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Phys Lect 1

Homeostasis Maintenance of steady states in the body (Internal environment) by coordinated physiological mechanisms. **Shows how the body heals itself**
7 Variables regulated by the body 1.CO2/O2. 2.BL pH. 3.Ions (K+ and Ca2+). 4.Temperature. 5.Glucose. 6.Plasma Osmolality. 7.BP.
3 main bodily control systems 1.Negative Feedback. 2.Positive Feedback. 3.Feedforward.
What is the most important function of Neg Feedback? Resist change within the body. Adjusting to a change in order to return to the set point.
Neg. Feedback: Set Point The desired homeostatic level that the body constantly maintains. Causes the Feedback Controller to activate the effector. **Ex: BP 120/80**
Neg. Feedback: Sensor Senses the regulated variable and signals to the feedback controller to stop signal activation of effector (if not at set point). (Carotid Sinus, baroreceptor, if overstretched, Inc signals will decrease BP back down to the SET POINT)
Neg. Feedback: Feedback Controller Controlled by the body's SET POINT and the sensor. Activates Effector via signaling.
Neg. Feedback: Effect of Increased Sensory signals on the Feedback controller Feedback controller stops activating the effector so the regulated variable returns to SET POINT
Neg. Feedback: Effecet of Decreased Sensory signals on the feedback controller Feedback controller signals/activates the effector so the regulated variable returns to SET POINT.
Negative Feedback on Baroreflex: High BP The baroreceptor overstretches, increasing its signals to the medulla. This Inhibits the medulla's signaling to Inc HR, Vasoconstrict BL vessels, and kidney deactivation.
Neg Feedback: Low BL Sugar would cause the feedback controller to inhibit insulin secretion and increase glucagon production, decreasing glucose uptake into cells and increasing the production/exportation of glucose from liver
Main function of Positive Feedback Promotes bodily change in the same direction as initial disturbance. **Sensor positively activates the effector to keep increasing the variable, bypassing the feedback controller.
Pos Feedback: LH LH causes the ovaries to increase production of Estrogen which thus increases LH
Main disadvantage to a feedback system's control over a variable? Can only RESPOND to CHANGES in variable. **Not able to ANTICIPATE a change
Importance/Advantages of FeedForward systems? They can respond in ANTICIPATION of a disturbance. **As opposed to having to wait until the regulated variable actually changes.
Feedforward: Ventilation prior to exercise Respiratory control center(Controller) anticipates the disturbance, activating respiratory muscles(Effector) thus increasing ventilation.
Function of both feedforward and feedback systems when combined 1.Feedforward: Anticipation activates effector and Feedback controller to change variable. 2.Negative Feedback: Maintains the regulated variable by controlling the Effector.
Combined system's effect on ventilation during exercise 1.Cortex (Feedforward) anticipates desired movement, activating the respiratory muscles and medulla (controller). 2. Medulla then works to keep Arterial PCO2 constant.
Type of Feedback system: Inc [salt] in the bodily fluids during exercise leads to water retention in the kidneys NEGATIVE because it is trying to correct the changed variable back to the SET POINT
What would happen if effector in a negative feedback system was damaged? The output of the feedback controller would increase due to decreased negative signals from the sensor. **Ex: Heart Failure: HR continues to decrease even though Sympathetic signaling increases
Neurocardiac Syncope (clinical Correlate) Results from the loss of the baroreflex (Neg Feedback) thus defective BP regulation
Created by: WeeG



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