14265_lecture7-8_16766_lec 6- homeostasis.ppt

7/17/2019 14265_Lecture7-8_16766_Lec 6- Homeostasis.ppt

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HomeostasisHomeostasis

• Balanced internal conditionof cells

•Also called equilibrium

• Maintained by plasmamembrane controlling what

enters & leaves the cell.

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DE!"!#!$"

• %rocess that regulates the chemical

and physical parameters in theinternal environment so that theconditions are always suitable to meetthe needs of the cell

2



3 components of homeostatic controlsystem:

• a receptor (detects signal),

•

a control centre (receives info andprocesses it)

• an eector (carries out appropriateresponse)

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Body Processes that needHomeostasis

1. hermoregulation

!. "smoregulation

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hermoregulation

• #egulation of temperature

• $ta%ility of the optimal %ody

temperature is very essential forthe normal functioning of all%iological reactions

•

&o types of animals: ectothermsand endotherms

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'ctotherms

• 'ctotherms use the eternalenvironment and %ehavioralmechanisms to maintain a thermal%alance

• 'ctotherms sho& %ehavioral andstructural adaptations, &hich help themto ad*ust to temperature changes.

• +or eample, – hi%ernation and aestivation.

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'ndotherms

• Have a constant %ody temperature and

use a variety of physiologicalmechanisms to maintain a constant

internal temperature.• '-P/'$

• $hivering

•

$&eating

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$smoregulation

•

0ater in an animals %ody is distri%uted %et&eenthe intracellular and etracellular compartments.

• 2n order to maintain osmotic %alance, the

etracellular compartment of an animals %ody(including its %lood plasma) must %e a%le to tae&ater from its environment or to ecrete ecess&ater into its environment.

• 2t eeps the organism4s 5uids from %ecoming toodiluted or too concentrated

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ransport through cellmem%ranes

• he phospholipid %ilayer is a good %arrier around cells,especially to &ater solu%le molecules. Ho&ever, for thecell to survive some materials need to %e a%le to enterand leave the cell.

• here are 3 %asic mechanisms:

1. P-$$26' #-7$P"#8 92++$2"7 and +-;2/2-'992++$2"7

!. "$"$2$

3. -;26' #-7$P"#

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$smosis$smosis

• Diusion of waterDiusion of water across a membraneacross a membrane

• Moves fromMoves from H!'HH!'H

waterwater

concentrationconcentration (low(low

solute) tosolute) to *$+*$+waterwater

concentrationconcentration (high(high

solute)solute)

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Diffusion across a membrane

Semipermeablemembrane



$smosis, Diusion of H$smosis, Diusion of H--$$

Across A MembraneAcross A Membrane

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High H2O concentration

Low solute concentration

Low H2O concentration

High solute concentration



copyright cmassengale 12

Water moves from areas of low solute concentration to areas of high solute

concentration.

Water molecules will cross membranes until the concentrations of water &solutes is equal on both sides of the membrane; called equilibrium

At equilibrium, molecules continue to move across membranes evenly so

there is no net movement



imple Diusionimple Diusion

• /equires "$"$energy

• Moleculesmove fromarea of H!'HH!'H

to *$+to *$+concentration

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D!0!$"D!0!$"

Diusion is a%A!1E%A!1E processwhich means no

energy is usedto ma2e themoleculesmove3 they

have a natural4!"E#!5 E"E/'6

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Diusion of *iquidsDiusion of *iquids

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16

Facilitated diffusion

Doesn’t require energy

Uses transport

proteins to moe fromhigh to low concentration!"amples# $lucose or!"amples# $lucose or

amino acids moing fromamino acids moing fromblood into a cell%blood into a cell%



acilitated Diusionacilitated Diusion

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Molecules will randomly move throughthe pores in hannel !roteins"



#ypes of #ransport#ypes of #ransport

%roteins%roteins• 5hannel proteins areem%edded in the cell mem%rane

< have a pore for materials tocross

• ;arrier proteins can change

shape to move material from oneside of the mem%rane to theother

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acilitated Diusionacilitated Diusion

• omeome 5arrier75haperone5arrier75haperoneproteinsproteins do notdo not

e8tend throughe8tend throughthe membrane.the membrane.• #hey#hey bond andbond and

drag moleculesdrag molecules through the lipidthrough the lipid

bilayer andbilayer andrelease them onrelease them onthe opposite side.the opposite side.

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5arrier %roteins5arrier %roteins

• $ther carrier$ther carrier

proteinsproteins

change shapechange shape to moveto move

materialsmaterials

across the cellacross the cellmembranemembrane

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&ctie 'ransport&ctie 'ransport

(equires energy or &')

*oes materials fromLO+ to H,$H concentration

&$&,-S' concentration

gradient

14265_lecture7-8_16766_lec 6- homeostasis.ppt

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