Cardiovascular Laboratory Biol 106 In this exercise, you will: 1) measure an electrical cardiogram of your own heart. 2) Investigate the human dive response 3) Dissect a mammalian heart 4) observe the heart of Daphnia in vivo
Part 2 Human diving response Many vertebrates exhibit a suite of physiological responses termed the diving reflex. It is most pronounced in marine and aquatic mammals such as cetaceans (whales and dolphins), sirenians (manatees), some carnivores (seals, walrus and otters) and rodents (beaver). Part of the response is increased blood pressure due to peripheral vasoconstriction mediated by the sympathetic nervous system. The diving reflex in mammals is partly controlled by receptors of the trigeminal nerve (cranial nerve V) in the face, nose and mouth, which respond to the temperature of the water. In diving mammals and humans as well, the stimulation of the trigeminal cold receptors in the nasal and pharyngeal passages results in powerful reflex apnea (cessation of breathing). In fact, approximately 30% of human drowning victims do not have water in their lungs because this powerful laryngeal reflex prevents breathing. In this lab we will use the EKG apparatus to monitor the effect of simulated diving by immersion of the face in water. Data from the class will be used to assess whether the simulated diving increases or decreases heart rate. The effect on heart rate will be determined in each student of one of the following: apnea, and apnea + simulated diving. Apnea monitor heart rate using the EKG monitor under normal resting conditions. Calculate heart rate as beats per minute. Hold breath (apnea) and monitor heart rate. Determine whether there is a change in beat frequency. If there is a change, how soon before the onset of the change. Repeat. Apnea + simulated diving monitor heart rate under resting conditions as described above. Immerse face in basin of cold water or ice water. Do not breathe during immersion. Determine whether there is a change in beat frequency. If there is a change, how soon before the onset of the change. Repeat. Tabulate data for the class as follows: Apnea Name resting heart rate apnea heart rate % change Average % change = Apnea+simulated diving Apnea Name resting heart rate apnea heart rate % change
Average % change Questions: What do you conclude about the affect of apnea and apnea+simulated diving on heart rate? When combined with increased blood pressure and constriction of peripheral blood vessels, what is the likely effect of the heart rate change on oxygen supply and oxygen consumption by peripheral parts of the body? oxygen consumption by the heart? Heat loss? What is the positive benefit of the dive reflex? Part 3 Mammalian heart dissection We will be dissecting the heart from a sheep or pig. See dissection guide provided in lab. Part 4 - Heart Rate in Daphnia Daphnia major, sometimes called the water flea, is a crustacean in the phylum Arthropoda. Like other arthropods, daphnia has an open circulatory system, that is, the blood is not confined to a heart, arteries, and veins. Instead, the heart pumps blood throughout an enclosed cavity called a haemocoel. This type of body cavity is well developed in arthropods and molluscs, where the coelom is small. An open circulatory system is not as efficient as a closed one, but for many ectotherms ( cold-blooded animals), it is perfectly adequate. Procedure work in pairs 1. Carefully pick up a single daphnia with a large-bore plastic pipet and place it in a depression slide. Note that daphnia are pretty sneaky and may be hard to catch! Observe the daphnia under a dissecting microscope. As you observe the daphnia, be sure to not let the specimen dry up! Add water as necessary. Because the exoskeleton, or carapace, of daphnia is clear, we can see its functioning heart and other intricate organs. Refer to the diagram above to help identify structures. The blood in daphnia is clear. The heart is also a small clear structure that is actively pumping. You may see reddish tissue running the length of the animal. What do you think this is? In addition to the heart, the thoracic appendages will be actively moving. They are used to generate feeding currents and for swimming. 2. Have one person count the heart beats in your specimen while another keeps track of the time. Count for 15 seconds. Do this several times to make sure that you have an accurate estimate of the heart rate. We provide space only for 4 measurements but you can put more than one measurement in a box. 3. When you are finished with the counts, carefully return the daphnia to the container in lab - you may need to gently wash the daphnia off of the slide using a transfer pipet. 4. Record the beats per minute for each count so that you can calculate the average and standard deviation. Measurements count / 15 sec count / minute 1 2
3 4 Average Standard deviation Do you think this is the normal resting heart rate of daphnia? Why or why not? How doe the daphnia acquire oxygen and expel CO 2?