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PSU BIOL 240W - Homeostatic Regulation of Blood Pressure

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BIOL 240W 1st Edition Lecture 20Outline of Last Lecture I. HomeostasisII. EquilibriumIII. Negative Feedback LoopsOutline of Current LectureI. Negative Feedback LoopsII. Homeostatic Regulation of Blood PressureIII. The Circulatory SystemCurrent LectureI. Negative Feedback Loopsa. Do not mean the same thing as homeostasis b. Mechanism that helps an organism maintain homeostasisc. Stimulus  sensor  signal  integrating center  signal  target  responsed. Physical parts are sensor, integrating center (often nervous system), and targeti. Examples: increase sodium being absorbed by kidneys, sweat when your body temperature gets too highII. Homeostatic regulation of blood pressurea. Means of communication may include hormone, neurotransmitter, nerve impulse, paracrines, autocrinesb. Stimulus change in blood pressurec. Sensor- baroreceptor (nerve cell sensitive to pressure). i. Does not make a decision, it just reports the change ii. These receptors are located close to the heart (close to aorta) and arteries going up neck toward brain (corroded arteries).d. Integrating center- vasomotor center i. Located in the brain (medulla oblongata) ii. Decisions are made here: if the blood pressure is too high, it needs to be lowered. If the blood pressure is too low, it must be increased. e. Response- attempt to bring blood pressure into ideal blood pressure range. Blood vessels may dilate or constrict (to decrease and increase blood pressure, respectively)f. Nerves transmit action potentialsg. Example:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. Blood pressure increases, and it goes above high limit. Baroreceptors respond tostretch, so when heart is pumping more and more blood into blood vessels, the amount of stretch is increasing. Baroreceptor creates more action potentials in response to this stretch. Nerves create more pulses transmitted to the vasomotor center. The vasomotor center creates a response to dilate blood vessels. The surrounding smooth muscle must also relax. In order to relax this muscle, fewer action potentials / second must be sent to the blood vessels and smooth muscles to dilate and relax.ii. If blood pressure is going down rapidly, the baroreceptors are not being stretched. Action potentials/second are decreased. As a result, the vasomotor center realizes blood pressure is low because there are less action potentials that it is receiving. The smooth muscles and blood vessels must contract, so the vasomotor center increases the number of action potentials in order to contract and constrict. This concept is centered around the need for blood flow. Vasoconstriction creates a pressure that keeps the blood flowing.iii. Regulation of blood pressure relies on more than just the vasomotor center. There is the cardioacceleratory center and the cardioinhibitory center that targets the heart. These speed up and slow down the heart. Think of these centers as a gas pedal and break pedal that are both pressed at the same time. They are always both active. One just becomes more active than the other depending on bodily needs.1. During times of low blood pressure, vasomotor center acts the same as described above. Heart must speed up to maintain flow. Cardioacceleratory center sends more action potentials per second to the heart to increase the heart rate. The cardioinhibitory center must become less active, so it sends fewer action potentials to the heart, which also increases heart rate. All of these integrating centers work together. III. The Circulatory Systema. Sphygmomanometer is used in lab to measure blood pressure b. Cuff is pumped by bulb. As it fills with air, it pushes down so there is no blood flow through the brachial artery.c. Pump pressure is released as you listen for the sound of turbulent flow. Pressure from heart squeezes blood past cuff. When sounds are first audible, the cuff pressure is equal to the systolic pressure (pressure when the heart contracts).d. The “lub-dub” you heart when listening to a heart is the heart valves vibrating because of the blood hitting them.e. Pressure continues to be released on the cuff. When the brachial artery is fully open, there is no more turbulent flow and the sounds cannot be heard. The cuff pressure is equal to the diastolic


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PSU BIOL 240W - Homeostatic Regulation of Blood Pressure

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