Cell nucleus: structure and function Nucleus: Think about your favorite superhero. Regular person by day, vigilante in spandex, and a cape by night. Saving the world isn’t an easy job, so most superheroes have support. Enter the guy behind the computer, the allknowing tech whiz that helps the hero succeed, hacking blueprints, giving directions during surveillance. The guy behind the computer does it all. And we can think of the cell nucleus like the guy behind the computer, making calls, sending directions, and overall being in charge of the superhero cell, despite always getting less credit than the superhero themselves. The nucleus is a multifunctional organelle that is found in eukaryotes. Generally, eukaryotes have only one nucleus, but this isn’t always the case. Certain eukaryotic cells, like red blood cells and prokaryotes, like bacteria and archaea, don’t have nuclei either. These are called enucleate cells. Other cells, like those of slime mold, have two or more nuclei and are called multinucleate cells. The nucleus, if there is one, makes up approximately 10% of the cell’s volume and has an incredibly important purpose in the cell. The cell nucleus functions as the information processing center of the cell, storing genetic material and organizing all of the cell’s activities, from cell division to synthesizing proteins. The nucleus is especially important for protein synthesis. Oh, yeah. It’s the site of transcription, where messenger rna, or mrna, is produced. The nucleus may appear to be one lone blob of an organelle, but in fact, it’s made of many different structures that contribute to the overall function of the nucleus. We’re talking about the nuclear membrane, the nucleoplasm, chromatin, and chromosomes, and the nucleolus. Now, let’s see what kind of programs the guy behind a computer nucleus runs in the superhero cell. The first important structure making up the nucleus is the nuclear envelope. The nuclear envelope is like your computer’s antivirus. It keeps everything where it should be and screens for everything before allowing it on your computer, or in this case, the nucleus. You can’t be a superhero sidekick with a virus on your computer, can you? The nuclear envelope consists of two phospholipid bilayers that act as a wall for the nucleus, keeping all of the contents in place. This protective envelope is actually composed of two membrane layers, an inner nuclear membrane, or INM, facing inside towards the inside of the nucleus, and an outer nuclear membrane, or ONM, facing away from the nucleus towards the cytoplasm of the cell. The ONM also connects directly to the rough endoplasmic reticulum and is covered in ribosomes. There is also a fluid filled space between the INM and the ONM called the perinuclear space separating the two membrane layers. Although the nuclear envelope acts as a wall to keep the nucleus in shape, it also has another important function, selectively allowing things into the nucleus. Small holes in the envelope, called nuclear pores, act as a safe passageway for different molecules, like proteins and rna. The pores are like a bodyguard. Unless you pass the check, you’re not allowed entry. And this keeps the nucleus safe and allows it to keep doing its job without issue. Next up, let’s talk Internet. The guy behind the computer can’t function without Internet, right? That magical, hidden network that can get you anywhere you need to go. Much like the nucleoplasm of the nucleus, the nucleoplasm, composed of water, salts, enzymes, and other organic molecules, helps the nucleus in a number of ways. First, it acts as a cushion for the nucleus, protecting all of the contents within the organelle, and also helps the nucleus keep its shape. But more importantly, the nucleoplasm acts as a transportation network for the nucleus, much like the Internet of the cell. Imagine you’re helping a superhero on a mission and search up bad guys near me, and you immediately get the perfect website back on your browser. Because of your super fast Internet. The nucleoplasm works in sort of the same way. Say the nucleus needs something like an enzyme, for example. The enzyme travels through the cell, right through the nuclear pores, into the nucleus. It’s like cellular level Internet, but cooler. Now, let’s think about how a computer actually works. If you’re a superhero’s right hand man, you have to have a top notch, state of the art computer, and you can’t run a computer without code. The code on your computer dictates how every single thing on it runs, so it’s really important. Chromosomes are like usb sticks for computers, but instead, they store the blueprint to our bodies. They store and share code in the form of DNA. Chromosomes have all our bodies information from howto manuals on cell growth to development and reproduction 101. Chromosomes live in the nucleus, but in a resting form when the cell is not in active reproduction stage, chromosomes exist in long, free floating strands of dna and protein called chromatin. And chromatin can be classified even further into heterochromatin, the inactive form of chromatin, and euchromatin, the looser, more delicate form of chromatin. Chromatin in all its forms, comes together during cell division to form chromosomes. The nucleolus is the final feature we’ll talk about, and it actually directly relates to chromosomes and chromatin. Think of the nucleolus like a temporary line of code that your guy behind the computer uses to save the day. It’s put on your computer to finish one job, and once it’s done, the code disappears until you need it again. The nucleolus is a membraneless feature that spends its time floating around in the nucleoplasm and also plays a big role in protein synthesis. The nucleolus, which stores proteins and rna inside, has features called nucleolar organizers that are integral for creating ribosomes during the process of protein synthesis. Ribosomes are formed during protein synthesis, and then when the cell is ready to divide, the nucleolus disappears. Talk about not taking

Cell membrane introduction Cell membrane: When you go swimming or showering, have you ever wondered, why don’t your cells in your body fill up with water? Or why don’t the substances in your cells leak into the pool? Well, the reason is because we actually have a very important structure that prevents this from happening. This is what we call the cell membrane. The cell membrane is what’s on the outside of a cell. So if we have a very basic picture of cell here with a little nucleus on the inside, this pink outside layer is what we call the cell membrane. The cell membrane can protect our cell from the outside environment, and it can determine what can enter and leave our cell. This is a property that we call semipermeability. It is somewhat permeable. Some things can enter while other things cannot. So since this is such an important part of our cell, in fact, it’s one of the reasons why we can actually survive in the world. So what actually makes up this structure? Well, the main building block of a cell membrane are what we call phospholipids. There are other substances that make up our cell membrane, but the most important building block are phospholipids. And so phospholipids have three major components. The first is a phosphate head group. The second is a glycerol backbone. And the third are two fatty acid tails. So the way we draw this is we give the phosphate head group, kind of like a head. It’s a circle, and two fatty acid tails hang down from it, kind of like strings on a balloon. So the way I kind of remember this is a phospholipid, looks like a balloon, but with two strings. Now, where’s our glycerol backbone? Well, our glycerol backbone is actually what it sounds like. It’s what holds the fatty acid tails to our phosphate head. It’s the backbone of this molecule. So it’s usually not drawn in the picture, but just remember that it’s there, and it holds our two fatty acid tails to our phosphate head group. So this structure actually has a very interesting property up here. This head group is actually hydrophilic, or polar. So hydrophilic means that it’s water loving. This phosphate head group will do whatever it can to get to water. It loves water, but these fatty acid tails, because they’re very, very long carbon chains, this is hydrophobic. I remember hydrophobic because a phobic or phobia is fearing. So hydro is water. So it’s water fury. These two fatty acids will do whatever it can to get away from water. A molecule that has both of these things together is what we call an amphipathic molecule. It means that the molecule has a hydrophobic section and a hydrophilic section. So in water, what would this do? So let’s say we put a ton of these molecules in water. Once in water, the hydrophobic heads want to be as close to water as possible, but the tails don’t. So what will happen is these phosphate groups are going to cluster together while the tails try to shield themselves away from water. But since this is a substance that’s in water, water is going to be down here, too. So this will actually form a really unique structure because the fatty acid tails are going to start grouping like this, and the phospholipids are going to be kind of upside down so that the phosphate head groups can be close to water, while this inside section can be hydrophobic and away from water. This is what we call a phospholipid bilayer. This is the basic structure of a cell membrane. And like we mentioned, this inside section is going to be hydrophobic. So now we have this structure that looks kind of like this. We call this our phospholipid bilayer or lipid bilayer for short. But doesn’t this section here also interact with water? How can this structure be like this if this section here still touches water? And we know that the fatty acid tails don’t want to touch water. Well, in a cell in real life, what actually happens is we end up with the structure that forms a circle like this. Now, this is a fairly crudely drawn picture. In a cell, this wall is actually pretty thin compared to the entire body. So you’ll notice that this water here doesn’t become a problem anymore, because in our actual cells, water can be on the outside and on the inside. And no matter where this cell membrane touches water, it’s always going to be the phosphate head groups that are hydrophilic, that are seeking out water. And inside the cell membrane, we actually have a hydrophobic section. So, moving on to a new picture, we mentioned before that the cell membrane is semipermeable, and we’re going to explore that a little bit more. So I’ve taken the liberty of pre drawing a very long picture of a cell membrane. So, as we mentioned, the cell membrane is actually a sphere that surrounds our cell. For the sake of this lesson, we’re going to draw it out in a straight line, and we’re going to say that this can be the outside environment or the extracellular, and this can be the inside or the intracellular. So you’ll notice that the cell membrane has these phospholipids packed really closely together. So usually small molecules are what can pass through the cell. Another property of the cell membrane that we’ve discussed is that this inside section right here is really hydrophobic. So generally, small nonpolar molecules can pass through our cell membrane. This is what we call passive diffusion. So what is a good example of a small nonpolar molecule? Well, the most common type of small nonpolar molecule tend to be gases, things like o two, for example, or co2. These are things that surround us every single

Cells Structure and Functions All living organisms are composed of cells. Cells are responsible for all anatomical and physiological features of all body systems. Different cell types can vary greatly in shape and size, but they all have a common structure and similar components. A typical cell cell is enclosed in a plasma membrane and contains a nucleus and a cytoplasm. The plasma membrane serves as the cell’s boundary, controlling the traffic of substances in and out of the cell. It is also the site of communication between the cell and its environment. The membrane consists mainly of two layers of phospholipids with their hydrophilic heads, the phosphate groups facing the aqueous environments inside and outside the cell, and their hydrophobic fatty acid tails facing in together. Other membrane lipids include cholesterol, which is essential to membrane structure and fluidity, and glycolipids, which maintain membrane stability and facilitate cell to cell interactions. The lipid membrane is dotted with membrane proteins, of which there are two types, integral or transmembrane proteins, which span across the membrane, some passing through multiple times. Some transmembrane proteins have a small carbohydrate chain on the outside of the cell and peripheral proteins, which attach to the membrane on the inside. A peripheral protein typically functions together with an integral protein. Membrane proteins fulfill a variety of functions. As receptors or receptorassociated proteins. They receive messages from outside the cell. For example, a nonsteroid hormone must bind to a membrane receptor and act via several other membrane proteins to activate a cellular response. Each receptor is specific to a certain molecule. As ion channels or transport proteins, they help move charged particles and large, uncharged polar molecules across the cell membrane. As adhesion molecules, they help cells adhere to each other and to the extracellular matrix. As enzymes, they catalyze reactions that are required outside the cell but in the vicinity of the cell membrane. Transmembrane glycoproteins also serve as surface antigens, determining the cell’s identity on top of the cell membrane. Some cells have surface extensions that carry out specialized functions. Examples include microvilli that increase the surface area in the small intestine cilia that move mucus in the respiratory tract, and flagella that are responsible for the movements of sperm cells. The nucleus contains genetic material, the DNA, and is where DNA replication and transcription, the major step of gene expression, take place. Most cells have one nucleus, with the exception of red blood cells, which have none, and some other cells that have multiple nuclei. The nuclear envelope surrounding the nucleus consists of two membranes, inner and outer, each of which is a phospholipid bilayer. The envelope is dotted with nuclear pores protein complexes that provide controlled passage between the nucleus and cytoplasm chromosomes are strands of DNA wrapped around proteins. Under a light microscope. Chromosomes are only visible during cell division when they are highly condensed. Instead, the most prominent feature of the nucleus is the nucleolus, the area around the clusters of ribosomal rna genes. This is where ribosomal rnas are made and where ribosomes are assembled. Ribosome then move to the cytoplasm to fulfill their function in protein synthesis. The cytoplasm includes a gel like liquid called cytosol, various organelles and cytoskeleton, the endoplasmic reticulum, ER, Golgi apparatus, and vesicles constitute the intracellular membrane system. The ER is a network of connected flattened sacs called cisterni. Its membrane is continuous with the outer nuclear membrane. Part of the ER appears rough, as it is covered with ribosomes. This is where the synthesis of secretary and transmembrane proteins take place. These proteins have a signal sequence within their amino terminus, which, as soon as it emerges from the ribosome, targets the rna ribosome complex to the ER membrane, where translation continues. The emergent polypeptide enters the ER membrane as it is being translated. Transmembrane proteins, identified by the presence of a hydrophobic stretch, stay in ER membranes while secretary proteins are released into the ER. Lumen, the smooth part of the ER, synthesizes lipids and lipid components of cell membranes. As lipids are produced, they are inserted into the ER membrane. Membrane proteins, lipids and secretary proteins are then packaged into vesicles to be transported to the Golgi, where proteins undergo post translational modifications. Vesicles pinch off from ER membranes, travel to golgi apparatus, fuse with golgi membranes, and release their content. The golgi is a stack of separated cisterni. Each contains a set of enzymes responsible for a certain step in protein maturation. Similar vesicles transport lipids and proteins from one cisterna to another and ultimately to their destinations. The plasma membrane lysosomes or storage vesicles the destination of a protein is typically determined by a signal sequence acting as an address tag within the protein. The ER is also a major site for metabolism and storage of calcium, whose release is a trigger for many cellular processes. Lysosomes are vesicles containing hydrolases that break down macromolecules into their building units, which can then be recycled. The enzymes are activated by the acidic environment within lysosomes. In white blood cells, lysosomes digest phagocytized bacteria and play a role in immune response. Mitochondria are best known as the cell’s powerhouses. This is where energy is extracted from food compounds and stored in energy rich molecules. A mitochondrion has two membranes. The inner membrane has multiple folds called christi. Two of the three main steps of cellular respiration occur in the mitochondria, citric acid cycle in the matrix and oxidative phosphorylation on the christi. Cytoskeleton is a network of protein filaments that fulfill a variety of functions. There are three types of filaments, microfilaments, intermediate filaments and microtubules. Microfilaments are made of the protein actin. They enable muscle contraction, provide support for microvilli, produce cell movements and play a role in cell division. Intermediate filaments are made of different proteins in different cells. Their roles are mostly supportive. Microtubules are large tubes of 13 protofilaments. Each is a long chain of

Tendinitis: Causes, Symptoms, and Proven Treatment Options Imagine getting a complete joint replacement without surgery. Believe it or not, this is the new reality for THOUSANDS of former arthritis sufferers… Triceps Tendinitis – Tendinopathy – Elbow Rehab Tendinitis a threeheaded muscle, hence the prefix tri that’s visible on the back of the arm. The medial and lateral heads originate on the humerus, while the long head actually attaches up at the shoulder blade. All three muscles insert on the electron of the ulna via a common tendon and act to extend or straighten the elbow. The long head also extends and stabilizes the shoulder due to its attachment up at the scapula. (Tendinitis) Although the diagnosis is often referred to as triceps tendonitis, triceps tendinopathy is a better descriptor for this condition because inflammation likely isn’t the primary driving factor. Instead, you can just think about it as an overload of the tendon, meaning that you probably just did a little bit more than what it could handle over a certain period of time. This is not to be confused with golfer’s elbow on the inside of the elbow, tennis elbow on the outside of the elbow, or anything to do with instability, trauma, significant swelling or numbness and tingling. (Tendinitis) I would expect fairly localized pain in the back of the elbow that worsens with increasing demands on the triceps. For example, I would expect a 40 pound dumbbell skull crusher to cause more issues than a 20 pound dumbbell skull crusher because it’s a greater load. Similarly, a very fast repetition would likely present more challenges than a very slow repetition because tendons are also affected by the rate or speed of loading, and triceps tendinopathy does not mean that you have to discontinue all training. (Tendinitis) Instead, you have to find a level of training that allows you to have tolerable symptoms somewhere around a three out of ten pain or less while making objective progress in your lifts. Symptoms for tendinopathies can often take three or more months to resolve, so the focus should be on improving function over the long term. The most important concept to understand for any teninopathy is load management. (Tendinitis) Essentially, you’re attempting to achieve a Goldilocks principal level of load, not too much where you’re exacerbating symptoms and prolonging recovery, but not too little where you’re deconditioning and not driving. Beneficial adaptations start with the big picture. (Tendinitis) Has your training changed significantly in the past three months? That may have contributed to symptoms? Did you alter frequency, volume, and or intensity? Analyze your current program to see if there’s any reasonable modifications that you can make based on any significant fluctuations in these variables that might have occurred over the past few weeks or months. (Tendinitis) The next things you’re going to look at are exercise selection, technique, and tempo as they relate to your compound multijoint exercises, assuming they’re part of your normal routine. The three main pushing movements that target the triceps include a vertical press where your arms end up overhead, a horizontal press where your arms end up straight out in front of you, and a dip where your arms end up down at your side. (Tendinitis) The easiest thing to start with here is finding exercise variations that are most comfortable for you. For example, an overhead press can be done with a barbell. Dumbbells, kettlebells, or unilaterally. Horizontal pressing can include any type of pushup, bench press, dumbbell press, machine press, or even incline options. Now, if your symptoms are exactly the same regardless of the movement, you can try to modify your technique to reduce the demand on your triceps. (Tendinitis) For example, a wider pushup or bench press will likely challenge the triceps less than a very narrow pushup or bench press. For an overhead press, you can shorten the range of motion. Bringing the bar all the way down where your elbows are maximally flexed will place more load on the triceps than if you limit the movement to about 90 degrees of elbow flexion. Finally, you can alter the tempo. A lot of tendinopathy protocols implement a three second eccentric, 1 second pause, and three second concentric. (Tendinitis) These aren’t inherently special numbers, but decreasing the speed of the movements can be helpful, as mentioned earlier. Also, it’ll force you to use a lighter load, and the consistent tempo can help with maintaining technique and tracking. Objective progress next up, examining single joint isolation exercises. There are four main types for the triceps elbow extension with the shoulder in maximal flexion, elbow extension with the shoulder flexed to 90 degrees, elbow extension with the shoulder in neutral, and elbow extension with the shoulder extended. (Tendinitis) While the multijoint exercises are optional, depending on your goals, picking one to two of the isolation exercises will be necessary to ensure appropriate loading of the triceps. Just like the compound exercises, though, you can try to find variations that work best for you. I’d try to implement a fairly strict, consistent technique with that same tempo initially for one to two exercises. For example, a dumbbell skull crusher can be done with shoulders maintained at 90 degrees of flexion, no shoulder, internal or external rotation, bringing the weight to 90 degrees of elbow flexion and then straightening the arms. A similar technique could be used for a standing triceps press down with a rope bar or band. I’d highly recommend executing these one arm at a time. These would be done for three to five sets of six to twelve repetitions, two to three times per week at a three out of ten pain or less at an intensity that is close to failure. I’ll give a sample routine at the end of the video. Lastly, accessory exercises. There’s no research to support this for tricep tendinopathy, but other elbow issues benefit from strengthening of the shoulder. (Tendinitis) Therefore, I would