Expert: John Locke - 6/25/2008

Question
Hi, my name is Mara and I am a tutor for a home-schooled 11 grader and came a cross a few questions I need help with. If you could help me it would be appreciated. Thank you.


1)A person with typo O blood can receive a transfusion from  wich other type with no clumping?

2) Describe the endocrine system's negative feedback mechanism.

3) What is the path of blood through the heart from entering through a vena cava to leaving through the aotra?

4)Is it true that when the amount of carbon dioxide in your blood increases, your brain slows your breathing rate?

5)Is Rh factor an inherited characteristic?  

Answer
Thank you for using AllExperts, Mara. I've responded to your questions below and have included some relevant links with them:

1. Blood types are determined by the presence of surface markers, or surface antigens, on red blood cells; these antigens will react with incompatible antibodies and clump if blood types are mixed incorrectly. There are two surface antigens, A and B, meaning that there are four possible combinations: A, B, AB, and no surface markers; these correspond to blood types A, B, AB, and O, respectively. People with type O blood will respond to antibodies against both type A and type B blood, meaning that people with type O blood can only receive type O blood.

http://anthro.palomar.edu/blood/ABO_system.htm

2. The negative feedback mechanism of the endocrine system uses the product of a series of reactions to inhibit some earlier step in that series. For example, if there's a reaction in which compound A forms compound D through this mechanism:

A-->B-->C-->D

Then negative feeback could be accomplished by having compound D inhibit the reaction of A-->B. Thus, as more compound D builds up, the overall reaction will slow down and the process will be inhibited. There are a variety of biological examples of this mechanism; one of the most direct is that of thyroid hormone regulation:

The hypothalamus gland in the brain secretes a hormone called TSH, which tells the thryoid gland to produce its own set of hormones called T3 and T4. These hormones affect all sorts of processes in the body, one of which is acting in a negative feedback mechanism on the hypothalamus. T3 and T4 decrease the secretion of TSH, so that the overall process is controlled.

http://www.easternct.edu/personal/faculty/saull/sect9/resous9/cartos9/homeos9.ht...
http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/basics/control.html

3. From the vena cava, blood enters the right atrium and flows to the right ventricle. Blood leaves the heart by the pulmonary artery to the lungs. From the lungs, blood returns to the heart by the pulmonary vein. From there it enters the left atrium, to the left ventricle, then leaves the heart into the aorta.

Vena Cava-->Right atrium-->Right ventricle-->Pulmonary artery-->Lungs-->Pulmonary vein-->Left atrium-->Left ventricle-->Aorta-->Body

4. No; in fact, just the opposite it true. Carbon dioxide builds up in the blood when there is not sufficient ventilation to remove it through the lungs. In the blood, carbon dioxide is converted by a chemical process as shown below:

CO2 + H2O --> H2CO3 --> H+ + HCO3-

The brain contains chemical receptors that measure the concentration of H+, or hydrogen ions; a higher concentration of H+ indicates that there is more carbon dioxide in the blood. The brain responds by increasing the force and frequency of respiration until the H+ levels decrease. Thus, a higher CO2 blood level leads to higher breathing rate.

http://www.mtsu.edu/~jshardo/bly2020/respiratory/regulation.html
(The relevant section is found near the bottom of the page, under "Ventilation activities are modified by:").

5. Yes, Rh factor is genetically controlled. Back in question 1, I described the surface antigens on red blood cells and how they control blood type. There are other surface antigens that exist on the cells of red blood cells, including the Rh factor; it is a dominant trait, meaning that it need be inherited from only one parent in order to display the antigen on one's red blood cells (this is referred to as being Rh-positive). If neither parent passes on the Rh trait, the individual does not display the Rh antigen and is referred to as Rh-negative.

http://anthro.palomar.edu/blood/Rh_system.htm

Good luck!