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Homeostasis and ExcretionHomeostasis and Excretion
Homeostasis – maintaining the internalHomeostasis – maintaining the internal
environment at a constant level orenvironment at a constant level or
between narrow limits.between narrow limits.
Involves nervous and endocrine systems:Involves nervous and endocrine systems:
– Receptors monitor level of “variable”Receptors monitor level of “variable”
– Brain regulates level of variableBrain regulates level of variable
– Effectors bring about changes as directed byEffectors bring about changes as directed by
the brainthe brain
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HomeostasisHomeostasis
The parameters controlled include:The parameters controlled include:
Body Temperature (Thermoregulation)Body Temperature (Thermoregulation)
Blood glucose concentrationBlood glucose concentration
Leptin and Clinical ObesityLeptin and Clinical Obesity
Melatonin and Sleep PatternsMelatonin and Sleep Patterns
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Negative FeedbackNegative Feedback
Has a stabilizing effect:Has a stabilizing effect:
change in “levels” alwayschange in “levels” always
causes an opposite change:causes an opposite change:
– Rise in levels = decrease inRise in levels = decrease in
production = reduction in levelsproduction = reduction in levels
– Decrease in levels = increase =Decrease in levels = increase =
raise the levelsraise the levels
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ThermoregulationThermoregulation
Temperature regulation: thermoreceptorTemperature regulation: thermoreceptor
– Endotherm – mammals and birdsEndotherm – mammals and birds
– Ectotherm – reptiles…Ectotherm – reptiles…
Source of heat: Aerobic Cellular RespirationSource of heat: Aerobic Cellular Respiration
Main methods of heat loss: Conduction,Main methods of heat loss: Conduction,
Convection, and Radiation.Convection, and Radiation.
Require coordination between nervous andRequire coordination between nervous and
endocrineendocrine
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Type I vs. II DiabetesType I vs. II Diabetes
Type IType I
Onset usually duringOnset usually during
childhoodchildhood
Beta pancreatic cellsBeta pancreatic cells
produce insufficientproduce insufficient
insulin.insulin.
Must take syntheticMust take synthetic
insulininsulin
Cannot be controlledCannot be controlled
by dietby diet
Type IIType II
Can occur at any ageCan occur at any age
Target cells showTarget cells show
insensitivity to insulininsensitivity to insulin
Does not requireDoes not require
synthetic insulinsynthetic insulin
Correlated to obesityCorrelated to obesity
Can be controlledCan be controlled
with low carb dietswith low carb diets
23. LEPTIN AND CLINICALLEPTIN AND CLINICAL
OBESITYOBESITY
LEPTINLEPTIN
Regulates amount ofRegulates amount of
fat storedfat stored
Secreted by AdiposeSecreted by Adipose
(Fat) tissue(Fat) tissue
Acts on theActs on the
Hypothalamus to inhibitHypothalamus to inhibit
appetite and increaseappetite and increase
metabolismmetabolism
Clinical ObesityClinical Obesity
Diagnosed: BMI over 30 kgmDiagnosed: BMI over 30 kgm-2-2
Patients generally have higherPatients generally have higher
levels of LEPTIN in Blood plasma.levels of LEPTIN in Blood plasma.
Counter to expectationsCounter to expectations
Physiological: reduced sensitivityPhysiological: reduced sensitivity
to leptin signal system into leptin signal system in
hypothalamus? (proposed)hypothalamus? (proposed)
Injections unsuccessfulInjections unsuccessful
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24. MELATONINMELATONIN
Stimulates the sleepStimulates the sleep
cyclecycle
Different for differentDifferent for different
agesages
Teenagers follow differentTeenagers follow different
cyclecycle
Traveling throughTraveling through
different time zonesdifferent time zones
quickly can disruptquickly can disrupt
rhythmrhythm
JET LAG – disruptionJET LAG – disruption
Melatonin tablets canMelatonin tablets can
alleviatealleviate
Circadian rhythm –Circadian rhythm –
based on light/darkbased on light/dark
cyclecycle
– Hormone release,Hormone release,
temperature, sleep-temperature, sleep-
wake cyclewake cycle
““Master” clock is aMaster” clock is a
group of cells (SCN)group of cells (SCN)
in the hypothalamusin the hypothalamus
Melatonin: secretedMelatonin: secreted
by Pineal gland in theby Pineal gland in the
brainbrain
– Higher at nightHigher at night
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