HEART OR PULSE RATE

 

INTRODUCTION: A healthy adult has a resting heart rate or pulse of 60 to 80 beats per minute, which is the rate of depolarization of the SA node. It should be noted that, the SA node actually has a slightly faster rate, closer to 100 beats per minute, but is slowed by parasympathetic nerve impulses to what we consider a normal resting rate.

PARAMETERS OF HEART RATE: A rate less than 60, except for athletes, is called bradycardia; a prolonged or consistent rate greater than 100 beats per minute is called tachycardia. A child’s normal heart rate may be as high as 100 beats per minute, that of an infant as high as 120, and that of a near-term fetus as high as 140 beats per minute. These higher rates are not related to age, but rather to size: the smaller the individual, the higher the metabolic rate and the faster the heart rate.

INTERPRETATION OF PULSE RATE: A pulse is the heartbeat that is felt at an arterial site. What is felt is not actually the force exerted by the blood, but the force of ventricular contraction transmitted through the walls of the arteries. This is why pulses are not felt in veins; they are too far from the heart for the force to be detectable. The most commonly used pulse sites are:

Radial; the radial artery on the thumb side of the wrist.

Carotid; the carotid artery lateral to the larynx in the neck.

Temporal; the temporal artery just in front of the ear.

Femoral; the femoral artery at the top of the thigh.

Popliteal; the popliteal artery at the back of the knee.

Dorsalis pedis; the dorsalis pedis artery on the top of the foot, commonly called the pedal pulse.

Pulse rate is, of course, the heart rate. However, if the heart is beating weakly, a radial pulse may be lower than an apical pulse. This is called a pulse deficit and indicates heart disease of some kind.

CONCLUSION: When taking a pulse, the careful observer also notes the rhythm and force of the pulse. Abnormal rhythms may reflect cardiac arrhythmias, and the force of the pulse (strong or weak) is helpful in assessing the general condition of the heart and arteries.

RELATED;

1.  CARDIAC OUTPUT

2. HEART MURMURS

3.  HEART FAILURE

REERENCES

ACIDITY AND ALKALINITY OF BODY SYSTEMS

 

INTRODUCTION: Acidosis also known as excess acid and alkalosis known as excess base in the human body, are not diseases but are symptoms of an underlying disorder. Acidic and basic agents may be administered to rapidly correct pH imbalances in body fluids, supporting the patient’s vital functions while the underlying disease is being treated. The degree of acidity or alkalinity of a solution is measured by its pH and a pH of 7.0 is defined as neutral, above 7.0 as basic or alkaline, and below 7.0 as acidic.

THE HUMAN BODY HOMEOSTASIS: To maintain homeostasis, the pH of plasma and most body fluids must be kept within the narrow range of 7.35 to 7.45. Nearly all proteins and enzymes in the body function optimally within this narrow range of pH values. A few enzymes, most notably those in the digestive tract, require pH values outside the 7.35 to 7.45 range to function properly. The body generates significant amounts of acid during normal metabolic processes. Without sophisticated means of neutralizing these metabolic acids, the overall pH of body fluids would quickly fall below the normal range. Buffers are chemicals that help maintain normal body pH by neutralizing strong acids and bases.

BODY BUFFERS: The two primary buffers in the body are bicarbonate ions and phosphate ions. The body uses two mechanisms to remove acid. The carbon dioxide (CO2) produced during body metabolism is an acid efficiently removed by the lungs during exhalation. The kidneys remove excess acid in the form of hydrogen ion (H⁺) by excreting it in the urine. If retained in the body, CO2 and/or H⁺ would lower body pH. Thus, the lung and the kidneys collaborate in the removal of acids to maintain normal acid–base balance.

PHARMACOTHERAPY OF ACIDOSIS: Acidosis occurs when the pH of the plasma falls below 7.35, which is confirmed by measuring arterial pH, partial pressure of carbon dioxide (PCO2 ), and plasma bicarbonate levels. In that case, diagnosis must differentiate between respiratory etiology and metabolic or renal etiology. It should be noted that, occasionally the cause has mixed respiratory and metabolic components. The most profound symptoms of acidosis affect the central nervous system (CNS) and include lethargy, confusion, and CNS depression leading to coma. A deep, rapid respiration rate indicates an attempt by the lungs to rid the body of excess acid. In patients with acidosis, the therapeutic goal is to quickly reverse the level of acids in the blood. The preferred treatment for acute acidosis is to administer infusions of sodium bicarbonate. Bicarbonate ion acts as a base to quickly neutralize acids in the blood and other body fluids. The patient must be carefully monitored during infusions because this drug can overcorrect the acidosis, causing blood pH to turn alkaline. Sodium citrate, sodium lactate, and sodium acetate are alternative alkaline agents sometimes used in place of bicarbonate.

RELATED;

1. ACID, BASES AND BODY BUFFERS

2. BODY FLUIDS

3. ANATOMY AND PHYSIOLOGY

REFERENCES

HEPATIC PORTAL CIRCULATION

 

OBJECTIVES OF THE TOPIC:  By the end of this discussion, a medical student will be able to;

1.  Outline the blood vessels that supply and drain the liver.

2.  Describe the importance of blood shunting through the liver from the GIT.

3.  Give examples of molecules moderated by the liver enzyme system.

NEW TERMS

1.  Portal vein:  This is a blood vessel that is shared between two organs in a series connection.  This scenario occurs majorly in two instances in the human body; between the intestines and the liver, and between the hypothalamus and pituitary gland.

INTRODUCTION: Hepatic portal circulation is a subdivision of systemic circulation in which blood from the abdominal digestive organs and spleen circulates through the liver before returning to the heart.  This is to ensure that all contents of the digestion from the intestines pass through the liver for regulation and modulation.

FORMATION OF THE PORTAL VEIN: Blood from the capillaries of the stomach, small intestine, colon, pancreas, and spleen flows into two large veins, the superior mesenteric vein and the splenic vein, which unite to form the portal vein. The portal vein takes blood into the liver, where it branches extensively and empties blood into the sinusoids, the capillaries of the liver.

BLOOD FLOW IN THE PORTAL VEIN: From the sinusoids, blood flows into hepatic veins, to the inferior vena cava and back to the right atrium. In this pathway, there are two sets of capillaries, and it is in capillaries that exchanges take place.

IMPORTANCES OF THE PORTAL CIRCULATION: Example 1: Glucose from carbohydrate digestion is absorbed into the capillaries of the small intestine; after a big meal this may greatly increase the blood glucose level. If this blood were to go directly back to the heart and then circulate through the kidneys, some of the glucose might be lost in urine. However, blood from the small intestine passes first through the liver sinusoids, and the liver cells remove the excess glucose and store it as glycogen. The blood that returns to the heart will then have a blood glucose level in the normal range.

Example 2: Alcohol is absorbed into the capillaries of the stomach. If it were to circulate directly throughout the body, the alcohol would rapidly impair the functioning of the brain. Portal circulation, however, takes blood from the stomach to the liver, the organ that can detoxify the alcohol and prevent its detrimental effects on the brain. Of course, if alcohol consumption continues, the blood alcohol level rises faster than the liver’s capacity to detoxify, and the well known signs of alcohol intoxication appear.

In summery: The portal circulation pathway enables the liver to modify the blood from the digestive organs and spleen. Some nutrients may be stored or changed, bilirubin from the spleen is excreted into bile, and potential poisons are detoxified before the blood returns to the heart and the rest of the body.

RELATED;

1.  THE LIVER

2.  FUNCTIONS OF THE LIVER

3.  PITUITARY GLAND

4.  ANATOMY AND PHYSIOLOGY

REFERENCES

THE HUMAN CIRCULATORY CIRCUITS

 

INTRODUCTION: The two major pathways of circulation are pulmonary and systemic. Pulmonary circulation begins at the right ventricle, and systemic circulation begins at the left ventricle. Hepatic portal circulation is a special segment of systemic circulation that will be covered separately. Fetal circulation involves pathways that are present only before birth and will also be discussed separately.

PULMONARY CIRCULATION: The right ventricle pumps blood into the pulmonary artery (or trunk), which divides into the right and left pulmonary arteries, one going to each lung. Within the lungs each artery branches extensively into smaller arteries and arterioles, then to capillaries. The pulmonary capillaries surround the alveoli of the lungs; it is here that exchanges of oxygen and carbon dioxide take place. Gaseous exchange

The capillaries unite to form venules, which merge into veins, and finally into the two pulmonary veins from each lung that return blood to the left atrium. This oxygenated blood will then travel through the systemic circulation. It should be noted that, the pulmonary veins contain oxygenated blood; these are the only veins that carry blood with a high oxygen content. The blood in systemic veins has a low oxygen content; it is systemic arteries that carry oxygenated blood.

SYSTEMIC CIRCULATION: The left ventricle pumps blood into the aorta, the largest artery of the body. The branches of the aorta take blood into arterioles and capillary networks throughout the body. Capillaries merge to form venules and veins. The veins from the lower body take blood to the inferior vena cava; veins from the upper body take blood to the superior vena cava. These two caval veins return blood to the right atrium.

THE AORTA: The aorta is a continuous vessel, but for the sake of precise description it is divided into sections that are named anatomically: ascending aorta, aortic arch, thoracic aorta, and abdominal aorta. The ascending aorta is the first inch that emerges from the top of the left ventricle. The arch of the aorta curves posteriorly over the heart and turns downward. The thoracic aorta continues down through the chest cavity and through the diaphragm. Below the level of the diaphragm, the abdominal aorta continues to the level of the 4th lumbar vertebra, where it divides into the two common iliac arteries. Along its course, the aorta has many branches through which blood travels to specific organs and parts of the body. The ascending aorta has only two branches: the right and left coronary arteries, which supply blood to the myocardium.

RELATED;

1.  CARDIAC FUNCTIONING AND THE HEART SOUNDS

2.  CHAMBERS AND CIRCULATION THROUGH THE HEART

3. ANATOMY AND PHYSIOLOGY

REFERENCES

BLOOD-BRAIN BARRIER

 

INTRODUCTION:  The blood–brain barrier (BBB) is a highly selective permeability barrier that separates the circulating blood from the brain extracellular fluid in the central nervous system (CNS).  The blood–brain barrier is formed by brain endothelial cells, which are connected by tight junctions with an extremely high electrical resistivity.

SELECTIVITY OF THE MEMBRANE:  The blood–brain barrier allows the passage of water, some gases, and lipid soluble molecules by passive diffusion, as well as the selective transport of molecules such as glucose and amino acids that are crucial to neural function.  On the other hand, the blood–brain barrier may prevent the entry of lipophilic, potential neurotoxins by way of an active transport mechanism mediated by P-glycoprotein.

CELLULAR ACTECTURE OF THE BBB:  Astrocytes are necessary to create the blood–brain barrier. A small number of regions in the brain, including the circumventricular organs (CVOs), do not have a blood–brain barrier.  The blood–brain barrier occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation.  Endothelial cells restrict the diffusion of microscopic objects such as bacteria and large or hydrophilic molecules into the cerebrospinal fluid (CSF), while allowing the diffusion of small or hydrophobic molecules including O₂, CO₂, hormones).  Cells of the barrier actively transport metabolic products such as glucose across the barrier with specific proteins. This barrier also includes a thick basement membrane and astrocytic end feet.

RELATED;

1.  IMPULSE PROPAGATION IN THE CNS

2.  METABOLIC PROFILE OF THE BRAIN

3.  ANATOMY AND PHYSIOLOGY

REFERENCES

HEART RATE

 

INTRODUCTION: A healthy adult has a resting heart rate also known as, pulse, of 60 to 80 beats per minute, which is the rate of depolarization of the Sinoartrial node abbreviated as SA node. The SA node actually has a slightly faster rate, closer to 100 beats per minute, but is slowed by parasympathetic nerve impulses to what we consider a normal resting rate. A rate less than 60, except for athletes, is called bradycardia; a prolonged or consistent rate greater than 100 beats per minute is called tachycardia.

FETAL AND INFANTS’ HEART RATE: A child’s normal heart rate may be as high as 100 beats per minute, that of an infant as high as 120, and that of a near-term fetus as high as 140 beats per minute. These higher rates are not related to age, but rather to size: the smaller the individual, the higher the metabolic rate and the faster the heart rate.

RELATED;

1. THE HEART AND CARDIAC FUNCTIONING

2. HEART SOUNDS AND CIRCULATION THROUGH THE HEART

3. BLOOD PRESSURE AND HYPERTENSION

REFERENCES

HUMAN PHYSIOLOGY

HUMAN PHYSIOLOGY:  Physiology is the science that deals with the way human body processes function normally.  As we look at huma body systems, we have parameters that are well known and studied over time.  Such parameters help us know whether the individuals health is normal or deviated from normal something we shall be calling pathophysiology in future.  In our discussion here, we are going to look at some of the divisions of the human body and look at the detailed systems and their expected normal physiological processes.  As we continue to discuss, it is worth remembering that; we have a separate discussion on Human anatomy which you can read through following the link below;  Anatomy of the human body.

1.  THE CENNTRAL NERVOUS SYSTEM

2.  THE CARDIOVASCULAR SYSTEM

3.  THE RESPIRATORY SYSTEM

4.  THE GASTROINTESTINAL SYSTEM

RELATED;

1.  ANATOMY OF THE HUMAN BODY