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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)