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Intoduction Into Phys

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Physiology 1021
John Ciriello

Modules May1011 1103 AM Module 11111 Physiology is the study of function in living organismsExplores mechanisms by which organisms control their INTERNAL ENVIRONMENT regardless of ywhat happens in the outside EXTERNAL ENVIRONMENT Also attempts to explain PATHOLOGY the physical and chemical factors responsible for both ynormal function and disease HomeostasisThe maintenance of relatively stable conditions within the internal environment regardless of ywhat is happening in the external worldThe INTERNAL ENVIRONMENT is the fluid in which the cells of the body are bathed It consists of the interstitial fluid and blood plasma y The EXTERNAL ENVIRONMENT is the region outside of the body It includes the space and contents of the digestive respiratory and urogenital tract your body is capable of maintaining our internal environment so that our cells can function regardless of what is happening in the external environment homeostasis The body maintains homeostasis using NEGATIVE and POSITIVE FEEDBACK CONTROL yMECHANISMSNegative Feedback Control SystemsFound throughout the body and perform different functions from maintaining bodytemperature yto maintaining body fluid volumesALL operate the SAME WAY to maintain homeostasis yContain a set point control centre integrator an effector a controlled variable and a ysensorreceptor SET POINTCONTROL CENTREEFFECTOR SENSOR CONTROLLED VARIABLEExample of Negative feedback is the heating system in your houseySet pointtemperature at which the room is set 20CyThe sensorcontrol centre not usually combined in the bodythermostatyEffectorfurnace yControlled variableheatyThis is a negative system because the controlled variable the heat which is detected by the ysensor eventually shuts off its own production by the effector furnaceHow Negative feedback controls body temperatureWant your body to maintain a temperature of 37C 986F set point for body temperature y Your actual body temperature could be different y It could drop on a cold day to 35C 95Fy The actual body temperature would be detected by sensors in the nervous systemNS which ywould then signal a control centre in a specific region of the brain called the HYPOTHALAMUSThe control centre would then notice a difference between the set point and the actual valuey The control centre would then activate organs and systems effector to generate heat the ycontrolled variable by shivering and conserving heat by decreasing blood flow to the skinOnce the body temperature rises back to set pointthe control centre would stop the shivering yand would return the blood flow to the extremitiesPositive Feedback Control SystemsUnlike NEGATIVE where the controlled variable eventually shuts off its own productiony Positive feedback system feedforward system is a mechanism where the controlled variable yactually stimulates its own productionThese systems are selfamplifying mechanisms that can produce a VERY RAPID change in a yphysiological system This leads to large amounts of the controlled variable being produced very rapidly yExamples of Positive Feedbackaction potentials in nerve cells the surge of luteinizing hormone ythat causes ovulation of the egg from the ovary Negative and Positive Feedback Control SystemsAll of the systems in our body used negative or positive feedback to regulate their functionsythese then maintain homeostasis These feedback systems rely on 2 control systems to function properlyy 1 The Nervous System 2 The Endocrine System The Nervous System brain spinal cord and all the nerves is especially adapted for rapid communication through its complex systems of neurons and nerves The Endocrine System responds more SLOWLY Communicating by the release and distribution of hormones in the blood y The Bodys Structural Hierarchy Atoms make up moleculesyMolecules make up macromolecules which can form cellular organelles yAlmost all cells of the body contain SIMILAR organelles like the nucleus the cell membrane yproteins Tissue groups of cells that have all the SAME specialization are grouped togetherExample muscle tissue is specialized because it contains cells that can contracty Organs when two or more types of tissues are combined to form a complex functional unit Example the heart y Organ systems When several organs cooperate for a common function
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