Introduction to PhysiologyIntroduction to Physiology

PhysiologyPhysiology• Science of body functionsScience of body functions• Homeostatic Example: shivering Homeostatic Example: shivering

• shivering elevates a low body temperatureshivering elevates a low body temperature• when body temperature drops below normal, a when body temperature drops below normal, a

reflex pathway causes involuntary oscillating reflex pathway causes involuntary oscillating skeletal muscle contractions which produce heatskeletal muscle contractions which produce heat

Body SystemsBody Systems• Groups of organs that perform related Groups of organs that perform related

functions and interact to accomplish a functions and interact to accomplish a common activity essential to survival of the common activity essential to survival of the whole bodywhole body

• Do not act in isolation from one anotherDo not act in isolation from one another• Human body has 11 systemsHuman body has 11 systems

Body SystemsBody Systems

Body SystemsBody Systems

Role of Body Systems in Role of Body Systems in HomeostasisHomeostasis

HomeostasisHomeostasis• Defined as maintenance of a relatively Defined as maintenance of a relatively

stable internal environmentstable internal environment• Homeostasis is essential for survival and Homeostasis is essential for survival and

function of all cellsfunction of all cells• Each cell contributes to maintenance of a Each cell contributes to maintenance of a

relatively stable internal environmentrelatively stable internal environment

Basic Cell FunctionsBasic Cell Functions• Sensing and responding to changes in Sensing and responding to changes in

surrounding environmentsurrounding environment• Control exchange of materials between cell and Control exchange of materials between cell and

its surrounding environmentits surrounding environment• Perform chemical reactions that provide energy Perform chemical reactions that provide energy

for the cellfor the cell• Synthesize needed cellular componentsSynthesize needed cellular components

HomeostasisHomeostasis

Body cells are in contained in Body cells are in contained in watery internal environment watery internal environment through which life-sustaining through which life-sustaining exchanges are madeexchanges are made

HomeostasisHomeostasis

Control of HomeostasisControl of Homeostasis

• Homeostasis is continually being Homeostasis is continually being disrupted bydisrupted by• External stimuli External stimuli

• heat, cold, lack of oxygen, heat, cold, lack of oxygen, pathogens, toxinspathogens, toxins

• Internal stimuliInternal stimuli• Body temperatureBody temperature• Blood pressureBlood pressure• Concentration of water, glucose, Concentration of water, glucose,

salts, oxygen, etc.salts, oxygen, etc.• Physical and psychological Physical and psychological

distressesdistresses• Disruptions can be mild to severeDisruptions can be mild to severe• If homeostasis is not maintained, If homeostasis is not maintained,

death may resultdeath may result

Control of HomeostasisControl of Homeostasis

Homeostasis of Blood PressureHomeostasis of Blood Pressure

• Baroreceptors in walls of Baroreceptors in walls of blood vessels detect an blood vessels detect an increase in BPincrease in BP

• Brain receives input and Brain receives input and signals blood vessels and signals blood vessels and heartheart

• Blood vessels dilate, HR Blood vessels dilate, HR decreasesdecreases

• BP decreasesBP decreases

YOUR TURNYOUR TURNConsider other situations:Consider other situations:

Describe another situation in which Describe another situation in which Homeostasis plays a role.Homeostasis plays a role.• What is the Normal situation?What is the Normal situation?• Suggest how the body may be put out Suggest how the body may be put out of Normal state.of Normal state.• Predict how the body will respond to Predict how the body will respond to return to normal.return to normal.