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The Study of Body Function CHAPTER 1• Physiology

– fundamentally represents the study of how living organisms work

• Molecules cell tissue organ organ system

• how organisms accomplish tasks essential for life

– function & integration• body parts work together at various

levels of organization (cellular and tissue organization) & whole organism

– mechanisms & their effects• sequence of events

– Parts of larger stories (workings of human organism itself)

– Nothing works in isolation– Integrated entity

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History of Physiology

http://www.awakenyourwarrior.com/pages/philosophercoach.htmlhttp://www.health.gov.mt/impaedcard/issue/issue1/ipc0012206.jpg

http://www.answers.com/topic/william-harvey?cat=health

http://www.nndb.com/people/033/000100730/

AristotleErasistratus

William Harvey Claude Bernard

speculated on fx of human body

good health assoc’d with balance of

humours

Father of Physiology

applied physical laws to study of human body

Studied cardiovascular and nervous systems

1st to study biology

quantitatively

Father of Modern Physiology

observed the milieu interieur remained remarkably constant despite constantly changing

environment

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Father of American Physiology• Early 19th century in US

– physiology treated as an aspect of theory & practice of physics

– 1824, Thomas Jefferson, Univ of VA• Robley Dunglison

– English physician– Professor of Anatomy,

Physiology, Surgery, Materia Medica, Pharmacy & History of Medicine, 1825

– teaching was an explanation of “successive theories”

– published several books & articles

» Human Physiologywww.healthsystem.virginia.edu

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Homeostasis & Feedback Control

• Homeostasis– maintenance of a relatively stable

internal environment• basically represented by the state

of equilibrium of the body’s internal environment by dynamic processes of feedback and regulation

– reason for regulatory mechanisms– not an easy accomplishment

• every organ system is involved with the maintenance and necessitates integrated function

– major foundation for medical diagnostic procedures

http://www.harvardsquarelibrary.org/unitarians/cannon_walter.html

Walter Cannon

1871-1945

coined the term homeostasis in his book, The Wisdom of the Body

How is the maintenance of homeostasis accomplished?

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Feedback mechanism

• Set point– normal range of

measurements & values– factor or event being

regulated is called the variable

• Control systems that promote homeostasis are characterized by 3 interdependent components:– receptor– control or integration center– effector

Why referred to as a “loop”?

“loop” emphasizes feedback mechanism because it is a continuous cycle to maintain homeostasis

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QUESTION

• Is our internal environment absolutely constant?

• Are we always in a state of balance?

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Negative Feedback Mechanism

• Most common homeostatic control mechanism

• Reverse direction control mechanism– works by output of system

causes a decrease or shuts off the original stimulus

– continuous, ongoing processes

• All negative feedback mechanisms have the same goal Preventing sudden severe

changes in the body

ANTAGONISTIC EFFECTORS

effectors have antagonistic (opposite) actions

allows for finer degree of control

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Positive Feedback Mechanism

• Same direction control system– enhance or exaggerate the

response over the original stimulus, thus the output is increased

• Usually control episodic or infrequent events that do not require continuous adjustments– examples?

• Limited – Proceed with very little control– Human body doesn’t use PFM alot

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MRI, T1 weighted

Goiter

Homeostatic Imbalance

Homeostatic imbalance places an individual at higher risk of disease,

which typically are a result of certain pathological conditions & aging

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Homeostatic Regulation

• Regulatory mechanisms for homeostasis– intrinsic

• within organ

– extrinsic• “outside” organ

– nervous & endocrine systems» innervation by nerve fibers» hormones

Advantages/Disadvantages?• Intrinsic mechanisms need to

focus the effect– More specific for organ

Can also be a disadvantage because have mechanisms that automatically turn on

– Bleeding out, but increase heart rate because of decreased heart rate so causes you to bleed out MORE.

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http://www.dundee.ac.uk/biocentre/SLSBDIV4ebl.htm

Cells basic unit of

structure &

function

simplest structural unit that complex, multicellular organism can be

divided into retaining functional characteristics of life

smallest unit of life

tissues (cells with similar functions )

primary tissue types

organ primary tissues grouped into anatomical & functional units

Activities & interactions of tissues determine the physiology of organ

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Muscle Tissue• Specialized for contraction• Three types of muscle tissue:

– skeletal - SkM• generally attached to bone via tendon;

exceptions (tongue & diaphragm)– myofibers

• 4th wk of development, myoblasts• arranged in bundles (variation in strength)• graded contractions

– controlled individually– cardiac - CM

• wall of heart, myocardial cells• form continuous sheet• intercalated discs

– couple cells mechanically & electrically– smooth - SmM

• nonstriated, fusiform (spindled) shape• forms sheet, circularly &/or longitudinally

arranged– peristalsis (wave-like contractions; lumen)

Which muscle type is termed voluntary muscle? involuntary muscle?

Skeletal

Cardiac

Smooth

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Nervous Tissue

• Consists of:– neurons

• highly specialized to generate & conduct nerve impulses

– an electrical event• constructed of cell body

(soma), dendrites & axon– each has structural

attributes & function– supporting cells

• also known as neuroglial, or glial cells

• nonconducting cells that support, insulate & protect neuron

• more abundant• limited ability to divide

http://www.mhhe.com/biosci/ap/histology_mh/neurons.jpg

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Epithelial Tissue

cover body surfaces & line body cavities

classified according to number of layers & shape

perform a variety of functions - boundary

Simple squamous epithelium

Simple stratified

transitional

Pseudo-stratified squamous epithelium

http://www.nature.com/nrm/journal/v2/n4/fig_tab/nrm0401_285a_F1.html

a | Schematic drawing of intestinal epithelial cells. The junctional complex, which is located at the most apical region of lateral membranes, is circled. b | Electron micrograph of the junctional complex in mouse intestinal epithelial cells. The tight junction is circled.

(Mv, microvilli; TJ, tight junction; AJ, adherens junction; DS, desmosome.)

ET forms boundaries &

thus serves as a barrier

to be effective

Site of regulation for substances

entering/leaving the body

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Glands

Exocrine duct

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• Components:– duct– secretory unit

• acinus• myoepithelial cells

Exocrine Glands

http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Epithelia/Epithel.htm

classification

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Connective Tissue

• Characterized by:– large amt of extracellular

material in the spaces between connective tissue cells

• extracellular matrix, or ECM

– fibers & ground substance

– vary in composition & arrangement between tissue types

– comprised of varied cell types

• Categorized into– CT proper– supportive CT– liquid CT

areolar CT

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Adipose tissue

BLOOD

BONE

Dense irregular CT

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Organs & Organ Systems

architecture of most organs are similar

organ described as a structure composed of 2 or more tissue types

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Stem cells• tissues of an organ are

comprised of differentiated cells– highly specialized

• differentiation begins during embryonic development– zygote/embryo

• totipotent stem cells– blastocyst

• pluripotent stem cells– trilaminar embryo

• ectoderm, mesoderm & endoderm

– give rise to 4 primary tissue types

• adult stem cells– multipotent

• form related cell types

http://www.scq.ubc.ca/stem-cell-bioengineering/

produce ALL specialized cells types

of body

capable of forming unrelated cell types

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Hierarchical system to structural organization

levels of cellular organization

human body is a complex society of differentiated cells, which combine structurally & functionally to carry out life-

sustaining processes

Cells are the basic units of the society & almost all exhibit

fundamental activities common to all forms of life.

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Body Fluid Compartments

• Extracellular fluid - ECF– fluid in blood & spaces that

surround cells• Plasma – found in blood• interstitial, or tissue fluid –

found between cells• Intracellular fluid – ICF

– fluid within cells• Mainly comprised of water

– aqueous compartments• Composition varies between

compartments– ECF considered more

“homogenous” than ICF• What organ plays impt role

in ECF composition/volume?– KIDNEYS

• Compartmentalization– who serves as the “barriers”?

• Plasma membranes of cells and Epithelial cells and blood vessel walls

Properties of these barriers determine what moves between

compartments