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

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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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