9.1 & 9.2: Homeostasis and Negative Feedback Regulation

Homeostasis

the physiological state of the body in which internal physical and chemical conditions are kept within a range that is suitable for life processes

The internal environmnet

The extracellula fluid which consists of interstitial fluid that fills the spaces between our cells and tissues, follow conditions approiprate for the cells to function properly

Nervous system

recieves sensory data from the environment, which informs the body of external conditions & transmits signals throughout the body

Excretory System

works to rid body of waste and maintain clean internal environment

Endocrine System

regulates the levels of various hormones throughout that are essential for life processes

Circulatory System

carries these hormones throughout the body & distributes thermal energy

Integumentary System

important for maintaining a constant body temp

Immune system

protexts body from infection and also fights it

Roles the liver has in maintaing homeostasis

1. Control amino acid levels by breaking down those not used

2. Detoxifies harmful chemicals

3. Manufactures important blood protein

When are feedback mechansims engaged?

If the conditions are outside the optiamal range

Steps in Negative Feedback

Stimulus (environmental change) - Sensor (nerve ending) - Integrator (the brain) - Effector (muscle/glands) - Response (system’s output)

Sensor

Detect changes in the environment

Integrator

Compares existing conditions with ideal conditions (set points)

Set Points

Idea condition ranges

Effector

Acts to return the system to it’s optical state

Negative Feedback Steps for High Body Temp

1) Sensor: thermoreceptors signal an increase in temp

2) Integrator: hypothalamus turns on cooling systems

3) Effector: skin blood vessels dilate, increased blood flow to sking (thermal energy lost) & sweat glands initiate sweating (evaporation causes cooling)

4) Result: Body temp decreases, hypothalamus turns off cooling system

Negative Feedback Steps for Low Body Temp

1) Sensor: thermoreceptors signal a decrease in temperature

2) Integrator: hypothalamus turns on warming systems

3) Effector: skeletal muscles contract, shivering generates energy production, body hair becomes erect to conserve thermal energy & skin blood vessels constrict which decreases blood flow to the skin, and reduces thermal energy loss

4) Result: body temp increases, hypothalmus turns off warning systems

Positive Feedback Mechanisms

response of a system to increase the effect of any changes made to the environmental conditions, DONT result in homeostasis

Ex of Positive Feedback Mechanisms

• flight or fight response when in danger

• uterine contractions during child birth