Critical Thinking Activity - Chapter 13

Objectives:

• Use the resources on the world wide web to investigate functions of the human heart .
• Investigate a common but deadly circulatory system disorder.

Approach:

• I have selected two topics about which I have been curious to find out more. For each topic I will review briefly what was covered in the text, then I will pose a question that extends beyond the information presented in the text. I will offer you some URLs where you can investigate additional information on each topic. You can use CUT and PASTE to bring information, including graphics, back to this web page to include in your answers in addition to the writing that you do. You do not have to do the questions in order. As is common on the web, there is always more that you can find to investigate beyond the suggestions I am providing for you.

Dr. Paul Tabor

OK, here are the questions:

1. Everyone who has watched any medical show on TV or action movie has seen the use of a defibrillator to bring an actor back to life. The strong electric current is aimed at the heart, but what is defibrillation intended to do? The second contraction in a heart beat cycle is the contraction of the ventricles that push blood through the arteries. The contraction is due to coordinated nerve impulses to the muscles. But sometimes the muscles of the ventricle start uncoordinated contractions. A description of ventricular fibrillation is found on this page by choosing Pathophysiology: Cardiac Arrythmias and Conduction Defects and thenchoosing Ventricular Arrhythmias. The diagnosis of ventricular fibrillation can be made by looking at an EKG. The EKG that is in Figure 1 of this page under The Normal Electrocardiogram shows a spike in the EKG called the QRS complex signal. When this spike is not normal on the EKG, that is a diagnosis of ventricular fibrillation (VF). What do you think the QRS complex signal would look like for a VF patient? Here is the procedure that actual emergency professionals are using when treating ventricular fibrillation. What do you think defibrillation (Choose DEFIBRILLATION) will do to the contraction of the ventricle? VF is the most serious type of arrythmia partially because patients are previously unaware of the problem. Why would that be? Finally, except for in front of the camera, how common is VF and is there a less drastic defibrillation treatment?

2. Carbon monoxide poisoning occurs because hemoglobin in the blood binds carbon monoxide much more strongly than oxygen. Therefore, among other problems, oxygen can not be delivered to the tissues of the body. Carbon monoxide not only binds very quickly and tightly to hemoglobin (see the figure in the middle of the document) but is carried in the plasma as well which creates problems for treating carbon monoxide poisoning. How does carbon monoxide affect your body and what symptoms would you expect from lack of oxygen in tissues? If carbon monoxide is so hard to remove from hemoglobin is there an effective treatment (check under Hyperbaric Oxygen Therapy) for severe cases of carbon monoxide posioning? How much carbon monoxide is harmful to the body? You may suspect that humans at different stages of development and at different ages are not affected equally by the same levels of carbon monoxide. There is a tremendous amount of carbon monoxide produced by cars, etc. and carbon monoxide levels can build in home with poor ventilation. There should be some air quality standards for carbon monoxide. Are there recommendations for protection from carbon monoxide poisoning? Do you think there are areas in the US that have not attained the carbon monoxide guidelines of the EPA? Do you know if your area of the country meets the guidelines?