Myasthenia Gravis

Myasthenia gravis is the prototype autoimmune disease mediated by blocking antibodies. A patient with this disease produces auto-antibodies that bind the acetylcholine receptors on the motor end-plates of muscles, blocking the normal binding of acetylcholine and also inducing complement-mediated lysis of the cells. The result is a progressive weakening of the skeletal muscles (Figure 20-5). Ultimately, the antibodies destroy the cells bearing the receptors. The early signs of this disease include drooping eyelids and inability to retract the corners of the mouth, which gives the appearance of snarling. Without treatment, progressive weakening of the

STIMULATING AUTO-ANTIBODIES (Graves' disease)

'Pituitary gland

'Pituitary gland

Tsh Receptor

TSH receptor

Regulated production of thyroid hormones

Auto-antibody-

to receptor

TSH receptor

Thyroid cell

Thyroid cell

Over Production Lymphocytes

Unregulated overproduction of thyroid hormones

Regulated production of thyroid hormones

FIGURE 20-4

Unregulated overproduction of thyroid hormones

In Graves' disease, binding of auto-antibodies to the receptor for thyroid-stimulating hormone (TSH) induces unregulated activation of the thyroid, leading to overproduction of the thyroid hormones (purple dots).

muscles can lead to severe impairment of eating as well as problems with movement. However, with appropriate treatment, this disease can be managed quite well and afflicted individuals can lead a normal life.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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