Homeostasis Human Dive Response Pre-Lab

Human Dive Response Pre-Lab Mammals demonstrate multiple strategies when diving into the water to survive. Though humans still possess some of these same homeostatic mechanisms, how marine mammals adapt to deep diving can be extreme. Scientists have measured different physiological responses to see just how extreme these can be. The dive response is characterized by three major physiological responses: apnea, bradycardia, and peripheral vasoconstriction. Define each one and explain what role each response plays in maintaining homeostasis as these animals dive. Your definition How maintains homeostasis Apnea This is considered breathing cessation, or when your breathing stops. This means there is no movement in your muscles for inhalation. This is used to reduce unnecessary consumption of oxygen from the limited capacity of your lungs. It makes sure that only your most essential organs and muscles are receiving oxygen. Bradycardia Bradycardia is when one has a particularly slower heart rate than the standard 60-100 bpm. Someone or something with bradycardia will have a heart rate fewer than 60 bpm. Reflex bradycardia is a response to the baroreceptor, which is a mechanism that the body uses to prevent hypertension. When hypertension is detected, reflex bradycardia will decrease blood pressure, as well as the cardiac output. (Amount of blood heart pumps per minute.) Peripheral vasoconstriction Peripheral vasoconstriction happens through the flow of blood through your body which boosts organs and allows for heat regulation. This will maintain organs keeping essential ones working at their best and keeps you from getÝng too cold. In order to investigate the factors that trigger the dive response, you need to design an experiment that measures heart rate and peripheral perfusion while a subject undergoes a simulated dive (dipping their head underwater). Which of the three physiological responses can you measure in class today? We could measure Bradycardia by checking the heart rate of a person as they are holding their breath. What kind of data can you collect on your group’s test subjects? We would need to collect data about our heart rate and the beats per second. This would allow us to determine how the Bradycardia effect is occurring for different people. How could you collect this data? We can collect this data through having test subjects dunk their head in cold water and record the effects of the dive response. Sea otter diving behavior Blue whales are the largest animals on Earth and can dive to great depths when foraging. Sea otters, as the smallest marine mammal, do not need to forage deep for the small mollusks, urchins, and crustaceans they consume. Observe the graph at the right and detail the trend you see: Sea otters that were under the water for shorter periods of time typically consumed less oxygen than the otters that were underwater for longer periods of time. Also, the graph appears to be in line with exponential growth, so the oxygen consumed over longer periods of time will rapidly increase. Identify conditions that a diving mammal like the sea otter might encounter that could initiate the dive response. Conditions that the sea otter would have to encounter to activate the dive response would be cold temperatures and being fully submerged underwater for periods of time. A number of parameters associated with underwater submersion will be varied in an attempt to identify the features of submersion that are important for the diving reflex. Here are some questions that should be answered to better understand the human dive response. Divide the questions among your group members to save time. ● Is just the presence of water a cue to trigger the dive response? This is only the case in the younger part of a mammal’s lifespan. As they age, their dive response reduces in reaction, so they must be submerged underwater for it to actually activate. ● Is the forehead critical in sensing the presence of cold water? Yes, the forehead and area around the nose are critical for the activation of the dive response. ● Do males and females respond differently to facial immersion? Both males and females have the dive response, but for females, their facial reactions are more in tune and sensitive compared to males. ● Can someone train to increase a dive response? Yes because when a person continues to deep dive they are training and improving the efÏciency of their dive response. This training allows their blood to transfer more efÏciently and improves their bradycardia, as well as the flexibility of their diaphragm and lungs. ● Does the size of the breath affect the dive response? No, the size of the breath does not affect the dive response. ● Are there any psychological factors that could affect the dive response? Yes, emotional factors can play a role in the effect of the dive response. Also, it is seen that anxiety levels drop during the activation of the dive response. Ask a testable question based on your baseline data. Provide a valid hypothesis to explain your observations and provide a prediction of the relationship between the variables. Question: Does the temperature of the water that a person is submerged in, have an effect on the dive response? Hypothesis: The temperature of the water does have an effect on the dive reflex in humans. Prediction: If a person is submerged in warmer water, then their dive response will be lessened/reduced because they will feel a sense of comfort (due to the warmth), and their mind will trick their body into thinking it is in a complacent state. Experimental Rationale & Design: Design an experiment to address your scientific question. Identify all variables (independent, dependent, controlled), and provide a detailed explanation that minimizes the chance of error and provides multiple trials. Independent: Temperature of the water Dependent: Dive response Controlled: The amount of water, the breath size, the submerged level of the face Control Group: Room temperature water Procedure: 1. Fill 3-5 tubs of water with 2 gallons of water with varying temperatures from the sink 2. The first bucket should be filled with water that is freezing cold (near 30 degrees Fahrenheit) 3. The second bucket should be filled with water that is cold (near 45 degrees Fahrenheit) 4. The third bucket should be filled with water that is at room temperature 5. The fourth bucket should be filled with water that is lukewarm (near 65-70 degrees Fahrenheit) 6. The fifth bucket should be filled with water that is warm-hot (near 80-90 degrees Fahrenheit) 7. We will have each of our group members dip their heads in each of the five buckets 8. We will measure the length they could stay submerged for each bucket using a stopwatch (in seconds) we can record the heartbeat through the number of beats per second. 9. We will repeat step 8 for all buckets and all group members