Chapter 2 Homeostasis - PDF

 At the completion of this unit, students will be able to:  Define the term homeostasis.  Discuss the factors which effect homeostasis.  Define feedback mechanism and its components.  Discuss the role of feedback mechanisms in maintenance of Homeostasis with examples. ...

 At the completion of this unit, students will be able to:  Define the term homeostasis.  Discuss the factors which effect homeostasis.  Define feedback mechanism and its components.  Discuss the role of feedback mechanisms in maintenance of Homeostasis with examples.  HOMEOSTASIS  The term ‘homeostasis’ is derived from two Greek words:  Homeo means ‘Same’ and Stasis means ‘To Stay’.  The process of maintaining a controlled ,stable internal environment is called homeostasis  The ‘internal environment’ refers to the conditions inside an organism.  These conditions remain more or less constant despite changes in the outside environment.  Your body has mechanisms to keep the cells in a constant environments  CONTI….  Homeostatic mechanisms keep the internal environment within certain limits (or set points)When the cells in your body do not work correctly, homeostatic balance is disrupted / imbalance  Homeostatic imbalance- resulting in disease  Homeostasis must be maintained for normal body functioning and to sustain life  Eg: Temperature, ph level, Blood Sugar level etc  BODY FLUIDS  Body fluids are define as dilute ,watery solutions containing dissolved chemicals inside or outside of the cell. Maintaining the volume and compositions of body fluids is important  Intracellular fluid (ICF) is the fluid within cells  Extracellular fluid (ECF) is the fluid outside cells  Interstitial fluid is ECF between cells and tissues  CONTI….  Some important body fluids:  Blood plasma is the ECF Within the blood vessels  Lymph is the ECF within the lymphatic vessels  Cerebrospinal fluid (CSF)is the ECF in the brain and spinal cord  Synovial fluid is the ECF in joints  Aqueous humor is the ECF in eyes  FACTORS EFFECTING HOMEOSTASIS  Disease  Stress  Life style (drinking smoking diet )  Injury  Illness (fever , infection)  Dehydration  Starvations  Environmental temperature  FEEDBACK MECHANISM DEFINITION  The feedback mechanism is the physiological regulatory system in a living body that works to return the body to the normal internal state or homeostasis.  The feedback mechanism is activated as a result of the change in the system that triggers an output.  The most important function of the feedback mechanism in any system is to bring the state of the body into a stable state.  COMPONENTS OF FEEDBACK MECHANISM  The feedback mechanism consists of three distinct components.  Receptor (nerve ending in the skin )  Control center (such as a brain )  Effectors (muscles and gland)  Receptor: A structure that monitors the body's internal functions and conditions; detects changes in the body's internal environment.  Control Centre: It receives messages from receptors about any change in the body's internal conditions.  Effectors: They receives messages from the control center to change its function in order to correct a deviation in the body's internal conditions  TYPES OF FEEDBACK MECHANISM:  Negative feedback systems: (Reverses a change).  A homeostatic mechanism that opposes or resists a Change in the body's internal conditions.  Positive feedback system:  Strengthens or reinforce a change in one of the body.  It increases or enhance any change in the body's internal conditions.  Example: Normal childbirth   ROLE OF HOMEOTASIS  There is no specific organs which controls homeostasis except, possibly, the brain.  The skin, kidneys, liver, endocrine system, nervous system and sensory system all play a part in maintaining the internal environment within narrow limits.  Example#1 The external temperature varies during the day and from season to season, sometimes by as much as 40 degree C, but the human body temperature stays at about 37 degree C  This is achieved by sweating, vasodilation, vasoconstriction, and shivering. Vasodilation If the body temperature Maximum Heat Loss rises, the blood vessels in the skin dilate (become wider) and allow more blood to flow near the surface. The heat loss from the blood through the skin helps cool the circulating blood Vasoconstrictions: If the body temperature falls. The blood vessels in the skin constrict. Less warm blood flows near the surface so less heat is lost. Minimum Heat Loss  Example # 2:  In the cells, the chemical breakdown of proteins produces the nitrogenous compound, urea. If this were allowed to accumulate in the cells it would damage or kill them.  This homeostatic functions are carried out by the kidneys through which urea are excreted from the body.