Homeostasis and Feedback in the Body

Colorado Life Science 2.6: Cells, tissues, organs, and organ systems maintain relatively stable internal environments,

even in the face of changing external environments

What is homeostasis?

Process that occurs in all living things

All organ systems work together to achieve ___________.

◦ Ability of an organism to maintain its internal environment, despite changes to its internal or ________ environment!

http://en.wikipedia.org/wiki/File:Tightrope_artist_Cologne_1.jpg

How does homeostasis work?

pathways◦ A cellular relay race!

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

Keeps levels of certain processes within a normal .

http://en.wikipedia.org/wiki/File:Southern_12_stage-02_1988.jpg

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

Body Temperature Blood pressure Blood pH O2 and CO2 concentration Osmoregulation-Water balance Blood glucose

How Does it Work?

Stimulus Receptor Integrating

center Effector Response

◦ Reverses the stimulus

Consider temperature in your home….Example:

Stimulus- low thermal energy in the room (it’s cold)

Receptor- sensor in thermostat

Integrating center- thermostat

Effector- Heater Response- increased

thermal energy (it’s warmer)

Also called feedback . Way in which MOST homeostatic mechanisms work

Stimulus produces a response that opposes or the original stimulus

◦ In other words, the product of a negative feedback pathway inhibits or shuts down the originalsignal.

Negative Feedback

Negative Feedback

Stimulus

Living Example

Negative Feedback

You can think of negative feedback like dueling mechanisms- What goes up, must come down!

_______________________ Sweating (cooling) vs. shivering (warming)

Blood PressureVasconstriction vs. vasodilation

OsmoregulationHypotonic vs. hypertonic

Positive Feedback Takes body out of

homeostasis (which can be necessary in certain circumstances)

Stimulus causes a _________ that causes more of the stimulus

A B

Examples

Positive Feedback

Increase in births increases population which increases births – and so on.

Positive Feedback

Examples in Our Body Blood clotting

Injured tissue signals platelets to be activated, activated platelets produce chemical signal that activates more platelets

______________ The hormone oxytocin signals a contraction, which

signals they brain to produce more oxytocin

Identify the following as examples of positive or negative feedback loops within the body?

Additional Examples…

Functions of Integumentary System:◦ Protection◦ Body Temperature Regulation◦ Excretion◦ Information Gathering◦ Vitamin D Production

Homeostasis & the Integumentary System

If cold, ___________ generates heat and goose bumps and constricted blood vessels help decrease the heat loss from skin

If hot, __________ blood vessels allows excess heat released from skin and sweating allows energy to leave the body

Homeostasis: Body Temperature Regulation

Body Temperature & Feedback

Positive or Negative?

Function of Circulatory System◦ Transport Oxygen, CO2, nutrients and wasteto and from cells, as needed

Homeostasis & the Circulatory System

_________ are exchanged in the lungs (Oxygen in and Carbon Dioxide out)

Heart pumps blood from the body to the lungs and then to the rest of the body

How the Heart Works

Blood has pH of 7.4 (7.35-7.45) Below 6.8 or above ______ cells stop

functioning

Homeostasis: Blood pH Buffering System

Homeostasis: Blood pH & Bicarbonate Buffering System

Positive or Negative?

Lack of Sleep & Stress Levels

Positive or Negative?

Homeostasis- The Digestive & Circulatory & Endocrine Systems!

Blood Sugar Regulation!

_________ – food into mouth Digestion – mechanical and

chemical break down – starts in mouth, continues to break down in stomach and small intestine

___________ – bloodstream absorbs nutrients in small intestine and absorbs water in large intestine

Elimination – Waste eliminated through anus

Processes of the Digestive System

Glycogen- Stored glucose (polysaccharide of glucose)

Glucagon- Hormone secreted by pancreas that _________ blood sugar (break down glycogen into glucose)◦ Produced by alpha-cells of the pancreas◦ Released into the circulatory system when blood glucose is low◦ Signals the liver to break down glycogen into simple glucose

Insulin- Hormone secreted by the pancreas that _________ blood sugar (glucose to glycogen)◦ Produced by beta-cells of the pancreas◦ Released into circulatory system when blood glucose is high◦ Facilitates the transport of glucose into target cells

Homeostasis- The Digestive & Circulatory & Endocrine Systems- Blood Sugar Regulation!

Blood sugar regulation:

Homeostasis & the Digestive System

Homeostasis & the Digestive System

Positive or Negative?

Food for thought…

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

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

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