homeostasis
The tendency of an organism to maintain a stable internal environment even though the external environment changes continuously.
with proper homeostatic function, internal conditions stay within a _____ range
narrow
normal arterial pH
7.35 - 7.45
homeostatic control systems
Mechanisms that monitor the internal environment and correct as needed
homeostasis: “local control”
Isolated change in a few cells or a tissue,
response emerges and acts locally.
-on the cellular level
homeostasis: “reflex control”
Long-distance signaling, typically involving endocrine (hormonal) or neural responses
-organ, whole-organism level
3 MAJOR components of homeostatic control systems
- input signal
- integrator (controller)
- output
state the order of the response loop
- stimulus (change in internal environment)
- sensor (receptor, detects change, conveys info)
- input signal (afferent neuron)
- integrator (controller)
- output signal (hormone, neuron)
- target effector (muscle, gland, etc.)
- response (change corrected)
function of “integrators”
control center
- posses a “set point” within a normal range
- look for error signals in the input
(hypothalamus, kidney)
fever
thermostat in brain increases set point for core body temp
acclimitization
adapting to certain conditions
-having more red blood cells when living in a higher altitude
negative feedback
- turns OFF response loop
- exerts control
- homeostasis
- self terminating
- prevent changes
- acts to oppose input
positive feedback
- turns ON response loop
- amplify changes
- no control
- not self terminating, need outside factor to shut them off
give an example of a negative feedback loop
glucose homeostasis
- insulin (lowers blood glucose levels)
- glucagon (raises blood glucose levels)
- opposite actions of these hormones maintain glucose homeostasis in the body
- also body temp
- blood pressure regulation
how are uterine contractions and lactation examples of a positive feedback loops?
non-self terminating
amplify effects
-more oxytocin release triggered by suckling/baby dropping in uterus amplifies the effects of lactation/uterine contractions