EKG analysis

An EKG (electrocardiogram) is a painless medical procedure that monitors the movements of cardiac muscles. EKG's are used to detect abnormalities in heart rhythm that may be indicators of serious defects in the heart. Electrodes are attached to the patient where the heart rhythms can be read, usually the chest area. Not too long ago, my class experimented with EKG's. I put 3 small electrodes on my arms. one on each wrist and another on my upper right arm. The placement of the electrodes resulted in how the graph looked on the computer I was monitoring on. If I switched two of the electrodes' places, the graph looked different.  For example, when I switched the places of the electrodes on my left wrist and right upper arm, the graph produced on the computer was the inverse of when they were in the normal positions. On the graph, my heart rhythms looked somewhat like this:

On this EKG graph, the P wave represents the depolarization of both atria. From the P wave to the Q wave, which may not always be present in a normal EKG, is the PR interval, the time from atrial depolarization to the start of ventricular depolarization. The Q waves are the first downward deflections before the R waves, the first upward deflections. After the S waves represent the time left for ventricular depolarization. The QRS complex is the electrical wave that signals the depolarizations of myocardial cells of the ventricles. The T wave represents the re-polarization of the ventricles. The ST segment is a period of diastole from the end of systole to re-polarization in the ventricles.

Getting this data from the EKG sensor was much easier than understanding just what it all meant. 

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Leech Neurophysiology Lab

Purpose- To record electrical activities of individual neurons while you deliver mechanical stimulus to the attached skin. Inject florescent dyes into the neurons to visualize their morphology.

Hypothesis- Each of the areas of the neurons are specialized to each do a different specific job.

Materials- Leech tank, dissection tray, 20% ethanol, dissecting microscope, oscilloscope, micromanipulator, scalpel, probe, forceps, scissors, dissection pins, leech tongs.

Procedure-

Anesthetize the leech with 20% ethanol and cut into it using the scissors.

Use forceps to pull skin flaps open and pin down with the dissection pins.

Remove leech innards with the probe and observe ganglion

Cut out the ganglion window using scissors

Isolate one ganglion

Cut the ganglion sinus using the scalpel

Probed and identified ganglion sensory cells using the forceps to pull the skin open and the pins to keep it open.

Observe cells under dissecting microscope, using the micromanipulator to inject dye into different areas of the neuron and put under UV light to identify the different cell types. Also, use different stimuli such as a feather or forceps to see if there is a reaction of action potential in the cell that is being probed.

Results- Each of the sensory cells examined in different areas of the ganglion had different shapes with different functions. Different stimuli produced different types of responses. The atlas used helped to identify which type of cell responded to which type of stimuli in which way.

Conclusions- Different cells in the neuron have different functions based on their structure and location. Also, the different stimuli (the feather, probe and forceps) made the different types of cells respond in different ways. The different types of cells and their locations were easily identified using the different stimuli used in combination with indication from the atlas below: