Each skeletal muscle is composed of bundles of myofibrils. The muscle fibers are composed of units called Sarcomeres. A sarcomere is a a series of thick and thin filaments that overlap longitunially. Where a sacromere meets its neighboring sarcomere, it is called the “z-line” Repeating units of sarcomeres account for the unique banding pattern that is seen in striated muscles. The thick filament in the sarcomere makes up the “A band”. This is in the center of the sarcomere. These thick filaments are made up of myosin. These Myosin molecules have two heads that are attached to a tail. Imagine as if they look like a hammer laying down with the head pointing up. These heads are what bind ATP (the energy source for the fiber) and create a cross bridge with the thin filament.
The thin filaments are anchored to the sarcomere at the Z line. When you see a diagram of the sarcomere, they make up the I band. There are intertwined between the thick filaments within part of the A band. These thin filaments are made up of actin, tropomyosin and troponin. Picture these thin filaments like spirals of thread with little dots of troponin along it. I have included a picture I google imaged to help you imagine a sarcomere:
In this image, you can see the heads on the myosin fiber scattered about.
Here is a picture of the interaction between the two fibers:
These diagrams are a little complicated but just pay attention to what we are talking about.
The troponomysin and troponin are attached to eachother. The tropomyson acts like a block for the myosin head preventing it from attaching to the actin, while the troponin acts as a regulatory protein. When the troponin is exposed to Calcium, it makes the tropomyosin shift out of the way and lets the myosin heads to have access to bind to the actin.
Surrounding these sarcomeres is a structure of channels called Sarcoplasmic reticulum and they are connected to the extracellular space (around the muscle fibers). The T -tubules are an extensive tubular network that opens to the sarcomere. These tubules are located at the junction between the A bands and the I bands. Action potentials travel down these T tubules to the cell interior at the sarcoplasmic reticulum.
In the beginning phases of muscle contraction, a “cocked” motor neuron in the spinal cord is activated to form a neuromuscular junction with each muscle fiber when it begins branching out to each cell. An action potential is passed down the nerve, releasing calcium, which simultaneously stimulates the release of acetylcholine onto the sarcolemma. As long as calcium and ATP are present, the contraction will continue. Acetylcholine then initiates the resting potential’s change under the motor end plate, stimulates the action potential, and passes along both directions on the surface of the muscle fiber. Sodium ions rush into the cell through the open channels to depolarize the sarcolemma. The depolarization spreads. The potassium channels open while the sodium channels close off, which repolarizes the entire cell. The action potential is dispersed throughout the cell through the transverse tubule, causing the sarcoplasmic reticulum to release
The cells are held together by regions known as intercalated disks. These overlapping, finger-like extensions of the cell membrane contain gap junctions and desmosomes. Gap junctions are protein-lined tunnels which allow currents to travel from cell to cell to ensure the cells contract in unison. Desmosomes are known for holding the Heart Cells together during a contraction. This is induced by the sliding of the cardiac
When a muscle contracts and relaxes without receiving signals from nerves it is known as myogenic. In the human body, the cardiac muscle is myogenic as this configuration of contractions controls the heartbeat. Within the wall of the right atrium is the sino-atrial node (SAN), which is where the process of the heartbeat begins. It directs consistent waves of electrical activity to the atrial walls, instigating the right and the left atria to contract at the same time. During this stage, the non conducting collagen tissue within the heart prevents the waves of electrical activity from being passed directly from the atria to the ventricles because if this were to happen, it would cause a backflow. Due to this barrier, The waves of electrical energy are directed from the SAN to the atrioventricular node (AVN) which is responsible for transferring the energy to the purkyne fibres in the right and left ventricle walls. Following this, there is a pause before the wave is passed on in order to assure the atria has emptied. After this delay, the walls of the right and left ventricles contract
...st the sacrolemma will depolarized, thus activation potentials along the T-tubules. This signal will transmit from along the T-tubules to sarcroplasmic reticulum's terminal sacs. Next, sarcoplasmic reticulum will release the calcium into the sarcroplasm leading to the next second event called contraction. The released calcium ions will now bind to troponin. This will cause the inhibition of actin and mysoin interaction to be released. The crossbridge of myosin filaments that are attached to the actin filaments, thus causing tension to be exerted and the muscles will shorten by sliding filament mechanism. The last event is called Relaxation. After the sliding of the filament mechanism, the calcium will be slowly pumped back into the scaroplasmic reticulum. The crossbridges will detach from the filaments. The inhibition of the actin and myosin will go back to normal.
(t)| (12) The −→ A , −→ C vectors are calculated as in equations 13 and 14 −→ A = 2 −→ A . −→ r 1 − −→ a (13)
Within skeletal muscle there are extremely small structures that form the muscle and allow contractions and movement to occur (epimysium, perimysium, endomysium, fascicles, fiber, sarcomere, sarcoplasmic reticulum and t tubules). These structures all play a role in protecting, connecting and transporting substances throughout the muscle fibers. They are also the main contributors to movement.
Repair after a muscle is damaged happens through the division of certain cells who then fuse to existing, undamaged muscle fibers to correct the damage. Different muscle types take different amounts of time to heal and regenerate after it has been damaged. Smooth muscle cells can regenerate with the greatest capacity due to their ability to divide and create many more cells to help out. While cardiac muscle cells hardly regenerate at all due to the lack of specialized cells that aid in repair and regeneration. In skeletal muscle, satellite cells aid in helping restoration after injury. Along with muscles, tendons are very important structures within the human body, and they to can be damaged. However, tendon repair involves fibroblast cells cross-linking collagen fibers that aid in not only reinforcing structural support, but also mechanical support as well (“Understanding Tendon Injury,” 2005). While quite different from muscle repair, tendon repair involves the similarity of reestablishing d...
Then, rigor mortis occurs. Rigor mortis is the stiffening of the muscles due to the disappareance of ATP (adenosin triphosphate). The proteins responsible for muscle contraction, actin and myosin, need ATP to create crossbridges and make the muscles contract, and then relax. When ATP is no longer produced by the cells, the cycle of contraction cannot be completed and the muscles remain contracted. [3]
Dendrites are located on either one or both ends of a cell.The peripheral nervous system then takes the sensory information from the outside and sends the messages by virtue of neurotransmitters. Neurotransmitters are chemicals that relay signals through the neural pathways of the spinal cord. The neurotransmitter chemicals are held by tiny membranous sacs located in the synaptic terminals. Synaptic terminals are located at the ends of nerve cells. The release of neurotransmitters from their sacs is stimulated once the electrical nerve impulse has finished travelling along a neuron and reaches the synaptic terminal. Afterward, neurotransmitters travel across synapses thus stimulating the production of an electrical charge that carries the nerve impulse onward. Synapses are junctions between neighboring neurons. This procedure is reiterated until either muscle movement occurs or the brain picks up on a sensory reaction. During this process, messages are being transmitted from one part of the body onto the next. The peripheral and central nervous system are two crucial subdivisions of the nervous system. The brain and spinal cord make up the central nervous
is the biggest of all. Myocardial Infarction is a disease later read about in this report. The pericardium is a fibrous sac which is very smooth lining. In the space space between the pericardium and epicardium is a small amount of fluid. This fluid makes the movement of the heart muscles smooth. Myocardium is the heart muscle itself.
The sarcomere is found in structures called myofibrils which make up skeletal muscle fibres. Within the sarcomere there are various different proteins. One of the most significant, myosin is found in the thick filaments of the sarcomere. Although both cells contain myosin, it is important to highlight that smooth muscle cells contain a much lower percentage of myosin compared to skeletal muscle cells. Despite this, myosin filaments in smooth muscle cells bind to actin filaments in a manner similar to that in skeletal muscle cells; although there are some differences. For instance, myosin filaments in smooth muscle cells are saturated with myosin heads so that myosin can glide over bound actin filaments over longer distances, enabling smooth muscle cells to stretch further, whilst in skeleta...
Action potentials are started at one end of the node, flow passively through the myelinated axon, and pop out the other side to jump to the next node. This jumping of action potentials is called saltatory.
stimuli, according to Brannstroms Hydrodynamic Theory. Anatomically, the areas of the tubules closer to the pulp activates the nerves associated with the odontoblasts at the end of the tubule, resulting in pain response.
The cytoskeleton is made up of three different types of filaments, actin filaments, intermediate filaments and microtubules. Actin filaments are the thinnest, they are also known as microfilaments. They create a band under the plasma membrane, this gives strength to the cell and links transmembrane proteins such as cell surface receptors to cytoplasmic proteins. Intermediate filaments include keratins, lamins, neurofilaments and vimentins. Keratins form hooves, horns and hair and are found in epithelial cells. Lamins form a type of mesh that ‘stabilizes the inner membrane of the nuclear envelope’ (Biology Pages). Neurofilaments bring strength to the axons of neurons and vimentins provide mechanical support to cells – particularly muscles. The cytoskeleton is also involved in cell
You will need to sum down for the first four orientations and sum across some of the rows, then sum down and divide by two for the last orientation. The chart should make it clear.