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BIOC34H3- Final Exam Guide - Comprehensive Notes for the exam ( 31 pages long!)


Department
Biological Sciences
Course Code
BIOC34H3
Professor
Stephen Reid
Study Guide
Final

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UTSC
BIOC34H3
Final EXAM
STUDY GUIDE

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Human Physiology Assignment #1
Wardah Irfan
999782025
BIOC34H3
Activity 1: Investigating the Refractory Period of Cardiac Muscle
Results
When the electrical stimulus was applied to the heart, a doublet peak containing an
extrasystole (an extra contraction of the ventricle) was observed on the oscilloscope. The peak
was followed by a compensatory pause that allowed the heart to return to normal beating.
Question 1
In order for the heart to function properly, the heart chambers need to expand as they are fill
up with blood during diastole, and they must contract during systole while they expel the
blood. The longer refractory period of the cardiac muscle cells ensures that the heart can
completely relax before it contracts again, allowing the chambers to fill to their maximum
capacity before pumping. If the refractory period was shorter, the heart would contract too
soon, and the chambers ould’t get a hae to rela opletel ad e filled to their
maximum capacity, therefore only pumping out a fraction of that amount. A longer refractory
period prevents tetanus from occurring.
Activity 2: Examining the Effect of Vagus Nerve Stimulation
Results
When the vagus nerve was electrically stimulated, the heart slowed to a stop before restarting
again. This was seen on the oscilloscope as a straight line.
Question
2a. Vagal escape is when the heart resumes to beat again (due to sympathetic activity) after
stimulation of the vagus nerve causes it to stop.
2b. In the case where SA node activity is inhibited due to vagal stimulation, vagal escape can
result from development of pacemaker activity in the Purkinjee-His system.
2. Spatheti erous sste atiit does’t eist i a isolated heart; therefore, the heart
will solely rely on the Purkinjee-His system to active vagal escape. In contrast, in a living
organism, both the sympathetic nervous system and the Purkinjee-His system can act to trigger
vagal escape.
Activity 3: Examining the Effect of Temperature on Heart Rate
Question
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3a. Heart rate would increase if temperature drops below the thermonuclear zone. This is
because the body will want to maintain homeostasis and keep up with the demands of the
metabolic rate.
3b. If an isolated heart was to be used in cold Ringer solution, heart rate would decrease due
to the lack of homeostasis regulation.
Activity 4: Examining the Effects of Chemical Modifiers on Heart Rate
Results
Question 4a. If an isolated heart was bathed in nicotine, the heart rate of decrease.
4b. Injecting nicotine in a live human heart would increase heart rate. This is because nicotine
stimulates the sympathetic nervous system, by stimulating nicotine-acetylcholine receptors and
causing them to release catecholamine. Nicotine also stimulates the release of adrenaline from
adrenal medulla, which also contributes to increase in heart rate.
Activity 5: Examining the Effects of Various Ions on Heart Rate
Results
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