Choking, chemoreceptors, and yawning

Some questions asked during the respiratory system discussion:

1. Why do some people choke themselves to get a high?

The choking game is a stupid and dangerous activity gaining popularity among teenagers and pre-teens. It involves asphyxiation (self-induced or caused by a friend), passing out, and feeling a kind of euphoria similar to a drug-induced high once oxygen rushes back to the brain. Click on the links for more information.

2. How do the sensors in the walls of the aorta and carotid// arteries work?

We said that the specialized cells in the walls of the aorta and carotid arteries are sensitive to blood pH, an indicator of CO2 levels. These cells are called chemoreceptors.

According to Duchen & Biscoe (1991), most evidence supports the theory that detection of pH levels is done by molecules called cytochromes in these cells. One type would be sensitive to high levels, one to low levels.

Depending on the level, these chemoreceptors send signals via nerves. Nerve signals are caused by K+ and Na+ ions being exchanged across the cell membrane. This movement causes an action potential that is like a pulse of electrical activity that travels the length of the nerve cells and ultimately ends up in the medulla oblongata.

We will discuss this more when we get to the nervous system. Meanwhile, you may feast your eyes on this flash animation.

// Why do we yawn?

Wong (2002), in his answer to a similar query in Scientific American, runs through what scientists now know about yawning–which is basically NOTHING conclusive. Although the “kulang sa oxygen” hypothesis is popular, there is no proof that this is true.

Click on the links and decide for yourself. 🙂

PS. You kids ask the darndest questions! Don’t ever stop. 😀


Individual HW on excretion

  1. Differentiate osmoregulation from excretion. What is the significance of each?
  2. How does the environment (marine, freshwater, terrestrial) affect the mechanism an animal uses for osmoregulation? Give concrete examples for each.
  3. What are the three forms of nitrogeneous wastes? Give examples of animals that would generate each type of waste.
  4. Describe the (4) fundamental processes involved in all excretory systems regardless of their anatomical differences.
  5. Tabulate the characteristics of the excretory systems of the following animals: flatworms, earthworms, insects, and vertebrates.


– On 1 whole sheet of pad paper

– due Friday (for all classes), 230 PM

I Am Joe’s (Right) Lung

I am Joe’s right lung, and I claim the privilege of speaking since I am slightly larger than my partner in the left side of his chest. I have three lobed-sections while the left has only two. Joe would be surprised if he could see me. He thinks of me as a kind of hollow, pink football bladder hanging in his chest I am not much like that at all. I am not hollow–if you cut through me, I would look something like a rubber bath sponge. And I am not pink. I was when Joe was a baby. Now, a quarter of a million cigarettes plus half a billion breaths of dirty city air later, I am an unattractive slate gray with a mottling of black.

Continue reading

Oxygen: more is not necessarily better

We know that during cellular respiration, 1 molecule of glucose is broken down in the presence of 1 molecule of oxygen to produce energy in the form of 36 ATP molecules (net). Compare this to the 2 ATP molecules produced during anaerobic respiration and we can see why animals with higher metabolic rates rely on aerobic respiration for energy.

In class yesterday, some of you asked if breathing in higher concentrations of oxygen would create more energy. Good question! You are not alone in thinking that more oxygen is better, oxygen bars started as a fad in Japan in the late 90’s. Basically, you would go in and pay a dollar a minute for a 5-10 minute dose of concentrated O2 fed through a “nose hose.” Alleged benefits range from a healthier immune system to helping with hangovers. For a first person account of such an experience, click here.

However, scientists warn against long-term exposure to pure oxygen because of oxygen toxicity. Breathing in oxygen at higher concentrations leads to the formation of free radicals that eventually lead to lung, and even brain, damage. Read some articles on the cons of breathing pure oxygen by clicking on the links: News-Medical and Science Daily as well as a scathing commentary on O2 bars at LiveScience.

What do you think?

Lab Activity # 2 – Factors that affect heart, pulse, and respiratory rates

The procedure for this quarter’s lab activity is now available here.

We’ll do it at ASTB 302. Please get a copy of the procedure and read it before the activity. You may obtain a copy from the friendly lib photocopy lady.

Please take note of our sked: Cs – 11 Oct (Thu), Li – 10 Oct (Wed), Mg – 11 Oct (Thu). Lab reports will be submitted exactly one week after performance.