Electrocardiography (ECG)

During lecture, we learned about electrocardiograms.  My first job in the medical field was an EKG technician.  I was only 19 and worked in the EKG department at Hudson Valley Medical Center in NY.  

 I enjoyed reviewing what EKG's can measure and what the waves represent.  It is always good to refresh your memory so when patients ask you why you are performing the test and what problems can be be assessed from the test, we will have good and clear informative explanations. 

An electrocardiogram is simply a recording of the electrical activity of your heart.  By interpreting an ECG tracing, your doctor can diagnose several abnormal conditions that can affect your heart.  Some of these conditions include: rhythm disturbances, a heart attack, or other abnormalities of the heart's structure.  Two rhythm abnormalities include: tachycardia, which is an elevated resting heart rate and bradycardia, which is a resting heart rate under 50 beats a minute.  Adult heart rates are normally about 75 beats per minute.  

Transmission of action potentials through the conduction system generates electric currents that can be detected by electrodes placed on the body's surface.  The ECG is a composite of all the action potentials, graphed as a series of up and down waves, produced by cardiac muscle fibers during each heartbeat.  The electrocardiograph amplifies the heart's electrical signals and produces 12 different tracings from different combinations of limb and chest leads.

It has been about 9 years since I got certified as an EKG technician.  I am now a Medical Assistant and I perform EKG's everyday at work. I realized in class that I had forgotten what parts of the wave represents.  I learned that the P wave, is a small upward deflection on the ECG. It represents atrial depolarization.  A fraction of a second after the P wave begins, the atria contract.  The second wave, called the QRS complex, begins as a downward deflection.  The QRS complex represents the onset of ventricular depolarization as the cardiac action potential spreads through ventricular contractile fibers.  Shortly after the QRS complex begins, the ventricles start to contract.  The third wave is a dome shaped upward deflection called the T wave.  It indicates ventricular repolarization and occurs just before the ventricles start to relax.  Repolarization (relaxation) of the atria is not usually evident in an ECG because it is masked by the larger QRS complex.

The simplest piece of information the ECG can provide is the rate of your heartbeat at the time you had this test.  If 10 QRS complexes are recorded on the ECG paper or monitor in 10 seconds, then your heart rate is 60 beats per minute.  The ECG can distinguish normal sinus rhythm from all types of tachycardia and bradycardia rhythms. 

The ECG can also tell a physician if a heart attack has happened in the past.  An elevated portion between the QRS complex and the T wave will show a strong indication that heart muscle injury, such as a heart attack, is occurring.  If there is a deep early portion of the QRS complex, this may be evidence that a heart attack may have happened in the past.

Even if your not a doctor, I feel it is important to know how to look for this if you are the person performing the EKG.  When I was only 19 and doing one of the morning rounds of EKG's for patients staying in the hospital, I noticed that there was a large rounded portion after the QRS wave. The patient was an elderly man and was sleeping.  Instead of bringing the EKG down to my department to be viewed later by the cardiologist that comes in the afternoon, I brought it to one of the physicians on the floors.  Indeed the patient was having a heart attack.  I was thankful that I trusted my gut, to show it to someone and was thankful that I had learned what to look for in an EKG.

Arterial thrombosis and embolism

Just as in the coronary arteries, blood clots can develop at other atherosclerotic sites.  They can rapidly block a vessel (thrombosis) or break into fragments and block branches of vessels farther downstream ( embolism).  This results in a sudden cessation of blood flow to the areas supplied by the artery and branches.  With a sudden blockage, there is no time for collateral arteries to develop.  The body can't compensate for this blood flow reduction.

After learning this, I wanted to know what can cause clotting in an unbroken blood vessel.  I learned that the endothelial surfaces of a blood vessel may be roughened as a result of atherosclerosis. Atherosclerosis is the accumulation of fatty substances on arterial walls.  This condition can induce the adhesion of platelets.  Clots may also form in blood vessels when blood flows too slowly, allowing clotting factors to accumulate in high enough concentrations to initiate a clot.

Clotting in an unbroken blood vessel is called thrombosis.  The clot itself is called a thrombus.  If it remains intact, the thrombus may become dislodged and be swept away in the blood.  This can lead to an embolism.  An embolus is a blood clot, bubble of air, fat from a broken bone, or even a piece of debris transported in the bloodstream.  An embolus that breaks away from an arterial wall may lodge in a smaller diameter artery downstream. If it blocks blood flow to the brain, kidney, or heart, the embolism can cause a stroke, kidney failure or even a heart attack.

I work as a Medical Assistant for family medicine.  Just recently, I had to set up a patient for a CT scan to rule out whether or not the patient had a pulmonary embolism.  His symptoms were shortness of breath and coughing that did not go away after various treatments. He also had an elevated D-Dimer level.  Luckily, the test was negative.  After taking care of this patient, and learning about clots and embolisms in class, I wanted to learn more about medications and treatments that can be used in case I know someone who does have one.

Through research, I learned that thrombolytic medication that dissolves the clot may be given through a catheter directly to the affected area.  If you've had arterial thrombosis or embolism or are at risk of their development, you'll receive blood thinners (anticoagulants) to reduce the likelihood of blood clotting and future problems.  I also learned that there are surgical treatments available.  A surgeon can remove a clot in an artery by making a small opening upstream from the blockage and passing a balloon-tipped catheter past the blood clot.  Once the balloon is downstream from the blood clot, the doctor inflates it and pulls the catheter back to the opening in the artery.  The balloon pulls the blood clot upstream where it can be removed.  Occasionally, it's necessary to replace or bypass the blocked vessel.

I found this very interesting.  I have many patients at my office who are on coumadin which is a type of anticoagulant.  It is nice to know that there are also some surgical options to help remove a clot once it has been formed and then to have medications to take afterwards to help prevent this from happening again.

ANS review for quiz 4/ lecture 3/11/09

The sympathetic and parasympathetic motor pathways consist of two motor neurons in series, one following the other. The first autonomic motor neuron has its cell body in the CNS while its myelinated axon extends from the CNS to an autonomic ganglion which is a collection of neuronal cell bodies outside the CNS. It is here that the autonomic ganglion contains the cell body of the 2nd autonomic motor neuron. It has an unmyelinated axon that extends directly from the ganglion to the effector(smooth muscle, cardiac muscle, or a gland).

Rami Communicans are the term used for a nerve which connects two other nerves. They are also bundles of nerve fibers connecting a sympathetic ganglion to a spinal nerve; categorized as gray rami(unmyelinated postganglionic fibers) or white rami (myelinated preganglionic fibers).

There are two groups of sympathetic ganglia. Group 1 are called: sympathetic trunk ganglia which are located near the spinal cord. Most sympathetic preganglionic axons are short. Post ganglionic axons from sympathetic trunk ganglia mostly innervate organs above the diaphragm. Group 2 are called: prevertebral ganglia. They are located anterior to the vertebrate column. Postganglionic axons innervate organs below the diaphragm. There are 3 types. These include: Celiac ganglion, superior mesenteric ganglion, inferior mesenteric ganglion.

I also learned about cholinergic neurons and receptors. Cholinergic neurons release ACH. ACH is stored in synaptic vesicles and released by exocytosis. It then diffuses across the synaptic cleft and binds with specific cholinergic receptors. There are two types called: nicotinic and muscarinic receptors. Activation of nicotinic receptors by ACH causes depolarization, thus causing excitation. Muscarinic receptors sometimes cause depolarization(excitation) or hyperpolarization (inhibition) depending on the cell.

Adrenergic neurons and receptors release norepinephrine also known as noradrenalin This is also stored in synaptic vesicles and released by exocytosis. NE diffuses across the cleft and binds to specific adrenergic receptors. There are two types of adrenergic receptors. They are Alpha and Beta.

Prior to lecture, I knew a lot about ACH from A&P I. I did not know a lot about Norepinephrine. I decided to look it up after class to learn more than what the book states. Norepinephrine is both a hormone and a neurotransmitter. As a hormone, it is secreted by the adrenal gland. It works alongside epinephrine to given the body sudden energy in times of stress, known as the "Fight or flight" response. It is a stress hormone that affects the part of the brain where attention and responding actions are controlled.

Thyroid Gland

While reviewing the Endocrine System, I was eager to learn as much as I could about the thyroid gland. This is due to the fact that a few months ago I was diagnosed with hypothyroidism.  During a routine check up, I mentioned how tired I was feeling . I was coming home from work and school with the desire to do more activities but the energy was not there to let me. I also was not sleeping well for about 2 weeks.  I do work 10 hour days and go to school and just related my symptoms to stress.  I also noticed that I had a harder time losing weight. At first I blamed it on moving to a colder climate and not being as active as I was when I lived in Florida.  My Doctor decided to check my thyroid just in case. He ran a TSH level.  The level came back high which meant that I had hypothyroidism.  He started me on a medication called Synthroid. I am taking 25 mg daily.  I have been feeling a little better but I am not good at taking medicine and I quite often forget to take my medicine when I am suppose to.

To understand why my thyroid gland could be the cause to some of my above symptoms, I needed to understand what thyroid hormones stimulate.  I learned that thyroid hormones stimulate protein synthesis and increase the use of glucose and fatty acids for ATP production.  They also increase the breakdown of triglycerides and enhance cholesterol excretion, thus reducing blood cholesterol level.

I also learned that if you are hyperthyroidism, that your thyroid is said to be hyperactive. Hyperthyroidism is a condition in which there is overproduction of the thyroid hormone thyroxine, causing the levels of thyroid hormones in the blood to be too high.  Hyperthyroidism can significantly accelerate your body's metabolism, causing sudden weight loss, rapid or irregular heartbeat, sweating, and nervousness, or irritability.

During lecture, Hasi-Moto Disease was mentioned.  I have never heard of this disease prior to lecture but it is related to hypothyroidism.  Our instruction told us the symptoms of it was increase weight in the face.  She also said, the disease made a persons face appear very round.  Since I have hypothyroidism, I wanted to know more about this. I actually went home and looked it up online after class.  It is also known as chronic lymphocytic thyroiditis. I learned that it is an auto immune disease that attacks your thyroid gland.  The resulting inflammation often leads to an underactive thyroid gland (hypothyroidism).

Sympathetic and Parasympathetic responses

Sympathetic Responses are also known as the "fight-or-flight" response. This response is important in emergencies that casue stress that require us to either fight or run away.
During activation of the sympathetic division, the release of hormones by the adrenal medullae create a set of responses. These responses include:
-Dilation of the pupils
- Increase in heart rate, force of heart contraction and blood pressure
- The airways dilate, allowing faster movement of air into and out of the lungs
-Blood vessels that supply kidneys and gastrointestinal tract constrict
-Blood vessels that supply organs involved in exercise or fighting off danger
-skeletal muscle, cardiac muscle, liver, and adipose tissue dilate, allowing greater blood flow through these tissues.
-The liver increases breakdown of glycogen to glucose and adipose tissue. This increases the breakdown of triglycerides to fatty acids and glycerol which raises blood levels of these molecules for greater ATP production.
-Release of glucose by the liver increases blood glucose level for greater ATP production
-Processes that are not essential for meeting the stressful situation are inhibited.


In regards to this last effect. I learned that some functions turn off or even stop during the fight or flight response. An example that I learned is that your digestive secretions may actually slow down. I guess if your about to get robbed and you want to turn around and run away as fast as you can, your body may be trying more to keep up with your faster breathing and faster body movements to get you away from the dangerous scene. I never really thought about this before but after reading and learning about it, it makes sense. It's pretty interesting how our body works and responds to our experiences and to our internal and external environment.

I also learned that the parasympathetic division is also referred to as the rest-and-digest division. This is important is non emergency situations. It enhances the rest and digest activities. This means that the parasympathetic responses support body functions that conserve and restore body energy during times of rest and recovery. There are five parasympathetic responses that are stimulated by this division. These include: salivation, lacrimation, urination, digestion, and defecation. These five responses increase when activated. There are also three more responses that have a decrease effect. During this division, there is a decrease in heart rate, diameter of airways known as bronchoconstriction, and a decrease in diameter of the pupils known as constriction.

A good way for me to remember when these responses come in to play is to put it into my real life experiences. When I thought about what would happen if I came home and ran into a robber, or if I was startled by one, this would be the type of situation where my sympathetic nervous system would be called into action. This system would use energy, increase my blood pressure, increase my heart rate and slow down my digestion. It would also help my run as fast as I can out of there!

Now imagine if my day was much different than this. If it was a beautiful sunny day and things were pleasant at work and I got home early and decided to sit down and relax on the couch, my parasympathetic nervous system would kick in. With my body now relaxing, it would also be time for my blood pressure to decrease, my heart rate to slow down and my digestion can start.

These responses remind me just how much our insides are effected by whats going on, on the outside or in our daily lives. It got me thinking how things like stress effect us internally and trigger responses. I think being aware of how much control we actually have over our health can help us improve the quality of our daily living.

From Lecture 2/11/09 12 cranial nerves

During Lecture, we learned more on the 12 cranial nerves and their function. Cranial nerve I. is the olfactory never. It is a sensory nerve and it functions to conduct nerve impulses for the sense of smell sending afferents to the olfactory bulb. Cranial nerve II is the optic nerve. It is a sensory nerve and its specific function is sending visual afferents from the eye to the brain.  Crania nerve III is the Oculomotor. It is a mixed nerve. This means is has both sensory and motor neurons. A function for this nerve is eye movement up, down and medial. It also helps with lens accommodation and pupil constriction.  Cranial nerve IV is called Trochlear. It is also a mixed nerve. It helps with eye movements down and lateral and has afferents from muscle receptors. Cranial nerve V is called Trigeminal. It is a mixed nerve. One function is to help with chewing.  Cranial nerve VI is called Abducens with is a motor nerve and it helps with lateral eye movements.  Cranial nerve VII is called Facial. It is a mixed nerve. One function is to stimulate salivary and tear glands. Cranial nerve VIII is called Vestibulocochlear. Is is a sensory nerve and its specific function is hearing and balance. Cranial nerve IX is called Glossopharyngeal. It is a mixed nerve. It also helps stimulate salivary glands. Help functions is swallowing muscles in the pharynx. Also taste from posterior 1/3 of tongue and blood pressure receptors.  Cranial nerve X is called vagus and is also a mixed nerve. Function/controls soft palate, pharynx, heart and digestive organs. Sensation from ear canal, diaphragm, abdominal and chest vesceral organs. Cranial nerve XI is called Accessor and is a motor nerve and helps control muscles of palate, pharynx, larynx, and some neck and shoulder muscles. The last of the 12 cranial nerves is Cranial XII, also known as Hypoglossal. It is a motor nerve and helps with tongue movement.

After learning about the nerves that help with eye movements, I began wondering why some people have one eye that is weaker/slower than the other.  I have worn glasses for quite a few years. One of the things my eye Doctor told me was that my left eye is weaker than the other and if I stare at something and look from left to right, the left eye takes a second to catch up.

I did some research on weak eye muscles in one eye. While looking at different website, I came across a term I haven't heard before. It is called: Amblyopia.  It is another name for Lazy eye. It occurs when one eye develops differently than the other eye. As a result one eye is weaker than the other. Sometimes a difference in focusing ability causes one eye to be used more often. Other times, misalignment of the eyes causes one of the eyes to shut off to avoid double vision. Regardless of the cause, the result is a weakened, or amblyopic, eye.

From lecture 2/4/09: Thalamus and Hypothalamus

During Lecture and studying at home for our upcoming test, I learned the functions of the thalamus and hypothalamus.  

The thalamus relays almost all the sensory input to the cerebral cortex. It provides crude perception of touch, pressure, pain and temperature. The thalamus also includes nuclei involved in movement, planning and control.

The Hypothalamus controls and integrates activities of the autonomic nervous system and pituitary gland. It also regulates emotional and behavioral patterns and circadian rhythms of daily living.  It also controls body temperature, regulates eating and drinking, helps maintain the waking state and establishing patterns of sleep. The Hypothalamus also produces the hormones oxytocin and antidiuretic hormone.

While learning about the hypothalamus, I also Learned that it is part of our Limbic system.  Our Limbic system is sometimes referred to as , "the emotional brain". It plays a primary role in a range of emotions, including pain, pleasure, docility, affection and anger.

If the hypothalamus/limbic controls our emotions, behavior and memory, I wonder what makes some people more emotional then others.  I was interested to learn that the amygdala which is one of the basal nuclei of the cerebrum, produces a behavioral pattern called rage. It is thought to be the negative aspect of our emotions. It was then discussed in class that there have been thoughts of removing this part of the brain to see how it affects criminals, people in jail, etc.   I wanted to know more about this idea and if anyone has ever tried it. I decided to do some research.  In the Handbook of Psychological Approaches by Bincent B. Van Hasselt and Michel Hersen, I learned that the most common symptoms of amygdala removal include placidity and an absence of fear, rage, aggression, hypersexuality, hyperorality and social initiation. Based on these observations, amygdalectomy, or surgical removal of the amygdala, has been performed in over 500 cases across several countries for the treatment of violent criminals. This surgery has been demonstrated to be adequately effective in reducing aggressive behavior, with a success rate of 75 to 85%. This surgery in not favored in the United States as of now. 

After reading this, I wondered what damage to the Hypothalamus would cause. Weight regulation, and sugar and fat metabolism are related to the hypothalamic processes. Disruption in the functioning of, or destruction in this area causes an imbalance in drive states resulting in such symptoms as anorexia. Under the same article of Psychological approaches, I learned that the hypothalamus may play a role in eating disorders.  This interested me because I had a friend back in high school who had an eating disorder.  Some people thought it was due to stress and negatives in her life. I now wonder if any of her symptoms were a results of damage to her hypothalamus or Limbic system.