Unit 1: Control of Internal Environment

Homeostasis

maintenance of constant internal environment

ex: body temp. blood pressure, body fluid balance

Steady state

a balance has been achieved between demands placed on the body and the body's response

Control system components (7)

1.stimulus

2. sensor/receptor

3. afferent pathway

4. integrating center

5.efferent pathway

6. effector/target

7.response

positive feedback

-direction of signal is same as original stimulus

-does not maintain homeostasis

-not as common as negative feedback

ex: giving birth--> signal for contractions to get stronger until baby is born

Negative Feedback

the response is to move the original signal in the opposite direction of the initial change of a variable

ex: body temp--> increases then body decreases it within a certain range

Set point

a specific value that the body tries to maintain within a tight range

Gain (of a physiological system)

the degree in which it can maintain homeostasis/how effective it is

-the larger gain the better at homeostasis maintenence

Gain (equation)

gain=correction applied/residual error

Dynamic Constancy

physiological variables are rarely held constant and instead fluctuate within a range