Biology
/
Regulation of blood pH

Regulation of blood pH

Shiken premium Upgrade Banner

Introduction

Blood pH is a measure of the acidity or alkalinity level of the blood. It is a key factor in homeostasis � the body�s ability to maintain a stable internal environment, which is essential for normal body functioning. The body is able to keep the levels of acidity and alkalinity within a precise range through several interrelated homeostatic mechanisms.

In this guide, we�ll explore the main components of these homeostatic processes, with a particular focus on the chemical buffers that contribute to the regulation of blood pH, the respiratory centre and the kidneys.

Introduction

Blood pH is an important measure of acidity and alkalinity in the body. It is measured on a scale of 0-14, with 7 being neutral. This number indicates the level of hydrogen ions present and how acidic or alkaline its environment is. Blood pH levels must stay between 7.35 and 7.45 in order for the body to function optimally. Homeostatic mechanisms are used to regulate blood pH, and maintain balance.

Overview of the Homeostatic Mechanisms to Regulate Blood pH

Our body has a number of mechanisms to maintain the proper acid-base balance in our blood. This is known as homeostasis and it is an important way our bodies maintain healthy levels of acidity in our blood. The pH level of the blood is an important measure of acidity and should be regulated to remain within a specific range. This regulation is achieved through a number of buffer systems, which are chemical and biological reactions that help keep the pH balanced.

In order to keep the blood in its desired pH range, the body relies on three main processes: the bicarbonate buffer system, respiratory centre, and the kidneys. In addition, the body also utilizes chemical acid/base buffer systems and chemoreceptors to detect any changes in the acid-base balance. Each of these processes play a role in keeping the blood at a healthy pH level.

pH

pH stands for 'potential of Hydrogen'. It is a measure of the acidity and alkalinity of a solution. The pH scale ranges from 1 to 14 - 7 being neutral. A pH below 7 is acidic and above 7 is alkaline (or basic). The pH scale is logarithmic, meaning that each number represents a 10-fold change in acidity/alkalinity, so a pH of 5 is ten times more acidic than a pH of 6.

What is pH?

pH stands for potentiometric hydrogen ion concentration. This is a measure of the amount of hydrogen ions present in a solution, and is expressed on a logarithmic scale. It ranges from 0 to 14, with 0 being the most acidic and 14 being the most alkaline.

A pH of 7 is considered neutral � neither acidic or alkaline. Most natural waters exist at a pH between 6.5 and 8.5. A normal healthy human blood pH should be between 7.35 and 7.45, otherwise known as slightly alkaline.

Blood pH Buffer Systems

Understanding the various mechanisms of pH regulation in the body is key to understanding how to keep blood pH levels stable. One of the major buffer systems is the bicarbonate buffer system, which helps to maintain a balance between acidity and alkalinity in the blood.

The bicarbonate buffer system involves bicarbonate ions (HCO3-) and carbonic acid (H2CO3) that interact with one another to help regulate the acidic and basic components of the body�s fluids. The system works according to Le Ch�telier�s principle which states that when a system is under stress, the reaction will move in the direction which relieves the stress.

When the bicarbonate buffer system is placed under stress, for example a sudden increase in acidity, HCO3- reacts with the extra acid and forms carbonic acid. This is an equilibrium reaction, meaning that the formation of carbonic acid is balanced out by the dissociation of carbonic acid into bicarbonate ions and hydrogen ions. The additional hydrogen ions reduce the acidity of the system, restoring it back to homeostasis.

Bicarbonate Buffer System

The bicarbonate buffer system is one of the main homeostatic mechanisms that help to regulate blood pH. This system consists of carbonic acid (H2CO3) and its conjugate base, bicarbonate (HCO3-). This system helps buffer the body against significant changes to blood pH by releasing hydrogen ions in an acidic environment and releasing bicarbonate into the bloodstream when the environment is too alkaline. The kidneys and lungs play an important role in maintaining the balance of this system.

When the body is exposed to an acid, the hydrogen ions from the acid bind with bicarbonate molecules in the bloodstream, turning them into carbonic acid. It is then removed from the bloodstream via the lungs, where it is exhaled as carbon dioxide (CO2). When the environment is too alkaline, the kidneys remove excess hydrogen ions and release bicarbonate molecules back into the bloodstream. By doing this, the bicarbonate buffer system helps maintain a steady blood pH level.

Le Ch�telier�s Principle

Le Ch�telier�s principle is a fundamental aspect of homeostatic mechanisms. It states that when external conditions affecting a system in equilibrium are changed, the system will adjust itself to re-establish equilibrium or balance. This principle is at the core of how our bodies work to maintain balance and regulate blood pH.

A change to the equilibrium of a chemical reaction can be seen as a shift in either direction; either creating more of the products of the reaction, or more of the reactants. The system will choose the path of least resistance and use whatever resources it has available to counteract the pressure applied. So if we increase the amount of an acid in a system, the body will take action to reduce the resulting acidity. It will do this by utilizing its chemical buffer systems, one of which is the bicarbonate buffer system.

Regulation of Blood pH

The pH of the blood is one of the most important homeostatic mechanisms in the human body and is closely monitored and regulated to remain within a narrow range. The pH of the blood is essential for life as most biochemical processes and cell functioning depend on an optimum pH. This section will discuss the regulation of the blood pH.

Chemical acid/base buffer systems

The primary chemical buffer systems in the body are the bicarbonate-carbonic acid system, the phosphate buffer system, and the protein buffer system. These buffer systems work to maintain the pH of the blood by absorbing any excess acid or alkaline substances. When the pH of the blood begins to move away from the normal range, these buffer systems act to neutralize the substance and restore the balance.

Respiratory Centre

The respiratory centre plays an important role in regulating the blood pH. When the pH of the blood begins to move away from the normal range, the respiratory centre increases or decreases the rate of respiration in order to increase or decrease the amount of carbon dioxide in the blood. In turn, this affects the amount of bicarbonate and hydrogen ions in the blood, thus restoring the balance.

Kidneys

The kidneys play an important role in regulating the blood pH by adjusting the amount of acids and bases in the blood. If the pH of the blood goes below the normal range, the kidneys work to excrete more acids into the urine. Conversely, if the pH of the blood goes above the normal range, the kidneys work to retain more bicarbonate in the blood and excrete less into the urine.

Chemical Acid/Base Buffer Systems

Chemical acid/base buffer systems help maintain blood pH within a normal range. These systems are composed of a weak acid and its conjugate base, which interact to quickly and efficiently adjust the concentration of hydrogen ions when either an acid or a base is present in the blood. The two components of a chemical buffer system are called the �buffer pair� and they work together to keep the blood pH stable.

The pH of a solution is determined by the balance of hydrogen ions (H+) and hydroxide ions (OH-). If the concentration of H+ is higher than the concentration of OH-, then the solution is acidic, and if the concentration of OH- is higher than the concentration of H+, then the solution is alkaline/basic. The aim of a chemical buffer system is to keep the balance between these two ions within a narrow range, thus keeping the pH from changing too drastically.

A common example of a chemical buffer system is the bicarbonate buffer system. This system consists of carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3). When an acid is added, it reacts with sodium bicarbonate to form carbonic acid, while at the same time releasing bicarbonate ion. On the other hand, when a base is added, it will react with carbonic acid, forming sodium bicarbonate and releasing carbonic acid. In this way, the bicarbonate buffer system can maintain the correct balance of H+ and OH- ions in the blood, and prevent the pH from deviating too much from the normal range.

Respiratory Centre

The respiratory centre is located in the brainstem and is responsible for breathing. It's primary role is to ensure that oxygen levels in the blood are balanced and maintained. When the body detects a change in the pH level of the blood, the respiratory centre responds by stimulating deeper, faster breaths to reduce the number of carbon dioxide molecules released. This can effectively reduce the concentration of hydrogen ions and restore the correct pH balance.

The respiratory centre is also able to detect changes in the rate of respiration needed by the body, responding to any short or long term changes in oxygen requirements. The respiratory centre can also adjust the rate of breathing naturally in accordance with a person's age, weight, and state of health.

Regulation of Blood pH by the Kidneys

The kidneys play an important role in regulating our blood pH. The kidneys produce hormones that work with our lungs to control the balance between acid and alkali chemicals (acids and bases) in our body. When the pH level of the blood decreases (becomes more acidic), the kidneys release a hormone called erythropoietin which causes increased breathing rate, leading to higher removal of CO2 from the blood, thus raising the pH of the blood. Conversely, when the pH of the blood increases (becomes more alkali), the kidneys release a hormone called renin which causes decreased breathing rate, leading to lower removal of CO2 from the blood and decreasing the pH of the blood.

The kidneys can also adjust the level of hydrogen ions in the blood by filtering them out and regulating their excretion from the body. This is done through a process called tubular cell replenishment, where the kidneys are able to absorb hydrogen ions from the urine and release them back into the bloodstream. This allows for a more accurate and rapid response to changes in the pH of the blood.

In addition to hydrogen ions, the kidneys are also involved in regulating other components of the acid-base balance such as ammonia, phosphate and bicarbonate buffers. By regulating these components, the kidneys help to maintain a stable pH level in the blood.

Respiratory Regulation of Acid-Base Balance

The lungs play an important role in maintaining the body�s acid-base balance. This balance is regulated by the amount of carbon dioxide (CO2) produced and expelled by the lungs. The production of CO2, which results from the cellular metabolism, increases the acidity of the body and must be offset by an opposite response.

In order to regulate this acidity, the body uses both hypoventilation and hyperventilation to help control the amount of carbon dioxide in the blood. Hypoventilation reduces the amount of CO2 expelled, while hyperventilation increases it. This is made possible by the presence of chemoreceptors, such as the carotid and aortic bodies, located in the neck that monitor the pH level of the blood. Once a change in acid-base balance has been detected, the respiratory center located in the brain sends messages to the body to modify its breathing.

With a deeper understanding of how the lungs are involved in regulating acid-base balance, we can begin to understand the complexity of pH regulation in the body.

CO2 Production

In order to regulate blood pH, our bodies produce carbon dioxide (CO2). This is done by the cells in our body releasing CO2 during the process of respiration. The CO2 is carried in the blood to the lungs where it is exhaled. When too much CO2 accumulates in the bloodstream, it can cause the pH of the blood to become more acidic, leading to an increase in acidity.

The respiratory centre in the brain helps control the amount of CO2 in the blood. When too much CO2 is detected in the blood, the brain sends signals to the muscles to increase the rate and depth of breathing. This process is called hyperventilation, and it helps to remove the excess CO2 from the bloodstream. Conversely, when there is not enough CO2, the brain decreases the rate of respiration, leading to a decrease in the amount of CO2 in the bloodstream. This process is known as hypoventilation.

Hypoventilation & Hyperventilation

Hypoventilation and hyperventilation are two ways that can affect the acid-base balance in the body. Hypoventilation is when a person breathes too slowly or shallowly, meaning the lungs do not get enough oxygen in the air to reach the blood. As a result, the concentration of carbon dioxide in the blood rises. The increased carbon dioxide causes an acidic reaction in the blood, lowering its pH.

Hyperventilation, on the other hand, occurs when a person breathes too quickly. This leads to too much oxygen in the blood, causing the levels of carbon dioxide to drop. This produces an alkaline reaction, raising the pH of the blood.

Chemoreceptors

Our bodies are equipped with mechanisms which allow us to detect changes in the environment. Chemoreceptors, located in the arterial blood vessels of our body, are one such mechanism that aids in the regulation of our blood pH. These chemoreceptors send electrical signals to the brain when there is a change in the amount of hydrogen ions (H+) present in our blood. In response, the brain activates different systems in order to restore the pH balance. For example, if the pH drops, the brain will stimulate the respiratory centre to increase respiration rate, and therefore increase the amount of carbon dioxide (CO2) in the blood. This will then cause the pH to rise back to normal.

Renal Regulation of Acid-Base Balance

The regulation of acid-base balance in the body is complex. It involves a number of systems working together to create a balanced pH level. One of these systems, the renal system, is responsible for the filtration of blood and regulation of electrolytes to help maintain normal blood pH.

The kidneys play an important role in regulating acid-base balance by controlling the amount of bicarbonate ions that are reabsorbed from the glomerular filtrate. They also help to replenish bicarbonate ions in the bloodstream through tubular cells. In acidosis or alkalosis, the kidneys secrete regulated amounts of hydrogen ions and bicarbonate ions to restore pH balance.

The kidneys also produce nitrogenous buffers like phosphates and ammonia, which help to reduce the effects of excessive acids and bases in the body. As the pH of the body rises above 7.4, the kidneys will excrete more bicarbonate ions and the concentration of phosphate ions increases, whereas as the pH drops below 7.4, the kidneys will reabsorb more bicarbonate ions and the concentration of phosphate ions decreases.

The kidneys are integral to regulating acid-base balance because they are able to respond quickly to changes in pH. The kidneys are constantly monitoring the body's levels of electrolytes and pH, and can make rapid changes in order to restore homeostasis. This is why the kidneys are so important when it comes to maintaining blood pH.

Tubular Cell Replenishment

The kidneys can detect changes in the body�s pH level and make adjustments to maintain the balanced blood pH. This process is known as tubular cell replenishment. The tubular cells of the kidneys contain potassium, sodium and hydrogen ions, which re-enter the bloodstream when triggered by changes in pH levels.

The kidneys use these ions to neutralize acids and bases in the blood, adjusting the pH to its optimal level. This buffering system helps to prevent drops or rises in pH that could lead to drastic health problems.

Phosphate & Ammonia Buffers

The phosphate and ammonia buffer systems are important regulators of blood pH. In the acid-base balance, these buffers neutralize excess hydrogen ions by combining them with molecules in the blood to form new compounds. The phosphate buffer system consists of phosphoric acid (H3PO4) and its conjugate base, bicarbonate (HCO3-). It works in two ways. First, when there is an increase in hydrogen ions, the phosphate molecule binds with hydrogen ions to create acidic phosphates which can then be released from the body. Secondly, when there is a decrease in hydrogen ions, the phosphate molecule binds with bicarbonate to create bicarbonate salts, which can be reabsorbed.

The ammonia buffer system consists of ammonia (NH3) and its conjugate acid, ammonium (NH4+). It works in the same way as the phosphate buffer system. When there is an increase in hydrogen ions, the ammonia molecules combine with hydrogen ions to form acidic ammonium salts, which can then be eliminated from the body. Conversely, when there is a decrease in hydrogen ions, the ammonia molecules bind with bicarbonate to create bicarbonate salts, which can be reabsorbed.

The Bicarbonate Buffer System in Acid-Base Balance

The bicarbonate buffer system is one of the main acid-base buffer systems, along with the phosphate and ammonia buffer systems. This buffer system is responsible for buffering the hydrogen ions, which contribute to the pH of the blood. The bicarbonate buffer system is made up of two parts�bicarbonate (HCO3�) and carbonic acid (H2CO3).

Bicarbonate is introduced into the blood from the lungs and kidneys, while carbonic acid is formed by the combination of carbon dioxide (CO2) and water. In a healthy individual, the levels of CO2 in the blood are kept within a narrow range, and the balance of bicarbonate and carbonic acid is maintained.

When the blood pH increases, the kidneys also play an important role in controlling it. When the body detects the increase in pH, the kidneys start to excrete hydrogen ions to bring the pH back to normal. This is done by secreting more bicarbonate ions into the urine, and reabsorbing them from the urine as well. At the same time, the kidneys also reduce the secretion of bicarbonate from the blood to the urine.

In cases of alkalosis, the kidneys will reduce the production of bicarbonate and increase its reabsorption from the kidneys to the blood. In addition to this, the kidneys will excrete more hydrogen ions in the urine, helping to restore the PH balance.

Therefore, the bicarbonate buffer system plays an important role in the regulation of the blood pH. By maintaining the correct levels of bicarbonate and carbonic acid, the body can keep the blood pH within the normal range.

The Bicarbonate Buffer System in Acid-Base Balance

The bicarbonate buffer system is a major component of the body�s homeostatic mechanisms to regulate blood pH. This buffer system helps to maintain the body's acid-base balance, which is essential for proper functioning. It is composed of bicarbonate (HCO3-) and carbonic acid (H2CO3). Bicarbonate molecules bind with hydrogen ions (H+), neutralising them, preventing them from becoming too acidic in the blood. Carbonic acid is the result of the combination of bicarbonate ions and hydrogen ions and forms an equilibrium between them.

The kidneys play an important role in the functioning of the bicarbonate buffer system. During metabolic alkalosis, the kidneys secrete more bicarbonate ions into the bloodstream. In metabolic acidosis, the kidneys reabsorb bicarbonate ions and excrete hydrogen ions.

Kidney Functioning in Alkalosis and Acidosis

The kidneys play an important role in maintaining the homeostasis of blood pH. In cases of alkalosis, the kidneys can excrete bicarbonate into the urine to reduce the amount in the bloodstream and thus lower the pH.

In cases of acidosis, the kidneys will reabsorb more bicarbonate and conserve it, thereby raising the blood pH.

The kidneys also regulate the concentrations of ions such as sodium and potassium, which are electrolytes that can affect the pH of the blood. In alkalosis, the kidneys can excrete extra sodium and potassium to offset the increased blood pH.

In acidosis, the kidneys will retain ions such as sodium to help raise the pH of the blood. Therefore, the kidneys are one of the major organs that help us maintain the delicate balance of blood pH.

Clinical Relevance: Respiratory Acidosis and Metabolic Compensation

Respiratory acidosis is a condition in which there is an imbalance in the balance of acid and base levels in the body due to decreased elimination of carbon dioxide by the lungs. In this condition, the pH of the blood is below 7.35. Metabolic compensation is the body's attempt to bring the pH of the blood back to a normal level.

The main way that the body compensates for respiratory acidosis is by increasing the amount of bicarbonate in the blood. The kidneys will increase the rate at which they reabsorb bicarbonate, allowing an increased amount to be present in the blood. This helps to counterbalance the respiratory acidosis and raise the pH level.

Metabolic compensation also involves the kidneys working to excrete more hydrogen ions, such as from ammonium, to further raise the pH of the blood.

Respiratory Acidosis

Respiratory acidosis is a condition caused by one or more factors that reduce the volume of oxygen being carried into the lungs. This prevents the body from releasing enough carbon dioxide, leading to an increase in acidity in the blood. It is usually diagnosed when the blood pH level and/or the partial pressure of carbon dioxide (PCO2) levels in the person�s blood are higher than normal.

The main cause of respiratory acidosis is hypoventilation, where the lungs are unable to adequately remove carbon dioxide from the blood. This can be caused by conditions such as sleep apnea, chronic bronchitis, or pulmonary edema. It can also be caused by certain drugs or other medical conditions.

Metabolic Compensation

Metabolic compensation is a process where the body's physiology compensates for respiratory acidosis, meaning the body tries to balance pH after an imbalance caused by inadequate ventilation. This compensation works by restoring the amount of bicarbonate ion in the blood. As a result, when the respiratory system fails to provide adequate levels of oxygen, the cells start to create more carbon dioxide to offset any changes to pH. The kidneys are responsible for helping to regulate the balance of bicarbonate in the body. As carbon dioxide builds up and reduces the blood pH, bicarbonate is either taken from the kidney�s reserve, or absorbed from the intestine, depending on the severity of the acidosis.

The body has two mechanisms for regulating acid-base balance. Firstly, it influences the amount of carbon dioxide produced, which can be done directly through changes in respiration, or indirectly by triggering hormones to produce more or less bicarbonate in the blood. Secondly, it can excrete both nitrogenous and non-nitrogenous acids through the kidneys, thereby changing the level of nonvolatile acidity. Either of these mechanisms works as an active defense to prevent pH from falling too far outside the normal range.

Join Shiken For FREE

Gumbo Study Buddy

Try Shiken Premium
for Free

14-day free trial. Cancel anytime.
Get Started
Join 20,000+ learners worldwide.
The first 14 days are on us
96% of learners report x2 faster learning
Free hands-on onboarding & support
Cancel Anytime