Tutor profile: Jenna A.
Describe the steps the body undergoes to regulate your glucose level when it drops below normal and what type of feedback loop this is.
1. Glucagon is released by the pancreas (removing sugar from your tissues) 2. Glycogen is broken down into glucose in the liver 3. Glucose levels increase, causing the stimulus for glucagon production to decrease. This is a negative feedback loop.
Subject: Biomechanical Engineering
Describe Wolff's Law and why the porosity of a bone substitute is important.
Wolff's law describes the effect a load has on a person's bone. If the bone is undergoing a large amount of stress, it will remodel to handle that load, but if it does not experience much stress, the bone will weaken. This is due to the varying stimulus levels of the osteoblasts. More load leads to more stimulation and thus more bone whereas less load leads to less stimulation and thus less bone. Porosity of a bone substitute needs to be taken into account for this exact reason. Too much porosity (a fairly holey substitute) can lead to decreased mechanical strength and cause the bone to be brittle. However, low porosity (a pretty solid substitute) would make the bone too stiff, preventing the natural bone from experiencing the required stimuli.
Subject: Biological Engineering
List the types of blood substitutes available and why they are needed.
Common blood substitutes include Perfluorocarbon emulsions (PFCEs) and Hemoglobin-based oxygen carriers (HBOCs). PFCEs are emulsified fluorinated polymers that reversibly bind with O2. They can carry 2-3x more oxygen than normal blood, are much smaller than Hemoglobin which allows them to perfuse more easily, and rely solely on synthetic polymers. HBOCs, however, are derived from biological components such as red blood cells from cows or expired human blood or genetically modified bacteria that can produce hemoglobin. They float through the plasma and act much like normal Hb, picking up O2 and depositing it in the lungs. Both substitutes are useful in that they are not specific to any one blood type so anyone can receive a blood substitute. Blood substitutes are needed for the battlefield where normal blood is either in low supply, can't be delivered quickly, or where refrigeration is difficult. They are also used to alleviate risks associated with certain blood transfusions and can be used in people who might have objections to blood transfusions due to religious reasons.
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