Muscle and Nerve Pathophysiology PDF

Muscle pathophysiology Muscle pathophysiology refers to the abnormal changes or diseases affecting muscle tissue That could be cause either as a result of: 1. Genetic mutations 2. Autoimmune responses 3. Neurological disorders 4. Metabolic disorders 5. Toxic exposures 6. inflammation/ Inflammatory i...

Muscle pathophysiology Muscle pathophysiology refers to the abnormal changes or diseases affecting muscle tissue That could be cause either as a result of: 1. Genetic mutations 2. Autoimmune responses 3. Neurological disorders 4. Metabolic disorders 5. Toxic exposures 6. inflammation/ Inflammatory infiltration 7. Trauma or injury caused by direct or indirect factors, such as overuse, compartment syndrome, or drug use. Resulting in pathophysiology changes such as: 1. Muscle fiber necrosis 2. Inflammation 3. Fibrosis 4. Muscle atrophy: Atrophy is the decrease in muscle fiber size and number, leading to decreased muscle mass cause by disuse or immobilization, neurological disorders (e.g., denervation), Hormonal imbalances (e.g., cortisol excess), malnutrition, systemic illness, chronic glucocorticoid use, muscular dystrophyor aging (sarcopenia) resulting in decreased protein synthesis, increased protein degradation, reduced muscle fiber diameter and altered muscle architecture 5. Weakness 6. Fatigue 7. Muscle wasting 8. Pain 9. Decreased mobility 10. Respiratory difficulties 11. Hypertrophy: Increase in muscle fiber size and number, leading to increased muscle mass resulting in pathophysiological changes such as increased protein synthesis, increased muscle fiber diameter, Altered muscle architecture. Note: Muscle hypertrophy may be beneficial for athletes, but excessive hypertrophy can lead to muscle imbalances and injuries. Examples of various muscle disorders (myopathy) Myopathies are muscular disorders in which the dysfunction of muscle fibers leads to muscular weakness. They may be genetically transmitted or acquired. Various muscle disorders include: A. Genetic muscle disorders Example: Muscular Dystrophy (MD): MD is a group of genetic disorders characterized by progressive degeneration of muscle fibers, muscle weakness and muscle wasting. It is a genetic disorder caused by defective proteins in muscle cells. It is characterized by progressive skeletal muscle weakness and death of muscle cells and tissues. They are of various types including: 1. Duchenne Muscular Dystrophy (DMD): Most common and severe form of muscle dystrophy. It is an sex-linked recessive disorder cause due to absence of a gene product called dystrophin (which is an important product necessary for the stability of sacrolemma) in the X chromosome. Resulting in progressive muscle fibre degeneration and necrosis. The degenerated muscle fibers are replaced by fats and fibrous tissues.the common symptoms is muscular weakness but sometimes there is enlargement of muscles (pseudohypertrophy) and in severe condition the respiratory muscles becomes weak resulting in difficulty in breathing and death. 2. Becker Muscular Dystrophy: It is also a sex linked disorder. It occur due to reduction in quantity or alteration of dystrophin thus milder than DMD. Common features of Becker Muscular Dystrophy include slow progressive weakness of leg and pelvis, pseudohypertrophy of calf muscle(muscle located in the rear portion of the leg below the knees), difficulties in walking, fatigue and mental retardation. 3. Limb-Girdle Muscular Dystrophy (LGMD): Progressive muscle weakness and degeneration. Affects muscles around shoulders and hips. 4. Facioscapulohumeral Muscular Dystrophy (FSHD): Affects face, shoulder, and upper arm muscles. 5. Myotonic Dystrophy: Characterized by muscle stiffness and wasting. 6. Congenital Muscular Dystrophy: Present at birth. 7. Emery-Dreifuss Muscular Dystrophy: Affects muscles and heart. B. Inflammatory disorders like 1. Polymyositis: Inflammation of skeletal muscle. 2. Dermatomyositis: Inflammation of skin and skeletal muscle. 3. Inclusion Body Myositis: Progressive muscle inflammation and weakness as a result of inclusion bodies ie abnormal protein aggregate that form within cells eg alpha synuclein. C. Autoimmune disorders cause by immune system dysfunction such as: 1. Myasthenia Gravis: it is an autoimmune disorder caused by an antibody-mediated blockade of neuromuscular transmission (primarily cholinergic transmission) resulting in skeletal muscle weakness and rapid muscle fatigue. It is characterized by severe muscle weakness due to the inability of neuromuscular junction to transmit impulses from nerves to the muscle. 2. Lambert-Eaton Myasthenic Syndrome: is an autoimmune disease whereby a disease in which the immune system attacks the body's own tissues. The attack occurs at the connection between nerve and muscle (the neuromuscular junction) and interferes with the ability of nerve cells to send signals to muscle cells. Specifically, the immune system attacks the calcium channels on nerve endings that are required to trigger the release of chemicals (acetylcholine). The lowered levels of acetylcholine are not sufficient to cause normal muscle contractions, causing muscle weakness. D) Metabolic Muscle Disorders such as 1. McArdle's Disease: Glycogen storage disorder causing muscle cramps and weakness. 2. Carnitine Deficiency: Impaired fatty acid metabolism affecting muscle. 3. Mitochondrial Myopathies: Energy production disorders affecting muscle. E) Acquired Muscle Disorders such as 1. Rhabdomyolysis: Muscle breakdown due to trauma, exercise, or medication. 2. Compartment Syndrome: Increased pressure within muscle compartments. 3. Muscle Strains and Tears: Acute muscle injuries. F) Toxin exposures muscle Disorders: such as Botulism: Neurotoxin affecting muscle contraction. Tetanus: Bacterial toxin causing muscle stiffness. Snakebite Myonecrosis: Muscle damage due to snake venom. G) Metabolic Muscle Disorders: 1. McArdle's Disease: Glycogen storage disorder causing muscle cramps and weakness. 2. Carnitine Deficiency: Impaired fatty acid metabolism affecting muscle. 3. Mitochondrial Myopathies: Energy production disorders affecting muscle. 4. Glycogen Storage Diseases: Impaired glycogen metabolism affecting muscle. 5. Lipid Storage Diseases: Impaired lipid metabolism affecting muscle. Other Muscle Disorders: 1. Fibromyalgia: Chronic muscle pain and fatigue. 2. Muscle Cramps: Sudden, involuntary muscle contractions. 3. Tendinitis: Tendinitis is inflammation of a tendon that occurs when it is over-extended or worked too hard without rest. Tendons that are commonly affected include those in the ankle, knee, shoulder, and elbow. The affected tendon depends on the type of use that causes inflammation. Rock climbers tend to develop tendinitis in their fingers, while basketball players are more likely to develop tendonitis in the knees, to name a few examples. 4. Peripheral Neuropathy: Damage to nerve fibers affecting muscle strength. Etc. Some common Cardiac Muscle Disorders: 1. Hypertrophic Cardiomyopathy: Thickened heart muscle, obstructing blood flow. 2 Restrictive Cardiomyopathy : Stiffened heart muscle, limiting filling. 3 Myocarditis: Inflammation of heart muscle. Usually as a result of infections or toxins 4 Cardiac Sarcoidosis: also an inflammation of the heart muscle cause by infiltration of heart tissue with granuloma ( cluster of immune cells that normally aggregate to combat infection, inflammation, or foreign substances). These Immune cells infiltrate the heart, causing tissue damage, scarring of heart tissue leading to fibrosis, replacing healthy heart tissue. 5 Cardiac Amyloidosis: Protein deposits in heart muscle. Nerve pathophysiology Pathophysiology of nerves involves the study of abnormal changes in nerve function, structure, and biology. These include: 1. Demyelination: Loss of myelin sheath, disrupting nerve conduction. 2. Axonal degeneration: Damage to axons, disrupting nerve function. 3. Neuroinflammation: Activation of immune cells, releasing pro- inflammatory cytokines. Resulting in Nerve Damage such as: 1. Neuropathy: Damage to peripheral nerves. 2. Radiculopathy: Damage to nerve roots. 3. Neuritis: Inflammation of nerves. 4. Neurodegeneration: Progressive loss of neurons. Causes of Nerve Damage This include: 1. Trauma (injury) 2. Infections (e.g., Lyme disease, HIV) 3. Autoimmune disorders (e.g., multiple sclerosis) 4. Diabetes 5. Toxic exposures (e.g., heavy metals) 6. Genetic disorders (e.g., Charcot-Marie-Tooth) Clinical Manifestations of nerve damage 1. Pain 2. Numbness 3. Tingling 4. Weakness 5. Muscle atrophy 6. Loss of reflexes 7. Sensory deficits etc. Wallerian degeneration Wallerian degeneration is an active process of degeneration that results when a nerve fiber is cut or crushed and the part of the axon distal to the injury (which in most cases is farther from the neuron's cell body) degenerates. In other words, it is a pathological process that occurs after nerve injury or transection, characterized by the degeneration of the distal segment of the nerve resulting in loss of nerve function, muscle atrophy, sensory deficits and pain Assignment Read on other nerve pathophysiology