Download Human Physiology: Advanced: Please only advanced Doctoral

Human Physiology: Advanced: Please only advanced Doctoral Level
TA//Cardiovascular//Respiratory//Metabolism,Growth,Energy Bal.//Metabolism
Posting
In the following questions, determine whether they are True of False, and explain your reasoning. (Text
may be helpful: Vander, Sherman & Luciano's, "Human Physiology The Mechanisms of Body
Function")
Please note that the following T/F are extremely misleading.
T/F The reason high humidity plays such a significant role in increasing the discomfort felt on very hot
days is that it decreases the cooling properties of conduction.
T/F When total-body energy balance is positive in an adult, energy is being stored as fat.
T/F In the normal lung, capillary osmotic pressure always exceeds filtration pressure and so absorption
of fluid is the rule.
T/F A failing heart does not respond to increased end-diastolic volume by increasing stroke volume.
T/F The medullary cardiovascular center is the only part of the brain involved with the regulation of
blood pressure.
Hello,
As you know from before, I cannot just answer the questions for you. But I will provide enough
information about each query so that you can accurately answer the T/F question yourself. Good
luck.
T/F The reason high humidity plays such a significant role in increasing the discomfort felt on very hot days is that it decreases
the cooling properties of conduction.
This involves a wee bit of physics. The body endeavors to maintain homeostasis through every available means. When the air
temperature is cold, the peripheral capillary and vessels constrict keeping the warmed blood in the body core. This is to prevent
loss of warmth. It the blood vessels allowed peripheral perfusion, the heat would escape by radiation and the body would have to
work harder to maintain warmth. This is why functional people in the cold have a pallid or pale look to them. The opposite is
true for warm air temperatures. Now, the job is to get rid of ‘warm’ as the body will heat up to its detriment if it doesn’t.
Remember, all chemical reactions in the body are dependent on pH and temperature to function. If homeostasis is not
maintained, the body will eventually stop functioning. So, in warm air, the body dilates peripheral vessels in an effort to lose
heat through radiation. When this does not work, it starts to sweat. By evaporative cooling, it decreases the skin temperature.
This diaphoresis is dependent on the sweat’s ability to evaporate. The lower the relative humidity of the air, the faster the
evaporation. The higher the relative humidity, the lower the evaporation.
T/F When total-body energy balance is positive in an adult, energy is being stored as fat
Body energy can be many things. I am going to assume, that we are referring to the production of ATP, the functional energy
packets made in the mitochondria on the cellular level that allow chemical reactions and cellular functions to occur. Cells make
up tissues, tissues organs, and organs, systems. For any of it to work, you need energy. ATP is made in the citric acid cycle and
any source of ‘fuel’ can make it run, whether it is carbohydrate, fat, nucleic acids or protein. If all were in balance, this would be
neutral. If there is a need for fuel, this is negative balance. If there is more fuel than necessary, it is positive. Dependent upon
the fuel, many things can happen. Once the body senses it has enough ATP, it does not utilize the available fuel. We cannot
store protein, so much of that is eliminated. An increase in carbohydrates however, can cause a release of insulin. If the cells do
not need the sugar, then it is most often stored as fat (lipids).
T/F In the normal lung, capillary osmotic pressure always exceeds filtration pressure and so absorption of fluid is the rule.
This question is a bit obtuse. Filtration is the process of removing particles from a solution by allowing the liquid portion to pass
through a membrane that have holes too small for the particles to pass. Osmosis is the passage of a solution of a membrane from
a region of lower concentration of solute to one of a higher concentration. The membrane does not allow the solute to pass.
They are not the same and I would be very wary of the use of “always” in any question. There are few absolutes, even in a
normal person. In the normal lung, the exchange at the alveolar level is taking place between dissolved gases in a thin watery
medium. It would not occur if the water were constantly being absorbed into the bloodstream. In addition, there is a tremendous
amount of water loss through exhalation.
T/F A failing heart does not respond to increased end-diastolic volume by increasing stroke volume.
Cardiac output is stroke volume X heart rate. Stroke volume is the amount of blood pushed through the heart by volume over
time. A failing heart is subjective. In a failing heart, with ventricular failure, both the inotropic (strength of contraction) and
chronotropic (speed of contractions) aspects can be affected. In a beating heart, the overall systolic pressure is the pressure of
blood as it is sent through the system (inotropy). The diastolic pressure is the resting pressure of the heart. It maintains a tone
even when not contracting. End-diastolic volume (EDV) is the amount of blood in the ventricles after it has been pushed there
through the atria (atrial systole). (EDV contributes to about 130cc of blood in each ventricle. Only about 40cc of this blood is
from the atria). The rest is left over from ventricular ejection and is the end-systolic volume. So, if a failing heart cannot push as
hard, it will have more blood left behind in its chambers, resulting in an increase in EDV. If it could get rid of the volume, this
would be through an increase in stroke volume, but if it could increase the stoke volume, there would not be an increase in EDV
in the first place. Based on Starling’s Law, the ventricles tend to eject as much blood as they receive. But that is in a normal
heart. If it cannot increase the cardiac output by increasing stroke volume, then it must increase the hear rate. Even this might be
impossible in a failing heart. We often give medication called dopamine to increase the force and speed of contraction in heart
failure, but it doesn’t always work.
T/F The medullary cardiovascular center is the only part of the brain involved with the regulation of blood pressure.
Just like the always from above, be wary of the use of the word only in questions. Blood pressure is regulated not only in the
brain stem, but also in the kidneys and lungs through the rennin, angiotension, tensinogen system, but through the carotid sinuses
in the body.
NEMM, Ph.D.