Be My Night Owl

I am not a morning person. Not now, not ever. I have punched a man for waking me too early (not intentionally, but still). You can imagine my sparkling demeanor when I awaken at 5 am each morning for work. But why is this? Why does my sense of humor disappear and leave a cranky, swearing, unkempt woman in a retainer behind? Circadian rhythm. No, that’s not something you should have studied for music theory, it’s the technical term for your “body clock”. And how does that work? Sit still and I’ll tell you.

First, let’s talk genetics. New research suggests that genes determine whether you’re a morning person or, like my father and I, are inclined to strangle overenthusiastic roosters and alarm clocks. These genes are likely related to clock protein and melatonin production (not to be confused with melanin, which is in your skin). Clock proteins are synthesized during the day and accumulate around the nucleus (site of DNA storage) of the cells in the superchiasmatic nucleus (region of the brain, just call it the SCN and don’t worry about it), at the end of the day the nucleus takes up the proteins and by the next day clock protein synthesis begins anew. Conversely, melatonin is secreted by your pineal gland (gland in the middle of your brain) at night. Secretion will vary depend on the season, but the general rule is that at night secretion is around 10 times that during the day. When you wake up in the morning, photoreceptors your eyes pick up the signal and transmit it to the SCN. These photoreceptors possess light sensitive proteins and are different from the rods and cones processing the light cues from those kitten pictures you have open in the other tab. Their light sensitive proteins do not aid vision, but instead receive light and use it to signal the SCN. The SCN will then alert the pineal gland and melatonin production will drop off. However, if you wake up before the sun (like me) it gets a lot harder to wake up fully, quickly. On a good day I’d say it takes an hour or so before I feel truly awake and alert. Thank God for long commutes. As I’ve gathered from my reading, research has not specifically outlined the biological difference between early and late risers. After a certain point, everyone is getting the light cues to wake up, so why the lag? Likely (and this is where I’m making my own inferences) late risers need stronger light to halt melatonin secretion, while early risers need only a little.

So I am fated to be forever a cranky. Of course, proper attitude (not focusing on sleep or resenting consciousness) helps IMMENSELY. As does getting some exercise so I’m tired at night. And yet…

Doom to all who disturb my slumber.

 

Source

Sherwood, Lauralee, Hillar Klandorf and Paul Yancey. 2005. Animal Physiology: From Genes to Organisms. Thomson Brookes/Cole, Belmont, CA.

Music of the Neuron: Schwann Lake or I, Robo-Ophid

OK folks, here’s where things get technical and y’all start liking me less. I mean, I don’t blame you; if you’re not at least an aspiring neurobiologist, learning how the movements of ions in and out of neurons control muscle flexion is less Music of the Spheres and more Music of the Drying Paint. But gaining at least a rudimentary understanding of how changes in electrical potential, running down wire-like axons through your body to conduct every movement you make and orchestrate each separate muscle to work in harmony with the others is pretty musical. At the very least you’ll feel like a badass robot. Who doesn’t want that?

Let’s talk about Robo-Ophid’s wires (in third person, apparently?). By wires, I mean the axons, the single, looooong branch of a neuron/nerve cell that is insulated by myelin, a lipid layer produced by Schwann cells on the axon and that increases the conduction speed of signals. The axons only conduct signals away from the main body of the neuron, dendrites (shorter branches) connect to other axons and receive signals. Signals for muscle movement are called action potentials, drastic changes in membrane potential that are propagated from one neuron to another in an un-diminishing fashion until the target muscle is reached. Neuron membrane potential, the difference in electrical charge between the inside and outside of the cell, is about -70mV. For Robo-Ophid to move, the membrane potential is depolarized (given a more positive charge), repolarized (given a more negative charge) and hyperpolarized (given a much more negative charge than it needs). Here’s the quick and dirty explanation of how: sodium channels open, allowing positive ions in; neuron becomes positive, hits peak of action potential/positive charge; sodium channels close; potassium channels open, allowing positive ions to exit; cell goes overboard and gets extra negative (perhaps even buys an emo CD) before returning to normal. Neurons like you, so the action potential itself is easy; the action potential just spreads down the axon to its target. In this case, lets say the spine, and that to another neuron that connects to a muscle. Not so bad, right?

Now, Robo-Ophid needs more than just one action potential to do things. Unlike the autoclave doors at her work, where you have to hold the damn button until the door is all the way shut or it comes open, Robo-Ophid needs multiple action potentials to do anything. Robo-Ophid doesn’t know if this makes her a worse machine than the autoclaves at work, but she doesn’t make inexplicable alarm noise for hours on end so I think we know who wins this round. Me. I win.

Anyway, along with other action potential-dependent signals (like skin temperature), graded contractions depend on the frequency of the action potentials. A higher frequency will lead to a stronger contraction and a lower frequency to a weaker contraction. Take physiology and you’ll get to test this out by poking your lab partners with electrical probes to force their muscles to contract. This is how biologists make friends; by poking people and laughing. Laughing so hard.

 

Source

Sherwood, Lauralee, Hillar Klandorf and Paul Yancey. 2005. Animal Physiology: From Genes to Organisms. Thomson Brookes/Cole, Belmont, CA.