biology stpm chapter 11 term 2

8/16/2019 BIOLOGY STPM CHAPTER 11 TERM 2

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CHAPTER 11

HOMEOSTASIS


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DEFINITION OF

HOMEOSTASIS


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Process involved in maintaining constant p!sical and cemical"actors in te internal environment o" an organism in a constantoptim#m condition to ens#re te s#rvival o" cells$

Often involves negative feedback mechanism


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Homeostasis involves %eeping te internal

environment &itin set ranges$


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∗ Life of organism become less dependant onthe external environment

∗ Ensure optimum internal environment (pH,

temperature, salt concentration) for cell tofunction, the organism to survive andreproduce eciently

∗ Enables biological system to function

eciently and smoothly ith minimumastage of energy

∗ Organisms can live in ider range of habitats

∗ Organisms can increase or decrease its

metabolic rate suit to its re!uirement

IMPORTANCE OF HOMEOSTASIS


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INTERNA' FACTORS THAT RE()'ATESHOMEOSTATIC MECHANISM


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HOMEOSTATIC CONTRO'S*STEM IN MAMMA'S

"# $timulus % & prod#ce cange in level o" an internal"actors +varia,les)

'# eceptor detect changes# *nput & in"o sent along AFFERENT pat&a! to control

center +,rain-

+# Output . in"ormation sent along EFFERENT pat&atto e/ectors

0$ Response o" e/ector "eed ,ac% to red#ce te e/ect o"original stim#l#s and ret#rns te varia,le toomeostatic level


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• Homeostatic mecanism are d!namic s!stem

&ic act to prod#ce a stead! state dynamice!ulibrium


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∗ Process &ic animals maintain an internaltemperat#re &itin a tolera,le range

"rom 234C in artic and 034C in desert region

Internal meta,olism and e5ternal environmentare te so#rce o" eat "or termoreg#lation

Heat gained 6 Heat lost Constant ,od!temperat#re

Termoreg#'ATION


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Heat gained ."ood meta,olisma,sorption o" solar energ! +radiation7-Cond#ction "rom &armer gro#nd and &armer parts o"

atmospereHeat lost . evaporation o" &ater 8 s&eat7 e5aled air "rom l#ng)rinating and de"ecating

Radiation to s#rro#ndingConvection+trans"er o" eat ,! c#rrents o" air or

&ater-Cond#ction +trans"er o" energ! ,! collision o"

molec#le-

Heat gain and eat loss


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∗ Organism are classi9ed ,ased on eat so#rce

∗ Ectoterm . ,od! temperat#re depends ontemperat#re o" environment$ Man! ave,eavio#ral startegies to reg#late ,od!temperat#re

∗ Endoterm . control teir ,od! coretemperat#re &it set range ,! p!siologicalmecanisms$


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Endoterm Ectoterm

Meta,olic rate Hig 'o&

Heat generation Eno#g to %eep ,od!&arm

Too little to &arm,od!

Internal ,od!

temperat#re

Sta,le7 regardless o"

e5ternal :#ct#ations

Determined ,!

environment


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/ehavioural 0hysiological $tructural%-natomical

Concio#s action. Altering post#re7

orientation and

microclimate toreg#late ,od!temperat#re

Ra,,its move into,#rro& to escapeeat

;anggaroo spreadsaliva on its arms tocool as salivaevaporates

Dag panting to getcool &en saliva

evaporates H#ddling


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3hermoregulation& Te process o" maintaining astead!

,od! temperat#re #nder a variet! o" conditions$

S!stems Involved.M#sc#lar?

Integ#ment +s%in-?Respirator!Circ#lator!

Nervo#s +!potalam#s in ,rain-Endocrine +ormones7 "eed,ac%-

@


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sweat poreevaporation

epidermis

dermis

sweat duct

sweat gland

blood vessel

Section

through skin

Te s&eat glande5tracts s&eat "rom

te ,lood andpasses it #p te d#ctto te s%in s#r"ace&ere it evaporates

0.25 mm

S&eat gland

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B


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much heat lost

=asodilationI" te ,od! temperat#re rises7

te ,lood vessels in te s%indilate +,ecome &ider- and allo&more ,lood to :o& near tes#r"ace$ Te eat loss "rom te,lood tro#g te s%in elps

cool te circ#lating ,lood

=asoconstriction

little heat lost

I" te ,od! temperat#re "alls$

Te ,lood vessels in te s%inconstrict$ 'ess &arm ,lood :o&snear te s#r"ace so less eat islost

=asoconstriction dilation

B


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biology stpm chapter 11 term 2

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