How Does Hair Know When to Stop Growing?

Have you ever wondered how a hair knows when to start and stop growing?

You know what I mean: why do eyelashes grow to a certain length? If you cut one of those small hairs on your forearm in half, somehow it knows it's been cut in half and grows to full length again--but only to it's normal length, and then no more. And why do some hairs grow really long (like those on your head) and some barely at all (like those on the inside of your wrist)?

I used to wonder this all the time.

One day, I decided to find out.

So, your hair grows out of what's called a hair follicle. This is basically a piece of skin that squishes old cells together and makes hair (what scientists call "keratin filaments"). With the follicle, there's this thing called the sebaceous gland. It produces an oily-waxy matter called sebum.

(Side note: The more hair, the more sebum. And the most sebaceous glands are found on your face and scalp, which is why your hair on your head gets greasy and your face gets oily.)

These glands are all over your body except your lips, palms, and the bottoms of your feet.

That's all great, right? But that still doesn't explain why the hair stops growing.

Well, these little hair-making machines, these follicles, like other machines can't run full-time without running themselves into the ground. They go through three phases: anagen (hair is growing), catagen (hair stops growing and falls out), thelogen (follicle recovery time before beginning production again).

So, here's the answer, are you ready???

The three phases run different lengths depending where they are on the body.

And the length of the phases dictates the length of time the hair has to grow.

So, an eyelash has an anagen phase of about a week or so, a pubic hair a few weeks, and a head-hair several years.

The varying lengths are mostly due to the genetic hard-wired info in the follicle, but sometimes hormonal or metabolic control (basically, changes in your body's chemicals).

That's why stress, malnutrition, and puberty can all affect the growth of hair on your body.

Now you know.

Just don't cut yourself shaving--that's a whole different matter.

Please comment below if you thought this was helpful!

Lastly...

there seems to be a pattern over there ------->

(and up...yeah, you have to scroll a bit)

Also seen right here:

To maintain this pattern, I either need to stop posting for the remainder of this year, post at least 117 times, or reach 171 posts (doubt I'll get to 711)...

I'm just saying.

Sources:

The Naked Science Forum

Wikipedia

second image, original source unknown

Unihemispheric Sleep

Define: Unihemispheric Sleep

Uni = numero uno

hemispheric = a half of a sphere (like that of the brain)

Okay, prepare yourself. Lately I've been learning about this really cool thing called Unihemispheric Sleep. I heard about it on a radio show. I know, just keep reading.

Dolphins are mammals, right? Therefore they need to breath above water. And not only do they need to breath, but they are conscious breathers, meaning they need to tell themselves to take a breath every time they jump out of the water. Crazy, right? That's not even the best part. In spite of their habitat being a great body of water and the fact that they need to remind themselves to gasp for air, they sleep. In fact, they sleep a full 8 hours every day. How? you might ask. I did. And the answer--unihemispheric sleep.

Do you remember that day last weekend that I went to Pinkberry? Well, over said frozen yogurt I told my lovely friends all about this new discovery; however, I dare say, I don't believe they were much impressed. So, unlike them, you have the freedom to pass up this post...but if I've managed to pique your interest, please stay tuned.

Ducks often sleep in rows of four with the outer two birds keeping one eye open for watch. If you wait around long enough, you'll see those two end birds get up and make a 180 degree turn before hunkering down in their guard-like positions again.

This is because the side of their brain connected to that one eye is alert and on watch; however, the other side is sleeping! They rotate to give the other side of their brain a chance to sleep as well.

You can see from these wave patterns that dolphins' brains do the same thing! When they sleep, dolphins go into a state animal experts call "logging." It's where they float along the surface like a log. Because this takes some attention on the part of the animal, not to mention the attention required for breathing, the dolphins must stay awake even in this relaxed state--but not all of them needs to stay awake. They rest half their brain at a time.

Some believe we humans used to be capable of this as well, but one day discovered houses with locks that kept us safe--so we didn't need to worry about protecting ourselves with one eye open.

At this point, "experts" have observed Unihemispheric sleep in birds and aquatic mammals (like those discussed above)...and possibly some reptiles, they're not exactly sure.

But half a brain a whole a brain,

everyone needs sleep.

Here's what happens when we don't get enough:

But surprisingly, in spite of the fact that we ALL sleep, doctors don't understand the necessity or process of sleep very well. Yes, we know the stages, but beyond that--little to none. Dreams? Why are brain is more active while we're asleep then awake? Why rats die after only a few weeks without it? How come our entire body is dependent on it?

No answers.

Well, I hope that didn't put you to sleep.

Like I said, I think it's fascinating!

I just wish we had more answers.

But in the meantime, I think up more questions.

Sweet dreams!

Background

So... if you haven't noticed, my background disappeared. I was "trying something" and poof! gone!

Quiz of the day:

A. Try to find my old background again.

B. Try to find a new background.

C. Leave it white like this.

You have 1.29 minutes.

Go!

The Winter's Tale is by Shakespeare

Do you ever wonder why people are so different? I mean, more than just outward appearances--the way we taste food, what makes us happy, what affects us emotionally. We all experience life as individuals, separate individual beings.

I saw this woman on the train today reading a really trashy novel. And my thought was: "What a really trashy novel...Well, at least she's reading."

Although I will always believe reading has great value, I did catch myself after such a critical thought. I started to wonder if all of my likes, dislikes, judgements and priorities were ever "right" or just "different." Of course, truth is truth, and I wouldn't "believe" in somethings, like religion, if I didn't in this.

However, spaghetti doesn't really taste all that bad--even though I swore this was a truth all my life, so obviously opinions change and we grow up.

But does this change the very things that make us who we are? Why do we have a central core that creates uniqueness?

I have so many journal entries from my 15 year old self asking where I "fit in," where my niche exists in this big world. But I don't know if that's what I should be doing, if those are the questions I should ask.

I think we're just supposed to find what makes us happy, endure what makes us sad, and learn from everything else.

Here are some things that define me and make me happy:

**start 1:00 into the video**

Workin' Out

All I could think of during my aerobics class was "I want a shake. I want a rich and creamy chocolate shake. I want an In-n-out shake and a burger and fries and a shake and a chocolate shake." ...is that bad?

I'm a Damsel in Distress--Save Me

You know those fairytale ideas you have about life, the kind you're told never come true? Well, at a certain age you finally realize you can't stand in the tallest tower in a poofy dress with elbow-length gloves and wait for Prince Charming (yes, that is a proper noun) to sweep you off your feet. You know why not? Because poofy isn't a real word. And because Prince Charming will never come. So, what do you do instead? you make a plan and you move forward in life. But! low and behold, the plan doesn't work out either.

I don't know. I simply don't know. Where is a magic 8 ball when you need one?

Social (adj.):

a1387 Designating a war fought between allies.

According to the Oxford English Dictionary, in the 14th century social meant fighting between friends?

I'm a fairly social person--so I've been told. Sometimes I enjoy this socializing, and sometimes all I want is to curl up in a warm blanket with the sole company of a good book. Yet quite frankly, in all reality, when I have the choice between people or paper, I drop the books and run.
The reason I'm bringing this up is I've noticed I allow people to dictate my mood far too easily. For example, when I actively socialize with all the "right" people, I've had a "good" day; otherwise, I've inexplicably had a miserable one. Well, now I'm explaining. In spite of internal and external professions, I must really care what people think of me. Actually, I know I do. Consequently, I suppose I interpret social action as an invariable reflection of that thought--that judgment of who I am, what I'm capable of becoming, and how much I'm worth. Don't get me wrong, I don't need every person to smile and pointedly tell me "hi" just so I don't kill myself. I do have self worth, and I do understand this without social reminders. But I think it's normal to define one's self based on social acceptance. I don't want this to be so, but it is, and I succumb to social pressures every day. Why can't I just not care? Or should I? Do you think socializing with the masses is important? Should we care what the masses think? say? do?

I Feel Your Pain and Wonder Why it Has to be This Way.

There is so much pain around me—pain that I cannot heal. I hurt, they hurt. And now I hurt from my own problems and from theirs. But I cannot heal them. Why does death take loved ones from us early? Why do illnesses debilitate the faithful, the righteous, and undeserving? But most of all, why can I do nothing?!

This week, more than ever before, the existence and prevalence of pain and problems in everyone’s lives has manifested itself strongly unto me. There are billions of people in the world, and yet we feel alone. People may reach out to us, but in fear we recoil back into our shells, our safe places—lonely, but not vulnerable. I now understand Christ’s willingness to give Himself for the pains of the world. If I could, I would. But even if our sacrifices could heal, I myself am not a worthy enough sacrifice to compensate.

I CAN’T TAKE IT ANYMORE!!!!!!!!!!!!!!

I feel sick. Fat. Ugly. Tired. Empty. Hurting. Angry. Stupid. –Probably all feelings coming from Satan, but he’s doing a really good job at convincing me I’ve had enough.

I’M SO CONFUSED!

Life doesn’t even make sense to me anymore. I use to be so sure about who I was, where I was going, and who I wanted to become in the meantime. Now I just don’t know. Nobody has any answers!

“REMEMBER: THERE’S NEVER A PERFECT MATCH”

Says the bus driver. I’ve always know that life isn’t perfect and I’m not perfect and that’s not going to change. But why can’t I at least have a perfect match?!
If God has all of the answers, then why doesn’t he share them with me?? I know he is there, I’m sure of that. But then why do I still feel so alone?

I FEEL LIKE I’M GOING TO BE SICK!

My head an stomach are swimming so much, I can’t even think straight.

HELP!