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Mechanisms of Homeostasis
Homeostasis• Process where the
body maintains a constant internal environment
• Reactions & enzymes work best in specific conditions
• Control systems adjust to internal/external changes– pH, temp, fluids
Control Systems• Sensors (aka: receptors)
– Gather information about the body and environment
– Ex: skin senses pressure• Communication Center
– Messages sent throughout the body to respond
– Ex: Impulse travel through your nerves
• Control Center– Receives information from the
sensors– Ex: Brain interprets the impulse
• Targets– Body part that changes its activity– Ex: Muscles in foot stretch/contract
abruptly
!*%!?%&#
Negative Feedback Loops• Regulates most
of the body• Counters
changes in the body that move conditions away from a set point– Reverses the
change
• Keeps internal environment stable
Positive Feedback Loop• Increases the
changes away from set points
• Important when rapid changes needed
• Ex: Oxytocin released– When uterus
contractions begin, oxytocin released to speed up the contractions (not stop them)
Working Together
• Thermoregulation: Maintenance of body temperature– Skin: sensors provide feedback to brain– Nervous & Endocrine system: send messages to/from brain– Muscles: Start to shiver
Homeostasis disruption
• Sensors fail
• Wrong messages sent
• Message doesn’t reach target
• Serious injury
• Microorganism infection
• Short Term– Temporary discomfort
(usually)
Long Term: Diabetes
• Normally
– Glucose in blood rises after meals
– Pancreas releases insulin
– Cells remove the glucose
• Type 1
– Immune system destroys pancreas cells
– Pancreas unable to make insulin
– Blood pH decreases as glucose builds up
• Type 2
– Pancreas does not make enough insulin
– Blood pH decreases as glucose builds up
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