… for twelfth standard MUSCLES: Physiology.. .. An illustration from … T. MADHAVAN, M.Sc.,...

… for twelfth standard

MUSCLES: Physiology.

An illustration from … T. MADHAVAN, M.Sc., M.L.I.S., M.Ed., M.Phil., P.G.D.C.A., Lecturer in Zoology....

This power . presentation is optimized for the Pre- Medical Students,

MUSCLES: Physiology

Muscles

elastic in nature,

capable of contraction

respond with the Central Nervous System.

convert bio-chemical energy in to Mechanical work.

Approximately 40% of the body is skeletal muscle and almost 10%

is smooth and cardiac muscles



Skeletal Muscles

Non striated Muscles

Cardiac Muscles

Muscles: Types



Structure of a Skeletal Muscle

Striated muscle is composed of many fibres arranged in bundles.

The diameter of each fibre varies from 10-100 micorns. The length of fibres ranges from 1-20 mm.

Each fibre is surrounded by a membrane called sarcolemma.

Each fibre is made up of 4-20 thread like structures called myofibrils which are parallel to each other.

Myofibrils are 1-3 micron in diameter.

A small segment of the myofibril is called as sarcomere.

In between the myofibrils, the sarcoplasm is present.



Ultra Structure of Skeletal Muscle



Structure of Sarcomere

The second set of thin filaments overlaps the long

filaments in `A band` are formed of the substance

called actin.

Myosin, Actin, Troponin and Tropomyosin are the 4

major proteins constitute the contractile machinery of

muscle fibres.

The energy of muscle action is provided by ATP

molecules.



Structure of Sarcomere

Electron microscopic studies have shown that the sriations are due to regular arrangement of 2 types of protein filaments.

`A band contains a thick filaments formed of the contractile protein myosin which may range upto 110°A in diameter and 1.5 micron in length.



ATP as the source of Energy for Contraction

For a muscle in action, energy is required. This energy is released by cleaving ATP molecules to ADP + Pi.

Greater amount work is performed by the muscle, with greater amount of ATP that is cleaved.

This energy bind with active site of actin filament to contract.



Neuro Muscular Junction

Write an assignment on the topic mentioned above



Initiation of Muscle contraction:

This activity begins with action potentials in the muscle fibres.

These elicit electrical currents that spread to the interior of the fibre, where the Ca+ ions are released from the sarcoplasmic reticulum.

The Ca+ ions in turn initiate the chemical events of the contractile process.

This over all process of controlling muscle contraction is called excitation.



Maximum strength of Contraction of a muscle operating at a

normal muscle length is about 3.5 Kg/ Sq.cm.

Changes in Muscle Strength:

When a muscle begins to contract after a long period of rest, its initial strength of contraction may be as

little as on half of its maximum strength.

It gains strength after 30-50 muscle twitches.

Weight lifters apply this to reach maximum capacity.



When the muscles are at rest, a certain amount of contractedness usually remains.

This residual degree of contraction in skeletal muscles is called Muscle

tone.

Muscle Tone



The skeletal Muscle tone is the result of nerve impulses coming from the spinal cord.

These inturn are partially controlled by impulses transmitted from the brain.

To some extent, the muscle tone is due to the muscle fibres itself.

Muscle Tone



Muscle Fatigue [Dimnished muscle contraction]

Prolonged and strong contraction of muscles leads to the state of muscle fatigue.

This is due to glycogen depletion.

Fatigue probably results from inability of the contractile and metabolic process of the muscle fibre.

Non-supply of blood to the muscles leads to almost complete fatigue within a minute.

This is due to non-supply of O2 and nutrients to the muscles.



Rigor Mortis:Several hours after death all the muscles of the body attain a state of contracture called Rigor mortis.

This is due to the complete depletion of ATP in muscle fibres.

The muscle remains in rigor, until the lysosomes enzymes completely destroy all muscle proteins.

This will takes place 15-25 hours after death.



Muscle Pull

Muscle pull is actually muscle tear.

A traumatic pulling of the fibres produces tear known as strain.

This injury can occur due to sudden stretching of muscle beyond the ir point of elasticity.

Strains may be the result of high velocity impacts and can be due to repetitive movements.

Back pain is a common problem, caused by muscle pull.



Hernia [Rupture] is usually noticed as a lump, commonly in the groin or in the umbliclal region.

It appears when a portion of tissue, which lines the abdominal cavity {Peritonium} breaks through a weakened area of the abdominal wall.

This gives discomfort and can be dangerous if a piece of intestine becomes strangulated inside.

The only way to stop hernia getting worse is to repair the defect surgically.



Hiatus hernia



Myasthenia Gravis

It is an auto immune disease.

It mostly affects women between the ages 20-30.

It causes the person become paralysed because of inability neuro-muscular junction to transmit signals from the nerve to muscle fibre.

The muscles affected include those used in walking, breathing, chewing and talking.

Symptom is dropping eyelids.

The disease can be cured by removal of thymus gland and by a blood –cleansing process called plasmapheresis.



Write an Summary of muscle structure & contraction



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… for twelfth standard MUSCLES: Physiology.. .. An illustration from … T. MADHAVAN, M.Sc.,...

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