Monthly Archives: February 2014

Me Talk Pretty – Nociceptive flexion reflex (NFR)

SU11_GTY_sb10064912a-001_a_hzKnown on the streets as the withdrawal reflex, NFR refers to our body’s involuntary, ninja-quick neuromuscular response to pain. It’s our super sexy physiology term of the week and quite possibly our spiciest one yet. I even like saying it out loud (sometimes in a French accent).

Isn’t it nice to know that our body has our best interests in mind despite our worst judgment? If you’ve ever not been paying attention for a moment and let your hand stray a little too close to a hot stove (like who hasn’t) then it’s highly likely that you’ve witnessed your NFR in action. You probably yanked your hand away at what felt like the same instant you experienced pain. We perceive pain and withdraw from it simultaneously and our body does this seamlessly. If you’re the least bit skeptical just think back to that scolding hot bowl of chili con queso you dropped. YOU didn’t drop it. Your hands let go of it.

What experience could be more direct than pain? In reality, pain may not be as direct a phenomenon as you might think. When it comes to our involuntary withdrawal from pain there are at least 3 stages that occur. Once any part of your body is injured nerves in the vicinity transform that moment into a lightning quick electro-chemical signal. That signal has to take a journey from the site of the injury to the spinal chord. A new signal is sent from the spinal column to the appropriate muscles to flex and manipulate that stray body part away from the pain stimulus. Perhaps one of the reasons this process is so blindingly fast is the fact that the nerve control center in this case is the spinal chord and not the brain.

Let me set the scene…

It’s a perfect July afternoon. The grills are out. The air is saturated in honeysuckle flowers and spicy, charcoal kissed meat. You’re barefoot in the grass, loving life in your favorite shorts and a barbeque stained t-shirt. Oh yeah, you know what I’m talking about. You have a half-eaten bratwurst in one hand. Your other arm is free, innocently reaching out to grab the Frisbee that your friend just tossed to you (you crazy kids). She tossed it high. You take a step back unaware that laying in wait in the grass is a jagged piece of gravel just begging to be stepped on by bare feet. You plant your foot on the rock…

1) Tiny, branching pain receptors suspended within the epidermal layer of your heel, like tree roots, transmit an electrical signal up a long network of neuron fibers that form an intricate junction at the spinal column not unlike a downtown D.C. intersection.

2) Once the message reaches the spinal column an alpha motor neuron sends a signal back down your leg.

3) The signal from the alpha motor neuron reaches a neuromuscular junction in the hamstrings of your leg, initiating their contraction. This flexes the knee, pulling your foot off of the ground to minimize damage to the soft tissue of your foot so you can frolic in the grass another day.

Stay curious, stay classy, and never stop learning my friends 🙂

Fun Facts – A Touch of Gray

ImageOh yes, it WILL happen to you. Don’t worry it happens to all of us, aging that is. More specifically, gray hairs happen. That’s right our bodies, unlike diamonds, aren’t forever. Hair follicles lose their pigment as we age. There is a family of pigments in our bodies called melanins that contribute to hair and skin coloration. So whether your complexion is Godiva, chocolate brown like Djimon Hounsou, salted caramel like Rosario Dawson (call me), or slow churned vanilla like Olivia Wilde, you have melanin to thank. Oh man, all this talk about race makes me want ice cream.

Anyway…

Hair is like sea coral. Yes, that’s random…try to focus. Much of the underlying structure of a coral is the deposited, calcium carbonate remains of dead cells that harden and accumulate while new cells grow over top of the layers. The structural anatomy of a hair follicle is actually curiously complex but the portion of that follicle that we see protruding from the skin (the hair shaft) is just the deposited remains of dead keratinocytes (keratin containing cells). However, unlike coral, the living cells are underneath. Keratin is the crazy strong protein that gives hair, nails, and skin their structure and durability. That same protein that allows Scarlett Johansson’s golden locks to flutter in the wind are what make a rhino’s horns hard enough to dent the door of a Jeep when the tourists get too close.

Clusters of rapidly dividing keratinocytes at the root of the follicle team up to produce keratin. Cell division and keratin production creates a dense mass of material that builds from the bottom up. Meanwhile, bordering those feisty root cells are melanocytes that pass their melanin granules to the keratin producing cells. So even as the cells die they retain whatever color was passed on.

As we age melanocytes become less active and die off and so more and more hair shafts reach the surface without pigment. So just to be clear, your body doesn’t produce gray hairs. It simply stops producing melanin pigment within the hair follicles. The resulting hair strand is actually colorless.

Now the rate at which our hair loses its color is largely genetic. In know, genetics seem to be the new cop-out answer. It’s like when they use “instinct” to explain why ducks fly south for the winter. However, this time we have to point the finger at inheritance for our sexy, silver sheen.

Stay classy, stay curious, and never stop learning my friends :-)

Fun Facts – toxic

Ever wonder where our word “toxic” comes from? That’s OK if you haven’t…I mean, that’s why you have me. The word actually has its roots in ancient Greek mythology (like what doesn’t). The Greeks have a word, toxon, which can refer to the bow, the arrows, or both. In fact there is another word, toxicum, which literally means poison for arrows. Random right? Don’t judge the ancient Greeks.

As the myth goes that legendary stud, Hercules once slayed a giant, nine-headed sea serpent called the Hydra. You know how it is, you’re surfing a half pipe wave off the coast of Baja when a giant serpent tries to eat you and every time you chop one of its heads off they just grow right back. Anyway, Hercules was having similar drama that day. Long story short, he puts the smack down on this monster and dips his toxons (arrows) in the serpent’s poisonous blood. BAM!!! That’s where we get toxic. No no, thank you.

Stay curious, stay classy, and never stop learning my friends 😉