Myocardiocytes or cardiomyocytes are cardiac muscle cells that keep the heart beating and ensure that heartbeats are synchronized. Communication between cells is important for growth and development, the formation of new blood vessels from the restriction in blood supply to the heart and for coordination.
Myocardiocyte-myocardiocyte interactions occur in various ways. One such way is by cell-ECM adhesion and this aids in the stabilization of these cells. They allow the heart to function as a electromechanical syncytium. The sinoatrial node sends an impulse that spreads to and stimulates the cardiac muscles. This impulse results in a contraction of the myocardium. Because the stimulation of the myocardium is ordered, the heart contracts effectively allowing blood to be pumped throughout the entire body.
Muscle cells have a negative cell membrane potential at rest and volted gated ion channels. Stimulation induces the opening of these ion channels thus allowing cations to flow into each of these muscle cells. The ions entering are positively charged and therefore cause rapid and coordinated depolarization. This results in Ca2+ being released from the t-tubules. The high amounts of calcium causes a calcium- induced calcium release from the sarcoplasmic reticulum therefore, free Ca2+ causes the coordinated muscle contraction After a delay, potassium channels reopen the flow of K+ out of the cell and causes repolarization to the resting state. The gap junctions are also important in the conduction pathway because the wave of depolarization moves from one cell to the other through them. Gap junctions are pores in the membrane of the cells. They are one of the fastest ways in which cardiac muscle cells communicate as they facilitate cell-cell interaction, allowing the exchange of small signaling molecules such as the Ca2+. Gap junctions also allow these heart cells to contract simultaneously.
Interactions between heart muscle cells ensure that the electrical conduction system of the heart functions efficiently to produce coordinated and synchronized heartbeats. The heartbeats are important to supply the entire body with blood.
Erythrocyte – myocardiocyte communication!
Erythrocytes, red blood cells, are found within the blood which is a specialized form of connective tissue. Red blood cells have one main job and that is to to transfer oxygen around the body. They contain a pigment called haemoglobin,which binds to four molecules of oxygen, and form oxyhaemoglobin at high oxygen concentrations and at low oxygen concentrations oxyhaemoglobin dissociates to haemoglobin and oxygen. Areas at high oxygen concentrations are inside the alveoli in the lungs, while areas of low oxygen concentrations can be anywhere close to working cells such as those hardworking myocardiocytes!
Although myocardiocytes are surrounded by blood which the heart pumps, it would take too long for diffusion to be the mechanism by which they get oxygen and get rid of carbon dioxide, as well as nutrients and so on so a direct cell-cell interaction might be ineffective. Therefore, there is a network of blood vessels on the heart to support these hard working muscle cells and this is the means by which they interact.
The presence of CO2 helps the release of oxygen from haemoglobin , known as the Bohr effect and this is the mechanism used in RBCs transferring their oxygen to working myocardiocytes. When carbon dioxide diffuses into the blood plasma and then into the (erythrocytes) in the presence of the catalyst carbonic anhydrase, most CO2 reacts with water in the erythrocytes.
Carbonic acid, H2CO3, dissociates to form hydrogen ions and hydrogencarbonate ions. This is also a reversible reaction and undissociated carbonic acid, hydrogen ions and hydrogencarbonate ions exist in a dynamic equilibrium with one another.
Inside the erythrocytes negatively charged HCO3– ions diffuse from the cytoplasm to the plasma. This is balanced by diffusion of chloride ions, Cl–, in the opposite direction, maintaining the balance of negative and positive ions either side. This is called the ‘chloride shift’.
The dissociation of carbonic acid increases the acidity of the blood (decreases its pH). Hydrogen ions, H+, then react with oxyhaemoglobin to release bound oxygen and reduce the acidity of the blood. This buffering action allows large quantities of carbonic acid to be carried in the blood without major changes in blood pH.
Hb.4O2 + H+ HHb+ + 4O2
The importance of erythrocyte – myocardiocyte cell communication is to aid in the transport of blood throughout the body. This ensures that the mouse’s cells and heart have a good supply of oxygen. Blood is also composed of white blood cells which are important in creating antibodies and ‘attacking’ any foreign particles such as viruses. The movement of blood in and out of the heart also causes contraction of the heart muscle cells.
Alberts Bruce, Johnson Alexander, Lewis Julian, Raff Martin, Roberts Keith, and Walter Peter. Molecular Biology of the Cell. 4th ed. New York: Garland Science, 2002.
It’s good to be back blogging after a long while. Previously, I’ve focused on Biochemistry but this time, it gets a little more interesting. The concepts posted would be based on my BIOL 2061 course this semester, Cell and Developmental Biology. So yea that’s right, I’m a cell for this semester! 😀 I chose a mouse as my model organism for this assignment! According to (Rosenblueth & Wiener, 1945), a model system is a simpler, idealized system that can be accessible and easily manipulated. When choosing models, there are particular things which must be taken into consideration. These include the size, growth patterns, availability and most importantly, the behavior of the organism and if it can be controlled easily. Model organisms therefore have to be relatively simple and inexpensive to work with. One of the main purposes of model organisms is for the study of health and diseases. Research on bacteria, yeast, insects, worms, fish, rodents and plants has proved that the basic operating principles are nearly the same in all living things and therefore the findings would be similar for humans. Apart from the lab setting, model organisms are important for teaching. They are used in the classroom to give students a hand on experience by having real life materials to work with which will retain their interest and gives them the opportunity to use the scientific method. The organism will also respond to different environmental conditions and will enhance learning.
Mice have an important role in research as they are primarily used to test medicine and chemicals. The safety level of certain chemicals and solvents must be tested before being introduced to humans. Genetically, they are similar to humans so test results are compared and altered to ensure safety.
So let me formerly introduce myself to the world! 😉
Hola! Bonjour! Shalom! Ni hao! I am a myocardiocyte (cardiac muslce cell) of a mouse and as my name suggests, I’m located in cardiac muscle tissues of the heart, more specifically the myocardium ❤ There, I join with my other fellow cells by intercalated discs that allow me to function to the best of my ability. We keep the heart beating and ensure that heartbeats are synchronized. When we contract, we ensure blood is propelled out of the atria and ventricles to the blood vessels of the left and right pulmonary circulatory systems. Additionally, we (cardiac muscle cells) originate from stem cells.
Cardiac cells are generally small, spindle shaped, striated and made up myofibrils (chains of sarcomeres) which allow them to contract. The fibres are branched and are mostly made up of actin and myosin and as mentioned before, are connected by intercalated discs and these discs have gap junctions. The intercalated discs are essential because they transmit forces durin muscle contraction. T-tubules are also present and they are important in ECC, Excitation contraction coupling. There is also a central nucleus and an abundant supply of mitochondria to generate ATP. Like most cells, the nucleus is the site of genetic transcription and protein synthesis. Cardiac muscle cells are well adapted to resist fatigue. With an abundant supply of mitochondria, aerobic respiration continuously occurs and produces ATP to build energy for muscle contractions. There is also an abundant supply of myoglobin and a good blood supply for oxygen.The sarcolemma (cell membrane of muscle fibre) has specialized ion channels and the fibres are not anchored at ends to allow a greater sarcomere shortening and lengthening. Cardiac muscle cells unfortunately do not undergo cell division like other cells. They become degenerated and recent studies show that some cardiac muscle cells regenerate after a person had been born.
That’s it for now guys! Keep viewing for more posts. Trust me it gets more interesting than this 🙂
Hey Biochemians! Well we’ve finally reached the end of the tunnel! I really can’t believe it because just the other day I was told to create a blog for my Biochemistry course. Time favors no one! Well what can I say? Honestly I have really enjoyed blogging as I said in a previous post. There are so many things we can learn from each other and there isn’t one particular way to learn. Learning is an experience and you should make it enjoyable. I can honestly say that my youtube addiction helped me lol Some of the videos I found were really helpful and interesting! There are sooo many resources and it’s up to us to go out there and search for them! Somehow I feel as though I’m saying goodbye but that’s one thing not true! iBiochem is here to develop further! In year 2 of university, I’ll be continuing my Biology major but I’d also be doing minors in Biotech and Biochem! I’d love to share my knowledge with my fellow bloggers! 🙂 I’d really like to give a special shoutout to Matt Russell ( from either Canada or the US…not sure) for liking my posts and for encouraging me to continue. He said we need more blogs about Biochemistry and this is quite true! I’m also grateful that I was able to connect with so many new people 🙂 Thank you to all of my followers! I had views from Egypt to India, and from some other countries as well. Sooo guys follow his blog http://mhrussel.wordpress.com/ Really good!
Lastly I’d like to thank my hokage :p Jason Matthew for giving us this assignment. Big up to you! It was a great experience and I hope that my other future lecturers are as creative and outstanding as you 😀 Well you basically helped me create iBiochem and it’s here to stay. Biol1362 may be over but I have more to share!
Fellow Biochemians worldwide take a look at JM’s Biochemistry youtube page http://www.youtube.com/user/BiochemJM The videos are great,detailed and very helpful!
Well till next time…hasta luego! 🙂 God Bless you guys!
Sun Z.S. Empie W.M. 2012, ‘Fructose Metabolism in Humans.’
Accessed on 10th April 2012. http://www.medscape.com/viewarticle/777692_1
Fruits and vegetables are good for you is what we constantly hear! Currently, there are studies being done on the consumption of fructose and its relation to public health. Fructose is found in most fruits and vegetables but a higher percentage in fruits! Fresh fruits are always good and refreshing! There’s nothing better than a cold piece of watermelon on a sunny day or a ‘bess’ pineapple chow on the beach. Although fructose occurs naturally, other sugars such as beet is produced industrially so there’s added sugars to our diet. Over the past few years, there has been an increase in metabolic syndrome and well to no surprise, obesity worldwide. Most of these health disorders are related to sugar intake. Also, the fructose moiety in sugars was hypothesized to be a cause of high serum uric acid which could lead to Type-2 diabetes. Another hypothesis stated that dietary fructose may cause Non Alcoholic Fatty Liver Disease (NAFLD) and augmented de-novo triglyceride synthesis, based on an analysis of hormone regulated lipid pathways in the liver. High levels of fructose on our diets increase serum triglycerides.
The metabolic fate of fructose was reviewed by doing isotope trace studies in humans. The first test was done on persons that do not exercise for 3-6 hours. The 2nd test was done on persons that exercise for 2-3 hours. The mean oxidation rate of dietary fructose was 45.0% ± 10.7 for those that didn’t do exercise and 45.8% ± 7.3 in persons that exercised. A test was also done for the consumption of both fructose and glucose. When fructose was ingested with glucose, the mean oxidation rate of the mixed sugars increased to 66.0% ± 8.2 for persons that exercise. The mean conversion rate from fructose to glucose was 41% ± 10.5 in 3–6 hours after intake. It was found that less than 1% of the ingested fructose is directly converted to plasma TG. Approximately a quarter of the ingested fructose can be converted to lactate just within a short period. This increases the blood lactate concentration. We all know the story about Mr. lactate don’t we? Additionally, at short periods, a minimum amount of fructose carbons enter the pathway of liponeogenesis after fructose intake.
The study was not a full representation of real life diets and the data was limited. However, the paper did give a general idea of how fructose is utilized in the body. The focus was mainly between individuals that exercise and individuals that don’t.
“It’s easy to stand with the crowd. It takes courage to stand alone”
DNA/RNA base pair friend necklace! 🙂