Physiology
study of how the body functions
Homeostasis
ability to maintain relatively stable conditions in the internal environment
Conditions that need to be controlled to maintain homeostasis
- pH
- temp
- blood gases (CO2, O2)
- blood pressure
- ICF and ECF fluid volumes
Disease
failure to maintain homeostasis
Control centres for homeostasis
endocrine and nervous system
Control centres for homeostasis do what
- maintain homeostasis
- permit departures from homeostasis in controlled manner (pregnancy)
2 types of NS/endocrine responses
- anticipatory responses
- feedback mechanisms
Example of anticipatory responses
rise in respiratory rate at start of exercise = proprioceptors single movement before a change in internal conditions
Anticipatory responses may be ..
learned or behavioural
Feedback mechanism
mechanisms that respond to change in a system
Feedback mechanisms consist of ..
set points, receptors, control areas, and effectors
Set point
range of values of a variable (body temp) that do not bring about a response
Steps of feedback mechanisms
variable is monitored by receptors –> info fed back to control area –> controls the effector
Types of feedback mechanism
- negative feedback
- positive feedback
Negative feedback
most common homeostatic control method. result of “output”, variable moves back toward the set point
Example of negative feedback
body temp (variable) set point 36-38, if increase temp core blood to skin surface and sweat evaporates = increase heat lose and decrease temp
Positive feedback
less common, NOT homeostatic, output intensifies the input, continues until endpoint
Example of positive feedback
childbirth
