Homeostasis (Michael Flores)
Title: Homeostasis (Keeping Body systems' balanced)
Principle(s) Investigated: Organ system regulation, equilibrium, and negative feed regulation
11-12th grade Physiology
9th AP/Honors Biology
Physiology: As a result of the coordinated structures and functions of organ systems, the internal environment of the human body remains relatively stable despite changes in the outside environment.
- 9B Students know how the nervous system mediates communication between different parts of the body and the body's interactions with the environment
- 9C Students know how feedback loops in the nervous and endocrine system regulate conditions in the body
Materials: Open space, stopwatches, thermometers, and willing attitudes
Procedure:
- Break up into groups of no more than 4 (if possible)
- Assign student roles:
- Athlete
- Materials/observer
- Data gatherer
- Time keeper
- (If 5th member = runner)
- Materials will collect supplies (stopwatch, thermometers)
- Data gatherer and time keeper will record resting heart/breathing rate and initial temperature of athlete (while standing) and record data
- Data gather will measure heart rate, take index and middle finger place them on thumb side of the wrist (athletes' palms facing upwards ). Count "beats" for 30 secs and multiply by 2.
- Time keeper will measure breathing rate, count amount of times chest rises and falls (one chest rise and fall counts as one count) for 30 secs and multiply by 2
- Observer will note athlete's skin color (pale, pink, red), and moisture of skin(dry, mild, sweaty) and take athlete's temperature
- Record your groups' initial data on worksheet provided
- Athlete will now engage in cardio exercise(jumping jacks, running in place, stairs if available) for period 2 mins
- During which time, materials/observer will record any physical changes and time keeper will track time. Data gather will record data on class data sheet.
- After 2 mins, athlete will stop and data/time keeper will repeat measurements and record data
- Round 2 of exercise ensues for 2 more mins
- When time expires, complete final data recording of heart, breathing, temperature and skin conditions
- Record own data and transfer data to class set
- Proceed to explain how organ systems send signals to brain which in turn sends out hormones to glands which keeps our internal environment balanced (homeostasis). Our bodies need to maintain a temperature of around 37 degrees Celsius to function normally
Student prior knowledge: Exercise causes a change in internal environment: skin color, sweat, rapid heart rate and deeper breath. Need to know organ systems, basic math, how to read thermometer and use of stopwatch.
Explanation: In order for the human body to work properly, it needs to keep its temperature, water, and blood pH all balanced. Keeping everything balanced is called Homeostasis. Information is given to the brain about internal changes and the brain responds by releasing hormones to specific glands. Also our body's temperature needs to be around 37 degrees Celsius. If temperature rises, blood vessels dilate (heat loss by radiation), sweat is produced(heat evaporation), and hair tends to lie flat(less insulation). If temperature is too low, blood vessels constrict(less heat loss due to radiation), hair stands up (traps more air=more insulation), sweat glands close up, and you start to shiver. (Shivering causes muscles to generate heat). Furthermore water balance is extremely important due physical nature that all cells thrive in, kidneys play role of conservation of water by reacting to levels of ADH (antidiuretic hormone) secreted by pituitary gland. Too much water results in diluted urine, and not enough water, results in very concentrated urine. Lastly, sugar levels also affect homeostasis. Regulating sugar levels is done by two hormones: insulin and glucagon. The pancreas releases insulin to lower blood sugar or glucagon to rise it. The liver responds to these two hormones and will act accordingly. During exercise, glucose levels drop which signals pancreas to release glucagon from the liver to keep sugar levels high enough for duration of activity. As sugar is the basic fuel for cells, regulation of it keeps us going.
This lab stimulates what occurs as we experience stress in our lives, the brain receives signals from various sensory nerves which the brain sends out hormones to specific organs.
Questions & Answers: Compare and contrast the body's mechanisms for dealing with hot temperatures and cold temperatures?
When dealing with increasing temperatures, the body will respond with dilating blood vessels, body will start to sweat, and hair will flattens out. When body temperature falls, the body will respond with constricting blood vessels, sweat glands close, and muscles start to shiver.
Summarize the events of a negative feed back loop.
A negative feed back loop operates with an initial change in homeostasis. Sensory organs pick up deviations of temperature which get sent to the brain. The brain in turn sends out hormones to various organs to fix "problem". For example, brain senses body temperature is falling, it sends out signal to hypothalamus. Hypothalamus sends out hormone to Thyroid gland. Thyroid gland sends hormone to cells to speed up metabolism, which can cause body to heat up. If body temperature is still too low, then signal is picked up again by brain and process starts all over again. But if the temperature stabilizes, the brain realizes this and stops sending signals to hypothalamus.
Why does your heart rate and breathing rate change due to exercise?
Your heart rate increases because your demand for materials has increased. Your cells require more energy to burn in order to make sufficient ATP. Your heart starts to increase to "ship out" materials quicker to your muscle cells. Breathing rate also increases due to demand of oxygen as the cells produce ATP through oxidative phosphorylation. We breath heavier to bring in the maximum amount of oxygen per breath.
Applications to Everyday Life: A Thermostat
A thermostat is a device that controls the temperature of a room by measuring the raising or falling of temperature and acts accordingly. For example if a room gets too hot, air conditioner turns on. If room gets too cold, heater is switched on. In both instances information is relayed back to thermostat: Negative feed back.
Certain amplifiers operate with a negative feed back loop. It can stabilize the voltage when frequency, temperature, and other variables disturbs sound. Certain circuits activate specific loops, when sensors detect deviation, to fix any distortions to maximize bandwidth and sound production. It also decreases output impedance and distortion by discriminating certain wavelengths when its senses disturbances and regulates certain "on" and "off" switches to fix distortions.
Centrifugal governor (steam engine) work on the basic principle of negative back. An upright frame rotates two heavy spheres and as their speed increases it creates lift due to centrifugal force. This lifting causes a closure of steam inlets, then as spheres slow down gravity cause them to fall then inlets to open up and continues in a cycle.
Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.
Documents:
Videos: Include links to videos posted on the web that relate to your activity. These can be videos you have made or ones others have made.
Remember doing this for Physiology course back in Community College
Last years demonstration: Mr. Sam Wright