each muscle is composed of several fascicles, each one composing of these 

each is made up of many myofibrils

1. motor neuron in cortex sends axon potential down axon into spinal cord to the motor neuron

2. motor axon leaves spinal cord and innervates muscle

autoimmune disease in which autoantibodies to the acetylcholine receptor at the neuromuscular junction are present which impair binding of Ach

thymus often reactive

results in decrease in antibody titer (concentration of a solution). 

happens in myasthenia gravis disease 

small groups of fibers composing individual motor units become atrophic when their motor axon is injured or destroyed 

toxins (chemotherapy, alcohol)

trauma

metabolic diseases (DM)

inherited diseases

nutritional deficiencies (vit B12)

 can regenerate if the agent or disease causing the peripheral neuropathy is removed or treated. muscle can then be re-innervated and become functional again

in neurogenic atrophy 

general term implying a muscle disease caused by a structural abnormality in the muscle. This can be due to loss of normal structure or function of proteins in the muscle membrane, sarcoplasm, myofilaments.

can be inherited or sporadic 

due to expansion of a genetically unstable triplet repeat (CTG repeat). 

characterized by myotonia or prolonged contraction with inability to relax

links structural proteins (actin) in the sacroplasm to the cell membrane and the extracellular connective tissue.

stabilizes the membrane during contraction 

weakness due to fiber necrosis and dropout, with replacement by fat and scar tissue.

weakness initially affects muscles of the pelvic girdle and lower extremities and spread to other muscles 

sxs begin in young males when parents notice their boy is clumsy and cannot keep up with peers or cant climb stair easily 

death usually in late teens or early 20s due to pneumonia, aspiration, or cardiac insufficency 

physical therapy

hydrotherapy 

drugs

assistive devices 

stem cell replacement

upregulation of other proteins

helps with spasms and stiffness

delay muscle deterioration by suppressing inflammatory response

severe (infantile) form that is present at birth with severe weakness, difficulty sucking and swallowing, little spontaneous movement

death usually occurs within a few months due to respirtaory failure or pneumonia

forms presents with same sxs but milder in degree. weakness is very slowly progressive or static and most patients can live an independent life. 

adults 20-50 generalized weakness

represent a structural abnormality of the Z line involving one of the proteins composing the Z lines in the myofilament, alphal-actinin. 

derived from a lateral explansion of the Z line

in nemaline myopathy

acquired, not inherited and Polymyositis and dermatomyositis are the two major kind

parasite present in undercooked pork which pigs get from eating infected pork or from rats

in human muscle, parasite causes marked inflammation and eventually develops a capsule, calcifies and dies

caused by immune mechanism in which lymphocytes react against muscle fiber proteins (PM) or against the vessels in the muscle (DM)

characterized by inflammatory cells within the muscle and necrosis of muscle fibers 

lymphocytes against the vessels in the muscle.

has an associated violaceous rash over the face and upper eyelids, chest, knuckles, etc.

risk for cancer stronger than PM 

coricosteroids and immunosuppressive drugs

mainstray of therapy for PM and DM

tumor of skeletal muscle of children and adolescents, and rarely adults

treat with combination of surgery and chemotherapy 

benign smooth muscle tumor

commonly arises in uterus, often in the wall. often multiple. 

most common neoplasm in women 

tumor of smooth muscle (uterus, GI tract, etc)

in adults, more often in men 

occur in skin and deep soft tissue of extremities and retroperitoneum where they can be very large and usually are not completely resectable