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Anatomy and Physiology II

J John Cohen, MDCM, PhD


 
Should someone with heart failure live at low altitude rather than high altitude?

It wouldn’t be necessary in most cases, and the disruption of moving might be an undue stress. But people with heart failure may become uncomfortable at high altitude, so “flat-landers” need to consult their physicians before going, say, over the Trail Ridge road. Note, from the heart’s perspective, Denver’s altitude is not considered high.

Is there a reliable non-invasive test to measure occlusions in the arteries? What is the best way to test for occlusions?

The cardiac catheterization test (invasive) is the gold standard, but it’s not the first thing to do. An electrocardiogram (EKG) is helpful, as oxygen-poor muscle conducts electrical signals abnormally. Then there is a stress (treadmill) test, which puts a bit more stress on the heart to reveal coronary artery narrowing by EKG. There are also various CT (x-ray) and MRI techniques, and echocardiography; all these are non-invasive.

Can emotion/stress cause the brain to have a slower supply of blood therefore unconsciousness?

Absolutely; it’s called a vasovagal response. The vagus nerve goes to blood vessels generally and also to the heart, and its output can be strongly influenced by emotions. People who receive a shock of some sort can get a sudden outpouring of signals down the vagus nerve, resulting in the heart slowing and blood vessels dilating, a big drop in blood pressure, and fainting due to reduced oxygen to the brain. Usually people wake soon after they get horizontal. They can show slight seizure-like twitchings while waking; those are almost always normal.

What is the time limit to heart myocardial and or brain tissue damage?

In 4 minutes of oxygen deprivation a person will become unconscious. For someone with a heart attack, treatment with clot-dissolving enzymes is best if begun within 30 minutes, but can be tried up to 12 hours after the event begins. It’s similar for stroke, though the enzymes can only be used in certain kinds of stroke. If someone thinks a heart attack is beginning, the patient should, if possible, take 2 aspirins while waiting for 911; aspirins reduce clotting.

Could someone live with only one lung?

Yes, in the old days many people had to have a lung removed because of scarring by TB. It’s less common now, but it’s certainly doable if necessary, though exercise tolerance is usually decreased.

Are there any specific enzymes that remove plaque formations?

Unfortunately not. If the narrowed artery is suddenly plugged by a clot, though, there are several enzyme preparations that can be injected to dissolve the clot.

Are there ways to keep cartilage healthy?

Basically, be kind to your cartilage. Non-weight-bearing exercises (rowing, cycling) are much better for cartilage than impactful ones (basketball, running). There does not seem to be much value in nutritional supplements.

Which animal has the biggest brain?

It seems to be the sperm whale, at 17 pounds! (We are at about 3 pounds.) In general, the bigger the body, the bigger the brain, to control the larger mass of muscles, blood vessels, intestines, etc. But it’s the wrinklier the better for the cortex, and us humans are the wrinkle kings!

Which animal has the smallest brain?

Not known for sure, though I think I went to school with him. There is a frog that is only the size of a pencil eraser; it must have a pretty tiny brain.

What causes tinnitus?

Tinnitus is a constant ringing in the ears. It originates from the inner ear, and there are several known and more unknown causes. Damage to the hair-like fringes on cells in the cochlea can do it; I have had tinnitus that lasted a day after a visit to a rock concert (I don’t go anymore because of that.) Meniere’s disease seems to be due to increased pressure in the fluid in the cochlea. For a list of causes, go to http://www.mayoclinic.com/health/tinnitus/DS00365/DSECTION=causes .

Can a functional MRI be used to determine the origin of or location of epileptic seizures?

It can be very useful, maybe even more for mapping where the important functional areas of the brain are precisely located so they can be protected if surgery is planned. There is an excellent video about it from the Cleveland Clinic on YouTube: http://www.youtube.com/watch?v=ZCcqGDCMMxA.

What are the names of the flaps in the heart?

The 2 that prevent backwards flow from ventricles to atria are the tricuspid valve (right side) and mitral valve (left side). The 2 that prevent backflow from the blood vessels are the pulmonic (between the right ventricle and the lungs) and the aortic (from the left ventricle to the aorta).

Can people donate cartilage? Is it something that can't be recovered?

It is difficult to work with cartilage because it has no blood supply; it is nourished by diffusion, and commonly does not survive attempts at transplantation. There are several labs trying to grow a person’s cartilage in a test tube so it can be used to repair a joint.

How much space would the brain take up if it was unfolded?

I’m not sure; but if you imagine the brain, the outer surface you see if about 1/3 of the total area of the cortex. So, maybe close to a couple of square feet?

What are the symptoms of a concussion?

From the Mayo Clinic: The signs and symptoms of a concussion can be subtle and may not be immediately apparent. Symptoms can last for days, weeks or even longer. The two most common concussion symptoms are confusion and amnesia. The amnesia, which may or may not be preceded by a loss of consciousness, almost always involves the loss of memory of the impact that caused the concussion.

How do you know if your brain is bleeding?

If it’s bleeding internally, there may be the signs of a stroke: any abnormality of function or sensation (one side suddenly weak, for example). External bleeding may cause gradual slipping into unconsciousness; see the next question.

Why does your head swell when you hit it really hard?

I think you’re referring to “subdural hematoma.” When the head receives a hard blow, the brain is accelerated and, when the head stops moving, the brain may bump into the skull, and this can tear a blood vessel under the outer coating, the dura. After the blood clots, the clot swells, and presses on the brain. Too much pressing may cause unconsciousness, even stopping breathing. So commonly, after checking someone with a head injury out in the ER, the staff will ask family to watch that person carefully for 24 hours, even waking them up occasionally to be sure they can.

Is it possible to develop brain areas out of order?

Probably not, though individual areas might not develop normally for many reasons, especially genetic ones.

Where does the body's electrical energy come from?

The cell membrane is an insulator, so when a membrane pump (that requires energy) moves a charged ion (sodium, potassium, calcium) from one side to the other, there will be a charge difference across the membrane. Then, if different pumps or pores get activated, the ions flow back and the membrane is discharged or “fires,” just like a little battery. Such a process flows along the length of a nerve until the end, where it signals the next nerve, or a muscle, to begin firing.

If you have a pacemaker, do you have a constant heart rate (even when excited)?

Some pacemakers do only one rate, some have the ability to measure demand and increase or decrease the rate.

We didn’t get to talk too much about the muscular and skeletal systems. Can you quickly talk about breaks and repair in those systems as well as how to stay healthy?

Muscles can get torn, and will repair well as they have a good blood supply; but it is better if they can rest during healing, and that isn’t always easy, so it takes time. Bones heal when broken, and new blood vessels will grow into them from surrounding muscle to help the process. So bones near the surface (ulna, tibia, clavicle, skull) may take longer to knit.

What is the benefit of the high surface area of the brain due to gyri and sulci?

The outer layer of the cortex is the most sophisticated signal processing region, so the more we have the smarter we can be.

Do humans get a congenital defect in the heart that involves a hole in the septum as some puppies get?

Yep. It can usually be repaired surgically. If detected in a adult, repair is not always necessary as the body has compensated.

What is the most important sense in the body or all they all equal?

It’s really your choice. Some would say sight, others hearing. If you really like food, taste? But you can live without those; you can’t live without your immune system.

What’s the current theory of Patent Ductus Arteriosus and migraine headaches?

I can’t find any articles about an association. If you’d like to try, go to the National Library of Medicine (the world’s largest repository of peer-reviewed medical publications) and search on whatever terms you want: http://www.ncbi.nlm.nih.gov/sites/entrez .

If glucagon helps utilize energy why can't they give it as a weight loss agent?

As a drug, it would increase raise blood sugar by stimulating the liver to break down stored glucagon. That isn’t why we’re overweight, though. What we need to do is use up the fat stored in fat cells, and glucagon would not be very efficient at that. As Dr. Michaels said, the best thing is, don’t put it in, in the first place.

Can you describe the difference between the kidney and the liver as filtration devices?

The kidney is a true filter, but also is very good at bringing back important things that were filtered but must be reabsorbed. It does not do much in the way of metabolizing or breaking things down. That’s what the liver does; it is full of enzymes that “de-toxify” molecules so they can then be safely filtered by the kidney or secreted into the intestines.

I think it is interesting that everyone always focuses on the negative aspects of being obese but nothing is ever really stated about being underweight and how this can be very bad for you too. What are the problems of losing weight too fast if any? i.e. The Biggest Looser.

I guess it is a problem, but statistically the overweight problem is so much more prevalent. People with anorexia nervosa can actually die when their weight gets too low; many body systems stop working well. There is quite a lot of research, actually, done on anorexia, starvation, low birth-weight, and so on, but it doesn’t get into the newspapers as readily. Losing weight too fast can be bad if there is a nutritional imbalance; we need certain elements in the diet no matter what.