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UMass Amherst KIN 470 - 1.23.14 kin 470 class notes

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1.23.14 kin 470 class noteschapter 2- Exercise physiology in the newso How inactivity changes the brain Why is it bad for you? Article summarizes an interesting study… Tested in rats less active, “physical changes to neurons in brain, changes in the heart” Things die when you become inactive Mechanisms of why exercise is good for you- Topic for today: homeostasiso Control of internal environmento How do we maintain bp, temp, blood glucose…o Guiding factors: How do we try to maintain homeostasis when facing excess demands of exercise Try to maintain constant cell, constant blood glucose Body isn’t good at maintaining homeostasis for many variables,good at steady stateo Question: Is homeostasis maintained during exercise?- How to understand graphso Picture from book; generico Y axis; dependent variable Ex. heart rate Look at it as a function of exercise intensityo X axis; independent Ex. exercise intensityo Linear relationship between the twoo Exams; may need to reproduce grapho Get familiar with it!- Homeostasis; dynamic constancyo Maintenance of a constant internal environment despite a changing external environmento Internal temp; 98.6, outside; -1o Internal temp doesn’t change (if you’re healthy)o Steady state Balance between demands placed on the body and the physiological response to those demands- Exampleo Analogy of the leaky bucketo Bucket has leak into as water is being poured ino Matching how much you put in to how much is leakingo Input=output Water level is constanto 1st bucket is homeostasiso 2nd bucket input < output too many holes, water leaving too quicklyo 3rd bucket; steady state water level drops quickly add water faster input=output run into this with exercise- Homeostasis; ocillation around a set pointo body isn’t perfect (too energy costly)o really sensitive pressure sensor on average, arterial bp is 93 mm Hg however there is a fluctuationo How responsive are our bodies to change in pressure?- Steady-state; rest vs. exerciseo Graph; temp vs exercise timeo Bodies ability to cool itself during exercise is overwhelmed to some extento What happens is that over 20-40 mins, temp increaseso At some point you can maintain higher tempo Even in cool environment, you can’t maintain tempo Hot environment; temp can keep going up (hypothermia)- How is homeostasis maintained?o Biological control systems Not one singular organ It is a system of organs May cross systems Series of interconnected components that work to maintain a physical or chemical parameter at a near constant valueo Examples Blood pressure Energy levels in cells- Atp Blood ph- 7.4 (slightly basic) amount of co2 in blood all affected by exercise- non-biological control system: thermostato 1. room temp falls below 20 degreeso 2. Thermostat, set at 20 degrees cm detects changeo 3. Heating system turns ono 4. Temp changes, thermostat stops sending message to heat system- biological control systemso components stimulus receptor/sensor – detect changes in internal environment integrating/control center- assesses input and triggers response effector- corrects disturbance to internal environment- breakdown of componentso shows direction it influences things (positive or negative)o 1. Stimulus excited receptoro 2. Positive effective on integrating centero 3. Turns on effectoro 4. Effector negative impact on stimulus (brings temp back up) because of this it is called a negative feedback loop- example; regulation of blood pressureo heart rate & strength of contraction increaseso pressure in vessels increaseo sensed at dif locations within cardiovascular system (carotid artery perhaps – baroreceptors)o relay info to braino brain becomes integrator receives signal signals heart to pump less slowly, with less force decreases blood pressureo occurs going from seated to standingo lying down to standingo high systolic bp when exercising- negative feedback loopo reason it is negative is because response reverses initial cause (stimulus)o find that almost every feedback example is negative (handful of positive feedback loops) positive; blood clotting (some positive and negative) example; going into labor, contractions- gain of a control systemo how sensitive is this system?o What defines how far that goes above homeostatic value?o How quickly does it return?o Gain; how much volume gained by passing a sound signal through an amplifiero Gain; ratio of output to input Influences degree to which we can control the system can control homeostasis System with large gain is more capable of maintaining homeostasis (blood flow to muscle)- Continuous adjustmentso Heater kicks on, comes on for a few minutes, then turns offo Not the case wit biological systemso Blood pressure is constantly making changeso At rest; this control system keeps arterial pressure fine tuned- Example; regulation of blood glucoseo Blood glucose spikes after meal, stimuluso Pancreas serves as receptor, integrator, and effectoro Releases insulin (decides how much, beta cells of pancreas release it)o Insulin allows glucose to leave blood and enter cellso Negative feedback loopo Reverses spike in blood glucose- Exercise; a challenge to homeostatic controlo Exercising muscle Increase energy usage Increase oxygen requirements Increase co2 and lactic acid production Increase in heat productiono Respiration increaseso Submaximal exercise Coordinated action of a lot of systems; nervous system in brain Cardiovascular system and respiratory systems enable maintenance of steady state- Failure of biological control systemso During intense exercise in hot/humid weather, severe disturbances can occur Hypothermia No longer able to cool themselves Core temp rises Nausea, vomiting, fatigue, weakness, rapid pulse, confusion, seizure, coma Affect vital organso Diabetes Blood glucose control breakdown Type I vs. type II Type 1- Beta cells no longer release insulin Type II- Focus of exercise physiology- In this case; beta cells are very healthy and able to release insulin- But cells are insensitive to insulin- Referred to as insulin insensitivity- Exercise physiologists; exercise is similar to insulin Healthy people- Won’t see the spike after meals…- Maintain constant level Diabetes; Can’t control blood glucose


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UMass Amherst KIN 470 - 1.23.14 kin 470 class notes

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