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Basic LifeProcesses &Homeostasis
August 2, 2012August 3, 2012
AgendaGeneral
HousekeepingReview Chapter 1
1.3 1.4
AssignmentsStations
Video Activity
Review!• Which level of organization focuses on different
types of tissue working together to perform aspecific function?
• Name one system of the human body
1.3 Characteristics of the LivingHuman Organism• Objectives
– Define the important life processes of thehuman body
– Define homeostasis and explain itsrelationship to interstitial fluid
The Six Basic Life Processes
Metabolism
Responsiveness
Movement Growth
Differentiation
Reproduction
• 1. Metabolism– The sum of all chemical processes that occur in
the body.– Catabolism: the breakdown of complex chemical
substances into similar components.– Anabolism: the building up of complex chemical
substances from smaller, similar components
• 2. Responsiveness– The body’s ability to detect and respond to
changes
• 3. Movement– Motion of the whole body
•Individual organs, single cell, tiny structuresinside cells
• 4. Growth– An increase in body size that results from an
increase in the size of existing cells, in increasein the number of cells, or both.
– Tissue can increase in size when the materialbetween the cells increases.
• 5. Differentiation
– The development of a cell from an unspecified toa specified state
•Stem Cells: precursor cells which can divideand give rise to cells that can differentiate
• 6. Reproduction
– Formation of new cells for tissue growth, repair,or replacement
– Production of a new individual
• When any one of the life processes ceases tooccur properly, the result is death of cells andtissues, which may lead to the death of theorganism.
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1.4 Homeostasis• Objectives
– Define homeostasis– Describe the components of a feedback
system
– Contrast the operation of negative andpositive feedback systems
– Explain how homeostatic imbalances arerelated to disorders
• Homeostasis is the condition of equilibrium inthe body’s internal environment due to theconstant interaction of the body’s regulatorysystems/processes.
– Equilibrium can shift within a narrow rangecompatible with maintaining life.
•Each structure contributes to thisbalance.
Homeostasis & Bodily Fluids• Bodily Fluids: dilute, watery solutions containing
dissolved chemicals found in cells andsurrounding them
– Intracellular Fluid (ICF): fluid within cells
– Extracellular Fluid (ECF): fluid outside cell bodies
•Interstitial Fluid: fills spaces between cells oftissue
•Blood Plasma: ECF within blood vessels
•Lymph: ECF within lymphatic vessels
•Cerebrospinal Fluid: ECF around the brain andspinal cord
•Synovial Fluid: ECF in joints
•Aqueous Humor & Vitreous Body: ECF of theeyes
• Interstitial fluid is often called the body’sinternal environment
– Requires precise regulation of composition
– Constant change and movement
– Exchange of materials in the bloodcapillaries
Control of HomeostasisExternal
Environment
InternalEnvironment
PsychologicalStress
Disruption
Mild & Temporary:Body cells respondquickly to restore
balance
Intense & Prolonged:eg. Poisoning, severe
infection, major surgery
Regulation(together orindividually)
Nervous System:Sends nerve impulses to
organs that cancounteract changes from
the balanced state
Endocrine System:Glands secrete
hormones into the blood
Feedback Systems• Cycle of events in which the status of a body
condition is monitored, evaluated, changed,remonitored, reevaluated, etc.
– Controlled Condition: monitored variable
– Stimulus: disruption that causes change inthe controlled condition
Three Basic Components• 1. Receptor
– Body structure that monitors changes in a acontrolled condition and sends input to acontrol center
– Afferent Pathway: information travelstowards the control center
– Input is in the form of nerve impulses orchemical signals
• 2. Control Center
– Sets the range of values within which acontrolled condition should be maintained (setpoint), evaluates the input it receives from thereceptors, and generates output commandswhen they are needed
– Efferent Pathway: information travels away fromthe control center
– Output in the form of nerve impulses,hormones, and chemical signals
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• 3. Effector
– Body structure that receives output from thecontrol center and produces a response ofeffect that changes the controlled condition
– Organs and tissues can act as effectors
• A feedback system involves a group ofreceptors and effectors communicating withtheir control center to regulate a controlledcondition
Stimulus disruptshomeostasis by
controlled conditionthat is monitored by
RECEPTORSthat send input
to a
CONTROLCENTER that
receives the inputand provides output
to
EFFECTORS thatbring about change
or
Response thatalters thecontrolledcondition
Returns tohomeostasis whenthe response brings
the controlledcondition back to
normal
Figure 1.2 - Operation of a Feedback System
Increasing ordecreasing a Negative Feedback Systems
• Reverses a change in a controlled condition
• Activity of the effector negates the originalstimulus
• Will slow and stop as the controlled conditionreturns to its normal state
• Regulates conditions that remain fairly stableover long periods of time
Stimulus disruptshomeostasis by
Blood Pressure(controlled condition)
Baroreceptors(RECEPTORS)
in certainblood vesselssend nerveimpulses(input) to
Brain (CONTROLCENTER) interpretsinput and send out
nerve impulses(output) to
Heart and bloodvessels
(EFFECTORS)
Decrease in heartrate decreasesblood pressure
Return tohomeostasis whenresponse brings
blood pressure backto normal
Figure 1.3 - Negative Feedback System
IncreasingPositive Feedback System• Strengthens or reinforces a change in one of the body’s
controlled conditions• Activity of the effector produces a physiological
response that adds to or reinforces the initial change inthe controlled condition
• Will continue until it is interrupted by a mechanism (anevent outside the system must shut it off)
• If not stopped it can “run away” and even produce lifethreatening conditions
• Reinforces conditions that do not happen very often
Contractions of theuterus wall force baby’s
head/body into the cervix
Stretching of cervix
Stretch-sensitive nerve
cells(RECEPTORS)in cervix sendnerve impulses
(input) to
Brain (CONTROLCENTER) interpretsinput and releasesoxytocin (output)
Muscles in wall ofuterus (EFFECTOR)
contract moreforcefully
Baby’s bodystretches cervix
more
Positive Feedback:increased stretching
of cervix causesrelease of moreoxytocin, whichresults in morestretching of the
cervix
Figure 1.4 - Positive Feedback System
Increasing
Interruption of Cycle: birthdecreases stretching of the cervix,
breaking the positive feedback cycle
Homeostatic Imbalances• The physiological processes responsible for maintaining
homeostasis are also responsible for good health. Factorsthat affect this balance include:– Environment/Behavior
– Genetics– The air you breathe, food you eat, even the thoughts you think
• The way you live your life can either support or interferewith your body’s ability to maintain homeostasis andrecover from stress
• Many diseases are the result of poor healthbehavior that interferes with the body’s naturaldrive to maintain homeostasis
• Need to develop a lifestyle that supports yourbody’s homeostatic processes– Maximize your potential for optimal health
and well-being
• If one or more components fail to contribute tohomeostasis, the normal balance is disturbed
• Moderate imbalances can lead to disorder ordisease– Disorder: abnormality of a structure or function– Disease: illness characterized by a recognizable set of
signs and symptoms• Local Disease: affects one part or a limited region of the
body• Systemic Disease: affects the entire body or several parts• Sign: (objective) changes that a clinician can observe and
measure• Symptom: (subjective) changes in function that are not
apparent to an observer
• Severe imbalances can result in death
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• Epidemiology: study of when, why, and wherediseases occur and how they are transmittedamong individuals in a community
• Pharmacology: study of the effects and uses ofdrugs in the treatment of disease
Clinical Connection• Autopsy (necropsy)
– Post-mortem examination of a body and dissection of itsinternal organs to confirm or determine the cause ofdeath.• Detect diseases not discovered during life• Evaluate the extent of injuries and how they
contributed to death• Reveal genetic conditions• Determine ultimate cause of death
Assignments• Review Feedback Systems & complete WS
• Read Sections 1.5 & 1.6
• Begin Anatomical & Directional Terms WS
• Go to http://www.hhmi.org and sign up toreceive the print copy of the HHMI Bulletin (it’sFREE!)
• Terminology Quiz next class (25 terms from1.1-1.4)