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Definition: Keeping the internal environment in a Steady state
It is controlled by Negative Feedback Mechanism
Homeostatic control system
The body can regulate its internal environment through a multitude of feedback systems
A feedback system is a cycle of events in which the status of body condition is continually monitored, evaluated, changed, re-monitored, re-evaluated and so on.
Any disruption that changes a controlled condition is called a stimulus
RECEPTOR
a body structure that monitors changes in a controlled condition and sends input in the form of nerve impulses or chemical signals to a control center.
CONTROL SYSTEM
evaluates the input it receives from receptors and generates output commands when they are needed.
output from the control center can occur in several forms: nerve impulses, hormones , or other chemical signal
EFFECTOR is a body structure that receives output
from the control centre and produces a response or effect that changes the controlled condition.
either depressing it (negative feedback) or enhancing it (positive feedback)
Feedback SystemNegative feedbackHomeostatic
mechanism that reduces the intensity of the original stimulus
Consequently causes a change in a variable that is opposite in direction to the initial change
Positive feedbackA feedback
mechanism in which the response enhances the original stimulus
Rise abovenormal value
Fall below normal value
normal value
Corrective Mechanis
m
Corrective Mechanis
m
NEGATIVE NEGATIVE FEEDBACK FEEDBACK
MECHANISMMECHANISM
normal
value
negative
feedback
negative
feedback
Parts of Body involvedParts of Body involvedkidneys :
regulate water & mineral salts concentration
skin : regulate body
temperatureliver & pancreas :
regulate blood glucose level
Excretory system
kidney
liver
pancreas
+
skin
tissue cells
blood
Osmoregulation Osmoregulation (Water & Mineral salts)(Water & Mineral salts)
Regulate water potential in Tissue Fluid
Organ involved: KIDNEYsSystem involved : Urinary system
Normal Water Content in
Blood
Normal Water Content in
Blood
After Sweating
After Sweating
Concentrated Blood
Concentrated Blood
Larger proportion of water is reabsorbed
Larger proportion of water is reabsorbed
ConcentrateConcentrated Urine is d Urine is producedproduced
ConcentrateConcentrated Urine is d Urine is producedproduced
Normal Water Content in
Blood
Normal Water Content in
Blood
After DrinkingAfter Drinking
Diluted Blood
Diluted Blood
Smaller proportion of
water is reabsorbed
Smaller proportion of
water is reabsorbed
Diluted Diluted Urine is Urine is producedproduced
Diluted Diluted Urine is Urine is producedproduced
Osmoregulation Osmoregulation (Water & Mineral salts)(Water & Mineral salts)
After having a very salty meal
produce concentrated urine to remove excess salts in solution form
extra water is needed to be excreted along with the excess salts
sensation of thirst (drink more water to compensate for the water loss)
ThermoregulationThermoregulation(Regulation of Body (Regulation of Body Temperature)Temperature)Cold-blooded animals
body temperatures vary with that of the environment
e.g. reptiles, fish, amphibians
ThermoregulationThermoregulation(Regulation of Body (Regulation of Body Temperature)Temperature)Warm-blooded animals
keep body temperature constant even in winter by increasing metabolic rate
e.g. birds, mammals
Epidermis
Dermis
Outermost layerMiddle layerInnermost layer
Sweat gland
Blood capillaries
Subcutaneous fat
Receptors
Erector muscle
Nerve fibres
Sebaceous gland
Hair follicle
Structure of Mammalian Structure of Mammalian SkinSkin
Functions of Our Functions of Our SkinSkin
protect the body (epidermis)to provide mechanical
protectionto prevent bacterial entryto reduce water loss
temperature regulation (hair)
Functions of Our SkinFunctions of Our Skin excretion of sweat (sweat gland) store fats (subcutaneous fat) sensation (numerous receptors ) production of vitamin D under ultra-violet
light (inner epidermis)
More sweat is produced by sweat glands
evaporation of sweat takes away heat which produces a cooling effect
Vasodilation of skin arterioles
arterioles near the surface of the skin dilates
to let more blood flows near the skin surface
to have more heat lost by conduction & radiation.
Muscles relaxhairs lie flat on the skinreduce thickness of air trapped among the hairs (not effective in human because human’s hairs are short)
Develop thinner fat & shed their furas long term responses increase heat loss
Decrease metabolic rate & muscle contractiongain less heat
Vasoconstriction of skin arteriolesarterioles near the surface of the skin constrict
to let less blood flows near the skin surface
to have less heat lost by conduction & radiation
Muscles contractpull hairs for trapping more air
thicker layer of air acts as a good insulator of heat
Less sweat is produced by sweat glandsreduce heat loss by evaporation
Develop thicker fat & thicker furas long term responses reduce heat loss
Increase metabolic rate & muscle contractiongain more heat
Regulation of Regulation of Blood Glucose LevelBlood Glucose Level
controlled by Negative feedback mechanism
controlled by insulin secreted from the islets of Langerhans in pancreas
Diabetes - malfunction of pancreas (does not secrete enough insulin)
Digestive system
Liver converts glycogen
to glucose
normal normal blood blood
glucose glucose levellevel
Blood glucose Blood glucose level fallslevel fallsSoon Soon
after after a a
mealmeal
Long Long after after
a a mealmeal
Blood Blood glucose glucose
level riseslevel rises
normal normal blood blood
glucose glucose levellevel
Too Too HigHighh
Too Too LowLow
PancreaPancreas s
secretes secretes insulininsulin
Pancreas Pancreas secretes secretes
less insulinless insulin
Liver coverts glucose
to glycogen