Physio I Lecture 1

8/4/2019 Physio I Lecture 1

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WINDSORUNIVERSITY SCHOOL OF MEDICINE

HOMEOSTATICREGULATION

Dr.VishalSurender.MD.



Learnin O!"e#$i%es•Defnition o physiology•Review o organ systems

•Explain homeostasis• Discuss the relationship between external andinternal environments•List the main body uid compartments, theirconstituents and their relationship to each other

•Defne equilibrium and steady state•ive examples o homeostatic mechanisms•Explain negative eedbac!•Defne controlled variable, sensor, comparitor and

set point and give examples o each in a negativeeedbac! loop•Discuss actors that may change set points•Defne redundancy and hierarchy with respect tohemoestatic control mechanisms•Explain positive eedbac!



• &h'si(l(' is the studyo the normal unctioningo a living organism and

its component parts,including all its chemicaland physical processes#

&h'si(l(' de)ned



$

Organization of the human body

Cells

Tissues

Organs

Organ

systems

Organisms

(Human body)



%rgan &ystems in Review

• 'ntegumentary

• (usculos!eletal

• Respiratory• Digestive

• Reproductive and )rinary

• *irculatory• +ervous and Endocrine

• 'mmune



%rgan &ystems in Review he integration between systems o the body



Body Fluid Compartments

Intracellular Fluid; 28

Interstitial Fluid; 11

Plasma; 3

Average Total Liters of Fluid-40(60%)

-./



Compartments and their

Relationship

Blood Plasma

3 L

Interstitial

11 LIntracellular

28 L

Transcellular

1 L

•most cases substances within the plasma mustpass through the interstitial uid beore enteringcells#• hereore the interrelationships between these $

compartments are crucial in underlying whole body



!ternal and Internal n"ironments“all the vital mechanisms, however varied they may be, have only oneobject, that of preserving constant the conditions of life in the internal

environment.” Claude Bernard (1!"#

• The *asis (+&h'si(l(i#al Reula$i(

• A S$a!le In$ernalEn%ir(n,en$ Is Esse

+(r N(r,al Cell Fun#$



n"ironments

p# $%&

&' mm #('%23 mm #(PC)2

Pa)2 *+ mm #(1,' mm #(P)2

3$ -C.1' and /&' -CTemperature

InsideOutsideVariable

#• stability o the internal environment is the

primary condition or a ree and independentexistence"By controllin( its internal en"ironment the

or(anism is no lon(er at the mercy o0 the en"ironment % –

p# "ariale



o summari0e1

H(,e(s$asis is $he

,ain$enan#e (+ a s$ead' s$a$e(+ $he in$ernal en%ir(n,en$ (+$he !(d'.



Body Fluid Constituents

45a/6 7 1&+

4/6 7 &%+

4Cl.6 7 11,

4Protein6 7 ' m9

)smolality

2*' m)sm

45a/6 7 1&2

4/6 7 &%&

4Cl.6 7 1'2

4Protein6 7 1

)smolality

2*' m)sm

45a/6 7 1+

4/6 7 12'

4Cl.6 7 2'

4Protein6 7 &

)smolality

2*' m)sm

Plasma Interstitial Cellular

•su!s$an#es aren-$ in euili!riu,/ !u$$here is a !alan#ethere is a di2erence between the basicconstituents o the body"uid compartments# hismeans that homeostasis is not about reachingequilibrium, but about maintaining a steady"state#

&ince the system is not necessarily in equilibrium



34

Homeostasis & Controls

•Successfulcompensation

• Homeostasis

reestablished•Failure to compensate

• Pathophysiology

• Illness

• Death



Feedac: ow o inormation along a closed

loop < = 5e(ati"e or Positi"e

• Negative = chan(e is sensed and action

ta:en to pre"ent 0urther chan(e e%(.

re(ulation o0 secretion o0 hormones%

• ositive = chan(e is sensed and action

ta:en to ampli0y chan(e usuallyassociated >ith a discrete end point?

e%(% irth? o"ulation<



#omeostatic 9echanisms

• 9ost homeostatic mechanisms are ased

on ne(ati"e 0eedac:

• specifc terms that are used to describe the

processes involved"

C(n$r(lled Varia!le

Sens(r

C(,0ara$(r/ se$ 0(in$

E1e#$(rs



Blood Pressure Re(ulation

Blood Loss

Blood Pressure

controlled "ariale<

Baroreceptor

sensor<

Brain

comparitor<

@asoconstrictionA Cardiac )utput

e00ectors<

Cardio"ascular

control

center = compares

BP to

set !oint andadusts

"ascular tone and

cardiac output

accordin(ly



Blood lucose ."e Feedac:

β.cell

@ariale

Blood lucose

β.celllucose

Insulin

secretion

Cells





Cutaneous Blood @essels

Dnticipation o0 e!ercise and durin( e!erciseEympathetic out0lo> increases

to maintain lood pressure




Dnticipation o0 strenous e!erciseEympathetic out0lo> increases

to maintain lood pressure

#ypothalamus detects heat increase

Dnd inhiits sympathetic out0lo>

@asodilation helps to di"ert lood 0lo> to the s:in

For heat loss




ith e!treme e!ercise the need to controlBlood pressure ta:es priority and the

@essels constrict

#ypothalamus detects heat increase

Dnd inhiits sympathetic out0lo>

@asodilation helps to di"ert lood 0lo> to the s:in

For heat loss





Feed.0or>ard Control

• Dnticipation o0 chan(e = (ets ody ready

0or chan(e

• e%(% heart rate and "entilation can

increase e"en e0ore e!ercise e(ins

• )r sali"ation and di(esti"e enGyme

production e(ins e0ore a meal is eaten



Redundancy

• #omeostatic mechanisms are important =

there0ore o0ten there is more than 1 control

mechanism

• I0 1 mechanism 0ails = then there is a ac:upsystem e%(% DTPadenosine in air>ay sur0ace

liHuid secretion or control o0 cutaneous lood

"essels y oth cardio"ascular control center

and temperature control center<• )r lood pressure ne!t slide<



"#!ovole$i &'o

B%P% 0alls

idne#*u+taglo$erular ells Aorti ar',arotid sinusenin

Ativit# dro!

"#!ot'ala$us

osterior ituitar#

.edulla

oblongata

Angiotensinogen

in blood

Angiotensin I

L/N

Angiotenin II

A,1

Adrenal

,orte+

"eart rate

ontratilit#

2lood

Vessels

idne#

&alt 3ater onservation

Aldosterone

A"

&#$!at'eti out!ut

Inc% "olume

In5 vas5 resistane

Inc%

B%P%



Eummary I

• "o$eostasis = maintenance o0 a staleinternal en"ironment

• &tead# state = unchan(in( >ith time

• 1uilibriu$ = >hen parameters aremaintained in an ener(etically 0a"oralesituation

• edundan# = more than 1 system tocontrol a "ariale ac:up systems<



Eummary II

• 5e(ati"e 0eedac: = 0eedac: causes a

perturation to e minimiGed or re"ersed

>ith "ie> to :eepin( parameter at a set

point

• Positi"e 0eedac: = ampli0ication o0 a

de"iation usually de0ined end point<

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Physio I Lecture 1