Homeostasis in Animals
AUSTRALIAN CURRICULUM ALIGNMENT:
- Conduct investigations, including using models of homeostasis and disease transmission, safely, competently and methodically for valid and reliable collection of data (ACSBL098)
- Represent data in meaningful and useful ways, including the use of mean, median, range and probability; organise and analyse data to identify trends, patterns and relationships; discuss the ways in which measurement error, instrumental accuracy, the nature of the procedure and sample size may influence uncertainty and limitations in data; and select, synthesise and use evidence to make and justify conclusions (ACSBL099)
An animal’s survival depends on its ability to maintain an internal environment that will enable individual cells to function properly. The maintenance of internal “normal” or steady state conditions is called homeostasis. In most animals, an internal transport system plays a major role in homeostasis. The circulatory system of animals delivers nutrients, oxygen, and hormones to the interstitial fluid (fluid between cells) and removes waste. The circulatory system provides cells the raw materials to perform their functions while ridding themselves of by-products that would be toxic in high concentrations. Like other body systems, the circulatory system is influenced by negative and positive feedback. In negative feedback, homeostasis is achieved as the nervous system responds to a stimulus by signalling the circulatory system to minimize or reverse the effects of the stimulus. Muscle tissue uses oxygen from the blood to produce energy required for muscle contraction. When we exercise vigorously, our muscles use more oxygen than normal. Heart rate must speed up to accommodate the increased need for oxygen. However, as the body recovers from periods of strenuous exercise, mechanisms within the body work to return the heart rate back to its resting set point, or normal range of physiological values. The body uses self-correcting actions (known as negative feedback mechanisms) to stabilize a body system, returning internal conditions to a steady state after a disturbance is detected, illustrating homeostasis
This practical is aimed at introducing the concept of homeostasis to students and allowing them to experience it first hand, as they feel their body begin to recover from strenuous exercise. In this practical, students will be required to act as the test subject and gather data on their peers. It is best to work in pairs or groups no greater than 4. To help reinforce their understanding of homeostasis, students will be tasked with graphing the data, interpreting it and relating it to negative feedback mechanisms. Through this practical, students should be able to explain how feedback mechanisms maintain homeostasis in animals, and the role of negative feedback mechanisms.
PREPARATION - BY LAB TECHNICIAN
- Demonstrate the correct procedure to finding a pulse on the neck and wrist.
- Demonstrate how to keep track and time a pulse.
- Instruct students on how to find the average pulse speed.
METHOD - STUDENT ACTIVITY
- Determine the resting heart rate of you and your group partner/s by taking each pulse 3 times for 15 seconds.
- Determine the average by adding the 3 resting pulse rates and dividing by 3.
- Run vigorously in place for 2 minutes (use a timer to ensure accuracy).
- Measure pulse rate for 15 seconds immediately after running.
- Measure the pulse again for 15 seconds then switch to intervals of one minute for a total of 5 minutes.
- Record each group member’s heart rate after exercise and compare the results.
- Draw a graph of every group member’s average resting heart rate and post- exercise heart rates (on the same axes). Plot these data sets on the same axes, and include units. Use a different colour pen to draw the line for each test subject and include a key. Mark the set point, where exercise is taking place, and where corrective mechanisms are activated.
OBSERVATION AND RESULTSBelow is an example of expected results for group heart rates at rest. However, this is to be used as a guide only, as individual results will vary. The normal range is generally considered between 60-100 beats per minute.
- Ask students to explain each segment on the graph using the concepts of homeostasis and negative feedback mechanisms.
- Ask students to consider whether the graph would change if you collected data for a positive feedback mechanism.
- Task students with converting their heart rates to beats/minute and comparing them to the normal range of 60 to 100 beats/minute.
- 30 mins
- Ensure students wear appropriate personal footwear when running to avoid injury.
- Be mindful of any physical restrictions or considerations when asking students to engage in physical activities.