Locomotion and Movement

(b) Myasthenia gravis is a chronic autoimmune muscular disease.

It causes breakdown of neuromuscular junction due to which the brain loses control over muscles.

The symptoms may include drooping eyelids, difficulty in swallowing muscle fatigue, difficult breathing and inability to control facial expressions.

Myasthenia gravis is a chronic (long-lasting) disease that usually worsens slowly over time.

Although symptoms may fluctuate in severity over the years, the disease rarely goes away on its own.

The patients should avoid dairy foods, except for yogurt which can sooth digestive problems.

Good choices include mild foods like bananas, white rice, eggs and chicken.

Diarrhoea can lower potassium levels.

Foods rich in potassium include orange juice, bananas, potatoes, avocados and apricots.

(d) Osteoporosis has 3 causes: excess parathyroid hormone, advanced age, and lack of estrogen in older females.

Estrogen promotes the activity of osteoblast and inhibits osteoclast.

Parathormone promotes mobilisation of calcium from bone into blood.

Excessive activity of parathormone causes demineralisation leading to osteoporosis.

(d) Alzheimer's diseaseis a neurodegenerative disorder due to deficiency of neurotransmitter acetylcholine.

Rheumatoid arthritis is an autoimmune disorder in which antibodies are produced against the synovial membrane and cartilage.

Vitiligo causes white patches on skin also characterized as autoimmune disorder.

Psoriasis is a skin disease that causes itchy or sore patches of thick red skin and is also autoimmune.

(b) Muscular dystrophy is a inheritable disease that gradually cause the muscles to weaken, leading to an increasing level of disability.

Tetany, Myasthenia gravis and Botulism are not inheritable diseases.

(b) Myasthenia gravis is autoimmune disorder that affects neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscles.

Arthritis is inflammation of one or more joints.

It is characterised by pain, stiffness and limited function of joints.

Gout, a type of metabolic arthritis (diet related) is inflammation of joints due to accumulation of uric acid crystals.

It can cause painful swelling in joints and typically affects the big toe.

Osteoporosis is age related disorder characterised by decreased bone mass and increased chances of fractures.

It starts with the roughening of cartilage.

An autoimmune disease is a condition arising from an abnormal immune response to a functioning body part.

There are at least 80 types of autoimmune diseases.

Nearly any body part can be involved.

Common symptoms include low grade fever and feeling tired.

Often symptoms come and go.

Autoimmune disorders in general cannot be cured, but the condition can be controlled in many cases.

Historically, treatments include: anti-inflammatory drugs to reduce inflammation and pain.

(c) Increase in $Ca^{++}$level into the sarcoplasm leads to the binding of calcium with a subunit of troponin on actin filaments and there by remove the masking of active sites for myosin.

Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.

This pulls the attached actin filaments towards the centre of A band.

The Z line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction.

It is clear from the above steps, that during shortening of the muscle, i.e., contraction, the I bands get reduced, whereas the A bands retain the length.

(b) Central part of thick filament, not overlapped by thin filaments is called the H zone.

H zone is also called Hensen's Line.

(b) Sliding filament theory was given by Huxley and Huxley (1954).

It states that Actin and Myosin filaments do not become short but rather slide past each other.

Because of the sliding of actin filaments over myosin, the length of the I-band will change.

(c) Sustained contraction with no relaxation phase is called muscle tetanus.

A tetanic contraction (also called tetanised state, tetanus, or physiologic tetanus, the latter to differentiate from the disease called tetanus) is a sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate.

(a) Ca2+ binds troponin → tropomyosin shifts → active sites on actin exposed → myosin can bind.