ARTERIOSCLEROSIS

INTRODUCTION: Arteriosclerosis, or “hardening of the arteries,” is the most common disease of the arteries. It is a diffuse process whereby the muscle fibers and the endothelial lining of the walls of small arteries and arterioles become thickened. Atherosclerosis primarily affects the intima of the large and medium-sized arteries, causing changes that include the accumulation of lipids also known as atheromas, calcium, blood components, carbohydrates, and fibrous tissue on the intimal layer of the artery. Lipids: Carbohydrates: Calcium  Although the pathologic processes of arteriosclerosis and atherosclerosis differ, rarely does one occur without the other, and the terms often are used interchangeably. The most common direct results of atherosclerosis in the arteries include narrowing (stenosis) of the lumen and obstruction by thrombosis, aneurysm, ulceration, and rupture; ischemia and necrosis occur if the supply of blood, nutrients, and oxygen is severely and permanently disrupted. Atherosclerosis can develop anywhere in the body but is most common in bifurcation or branch areas of blood vessels. Atherosclerotic lesions are of two types: fatty streaks which is composed of lipids and elongated smooth muscle cells, and fibrous plaques which are predominantly found in the abdominal aorta and coronary, popliteal, and internal carotid arteries.

RISK FACTORS: Many risk factors are associated with atherosclerosis; the greater the number of risk factors, the greater the likelihood of developing the disease. The use of tobacco products is the strongest risk factor. High fat intake is also a suspected risk factor, along with high serum cholesterol and blood lipid levels. Others include; Hypertension:  Diabetes, Obesity, stress, and lack of exercise continues to be among the contributing factors.

Clinical Manifestations: Clinical features depend on the tissue or organ affected: in case the heart is involved, expect angina and Myocardial infaction (MI) due to coronary atherosclerosis. In case the brain is involved, expect transient ischemic attacks and stroke due to cerebrovascular disease, Cerebral vascularaccident peripheral vessels (includes hypertension and symptoms of aneurysm of the aorta, renovascular disease, atherosclerotic lesions of the extremities).

Management: The management of atherosclerosis involves modification of risk factors, a controlled exercise program to improve circulation and its functioning capacity, medication therapy, and interventional or surgical graft procedures (inflow or outflow procedures). Several radiologic techniques are important adjunctive therapies to surgical procedures. They include arteriography, percutaneous transluminal angioplasty, and stents and stent grafts.

RELATED;

1.  HEART FAILURE

REFERENCES

EPINEPHRINE (ADRENALIN)

Therapeutic Class: Drug for anaphylaxis and shock

Pharmacologic Class: Nonselective adrenergic agonist; vasopressor

ACTIONS AND USES: Subcutaneous or IV epinephrine is a preferred drug for anaphylaxis because it can reverse many of the distressing symptoms within minutes. Epinephrine is a nonselective adrenergic agonist, stimulating both alpha- and beta-adrenergic receptors. Almost immediately after injection, BP rises due to stimulation of alpha1 receptors. Activation of beta2 receptors in the bronchi opens the airways and relieves the patient's shortness of breath. Cardiac output increases due to stimulation of beta1 receptors in the heart. In addition to the subcutaneous and IM routes, topical, inhalation, and ophthalmic preparations are available. The intracardiac route is used for cardiopulmonary resuscitation under extreme conditions, usually during open cardiac massage, or when no other route is possible.

ADMINISTRATION ALERTS: Parenteral epinephrine is an irritant that may cause tissue damage if extravasation occurs. It is Pregnancy category C.

ADVERSE EFFECTS: The most common adverse effects of epinephrine are nervousness, tremors, palpitations, tachycardia, dizziness, headache, and stinging/burning at the site of application.

When administered parenterally, hypertension and dysrhythmias may occur rapidly; therefore, the patient should be monitored carefully following injection.

CONTRAINDICATIONS: In life-threatening conditions such as anaphylaxis, there are no absolute contraindications for the use of epinephrine. The drug must be used with caution, however, in patients with dysrhythmias, cerebrovascular insufficiency, hyperthyroidism, narrow-angle glaucoma, hypertension, or coronary ischemia, because epinephrine may worsen these conditions.

INTERACTIONS: Drug–Drug: Epinephrine may result in hypotension if used with phenothiazines or oxytocin. There may be additive cardiovascular effects with other sympathomimetics. MAO inhibitors, tricyclic antidepressants, and alpha- and beta-adrenergic drugs inhibit the actions of epinephrine. Epinephrine will decrease the effects of beta blockers. Some general anesthetics may sensitize the heart to the effects of epinephrine.

RELATED;

1. BETA BLOCKERS

2. CATECHOLAMINES

3.  PHARMACOLOGY AND THERAPEUTICS

REFERENCES

SIDE EFFECTS Vs ADVERSE EFFECTS OF DRUGS

SIDE EFFECTS Vs ADVERSE EFFECTS OF DRUGS:  In the drug use, we normally experience undesired effects either as a result of drug toxicity to the patient or patient's over responsiveness to the given drug.  But to be sincere, there is no drug that is free from side effects, and actually this is not for drugs alone, but for anything that goes in our bodies, there will always be a way they can disrupt our normal physiology.  This is just because they are taken to be foreign and whatever they are composed of, may not be part of our genetic make-up.  I give an example of food, something that we take in on a daily basis and compulsory.  Take it when you are not compatible with it, you have allergy for it, it is half baked or you just take too much of of it and the next episode will be nausea and subsequent vomiting.  I have already discussed about nausea and vomiting and the conditions that can lead to that unpleasant situation you can read more about it from here.  On the other hand, you may just be allergic to such foods or have deficiency in some biochemical components necessary for digestion and absorption of such foods as it is the case for lactose intolerant individuals.

But for the drugs because we take them with a purpose, it would be assumed that they are 100% free from side effects.  This is not possible even with the finest new drugs developed as they are foreign to the human body.  So, with any drug compound taken, expect some sort of problems or disturbances that come along with the drug and in most cases these are documented and we collectively call them side effects.

EMERGENCE OF SIDE EFFECTS:  Side effects occur due to three main instances in the human body as described below;

1.  Side effects of drugs occur when there is a drug interaction with the receptors else where in the body other than the intended site.  This is especially true if the intended system shares some common characteristics and or receptors with other systems.  I have already talked about drug receptors in one on my previous discussions you can read about them here.  One example of such instance is the adrenergic receptors that are located both in the cardiovascular system and in the respiratory system.  In that respect, adrenergic antagonists administered for respiratory purposes may end up causing cardiovascular disruptions as detailed in the discussion  here.

2.  The other emergence of side effects is concerned with more than the recommended drug dosage.  Though this tends to be more health worker centered, it can as well be patient related in most cases.  We all know the drugs have a predetermined dosage that should be administered to the patient per Kg body weight in a specified time interval.  For some drugs however, there is no fixed dosage for a given disease and the clinician may decide to give a little bit more than the documented initial dosage, basing on the severity of the patient's condition.  This is where the concept of therapeutics window/index comes into play.  I have already discussed about therapeutic window and drug use in my previous discussions and you can read about it from here.

ADVERSE EFFECTS....................

RELATED;

1.  DRUG RECEPTORS

2.  NAUSEA AND VOMITING

3.  ADRENERGIC ANTAGONISTS

4.  THERAPEUTIC INDEX/WINDOW

5.  LACTOSE INTOLERANCE

REFERENCES

THE CARDIAC CYCLE AND HEART SOUNDS

INTRODUCTION: The cardiac cycle is the sequence of events in one heartbeat. In its simplest form, the cardiac cycle is the simultaneous contraction of the two atria, followed a fraction of a second later by the simultaneous contraction of the two ventricles. Systole is another term for contraction. The term for relaxation is diastole. You are probably familiar with these terms as they apply to blood pressure readings. If we apply them to the cardiac cycle, we can say that atrial systole is followed by ventricular systole. There is, however, a significant difference between the movement of blood from the atria to the ventricles and the movement of blood from the ventricles to the arteries.

THE SEQUENCE OF BLOOD FLOW: Blood is constantly flowing from the veins into both atria. As more blood accumulates, its pressure forces open the right and left AV valves. Two-thirds of the atrial blood flows passively into the ventricles; the atria then contract to pump the remaining blood into the ventricles. Following their contraction, the atria relax and the ventricles begin to contract. Ventricular contraction forces blood against the flaps of the right and left AV valves and closes them; the force of blood also opens the aortic and pulmonary semilunar valves. As the ventricles continue to contract, they pump blood into the arteries. The ventricles then relax, and at the same time blood continues to flow into the atria, and the cycle begins again.

CHARACTERISTICS OF THE BLOOD FLOW: The important distinction here is that most blood flows passively from atria to ventricles, but all blood to the arteries is actively pumped by the ventricles. For this reason, the proper functioning of the ventricles is much more crucial to survival than is atrial functioning. The cardiac cycle is this precise sequence of events that keeps blood moving from the veins, through the heart, and into the arteries. The cardiac cycle also creates the heart sounds: Each heartbeat produces two sounds, often called lubdup, that can be heard with a stethoscope. The first sound, the loudest and longest, is caused by ventricular systole closing the AV valves. The second sound is caused by the closure of the aortic and pulmonary semilunar valves. If any of the valves do not close properly, an extra sound called a heart murmur may be heard.

RELATED;

1.  CHAMBERS AND CIRCULATION THROUGH THE HEART

2.  ANATOMY AND PHYSIOLOGY

REFERENCES

RIBONUCLEIC ACID (RNA)

 

Objectives of the discussion:  By the end of our discussion here, the reader/medical student will be able to;

1.  Explain the difference between DNA and RNA

2.  Clearly describe the sequential transfer of information from DNA to RNA to proteins

3.  Outline the different types of RNA

Introduction:  Ribonucleic acid (RNA) is also a polymer of purine and pyrimidine nucleotides linked by phosphodiester bonds.  RNA differs from DNA in a number of ways.  First, in here in RNA the nucleotide sugar base is Ribose while in DNA the sugar is  Deoxyribose.  Secondly, RNA is always a single stranded molecule and shorter than DNA, where as DNA is double stranded and extremely long molecule.  About 50% of cellular RNA is distributed in the ribosomes and endoplasmic reticulum; 25% in cytoplasm; 15% in mitochondria and the rest 10% in nucleus.  Cellular RNAs are of 5 types varieties. They are very stable. Small Nuclear RNAs (SnRNAs) are a subgroup of small RNA.  Some important species of SnRNAs are U1 (165 nucleotides), U2 (188 nucleotides), U3 (216), U4 (139), U5 (118), U6 (106).  They are involved in mRNA splicing that is to say Micro-RNA (miRNA). They alter the function of mRNA. They are moderately stable.

Central Dogma of Molecular Biology:  The information available in the DNA is passed to messenger RNA, which is then used for synthesis of a particular protein.  In this process, we find Replication, Transcription and Translation.  DNA replication is like printing a copy of all the pages of a book. The replication process occurs only at the time of cell division.  But transcription is taking place all the time. Only certain areas of the DNA are copied (selected regions on the sense strand). This is like taking a copy of particular page of the book.  So, the genetic information of DNA is transcribed (copied) to the messenger RNA (mRNA). During transcription, the message from the DNA is copied in the language of nucleotides (4 letter language).  The mRNA then reaches the cytoplasm where it is translated into functional proteins.  During translation, the nucleotide sequence is translated to the language of amino acid sequence (20 letter language).

RELATED;

1.  NUCLEOTIDES

2.  DNA THE GENETIC MATERIAL

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