Skeletal Muscle Contraction

Myasthenia Gravis affects the neuromuscular junction. Neuromuscular junction is the connection or meeting place of the nerve and a muscle fiber. The nerves communicate with the muscle fiber by telling it to move or contract. The nerves

The structure of neuromuscular junction consists of a neuron and skeletal muscle cell. The motor neurons, which arise from the spinal cord, supply the skeletal muscle fibers. The neuromuscular junction is un-myelin nerve with a bulb shape at the endings that contract the muscle fiber. The schwann cells form a covering over the postsynaptic membrane and nerve membrane of the fiber that is located under the terminal and is categorized as a post-junction folds. The area between the folds and the bulbs create the synaptic cleft. This consists of proteins and proteoglycans. The enzyme acetylcholinesterase; exist only at high levels in the synaptic basal lamina (UMN,

The functional loss of AChRs reduces the probability of successful neuromuscular transmission following adequate release of acetylcholine by the motor nerve terminal (Gardener,1968).The relationship between myasthenia gravis and thymoma was noted more than 200 years ago,thymic abnormalities are found in nearly 75% of patients with myasthenia gravis.Of these ,germinal hyperplasia is noted in 85% and thymic tumours in 15%.Antistriated muscle antibodies are present in 90% of patients with myasthenia gravis and athymoma (B Thanvi and lo ,2004).

First, before this assignment I had no idea of the levels involved in a muscle contraction. We can directly control or regulate the activity of our skeletal muscles. Striated muscle movement, produced by the interaction of filaments containing the proteins myosin and actin, is regulated by the proteins tropomyosin and troponin on the actin filaments. When an electrical signal passes down the motor nerve to a muscle it triggers a depolarization of the muscle membrane (sarcolemma). In results, triggers the sarcoplasmic reticulum to release calcium ions into the muscle interior where they bind to troponin, which causes tropomyosin to shift the actin filament to which myosin heads need to bind to produce contraction.

Myasthenia Gravis is a weakness and rapid fatigue of muscles under voluntary control. This disease is caused by an interruption in communication between nerves and muscles at the neuromuscular junction; this is the place where nerve cells connect with the muscles they control. The muscle weakness increases through periods of activity and then improves during rest. For example, muscles that control eye and eyelid movement, facial expression, chewing, talking, and swallowing, these are the most often muscles affected. Other muscles that can be affected are muscles that control breathing and neck and limb movement can be affected. Symptoms include, difficulty swallowing, double vision, unsteady walk, weakness in arm and leg muscles, and difficulties

Myotonic is the most known condition, it could occur from childhood to adult life. It affects the nervous system, eyes, hormone producing glands, and gastrointestinal tract. Myotonic stiffens the muscles after you use it. Duchenne is most common in children and only found in males. Occurs at a young age; two to six years old. It affects arms, legs, spine, and the heart.

Neck and limb muscles- Myasthenia gravis can cause weakness in your neck, arms and legs, but this usually happens along with muscle weakness in other parts of your body,such as your eyes,face and throat.

Myelin is an isolating covering consisting in repeating layer around the axon. It is high in lipids and low in proteins, thus its white color and isolating power. Because many axons are myelinated, electric impulse is able to undergo salutatory movement which accelerates its transmission. Myelination is completed by oligodendrocytes in CNS and neurolemmocytes in the PNS.

Affecting about 20 out of 100,000 people per year in the United States, myasthenia gravis (MG) is an autoimmune muscular junction disease that targets nerves and muscles (What is Myasthenia Gravis, 2010). Myasthenia gravis attacks voluntary muscles such as the facial muscles, limbs and other muscles, making these muscles weak and sometimes immovable. Someone who has myasthenia gravis that has attacked the face can have droopy eyes, blurred vision and might lack the ability to smile because of the weakening of muscles (Pressman 2014). Patients with the disease in other muscles might have a hard time stabilizing their neck and even performing simple everyday tasks. When a person becomes tired, the symptoms worsen. However in most cases, when

Your arms are too weak to pick up the remote control, your eyelids too droopy to watch your favorite show, your jaw too weak to chew and enjoy your meal. Episodes like these are all too familiar to individuals suffering from Myasthenia Gravis, a rare & debilitating chronic autoimmune disease. This disease can affect people of all ages and like all autoimmune diseases, sufferers of Myasthenia Gravis have immune systems that attack the body, in this case, targeting an important neurotransmitter known as acetylcholine. This prevents acetylcholine from binding with the acetylcholine nicotinic receptor thereby preventing the muscle from carrying out the signal and contracting. The nature of this disease sometimes makes it difficult to diagnose as the definitive causative agent is unknown, however, distinct clinical presentation, etiology and an understanding of the

Myasthenia Gravis, commonly abbreviated MG, literally means "grave muscle weakness". This autoimmune disease is characterized by antibodies being misdirected to block ,alter, or destroy acetylcholine (ACh) receptors at the motor end plate in the neuromuscular junction. ACh is the neurotransmitter used by motor neurons to stimulate skeletal muscle fibers to contract and as receptors for this neurotransmitter are increasingly attacked, it becomes more difficult for individuals to move their muscles. The hallmark of MG is muscle weakness that increases during periods of activity and improves after periods of rest. Any voluntary muscle is at risk of being affected but those that control eye and eyelid movement, facial expression, and swallowing are most frequently affected. The degree of muscle weakness can range from these localized

Skeletal muscle is the organ responsible for movements in the locomotor system. Skeletal muscle is under voluntary control, unlike smooth and cardiac muscle. Nerve impulse is the source of stimulation for the skeletal muscle activity, because skeletal muscle has no intrinsic activity because of the lack of ion channels that are responsible for the depolarization of membrane (Philip M., 2006). Muscle contraction results from the interaction of the filamentous proteins, actin and myosin. It starts when an action potential travels to the skeletal muscle along the motor neuron, where the neuromuscular junction releases acetylcholine that binds to the sarcolemme receptor, which cause Na+ to enter the muscle fiber and generate another action potential inside the muscle

Myasthenia gravis may affect any voluntary muscles. They may affect muscles that control the eyelid movement, facial expression and swallowing. The most symptoms of myasthenia gravis that can be noticed are the weakness of the eye muscle that causes double vision. Some symptoms of myasthenia gravis may include unstable walk, arm weakness, weakness in hands, fingers, legs and neck, change in facial expression, having a hard time swallowing, shortness of breath, and having problems with

There are several steps that are needed to complete muscle contraction. First a neuron action potential arrives at the end of the motor neuron. Acetylcholine (ACh) is later released from the axon to receptors, which is located on the sarcolemma. The sarcolemma is stimulated and a muscle impulse travels over the surface of the muscle fiber and deep into the fiber through the transverse tubules and reaches the sarcoplasmic reticulum

Myoneural junction. This is where the nerve and muscle join. A synapse forms between the motor neuron and the muscle fiber. This is where the motor neuron is able to send a signal to the muscle fiber, which makes the muscle contract. The brain then sends a signal to the muscle fiber to contract. The signal moves down the neuron and gets to the chemical junction between the neuron and the muscle. The signal goes over the synapse and comes to the the muscle which in turn causes the muscle to