptor , the regulating centre, and the effector temporarily cease their activities, this process is called control by negative feedback. Regulating centres are located in the CNS, consisting of the brain and spinal cord. The hypothalamus is a portion of the brain particularly concerned with homeostasis ; it influences the action of medulla oblongata, a lower part of the brain, the autonomic nervous system, and the pituitary gland.

10. CONT… ENDOCRINE SYSTEM: Endocrine system consist of glands which secrete hormones into the blood stream. Each hormone has an effect on one or more target tissues, in this way the endocrine system regulates the metabolism and development of most body cells and body systems. Sex hormone activate sebaceous glands, development of mammary glands, alter dermal blood flow and release lipids from adipocytes. E ndocrine system help with the mobilization of calcitonin and calcium. In the muscular system hormones adjust muscle metabolism , energy production and growth. In the nervous system , hormones affect neural metabolism, regulate fluid/electrolyte balance and help with reproductive hormones that influence CNS development and behaviours. In the cardiovascular system we need hormones that regulate the production of RBCs,

11. CONT… Which elevate and lower the blood pressure. Hormones have inflammatory effects and stimulate the lymphatic system. INTEGUMENTARY SYSTEM: The integumentary system (the skin) is involved in protecting the body from invading microbes , regulating body temperature through sweating and vasodilatation/vasoconstriction, or shivering and piloerection (goose bumps) and ion balance in the blood . Synthesize vitamin D which interact with calcium and phosphorus absorption needed for bone growth, maintenance and repair. Skin help to maintain balance by excretion of water and other solutes.

12. CONT… Hair on the skin guards entrance into the nasal cavity or other orifices, preventing invaders, from getting further into our body. Provide mechanical protection against environmental hazards, we need to remember that our skin is integumentary; it is our first line of defence. SKELETAL SYSTEM: As the structural framework for the human body, the skeletal system consist of the 206 or so bones but also includes cartilages, ligaments and other connective tissues that stabilize and interconnect them. Bones work in conjunction with the muscular system to aid in posture and locomotion. Protection is the pivotal role occupied by the skeletal system.

13. CONT… As many vital organs are encased within the skeletal cavities (cranial, spinal) and bones from much of the structural basis for the other body cavities. (thoracic, pelvic cavities) The skeletal system also serve as an important mineral reserve. Also provide calcium needed for all muscular contraction. Finally RBCs lymphocytes and other cell relating the immune response are produced and stored in the bone marrow. MUSCULAR SYSTEM: One of the most versatile system in the body. Muscular system Contains heart which constantly pumps blood through the body. Also responsible for involuntary(breathing, digestion) and voluntary (walking, picking up objects) actions.

14. CONT… Muscles also helps to protect organs in the body cavities. Muscles in your body contract which increase your body heat when you’re cold, the act of shivering occurs when the internal temperature drops. Muscles around the vital organs contract, breaking down ATP and there by expanding heat, which is then distributed to the rest of the body. CARDIOVASCULR SYSTEM: The cardiovascular system, in addition to needing to maintain itself within certain levels, plays a role in maintenance of the other body system by; -Transporting hormones (heart secretes atrial natriuretic peptic) -Transporting nutrients (oxygen, EPO to bones) -taking away waste products.

15. CONT… -providing all living body cells with a fresh supply of oxygen and removing carbon dioxide. Homeostasis is distributed if the cardiovascular or lymphatic systems are not functioning correctly. The cardiovascular system also contains sensor to monitor blood pressure, called baroreceptors, that works by detecting how stretched blood vessels is, this information is relayed to the medulla oblongata in the brain where action is taken to rise or lower blood pressure via autonomic nervous system. LYMPHATIC SYSTEM: The lymphatic system has three principal roles. 1) maintenance of blood and tissue volume. Excess fluid that leaves the capillaries when under pressure would build up and cause oedema.

16. CONT… 2) Lymphatic system absorbs fatty acids and triglycerides from fat digestion so that these components of digestion do not enter directly into the blood stream. 3) Lymphatic system involved in defending the body against invading microbes, and the immune response. This system assist in maintenance such as bone and muscle repair after injuries. Maintaining the acidic pH of urine to fight infections in the urinary system. The tonsils are our bodies “helpers” to defend us against infections and toxins absorbed from the digestive tract. Tonsils also protect against infections entering into our lungs.

17. CONT… RESPIRATORY SYSTEM: Respiratory systems works in conjunction with the cardiovascular system to provide oxygen to cells within every body system for cellular metabolism. Also remove CO2 Helps in maintain proper blood pH levels. Helps the lymphatic system by trapping pathogens and protecting deeper tissues within. Organs of respiratory system permit the movement of air into the tiny, thin walled sacs of the lungs called alveoli. It is in the alveoli that oxygen from the air is exchanged for the waste product carbon dioxide, which is carried to lungs by the blood so that it can be eliminated from the body.

18. CONT… DIGESTIVE SYSTEM: Without a regular supply of energy and nutrients from the digestive system, all body system would soon suffer. The digestive system absorbs organic substances vitamins, ions, and water that are needed all over the body. Helps in digestion, absorption and elimination. In order to maintain a healthy and efficient digestive system, we have to remember the components involved, if these are disturbed digestive health may be compromised. Mechanics of digestion can include chemical digestion, movements, ingestion absorption and elimination.

19. CONT… URINARY SYSTEM: Toxic nitrogenous waste accumulate as proteins and nucleic acids are broken down and used for other purposes. It rids the body of these waste. Directly involved in maintaining proper blood volume (and indirectly blood pressure) and ion concentration within the blood. Kidney produce a hormone (erythropoietin) that stimulates red blood cells production. Play an important role in maintaining the correct water content of the body and the correct salt composition of ECF. External changes that lead to excess fluid loss trigger feedback mechanisms that act to inhibit fluid loss.

20. CONT… REPRODUCTIVE SYSTEM: The reproductive system is unique in that it does little to contribute to the homeostasis of the organisms. Rather than being tied to the maintenance of the organism, the reproductive system relates to the maintenance of the species. Having said that, the sex hormones do have an effect on other body systems, and an imbalance can lead to various disorders. Eg : A woman whose ovaries are removed early in life is at much higher risk of osteoporosis.

21. CONT… EXCRETORYSYSTEM: Responsible for removing wastes, excess water and salt in the urine. Regulates the volume and pH of the internal environment. Maintains homeostasis by removing metabolic waste such as water, salt and metabolic concentrations in the blood. The kidneys are the primary excretory organs of homeostasis because they excrete nitrogenous wastes, and regulate water-salt balance and acid base balance.

22. MECHANISM OF ACTION OF HOMEOSTATIC SYSTEM Homeostasis is an important characteristic of living things. Maintaining a stable internal environment which requires adjustments as condition change inside and outside the cell. The maintenance of the system within a cell is called homeostatic regulation. The continuous adjustments are made to meet the set point. Homeostasis is regulated by feedback mechanism. FEEDBACK REGULATION: Homeostatic mechanism in the body is responsible for maintaining the normalcy of various body systems.

23. CONT.. Whenever there is any change in behavioural pattern of any system, the effectors bring back the normalcy either by inhibiting and reversing the change depending upon requirement of the situation, this is achieved by means of feedback signals. Feedback is a process in which some proportion of the output signal of a system is passed back to the input This is done more often intentionally in order to control the behaviour pattern of the system,. Whenever any changes occurs, system receives and react to two types of feedback Negative feedback Positive feedback

24. CONT.. NEGATIVE FEEDBACK: Negative feedback is the most common feedback loop in the biological system. Negative feedback is the one to which the system reacts in such a way as to arrest the change or reverse the direction of change. After receiving a message, the effectors send negative feedback signals back to the system. Now the system stabilizes its own function and makes an attempt to maintain homeostasis. Many homeostatic mechanism in the body function through negative feedback.

25. THYROID STIMULATING HORMONE Pituitary gland stimulates thyroid gland to secrete thyroxine. When thyroxine level increases in blood, it inhibits the secretion of TSH from pituitary so that, the secretion of thyroxine from thyroid gland decreases. On the other hand, if thyroxine secretion is less, its low blood level induces pituitary gland to release TSH. Now TSH stimulates thyroid gland to secrete thyroxine.

26. MAINTTENANCE OF WATER BALANCE If the level of the fluid in the body falls below normal , the subsequent increase in osmolarity is detected by osmoreceptor in the hypothalamus. In response, the hypothalamus releases ADH and also makes you thirsty. In combination, drinking additional fluid and also recovering the maximum fluid volume possible from the urine will be restore fluid volume and osmolarity very rapidly, usually within the minutes. If the level of fluid in the body rise above normal, this will also change the osmolarity of the circulating fluid. The fall in the osmolarity is detected by the hypothalamus, which stops producing ADH. In the absence of ADH the kidneys allows fluid loss from the body.

27. BLOOD SUGAR REGULATION The human body maintain constant levels of glucose throughout the day, even after fasting. During long periods of fasting, glucose levels are reduced only very slightly. Insulin transport glucose to the body cells for use in cellular metabolic function. The cells convert excess glucose to an insoluble substance called glycogen to prevent it from interfering with cellular metabolism, because this ultimately lowers blood glucose levels, insulin is secreted to prevent hyperglycaemia. Another hormone called glucagon performs the opposite function of insulin, causing cells to convert glucogen to glucose and stimulating new glucose production (gluconeogenesis) to raise blood sugar levels. Negative feedback between insulin and glucagon levels controls blood sugar homeostasis.

28. REGULATION OF BODY TEMPERATURE Body temperature control is another negative feedback mechanism. Nerve cells relay information about body temperature to the hypothalamus. The hypothalamus then signals several effectors to return the body temperature to 37 degree Celsius. The effectors may signal the sweat gland to cool the skin and stimulate vasodilation so the body can give off more heat. If body temperature is below the set point, muscles shiver to generate heat and the constriction of the blood vessels helps the body retain heat. This example is very complex because the hypothalamus can change the body temperature set point, such as raising it during a fever to help fight an infection. Both internal and external events can induce negative feedback mechanism.

29. REGULATION OF BLOOD PRESSURE Regulation of blood pressure is an example of negative feedback. Blood vessels have sensors called baroreceptors that detect if blood pressure is too high or too low and send a signal to the hypothalamus. The hypothalamus sends a message to the heart, blood vessels, and kidney, which act as effectors in blood pressure regulation. If blood pressure is too high, the heart rate decreases as the blood vessels increase in diameter (vasodilation) while the kidneys retain less water. This changes would cause the blood pressure to return to its normal range. The process reverse when the blood pressure decreases, causing blood pressure to constrict and the kidney to increase the water retention.

30. CONT… Regulation of blood pressure depends upon a constant series of negative feedback loop. It involves sensors and receptors in body, cardiovascular control centres in brain stem, as well as many effectors ; heart, blood, vessels, kidney etc. All working together to maintain homeostasis.

31. REGULATION OF ACID BASE BALANCE Stimulus: blood pH moves beyond normal levels. (7.38 to 7.42) Receptor: located in the neck, the parathyroid gland monitors the pH of blood . -the glands are small endocrine glands that produce the parathyroid hormone, as well as monitoring blood pH. Integrating centre : the brain receives the message from the parathyroid gland. -the brain than sends a message to either the lungs or liver. Effector: there are two effectors of blood pH. -the first are the lungs, which is more temporary solution. -acidity in the blood can be regulated by the bodies natural CO2 level.

32. CONT… - The CO2 can react with water to increase acidity in the blood. -The second effector is the liver. - A lthough it is slower to compensate for difference in blood pH, it works better for the longer term. Response: The response of the first effector is increase or decrease respiration rate. -This regulate the CO2 levels in the body, increasing or decreasing the balance. -The response to the second effector is excess acid or base through the bodies natural water system.

33. REGULATION OF BREATHING Breathing results from a sensory system, respiratory control, and effector system. The effector system sends commands to the muscles and organs that regulate breathing. Breathing is regulated by ‘’homeostatic control’’ that is, it strives to maintain stability within the bodies internal environment by way of negative feedback. High levels of CO2, for example triggers faster and deeper breathing, this increases breathing decreases the amount of CO2 in the body by increasing the amount of O2 taken in. The centre for breathing is respiration control centre. The respiration control gets information from other body parts and then coordinate automatic responses, which sets off other organs and muscles involve in respiration. The respiration control centre is in the medulla, which itself is in the lower part of the brain stem, within the medulla are neurons , which are specialized breathing cells.

34. CONT…. There are two types of neurons, inspiratory and expiratory. Inspiratory are active during inhaling, expiratory are active during exhaling, they two work together, maintaining a constant, automatic cycle. Depending on the information receive by the neurons, from a many origins, the automatic cycle can be alter or even briefly stopped.

35. POSITIVE FEEDBACK Positive feedback is the one to which the system reacts in such a way as to increase the intensity of the change in the same direction. The positive feedback is less common than the negative feedback. However , it has its own significance particularly during emergency condition.

36. COAGULATION OF BLOOD One of the positive feedbacks occurs during the blood clotting. Blood clotting is necessary to arrest the bleeding during injury and its occur in three stages; Formation of prothrombin activator Conversion of prothrombin into thrombin Conversion of fibrinogen into fibrin. Thrombin formed in the second stage stimulates the formation of more prothrombin activator in addiction to converting fibrinogen into fibrin. It causes formation of more and more amount of prothrombin activator so that the blood clotting process is accelerated blood loss prevented quickly.

37. parturition Normal child birth is driven by a positive feedback loop. A positive feedback loop results in a change in the body’s status, rather than a return to homeostasis. The first concentration of labor ( the stimulus) push the body towards the cervix ( the lowest part of the uterus) . The cervix contain stretch-sensitive nerve cell that monitor the degree of stretching (the sensor). This nerve cells send the messages to the brain, which in turn causes the pituitary gland at the base of the brain to release the hormone oxytocin into the blood stream. Oxytocin causes stronger contraction of the smooth muscles in of the uterus (the effectors) , pushing the body further down the birth canal. This causes even greater stretching of the cervix. The cycle of the stretching, oxytocin release, and increasingly more forcefully contractions stop only when the baby is born. At this point, the stretching of the cervix halts, stopping the release of oxytocin.

38. LACTATION Lactation is a process of mother feeding her baby. The processes starts with the baby suckling its mothers breast. That stimulate the nipple, which sends a signal to the hypothalamus gland in the brain. The hypothalamus gland makes a chemical called oxytocin, which is sent to the posterior pituitary gland, which releases the chemical (prolactin) back to the breast, which looses the muscle that opens the hole to release the milk. Lactation relates to positive feedback loops because it is an amplifying process. The more baby suckles the more is released. When the child is no longer breast feeding, the prolactin drops off and milk production goes down.

39. FINAL OUTCOME OF HOMEOSTAIC PROCESSES