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Pg. 8 #10-12

Pg. 8 #10-12. Homeostasis and Feedback Loops. Definitions. Homeostasis – state of balance in the body Stimulus- something in the environment that causes a change (can be internal) Response – action of organism as a result of stimulus

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Pg. 8 #10-12

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  1. Pg. 8 #10-12

  2. Homeostasis and Feedback Loops

  3. Definitions • Homeostasis – state of balance in the body • Stimulus- something in the environment that causes a change (can be internal) • Response – action of organism as a result of stimulus • Feedback mechanisms/loops – processes by which the body maintains levels • Usually uses nervous and hormonal cues to conduct processes

  4. Steps in a Homeostatic process • When a stimulus occurs, each of these steps must occur in order for a response to be initiated • 1) receptor must recognize stimulus • Must be enough of a stimulus to surpass nervous threshold

  5. Sensory Neuron • 2)sensory neuron must transmit message from the receptor, to a control center • Neuron = nerve cell • Most receptors are bundled together on individual neurons by region

  6. Control center • 3)message is carried to a control center (usually in brain), where the message is interpreted, and the correct response is coordinated. • In the case of a reflex action, spinal chord is C.C.

  7. Motor neuron • 4)Carries message from control center to effector organ dictating response

  8. Effector organ • 5)Receives message and conducts actual response

  9. Afferent pathway Includes receptor and sensory neuron (aka afferent neuron) Efferent pathway Includes motor neuron (efferent neuron) and effector organ Afferent vs. Efferent pathway

  10. Positive Feedback loop • Process by which stimulus causes a response which will increase the stimulation • Ie. Oxytocin in childbirth • Rate constantly increases until action is complete • Least common

  11. Graph of Positive Feedback • X-axis is time • Y-axis is hormone secreted

  12. Negative Feedback loops • Receptors detect change and initiate response that will counter that change • Tries to maintain a median • Ie. Blood glucose, temp, blood O2/CO2 levels • (draw graph from board into your notes)

  13. Example: Breathing Pattern • Body is designed to detect blood pH. • Too high = too much CO2 • Receptor = chemoreceptors in arteries • Afferent neuron = vagus nerve • C.C. = brain stem • Efferent neuron = phrenic nerve • Effector organ = intercostals and diaphragm • High pH will trigger quicker breathing, lower pH will slow it down (negative feedback)

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