Download The Muscular System overview INSTRUCTOR: UNIT: Explanation of

The Muscular System
OVERVIEW
INSTRUCTOR:
UNIT: Explanation of Animal Anatomy and Physiology Related to Nutrition, Reproductive
Health, and Management of Domesticated Animals.
LESSON:
The Muscular System
IMS REFERENCE: #8646-D
SELECTED STUDENT ACTIVITES
1. The purpose of the animal’s muscular system is to move the animal and the materials
within the animal’s body. The muscles are important to the locomotion and life support
of animals. They are the lean portions of the carcasses of meat animals used for human
consumption.
2. Muscles are either voluntary or involuntary. The animal can control voluntary muscles
(for example, leg muscles) but not involuntary muscles (for example, heart muscles). All
voluntary muscles are striated, but involuntary muscles may be smooth muscle, striated
muscle, and cardiac muscle.
3. The muscle responsible for decreasing the angle between two bones when the muscle
contract is a flexor, such as the biceps of the forearm. Conversely, the muscle on the
opposite side of the same two bones that is responsible for increasing the angle between
them is an extensor. The triceps, which are responsible for extending the elbow, are a
good example of an extensor.
4. Muscles producing a desired action are agonists, while muscles producing the opposite
of a desired action are antagonists. Using the same example of the forelimb, if the desired
action is extension of the elbow, the triceps are the agonists and the biceps are the
antagonists. However, the roles reverse if the desired action is a flexed elbow.
5. Muscles also may be classified as adductor and abductor. Muscles that pull parts of the
limbs toward the middle of the animal’s body are called adductors. The pectoral muscles
of the front leg are strong adductors and move the animal’s body forward if the foot is
fixed on the ground. Muscles that tend to pull the limbs away from the middle of the
body are called abductors. The deltoid muscles of the front leg are abductors; they also
are flexors of the shoulder joint.
6. The scientific name of a muscle is usually partially descriptive of the muscle and is
determined by its action, attachments, shape, position, direction, function, kind of tissue,
or a combination of these factors.
7. A pennate arrangement causes a muscle to have the greatest power but decreases its
potential for contraction. A parallel arrangement of muscle fibers allows for the greatest
contraction but does not produce the greatest strength.
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The Muscular System
8. A voluntary muscle fiber consists of a multinucleated body enclosed by a thin
membrane (sarcolemma). A muscle fiber also contains many smaller fibers with cross
striations (myofibrils) that run parallel to the elongated axis of the muscle fiber. The
muscle fiber is filled with sarcoplasm. The sarcoplasm contains delicate filaments
(endoplasmic reticulum) that are involved in the metabolism of the fiber as well as in the
reaction to nerve messages. The sarcolemma is the main contributor to the elasticity of
the muscle fiber. It acts as the vehicle of attachment to the tendenous tissue of other
muscle fibers or to the tendon that connects to the skeletal system.
9. Some muscles may appear connected directly to the bone by a fleshy attachment.
Actually, the muscle fibers connect to short tendons that attach to the periosteum of the
bone or that may even slightly penetrate the surface of the bone.
10. Synovial structures reduce friction and allow for free movement of body parts.
Examples include capsules, bursae, and synovial sheaths.
11. Arthritis is caused by excess synovial fluid in joint capsules that causes inflammation
of the joint and results in swelling and pain.
12. The chief source of energy for muscle contraction is from the breakdown of
adenosine triphosphate (ATP).
13. Striated muscle fibers consist of bands of light and dark fibers from which they get
their name. The lighter bands, called isotrophic bands, contain small filaments of the
protein actin. Darker bands, called anisotrophic bands, consist of filaments of the protein
myosin.
14. A branch of a voluntary nerve, or motor neuron, controls each voluntary muscle fiber.
A motor neuron and its many branches connected to muscle fibers are called a motor unit.
15. The nerve impulse that stimulates muscle contraction does not travel beyond the
nerve ending. The electrical stimulus provided by the nerve is passed to the muscle by a
chemical reaction that passes through the nerve and muscle membranes. An electrical
action potential is produced by a change in the balance of ions inside and outside of the
nerve ending membrane. The resulting chemical ions on the outside of the nerve
depolarize the muscle fiber membrane resulting in muscle fiber contraction.
16. Only 25% of the energy produced for muscle contraction is actually used by muscles.
The remainder of the energy generates heat. This heat is important in maintaining body
temperature when the environmental temperature decreases. Two general types of heat
are involved - initial heat or heat given off during muscle contraction and heat of
recovery given off when the muscles are rebuilding energy.
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The Muscular System
17. The organ walls of many body systems - digestive, reproductive, circulatory, etc. –
consist of involuntary muscles. In addition, most secretory organs have involuntary
muscles to force secretions out of the body.
18. Smooth muscles contract as a result of nerve impulses, chemicals, hormones, or
electrical stimulation.
19. Trapezius, rhomboid, serratus ventralis, brachiocephalicus, latissimus dorsi, pectoral
muscles, deltoid muscles, biceps, triceps, carpi radialis, digital extensors, and digital
flexors.
20. Hamstrings (biceps femoris, semitendinosus, and semimembranous), middle gluteus
muscle, iliacus, psoas major, psoas minor, deep gluteus muscle, gracilis, adductor muscle,
quadriceps femoris, gastrocnemius, superficial digital flexor, tibialis anterior, peroneus,
digital extensors, and digital flexors.
21. Longissimus dorsi, splenius, complexus, rhomboids, dorsal oblique, dorsal straight,
ligamentum nuchae, sterno-cephalicus, sterno-thyro-lyoideus, longus coli, ventral
straight, external abdominal oblique, internal abdominal oblique, cremaster, transversus
abdominis, rectus abdominis, diaphragm, external intercostal, and internal intercostal.
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