Applied Aspects(Clinical Consideration)

Dr. Abdelrahman MustafaDepartment of Basic Medical Sciences

Division of Physiology Faculty of Medicine Almaarefa Colleges

بسم الله الرحمن الرحيم

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 virusFirst described by Michael Underwood in 1789First 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• Astrain 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 HypertrophySize 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, 7th edition

• Text book physiology by Guyton &Hall,12th edition

• Text book of physiology by Linda .s contanzo,third edition

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