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Orlando Paciello » 1.Introduction to the study of Veterinary Myopathology

Introduction to the study of Veterinary myopathology

Skeletal muscle has a number of functions within the body. It maintains posture, is responsible for movement and the rhythmical contraction of the respiratory muscles, the intercostals and diaphragm, which is essential to life.

Diagram of musculature in a horse. Taken from Horse Disease

Muscles (cont.)

Muscles are important for homeostasis in the body, as they are involved in glucose metabolism and regulate body temperature too.
Glycogen metabolism

Calcium enters the muscle cell thanks to the release of acetylcholine by the motor nerve.
The calcium activates the “phosphorylase kinase” discovered by Fischer and Krebs.
The “Phosphorylase kinase phosphorylates phosphorylase” enzyme is active.
The glycogen is then broken down into glucosium and used to generate ATP.
Muscles need energy in the form of ATP to work.
Muscle is made up of muscle fibres.
The contractile muscle fibres are activated by calcium.

Credits and References for the 1992 Physiology or Medicine Nobel Poster

Muscles (cont.)

Muscles, from a purely aesthetic point of view, make the body look more attractive.

Muscles (cont.)

Muscles determine the morpho/functional characteristics of work or show animals and, in animals destined for human consumption, they are the principal source of meat.

Young piemontese bull with characteristic "double muscled”

Loin comes from the lungissimus dorsi muscles of a cow. It is a prime quality meat, one of the classic cuts, and one of the tastiest and most prestigious

Muscle disorders

It is interesting to compare the effects of muscle disorders in people and animals.

The four legged stance makes for greater stability and animals affected by muscle pathologies can manage to walk for longer, whereas a person with the same problem would be confined to a wheelchair.

However, disorders leading to decubitus, even if temporary, can have devastating effects on large animals. In fact, it is much harder to look after a sick horse than a child or a dog.

Skeletal Muscle

Skeletal muscle function is closely related to the functioning of the peripheral nervous system. The physiological properties of a muscle fibre, its ability to contract and the type of metabolism (oxidative, anaerobic or mixed) depend on the neurone responsible for its innervation.

Diagram showing the relationship between central nervous system and skeletal muscle

Neuromuscular disorders

Neuromuscular disorders include problems relating to lower motor neurons, peripheral nerves, neuromuscular junctions and muscles.

Muscle fibre lesions

Muscle fibre lesions can be divided into two major categories neuropathic and myopathic.

Neuropathic lesions are those caused by the effect or absence of a nerve impulse (denervation atrophy).

The term “myopathic” should only be used to describe those muscular illnesses which are caused by primary damage to the muscle fibre, not to the interstitial connective tissue or to the blood vessels.

Neuromuscular pathologies

Neuromuscular Pathologies:

are difficult diagnostic dilemmas;
require new diagnostic skills.

There is no such thing as a “table top diagnosis” for any of the neuromuscular diseases. (Diana Shelton)

Muscular pathology

Knowledge of normal muscle structure and function, the macroscopic features as well as the histology, biochemistry, electrophysiology and ultrastructure of muscle is vital to an understanding of muscular pathology.