Applied Aspects (Clinical Consideration) Dr. Abdelrahman Mustafa Department of Basic Medical Sciences Division of Physiology Faculty of Medicine Almaarefa Colleges

Learning Objectives Over view of diseases of motor neuron, chemical agents & diseases that affect Neuromuscular Junction and muscle dystrophies. Identify the concepts of muscle hypertrophy and muscle atrophy

Disease of motor neurons Poliomyelitis: cell bodies of motor neurons are destroyed by polio virus First described by Michael Underwood in 1789 First outbreak described in U.S. in 1843 Virus localized in the anterior horn cells of the spinal cord and certain brain steam motor nuclei.

Clinical features : – muscleweakness initially associated with the proximal muscles of the limbs, – making it hard to get up from a chair or use the stairs. They may have difficulty in routine work.

Disease of motor neurons (continues) Amyotrophic lateral sclerosis: It is a progressive neurological disease that affects the control of muscle movement due to its damaging affects on motor neurons in the spinal cord and the brain

Amyotrophic lateral sclerosis First signs and symptoms – Stiffness – Weakness (especially in hands, arms and legs) – Slurred speech Later signs and symptoms: – Difficulty chewing and swallowing – Shortness of breath – Muscle weakness due to wasting away of muscles Causes muscles to become smaller – Respiratory failure – Paralysis

Diseases of Neuromuscular Junction MyastheniaGravis Acquired autoimmune disorder First clinical description in 1672 by Thomas Willis Clinically characterized by: – Weakness of skeletal muscles – Fatigability on exertion. weakness increased by exertion – Weakness increases during the day and improves with rest Extraocular muscle weakness – Ptosis is present initially in 50% of patients and during the course of disease in 90% of patients Head extension and flexion weakness – Weakness may be worse in proximal muscles

Chemical agents & diseases that affect Neuromuscular Junction

Strain Injuries to Muscle A strain is an injury to a muscle or tendon Can be as simple as overstretching a muscle or tendon, or it can be a partial or complete tear The muscles most susceptible to injury are those of the limbs Predisposing factors causing a muscle strain injury – Relative weakness of a given muscle, resulting from a lack of training. – Fatigue, which leads to increased injury late in an athletic event.

Carrying, holding, or restraining items, people or animals Lifting, pushing, holding or pulling loads Working in a fixed position with the back bent, sitting or standing continuously, or driving vehicles for long periods Repetitive tasks such as reaching to lift or lower objects, or to grip tools continuously Working in awkward positions involving bending or twisting your body to reach items Vibrations through the body like driving a truck or using a powered hand tool

Clinical features Pain muscle spasm muscle weakness, swelling limitation for moving the muscle

Muscle Hypertrophy Size of muscles can be increase by regular bouts of anaerobic, short duration, high intensity, resistance training, such as weight lifting -Increase in diameter of fast glycolytic fibers - increased synthesis of actin and myosin filaments -Stress triggers signaling proteins that turn on genes that direct the synthesis contractile proteins

Muscle Atrophy Skeletal muscle atrophy can result from a large number of causes: Immobilisation (space flight, cast immobilisation, physical inactivity); Disease-related (cancer, HIV, rheumatoid arthritis, renal failure, burns, sepsis); Drug-related (glucocorticoids); Inadequate nutritional intake or digestion (starvation, protein malnutrition, impaired digestion); Ageing.

Muscular Dystrophy A fatal Hereditary pathological conditions characterized by progressive degeneration of contractile elements. Affects young boys leading to death before age of 20. There are many different types of muscular dystrophy. They include: Becker muscular dystrophy Duchene muscular dystrophy Emery-Dreifuss muscular dystrophy Limb-girdle muscular dystrophy

Duchene Muscular Dystrophy X-linked recessive disorder Defective gene responsible for Duchene muscular dystrophy- gene normally produces dystrophine

Common Signs and Symptoms Difficulty taking first steps Difficulty getting up from sitting or supine position – Gower sign Unusual gait – may walk on toes or balls of feet – belly pushed out and shoulders back Weak muscular strength tests Treatment under research – Gene Therapy – Cell Transplantation Approach

References Human physiology by Lauralee Sherwood, 7 th edition Text book physiology by Guyton &Hall,12 th edition Text book of physiology by Linda.s contanzo,third edition 17