STAIRCASE EFFECT OR TREPPE

• The graduated series of increasingly vigorous contractions that results when corresponding increase series of identical stimuli is applied to rested muscle

• Muscle contraction after a long period of time

• Initial contraction become only half as strong as those occur in later in response to stimuli of same strength

STAIRCASE EFFECT OR TREPPE

• Increased Ca ions in cytosol

• Failure of sarcoplasm to pump back to sarcoplasmic reticulum

• Warm up period by athletes

SKELETAL MUSCLE TONE• Tautness occurs in muscles in relaxed condition

• In case of skeletal muscles •

• CAUSES• Generation of low rate of nerve impulse coming from spinal

cord

• Unconscious nerve impulses

• Tone enables the muscles to go quickly in action

SKELETAL MUSCLE TONE

• Tendons are toned

• Controlled partly signals transmitted from brain and partly by signals originate in muscle spindles

• Example• Maintain posture, prevents from injury from sudden

pull

MUSCLE FATIGUE• Prolonged and strong contraction

• Depletion of muscle glycogen

• Inability of metabolic machinery

• Inability contractile machinery

• Diminishing nervous signal

MUSCLE FATIGUE

• Diminishing muscle contraction

• Interruption of blood flow to contracting muscles

• Complete muscle fatigue

CO-ACTIVATION

• Simultaneous contraction of agonist and antagonist muscles on opposite side of joints

• Controlled by motor control centers of brain and spinal cord

• Nervous system directs the position of muscles

Remodelling of muscle• Reorganization or reconstruction or renovation of

old structure

• Muscles are remodeled• Alteration in their lengths• Alteration in their diameters• Alteration in their strengths• Alteration in their types of fibers• Alteration in their vasular supply• Process in weeks

MUSCLE HYPERTROPHY• Increase in total mass of muscles

• Mechanism• Increase in number of actin and myosin filaments in

each muscle fiber• Enlargement of individual muscle fiber

• Simple fiber hypertrophy• Loading of muscles during contractile phase

MUSCLE HYPERTROPHY

• Reasons• Rate of synthesis of muscle protein is greater• Increase in number of actin and myosin

filaments to almost 50%• Splitting of myofibrils• Rapid supply of energy • Increase in number of enzymes especially for

glycolysis

MUSCLE ATROPHY

• Muscles remain unused for many weeks• Decay of contractile proteins• More rapid

Hypertrophy

• Examples• Weight training• Steriod use• Enabling these cells to mature in size

Adjustment of muscle length

Another type of hypertrophy Stretching of muscles to maximum length Adding of new sarcomeres• Shortening of muscles to maximum• Disappearance of sarcomeres at end

HYPERPLASIA

• Hypergenesis• Proliferation of cells• Gross enlargement of organ• Physiological phenomenon• Microscopically visible as normal• Normal regulatory control mechanism• In addition to hypertrophy increase in number of

fibers• Linear splitting of enlarged fibers

REASONS OF HYPERPLASIA

• Increased demand• Chronic inflammatory response• Compensation for damage and tissue injury• Harmless• Occurs at particular tissue

HYPERPLASIA

• Example• Growth and multiplication of milk secreting

glandular cells in the breast in response to pregnancy

• Artificially produced by injecting hormones such as IGF-1

• Human growth hormone

HYPERPLASIA

Abnormal Hyperplasia

• Cushing syndrome• Congenital adrenal hyperplasia• Benign prostatic hyperplasia• Endometrial hyperplasia • Breast hyperplasia• Compensatory liver hyperplasia

PLASIA

• Anaplasia; Dedifferentiation• Neoplasia; Abnormal proliferation• Dysplasia; Maturation abnormality• Metaplasia; Cell type conversion• Desmoplasia; Connective tissue growth

NEOPLASIA

• Genetically abnormal cells proliferate in non-physiological manner

EFFECT OF MUSCLE DENERVATION

• No nerve supply, no signal• No contractile signals to maintain normal size• Atrophy occurs• Appearance of degenerative changes• after 2 months• If nerve grows rapidly• Return of muscle within 3 months• Incapability of muscles after three months

EFFECT OF MUSCLE DENERVATION

• At final stage of denervation• Fibers are destroyed• Replacement by fibrous and fatty tissue• STRUCTURE• Long cell membrane• Nuclei in series• No contractile apparatus• No regeneration of myofibrils• Capability to continue shortening• Contracture

Recovery of muscle contraction in poliomyelitis

Some nerve fibers are destroyed• Remaining nerve fibers branch off to form

new axons• Innervation into paralyzed muscles• Formation of large motor units• Macromotor units• Decrease in fitness of control