How The Body Responds

Changes

• Close your eyes…• I am going to give you a scenario

to imagine…• Really close your eyes…• I will say a series of sentences

and I want you to tell me your initial emotional reactions• Ready?

• Your parents got new jobs and you are going to have to move to Togo.• You just found out that your best

friend is hanging out with the new kid in class behind your back. • I am about to sneak up behind

you while your eyes are closed and buzz your hair!

Changes

• At least one of the previous statements might have made you feel a little unsettled• That is because humans often

resist change• We really enjoy the fact that

things will remain consistent• The human body works in a very

similar manner

Homeostasis

• The human body works more efficiently when it can maintain a certain set of internal conditions• This also helps prevent harmful

changes in internal conditions• Homeostasis is the ability to maintain

a set of stable internal conditions• Homeostatic regulation are the

physiological changes needed to maintain homeostasis• FUN FACT: Every death in human

history is due to a loss of homeostasis

Homeostasis

• Homeostasis can be maintained two different ways• Autoregulation is the way to

maintain homeostasis that comes from within a cell, organ or organ system• An example is when oxygen levels

decline in an organ system• Cells will produce chemicals to

dilate blood vessels in order to get more oxygen

Homeostasis

• Extrinsic regulation is when the activities of an outside system (mostly nervous or hormone) regulate homeostasis • An example of this is when you

work out• Based on your level of activity,

your nervous system sends signals to your heart to beat faster to maintain proper oxygenation of cells

Homeostatic Regulators

• Regardless of the systems or mechanisms involved it is the job of the body to maintain homeostasis• Each homeostatic regulator has

three basic parts• A receptor responds to a stimulus• A control center receives and

processes the information• An effector makes a change based

on the stimulus

Homeostatic Regulators

• It is very similar to the way you regulate temperature in your house• A small thermometer detects

the temperature of the house (receptor)• A thermostat detects this

information and decides to turn on the air conditioning (control center)• The air conditioner will turn on

(effector)

Homeostatic Regulators

• The set point is the desired value that the control center tries to maintain• Often the level of homeostasis

will fluctuate around the set point by a small percentage • Fulgurations are not generally

not a problem as long as they are not too large

Feedback

• Lets try a fun exercise!• Turn to the person next to you and

give them some observations about their outfit• These observations can be

constructive criticism or they can be complements, it is up for you to decide• Hopefully that was not too traumatic of an experience

Feedback

• What you just received from the person next to you was called feedback• Feedback is information that is

given to an organism that allows them to understand their environment better• In this scenario the feedback you

gave to your partner next to you was based on their appearance in this classroom

Positive Feedback

• Positive feedback is a type of feedback that produces a larger or exaggerated response based on the feedback• For example, if you told your

partner that they had a really nice pair of shoes, they might be included to wear those shoes more• The feedback you gave will cause

them to have a larger positive response the next time the see those shoes in the closet

Positive Feedback

• Positive feedback is used in the body, but it is pretty rare• This is because it tends to lead to

very extreme responses to stimuli• One example is if you receive a

large cut or wound• The release of blood clotting

factors by a small amount of cells will stimulate the release of other clotting factors in other cells

Positive Feedback

• http://www.youtube.com/watch?v=65U3NSDn2dg&t=6m41s

Negative Feedback

• Negative feedback is a type of feedback that leads to counteracting the feedback• When you asked the person to

evaluate your outfit they may have been a bit critical of your shirt• Next time you see the shirt in

the mirror, you may not be as inclined to wear that shirt

Negative Feedback

• This happens frequently in the body• Thermoregulation is the

regulation of body temperature• When your hypothalamus

receives information that your body is above ~37.2OC your body sets things in motion that will cool your body• This will bring your body below

37.2OC

Equilibrium

• Homeostatic regulation is not an easy thing for a body to achieve• It often takes many integrated

organ systems to help maintain homeostasis• It often takes many different

organs releasing signals, turning on and off feedback loops and coordinating set points

Equilibrium

• A state of equilibrium is maintained when several processes are balanced and homeostasis is maintained• This is a scenario that allows

allow all body systems to function at a high potential