Homeostasis and Feedback in the Body Colorado Life

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 http: //en. wikipedia. org/wiki/File: Southern_12_stage-02_1988. jpg levels of certain processes within a normal.

What things in your body need to be kept within a range? � Body Temperature � Blood pressure � Blood p. H � O 2 and CO 2 concentration � Osmoregulation-Water balance � Blood glucose

How Does it Work? � Stimulus � Receptor � Integrating center � Effector � Response ◦ Reverses the stimulus

Example: � Consider temperature in your home…. Stimulus- low thermal energy in the room (it’s cold) � Receptor- sensor in thermostat � Integrating centerthermostat � Effector- Heater � Response- increased thermal energy (it’s warmer) �

Negative Feedback � 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 original signal.

Negative Feedback Stimulus

Negative Feedback � Living Example

You can think of negative feedback like dueling mechanisms- What goes up, must come down! ____________ Sweating (cooling) vs. shivering (warming) Blood Pressure Vasconstriction vs. vasodilation Osmoregulation Hypotonic 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

Positive Feedback � Examples 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

Additional Examples… � Identify the following as examples of positive or negative feedback loops within the body?

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

Homeostasis: Body Temperature Regulation � 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

Body Temperature & Feedback

Positive or Negative?

Homeostasis & the Circulatory System � Function of Circulatory System ◦ Transport Oxygen, CO 2, nutrients and waste to and from cells, as needed

How the Heart Works � _____ 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

Homeostasis: Blood p. H Buffering System � Blood has p. H of 7. 4 (7. 35 -7. 45) � Below 6. 8 or above ______ cells stop functioning

Homeostasis: Blood p. H & Bicarbonate Buffering System

Positive or Negative?

Lack of Sleep & Stress Levels

Positive or Negative?

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

Processes of the Digestive System � _____ – 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

Homeostasis- The Digestive & Circulatory & Endocrine Systems- Blood Sugar Regulation! � 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 System � Blood sugar regulation:

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?