HomeostasisHomeostasisNegative feedback systems in Negative feedback systems in

the human bodythe human body

.

What is homeostasis?What is homeostasis?

Process that occurs in all Process that occurs in all living thingsliving things

All organ systems work All organ systems work together to achieve together to achieve homeostasishomeostasis

Ability of an organism to Ability of an organism to maintain its internal maintain its internal environment, despite environment, despite changes to its internal or changes to its internal or external environmentexternal environment

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How does homeostasis work?How does homeostasis work? Feedback pathwaysFeedback pathways

A cellular relay race!A cellular relay race!

Specific organs and Specific organs and structures must structures must communicate with each communicate with each other in response to other in response to changes in the bodychanges in the body

Keeps levels of certain Keeps levels of certain processes within a processes within a normal rangenormal range

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What things in your body need to be What things in your body need to be kept within a range?kept within a range?

Body TemperatureBody Temperature Blood pressureBlood pressure Blood pHBlood pH OO22 and CO and CO22 concentration concentration Osmoregulation-Water balanceOsmoregulation-Water balance Blood glucoseBlood glucose

Cellular Relay RaceCellular Relay Race

StimulusStimulus ReceptorReceptor Integrating Integrating

centercenter EffectorEffector ResponseResponse

Reverses the Reverses the stimulus stimulus

Negative Feedback PathwaysNegative Feedback Pathways

Way in which most Way in which most homeostatic homeostatic mechanisms workmechanisms work

The product of the The product of the pathway inhibits, or pathway inhibits, or shuts down, the shuts down, the original signaloriginal signal Why is this an Why is this an

important feature in important feature in living things?living things?

Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows

of Harvard College.

Why is feedback important in Why is feedback important in living things?living things?

Allows baseline to be Allows baseline to be regainedregained

Conserves resourcesConserves resources Cellular MaterialsCellular Materials Energy (ATP)Energy (ATP)

mouth

Stomach

Sm. Intestine

Pancreas

ß-cells

Target cells-Muscle

Target cells- Liver

Target cells- Brain

Circulatory Runners

Game set-up

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Life Sciences-HHMI Outreach. Copyright 2009 President and Fellows of Harvard College.

mouth

Stomach

Sm. Intestine

Pancreas

ß-cells

Target cells-Muscle

Target cells- Liver

Target cells- Brain

Circulatory Runners

“Glucose!! Release the insulin!”

Lots of glucose circulating, so Pancreas calls out for insulin

.

mouth

Stomach

Sm. Intestine

Pancreas

ß-cells

Target cells-Muscle

Target cells- Liver

Target cells- Brain

Circulatory Runners

“Glucose!! Release the insulin!”

Insulin has been passed to the target cells. Targets can now receive glucose.

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mouth

Stomach

Sm. Intestine

Pancreas

ß-cells

Target cells-Muscle

Target cells- Liver

Target cells- Brain

Circulatory Runners

“Hold insulin production”

Pancreas stops insulin from being passed once there is no more glucose circulating

Dueling HormonesDueling Hormones What goes up, must come down!What goes up, must come down!

InsulinInsulin Produced by Produced by -cells -cells

of the Pancreasof the Pancreas Released into Released into

circulatory system circulatory system when blood glucose is when blood glucose is highhigh

Facilitates the Facilitates the transport of glucose transport of glucose into target cellsinto target cells

GlucagonGlucagon Produced by Produced by -cells -cells

of the pancreasof the pancreas Released into the Released into the

circulatory system circulatory system when blood glucose is when blood glucose is lowlow

Signals the liver to Signals the liver to break down glycogen break down glycogen into simple glucoseinto simple glucose

Dueling MechanismsDueling MechanismsWhat goes up, must come down!What goes up, must come down!

ThermoregulationThermoregulationSweating (cooling) vs. shivering (warming)Sweating (cooling) vs. shivering (warming)

Blood PressureBlood PressureVasconstriction vs. vasodilationVasconstriction vs. vasodilation

OsmoregulationOsmoregulationHypotonic vs. hypertonicHypotonic vs. hypertonic

Food for thought…Food for thought…

On average, how many organ systems are On average, how many organ systems are involved in each of the processes we’ve involved in each of the processes we’ve explored?explored?

Are there any organ systems that you see in Are there any organ systems that you see in allall of these processes? of these processes?

What might happen to these pathways if just What might happen to these pathways if just oneone system was not functioning properly? system was not functioning properly?