Directional Terms - human

Here is a handy reference on directional terms used for human anatomy.  I was nice enough to choose the pictures of people with clothes on.  You're welcome.

Here are some specific to the brain, because for humans our brain as we are standing is tilted compared to the way we hold up our heads, like so:

Source on Studyblue

So simply using superior/inferior and anterior/posterior doesn't quite work for how we normally think of orienting the brain, which is why we use dorsal/ventral and rostral/caudal.

Here is a memory aid for this.  I had a hard time keeping dorsal/ventral straight, so this is what helped me.

When I think of dorsal, a shark comes to mind with its iconic dorsal fin on its back or in this case top:

For ventral being the bottom or down, I had to think about stingrays.  They take water in on the top of their bodies and then shoot the water out the bottom over their gills.  So they vent the water out the bottom side of their body.  Hope that helps.

Left image: top/ dorsal side of stingray.  Right image: bottom / ventral side of stingray

There ya go, have fun in anatomy or whatever class brought you to find this blog!

Stay curious.

Blood Brain Barrier

No one would argue blood is very important to our bodies!  It carries very important things to all parts of the body we need such as glucose and oxygen.  It also takes out the trash by removing wastes like lactic acid and carbon dioxide.

Blood is the highway by which our immune system cells gets around our body to take care of anything that invades.  Blood is also how medications, drugs, poison and toxins, hormones, etc. can get around our bodies.

But let's talk about blood and the brain.  Our brain is a very special organ that deserves special protection.  It's the only part of our body that is protected by a 7 mm thick covering of bone, in addition to cerebrospinal fluid cushioning and protective layers of meninges.  That protects from the outside in, but we also have protection from the inside out, called the blood-brain barrier (I will abbreviate it BBB).

Blood supply is very important to the brain so it has a constant supply of energy and waste removal.  Here are some diagrams showing the blood vessels supplying the brain.

Notice the arch at the bottom of this diagram is the aorta which comes right off the heart itself

The Common carotid artery is the one you are feeling when you take your pulse on your neck

This "Circle of Willis" shows the blood supply on the inferior/ ventral side of the brain.  You can see in the image on the right where this is in relation to the brain.

Alright, so we need that blood and it definitely is there.  But how to protect it?  Some may think the "Blood-brain Barrier" is some kind of a gate the blood goes through when it enters the vicinity of the brain, but that isn't the case.  There isn't a particular spot for the BBB, but rather, it exists as protection on the capillaries (smallest blood vessels where material exchanges happen) themselves in EVERY location within the area of the brain.  It's not a matter of filtering all the blood as it travels through your head, but it's a matter of being more selective about what things cross over FROM that blood into the brain tissue.

We have special gate-keepers to protect things from getting into our brains.  Here's a cross-section of what a blood vessel in the brain looks like compared to a regular one elsewhere in the body:

Not only are the capillary cells (red in the diagram) closed more tightly so things can't leak through, but the entire blood vessel is covered with the "feet" of astrocytes.  (My favorite glia!  Here's a post about them.)

Here's a more 3D view:

See how is it a gatekeeper?  Anything in the blood must go through the astrocyte in order to get to the neuron.  Astrocytes are like the bouncer, protective big brother, or best friend: "if you want to get to the neuron, you have to [quite literally] go through me first!"

Astrocytes are really integral to the chemical integrity in the brain and are a bit of the "unsung heroes" of the brain.  Not only are they gatekeepers, but they act as a kind of mop-up crew and storage unit for any leftovers the neurons leave around (like ions, some neurotransmitters), and they serve to make sure the neuron stays well-fueled, like a mother who keeps snacks in her purse for her toddler.  No wonder astrocytes far outnumber neurons in the brain.

How do these tight blood vessels and "feet" of the astrocytes actually protect it? They are cells, which means they are surrounded by membrane- a phospholipid bilayer, which looks like this up close:

Because of this configuration, stuff that is polar (charged) or water-soluble can't get through the membrane- it can't get past all those hydrophobic fatty tails. 

YOU SHALL NOT PASS!!!
Water-soluble stuff such as nutrients (Amino Acids, Glucose, vitamins)
Polar stuff
Chemicals & toxins
Viruses
Bacteria

Stopping viruses and bacteria for the win.  Stopping nutrients? FAIL.

So to fix that, we have special transporters to let the good stuff in.  They can be super specific, so a glucose transporter will ONLY let glucose in.

Okay, you can go in...
Non-polar/ uncharged/ fat soluble stuff: this includes oxygen going in and carbon dioxide going out
Drugs that are fat-soluble
Other important stuff with special transporters embedded into the membrane to let them in, like water, glucose, amino acids, vitamins, etc. (Glucose has a wicked-awesome backstage pass, AND it knows the lead singer of the band.)


Whew!  That's a big job and an important one for the BBB.

Stay curious!

Brain Development

It astounds me how much brain development takes place in a fetus before a woman even usually knows she is pregnant.  This is an important reason why many foods are fortified with folic acid.  Folic acid (or folate) is essential in early brain development to the point that in its absence, there can be severe defects (such as spina bifida), but by the time the woman discovers she is pregnant, damage is already done, because it affects the neural tube which has already developed by day 21 of pregnancy!

Quote from the Mayo Clinic:
"Spina bifida is part of a group of birth defects called neural tube defects. The neural tube is the embryonic structure that eventually develops into the baby's brain and spinal cord and the tissues that enclose them.
"Normally, the neural tube forms early in the pregnancy and closes by the 28th day after conception. In babies with spina bifida, a portion of the neural tube fails to develop or close properly, causing defects in the spinal cord and in the bones of the backbone."

The Spina Bifida example serves to show how quickly brain development takes off.  This video has an excellent animation of brain development in a human fetus.




A couple other visualizations of the neural plate becoming the neural groove and then neural tube:

Lastly, here's a nice TED talk to get you thinking about infants in a different light. thanks for sharing Claudia Lieberwirth.

Neuron Ion Channels - Detailed

Inward rectifying potassium channels.  This is what started all this.  Just a little paranthetical aside in my Neuroscience teacher's notes that left me curious.  One thing led to another, and here we are.  Ion channels.  Hope you learn something like I did.  Enjoy!

A plethora of potassium channels
Here is a short video showing the molecular structure of a Potassium channel and how it can be perfectly selective to allow Potassium and not Sodium through.

And look at this beautiful top view of a potassium channel with a little purple potassium ion in the center.

Inward-Rectifying Potassium Channels
What does inward-rectifying mean?  Simply put, it just means that voltage travels inward more easily than outward.  So this name tells us that Potassium will move into a cell when open.
(Example - cardiac muscle cells- responsible for the long refractory period between beats, to avoid tetany; kidneys, regulating potassium ions

Action Potentials: Delayed Rectifier Potassium Channels & A Type Channels (outwardly rectifying)



Tandem Pore Domain Potassium Channels (Leak Channels)

Voltage Gated Potassium Channels




********This post under construction!  I just found a textbook with an entire chapter on ion channels, so after I study for my test I will dive into this and finish the post...  thank you for not hating me too much for leaving you hanging.  You'll just have to subscribe to learn more! :)

Neuroglia

Neuroglia are support cells for the neurons in the nervous system.  They have a very wide variety of functions, and I'm sure it hasn't all been discovered.

Now, here's the interesting thing.  Studies done on (supposedly) Einstein's brain, show that he didn't really have any greater number of neurons, but actually had more neuroglia, particularly astrocytes, which were concentrated in the area of the brain involved in imagery and complex thinking (NPR news article on the subject, June 2010).

Picture source

My thought is that we don't know which came first - the astrocytes or his genius.  Perhaps using your brain well leads to making more astrocytes in order to support how much you're using certain areas of the brain, rather than the astrocytes coming first and giving natural intellectual ability.

So, on that note, we'll take a look at these cells. :)  Here is a good way to categorize them, from interactive-biology.com.  I'll expound on these more.

Source (interactive-biology.com)

 And for the visual folks out there, here are a couple of diagrams.

Source

Source

Neuroglia in the Central Nervous System 

Source

Oligodendrocytes (a type of macroglia)

• Support neurons in the CNS by myelinating.  Have multiple "arms" with which they myelinate several axons.
• Myelination insulates axons of neurons which allows their conduction to go much more quickly.  (For some info on how this works, go to this post on action potentials and scroll to the bottom for "saltatory conduction".)
• Similar function in PNS is performed by Schwann cells

Astrocytes (a type of macroglia)

• Named for their star appearance (astro = star, cyte=cell)
• Maintain neuronal environment
• Part of the blood-brain barrier
• Control what substances are transported from blood to neural tissue (Source article)
• Have their own signalling system and can regulate messages of neurons
• Topic of much research - some are calling these "the other brain" (Source article)

  

  Source

  
  

My note on Astrocytes: wow, these look like such an exciting topic right now!  These are the cells that Einstein's brain had more of, and it looks like we are just discovering how integral they really are to the function of neurons!

Microglia

• Immune cells of the CNS - these bad boys take care of infection by foreign pathogens, and keep any abnormal neurons in check, gobbling up anything that shouldn't be there.  In short, they are the macrophages of the brain and spinal cord.
• Named for being small (micro), which allows them to get around to whatever small spaces necessary for fighting infection.

Source

Ependymal glia

Source on brainyinfo.com

• Ciliated epithelial tissue
• Line the ventricles and choroid plexus of the brain
• Make Cerebrospinal fluid (CSF)
• (Very good source article on brainyinfo)

Neuroglia of the Peripheral Nervous System
Schwann Cells/ Neurolemmocytes

Source

• Schwann cells have the same function in the PNS that Oligodendrocytes have in the CNS, namely myelination.
• The cell wraps itself around the axon of a neuron, insulating it, as seen below.  Pretty cool, eh?

Source on brainyinfo.com

Satellite Cells

• Cushion neurons
• Help control the environment of neurons and maintain synaptic integrity by insulating areas where there shouldn't be additional synapses on the neuron.

Kidney Physiology

Great overview

Urine Production Video - Osmotic Gradients

This is kind of fast, but it shows the counter-current diffusion of water and ions from the Nephron loop and vasa recta.

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Here's a fun video - why coffee and alcohol make you pee more.

Respiration, Oxygen, and Hemoglobin

By decreasing pressure inside the thoracic cavity, we are able to inspire air.  By contracting the diaphragm, intercostal muscles, and others, we increase the size of the thoracic cavity, which in turn lowers the pressure to the point that it is lower than the outside air, causing a pressure gradient so the air rushes into the lungs.  To exhale, it is the opposite- relax the muscles, decrease the space in the cavity, which increases the pressure inside until higher than outside, so the air rushes out to where the pressure is lower.

This video is a good summary.  The embedding doesn't work, so you'll have to click the link instead.  Just left the embed on there for the picture. :)

http://youtu.be/V1FAnE31AYs

Partial Pressure
Total Pressure of air can be broken into the partial pressures of all the gases contained in that air.  For instance, if the atmospheric pressure is at 760 mm Hg, and 20% of that is Oxygen gas, 80% Nitrogen gas, then the partial pressure of O₂ would be 20% of 760 = 152 mm Hg.  Partial Pressure of N₂would be 80% of 760 = 608 mm Hg.

This illustrates how increasing the pressure, as in the B picture, causes more gas to diffuse into the liquid.  A simple way to think about it is just that the higher the partial pressure of that gas, the less space it has to bounce around in the air, so more of it will end up in the liquid.

Here's a long video on partial pressure and gases getting into solution, I didn't watch the entire thing yet but it looks like a good detailed explanation for those who feel they could use more information.

Deer Carcass - Determining the Cause of Death

I was wandering around the Dry Canyon area with my boyfriend and we ran across some awesome stuff.  First off, we found a partial skull, which I of course kept, and not far off, we found a mule deer carcass!  There was fur everywhere and even looked as though the animal had been dragged to a more protected area in the bushes, as you can see in this picture:

Here I am next to the carcass, holding the skull

However, it didn't appear that any of the bushes were broken from the animal being dragged in there, and the way the animal was prostrated (particularly the position of the front limbs) didn't seem to indicate dragging but almost rather that it had laid down there.

See my geeking-out face?  Also notice the front limbs curled neatly under the animal.

So, obviously I'm no expert in forensics or animal behavior, but it was fun to try to guess how the animal died and how its body came to be where and in what condition it is.  Did it die of natural causes, and was later ravaged by scavengers who tossed hair to and fro so the surrounding area is littered with it?  Did a predator kill it and drag it out of the way?  Could it even have been a cougar cache at one point?  Let's look at each possibility.

Cougar Cache
There is evidence that could be consistent with dragging a killed animal to a safer place.  However, there is no evidence that any attempt was made to bury or cover it as cougars usually do with their caches, as in these pictures:

There also doesn't seem to be a lot of blood soaked into the fur of the animal as would be expected if it had been killed by a predator.  I would think the neck would be covered with blood if a cougar had brought it down.

Head, neck and open thorax of deer.  Notice lack of blood on fur.

Based on the evidence and that information, my conclusion is it's definitely not a cougar cache.

Another Predator
Perhaps a coyote or even dog brought down the deer?

Died naturally & later scavenged

Regulation of Blood Pressure

Blood Pressure is a very important aspect of homeostasis.  So naturally the body has many methods of monitoring and adjusting blood pressure to keep within a range that is functional for life.


Baroreceptor Reflex
Baroreceptors are located in the aortic arch and carotid sinuses (pictured below).  These are mechanoreceptors that respond to stretching of the arteries in response to blood pressure.

When these receptors are stimulated, nervous impulses are sent to the medulla oblongata of the brain where the reflex centers for vasomotor, cardiac, and respiratory are.

Vision - colors

This podcast about color is so awesome.

Wish I could have the eyes of a mantis shrimp!  We have only 3 types of cones (photoreceptors) for color vision, they have SIXTEEN!  I always feel like there must be colors that I can't see and wonder what they would look like.  I will be coloring a picture and looking around for different colors to use and I just can't find them and I realize that's all that I can see.

Heart

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Here is a pretty good visual to show what gap junctions and desmosomes are.  The heart has both.

Muscle Contraction

Muscle Contraction is a very cool, amazing process.

Within the myofibrils, this is what's happening:

Source

Here's the explanation of the picture from the source's website:
a. Without calcium ions (in relaxed state). Because tropomyosin completely covers the sites (indicated in blue) of actin binding to myosin, myosin cannot bind to actin.
b. When calcium ions released from excited muscle cells bind to troponin, the binding sites of actin are exposed owing to the shift of tropomyosin; however, the extent of the shift is not sufficient for myosin to bind to actin.
c. When small amounts of myosin heads bind to the binding sites of actin under state b, tropomyosin shifts further, resulting in the complete exposure of the binding sites of actin.
d. Because the binding sites of actin are completely exposed, many myosin heads can bind to actin, which enables the generation of a large muscle contraction power. 


I love that it is showing the myosin heads (green globs) all the way around the actin.  Most of the time we look at it as a very 2-dimensional thing, but when you look at the picture below, you can see that it is a very 3-dimensional process, with myosin heads able to bind all the way around.  Each of the small dots represent actin, the bigger ones are myosin (seen on the ends of the myofibrils).

Source

Keep in mind, myofibrils are organelles within a muscle cell.  So the sarcoplasmic reticulum is the muscle version of ER, wrapped around each myofibril.  Stuff is diagrammed 2D to make it simpler and more understandable.  Once you understand it, it's cool to look back and imagine the bigger picture.




Videos!

Love to weed through the options and find a few good ones for you, this time I've included a song, rap, and skit!

Very short and sweet, this is just a good little animation to show how the filaments slide past each other, with the myosin heads moving along at different times.

One recommended by a student.  It says it's for invertebrates, but looks like it's accurate for us as well.

Hahaha, this is a fun one.  A song/rap explaining the whole process.  I probably like it because the background music is Daft Punk (they did the music for Tron Legacy).  Anyway!  Maybe it's helpful for someone, and it's kinda fun to listen to.

This skit is a great idea.  It's hard to read their signs some times, but this was a fun little video and it might help a couple things click for you like it did for me.  I want to get a bunch of people to act something like this out some day! :P  (Don't worry, no plans to make my study sessions do this...)

The singing on these videos often leaves much to be desired!  But the info in this one is pretty good...

Here's Dr. Ashworth's explanation she gave permission to share.  Thanks Jessie for recording and sending it.

Enjoy. :)

Plastic Beaches

Plastic sand is NOT a sand I would collect except to throw it away.  Look at how we humans are destroying things for all the other living things on the planet.  I can't wait to see this movie when it comes out later this year.

www.midwayjourney.com

Trailer for the new documentary Midway, coming out later this year.  Really beautiful photography that is shocking.  A must watch.  http://vimeo.com/midway/midwayfilm
It didn't have a way for me to embed it, so go to that link to watch it first.

Then watch this one:

Nervous System

The nervous system is divided into Central Nervous System (brain and spinal cord) and Peripheral Nervous System (nerves, ganglia, etc).
Here's a little chart, courtesy of a great Physiology student:

Peripheral Nervous System	Central Nervous System
nerves	tracts
ganglia	nuclei
Schwann cells	oligodendrocytes

Part of the Peripheral Nervous System (PNS) is the involuntary part, consisting of efferent neurons controling visceral organs.  This is called the visceral nervous system, but more commonly known as:
Autonomic Nervous System
Autonomic = Automatic = Involuntary
Sympathetic & Parasympathetic divisions.  Here's a silly little video that shows the functions of each.

Sympathetic Division
Location: Thoracic and Lumbar regions of spinal cord

3 Kinds of pathways

Parasympathetic Division
Location: Brain, and Sacral region of spinal cord

Receptors

This is super fun, talks about the brain, gets deep and slightly philosophical, and mentions reflexes.  It's all about the brain! :)

Reflexes

Reflex Arcs involve the spinal cord and leave the brain out of the picture, in order for the compensatory action to happen very quickly and avoid tissue damage.  Here is a short and sweet explanation:

Action Potentials Up Close

Here is a pretty nice video showing action potentials and how they are propogated without decreasing.

Another one which shows the voltage-gated Sodium and Potassium channels:

This animated image is a bit difficult to follow because it's so fast, but seems like it could be helpful to someone, especially if you know how to slow it down (which I don't- if you know, please teach me!).  So here it is.

Source

Here are a few various visualizations I liked

Source - awesome nervous system/eye/ear post!

Source

Source - great post with lots of details!

The following images were all from this excellent source: http://mikeclaffey.com/psyc2/notes-neurons.html

First, we see the steps of the action potential and what is going on with the various channels:

Source

Next, here is a nice depiction of how the action potential moves down the axon and why impulses travel one-way.

Source

Lastly, we see how saltatory conduction works.  This is the fastest way to conduct an impulse because it gets to "skip" all that length of the membrane on the axon that is myelenated.

Source

There you are, folks, another deeper view into the amazing world of Action Potentials and your nervous system...isn't this awesome!?

(If you missed the first post, here is a link to it)

Action Potentials - What Make Your Brain Work