EKG Lab

Yet again, we had some more fun tests to perform in the lab.  This time it was an EKG lab.  In this lab we got to play around a lot with different ways of taking blood pressure.  Everything from blood pressure cuffs to more accurate hand grips that hooked up to a recording program on a computer.  I’m really not a fan of blood pressure cuffs…they just freak me out…claustrophobia…ew, ew.  So, I decided to watch rather than volunteer my scrawny arm! 

An EKG is first and foremost, a graphical recording of the events occurring within the heart.  It records the natural pace and movement of the heart and can give good insight into the health of the heart and thus the rest of the body.  There are five parts to a single heartbeat, the P wave or atrial contraction, the QRS or ventricular contraction and finally the T wave which is the ventricular repolarization.  Viewing the EKG tracing of the heart can prove disorders or abnormalities in the heart.  For our lab we recorded for five seconds the electrical activity of the heart.  We then switched the red and green leads to simulate the change in electrical activity.  We started by connecting a green(negative) and black(ground) cords to the right arm and red(positive) cord to the left forearm.  The cords were connected to the recording program on the computer, we then collected the data from the model.  We then exchanged the clips with the other arm and recorded again.  Here is our data.

Interval                       Time

P-R                         .089s  .104s

QRS                        .079s  .069s

Q-T                         .257s  .140

R-R                         .666s  .562

Heart Rate (BPM)            39.96   33.72

After researching this data we could explore further on what a healthy/average heart rate would be for different ages, genders etc.  This may be something I will be looking into further for another post.  

This lab taught quite a bit on simply how to record heart rate and how to analyze it afterwards.  I think it's a skill that's a bit more likely to be used in daily life.  I think our previous heart dissection lab really helped close the gap with this one.  The dissection lab discussed what everything was, and this EKG lab showed what those parts did and how they relate to the proper functions of the rest of the body.  For me it really made the connection.  I think this is also something that could be explored further.  I may be looking back at this post for an outside research blog.  We'll see!

Reflex Lab

This quarter we’ve been doing a lot of work in the lab.  Recently, we performed a reflex lab.  This was probably one of my favorite labs because I got to smack my best friend with a mallet!  Fun fun!  The purpose of this lab was to see how long it took the reflexes of the body to react to the hit of mallet on the reflex point of their knee.  We first connected adaptor cords to various parts of the leg and body that then connected to a computer with a recording program.  The first step was to hit the mallet on a hard surface and have the model kick their leg according to the timing of the hit.  The computer would then record the exact timing of the hit in comparison to the reflex kick of the model’s leg.  After the given number of hits had been made and recorded we moved on to direct reflex.  This consisted of literally locating and hitting the reflex point on the knee cap of the model.  The computer would record the accuracy of the kick in response to the hit.  It was clear just how accurate a direct hit was in comparison to a hit to the table.  Here are our results:

1st Recording of mallet on table.

2nd Recording of mallet on knee.

After reviewing the results it's easy to see that the direct hit to the reflex point on the knee is much more accurate than the hit to the table.  This would be because the direct hit only takes time to connect to the spinal cord back to the knee point.  Whereas the hit to the table takes more time to connect with thought before running down the body to the reflex point.  

BRAINS!!

We recently performed a brain dissection lab in class.  It was a fairly quick lab but reeked of formaldehyde nonetheless. Each group received a lamb brain.  Some groups, such as ours, received a brain that still had the tough outer layer protecting it called the dura mater, or outer meninges.  We first had to remove this protective outer layer.  We then were assigned to cut the brain horizontally.  This took quite a bit of time because none of us could agree on the right size cut.  Once we had accomplished this we sliced the brain into various pieces and identified them.  

Here is a shot of the final outcome.

These are the parts identified on the brain itself. 

Eat Your Hearts Out!

Rawr.

We recently performed another dissection lab and oddly enough it didn't reek of formaldehyde!  This time we performed our dissections on hearts, on Valentine's day nonetheless!  There were three hearts to choose from sheep, cow, and pig.  Our group decided to go with the smallest of the three, the sheep. 

Throughout the lab we were required to measure various sections and pieces of the heart to compare to the other animals hearts.  Once the outer parts were recorded we sliced the heart open "clam shell" style and inspected the inside.  

Here are our records:

Aorta- 1.5cm
Pulmonary Trunk- 1cm and 2.5 Length
Right Atrium Diameter-4cm
Left Atrium Diameter- 3.5cm
Right Ventricle Diameter-1.5cm and 5cm in length
Left Ventricle Diameter-1.5cm and 5.5 in length
Outer Wall thickness- 1cm

Some of the areas identified.

We then compared our results to other group's results of the cow and pig.  Here are the results.

Pig:                                    
Right Atrium: 4.5cm
Left Atrium: 4cm
Right Ventricle: 3cm
Left Ventricle: 2.5cm
Outer Wall:  .5-1cm
Aorta: 5x3cm
Pulmonary Trunk: 4cm

Cow

Right Atrium: 3cm

Left Atrium: 3cm

Right Ventricle: 3cm

Left Ventricle: 4.5cm

Outer Wall:  1-1.5cm

Aorta: 3cm

Pulmonary Trunk: 2.5cm

After reviewing the three hearts we agreed that the three hearts are all the same in structure, the only major difference was the size.  This is obviously due to the size of the animal and what is needed to carry out basic functions.  After we performed the dissection we reviewed an assortment of slides relating to sections and parts of the heart.  After comparing the slides of artery and vein, we agreed the artery has the thickest wall because more blood passes through more quickly. The cardiac muscle was next which we discovered was indeed striated.  We decided that having atherosclerotic plaque on the coronary artery could possibly lead to the heart clogging and thus heart attacks due to build up.   

Alzheimers

As a group, we recently created and presented a Prezi for the class.  The base of our project surrounded neurons and the brain and how that is related to alzheimers.  Our work can be seen here.  

http://prezi.com/ehnj2if1x4ud/alzhimers-cant-spell/

Neurophysiology Lab

Objective Record electrical activities of individual neurons while you deliver mechanical stimulus to the attached skin. Inject flurescent dyes into the neurons to visualize their morphology. Identify the neurons based on the morphology and the response to stimuli, comparing them to previously published results.

Equipment List
	Feather: Used to give the leech skin a very gentle touch stimulation. It really doesn't need to be a feather, it could be q-tips or something. Cost: free.
	Probe: A blunt metal rod attached to a wooden handle useful for lifting, pushing, pressing, moving of specimen. Here you use it to lift tissue, and to push the skin as a stimulus. Typical price: $1.00 ~ 10.00
	Forceps: Fine forceps for very fine manipulations. The very fine ones are known as Dumont #5 forceps, with tip size of about 0.1 mm X 0.06 mm or smaller. Typical price: $15.00 ~ 45.00
	Scissors: Good dissecting angled scissors used here to cut open the body wall. Teaching scissors are cheaper, but some ultra-fine dissecting scissors could cost upward of $400, and you better not drop that, because once you drop it, chances are, it's ruined. Typical price: $15.00 ~ 60.00
	Pins: Stainless steel dissecting pins for pinning tissue to a dissecting dish or board. You can drop these and not worry about it. $1.00
	Scalpel: For microsurgery, disposable scalpel blades are better and much more economical than the fixed blade scalpel which needs to be sharpened periodically. Blade: $0.50 Handle: $10.00 Used here to cut all kinds of things.
	Dissection Tray: A tray half-filled with hard wax so that you can stick pins into it to stabilize specimen for dissection.
	Leech Tank: Leeches are kept in pond-water (you can actually buy an instant pond-water mix to add to tap water.) If kept in a refrigerator, they can stay happy in it for weeks at a time without feeding.
	20% Ethanol: Used to anesthetize the leech. Besides being more humane, it has the added benefit that it stops them from moving, making it easier to pin down the leech.
	Leech Tongs: These are basically gross anatomy forceps with blunt tips so that you will not harm the leech as you pick it up. Maybe about $ 10.00
	Dissection Microscope: These are binocular microscopes specifically designed for dissection and other micromanipulations. Essentially, it's a high quality high power magnifying glass. The price varies on quality and if you've looked through binoculars of different quality, you can appreciate what a difference good optic makes. On a good one, you can clearly see individual cells in a leech's nervous system. Cost about $1,000.00 ~ $7,000.00
	Micromanipulator: A device used to position items with sub-micrometer precision in three dimensions. Here we mount our electrode on it to guide it accurately to a neuron. For work on a leech, a mechanical manipulator would suffice which is about $700.00. More accurate hydraulic or electronic ones may cost up to $10,000.00
	Oscilloscope: Basically a sophisticated voltmeter. What you see on the screen is a real time display of voltage (vertical) plotted against time (horizontal). Useful because voltmeters can't track rapidly changing voltages, and even if they could, you couldn't read anything. Cost $2,000.00 and up.
	Leech: Medicinal leeches are about $15.00 each. When fully extended, they can reach 15 to 20 cm long. When fully contracted, diameter is roughly 1 ~ 2 cm.

Procedure

Step 1

Catch and anesthetize the leech in 20% ethanol solution. Ethanol is not an anesthetic for vertebrate animals, but can be an effective anesthesia for small creatures that breathe through the skin like the leech. Like in many things, too high a concentration will be harmful or fatal. 

Step 2

Pin the animal dorsal side up through the anterior and posterior suckers onto a dissection tray, stretching the animal in the process.

Step 3

Using scissors, make a cut in the skin along the mid-line on the dorsal surface, taking care not to damage deep structures.


Using forceps, carefully tease apart the skin along the cut and pin down the left and right halves of the skin to each side, so that the leech is pinned open with the inside of the skin facing up. This exposes the innards of the leech, including the digestive, excretory and reproductive organs. You cannot see the nervous system yet, because they are located ventrally.

Step 4 Carefully remove the gut and other internal structures to expose the ventrally located nerve cord. The nervous system of the leech is encased within the ventral sinus, which is dark green in color. Step 5 Notice that there are many swellings up and down the sinus. These contain the segmental ganglia of the nervous system. To make one of them accessible, first we cut a window in the body wall underneath a ganglion, taking care not to damage the nerve cord or any attached nerves in the process.  Step 6 Isolate a section of the animal by making 2 parallel cuts across the animal (perpendicular to the anterior-posterior axis), but sufficently separated so that the strip you remove contains at least one ganglion. Then, with forceps, flip the piece of skin over so that the outer skin is now face up. Pin the skin down. If you don't know why you are doing this, go read the Why are we doing this? of Step 5 and come back.  Step 7 Cut the sinus with an ultra fine scalpel and using fine forceps, carefully tease apart the sinus to expose the ganglion In reality, you would only use the scalpel here only if you are extremely good at microdissection. It's very difficult to cut just the sinus without accidentally damaging the ganglion underneath, but hey, we are all perfect in cyberland. Normally, this is done with a pair of very fine forceps. Step 8 Now you've come to the crux of the matter. All the preparation so far has been to make this step possible. You might want to review Nervous System background or Electrical Equipment background at this point. Click on the electrode to gain control of it. Move the electrode to somewhere over the ganglion then click on the mouse button. This simulates the process of penetrating the cell, which is much more demanding in reality (see "What it's like in reality." for details). Keep your eyes glued to the oscilloscope display while you are doing this. If you find a cell, the display will change. If you see no change, then you have not found a cell. Keep moving your electrode around and clicking until you find a cell. The sound you hear is the oscilloscope display you are seeing fed into an audio amplifier. It provides an audio feedback to what you see on the screen. Now using a feather, probe or forceps, push around the skin of the animal. Observe if the cell you have penetrated responds to weak (feather), medium (probe), strong (forceps) or any stimulus. Note the pattern of response. The cell may fire action potentials or spikes. The response characteristics will be used when you are comparing your data with published data compiled in the atlas. When you are satisfied with the electrophysiology, you can start the anatomical investigation by injecting the cell with a fluorescent dye. Push the button labeled "Dye Injection."  Step 9 Next, we will visualize the morphology of the neuron from which you have just recorded using a fluorescent dye. Having pushed the button labeled "Dye Injection," the amplifier system has passed an electric current from the electrode that resulted in the ejection of Lucifer Yellow from the tip of the electrode into the intracellular space. Lucifer Yellow will passively spread throughout the cell after a while. Now you can turn on ultraviolet (UV) light by pushing "UV Switch.". Lucifer Yellow fluoresces bright yellow-green under UV and you will be able to visualize the cell in question, including its axon, dendrites, cell body and so on. Step 10 You now have electrophysiological data and neuroanatomical data from your experiment. Try to identify the cell based on published data (Atlas)There are many cells in different locations of this ganglion. Repeat the whole procedure for as many cells as you would like. Go to the Atlas page to identify the cell.  Results Review Really, I thought this was a nice way to perform a dissection based lab.  I don't have serious issues with dissections but it's always been rather unsettling, cutting up and poking around in dead things.  It was nice going step by step with the computer so as not to forget anything,  which we seem to do rather often in real labs.  It was also nice to have explanations as to what exactly each step meant and what we were supposed to be getting out of it.  I didn't do extremely well at the quiz section at the end mainly because my computer refused to give me proper options....still unsure as to why this happened.