1. MUSCULAR SYSTEM “the power system” Muscle is an organ that contracts to move, support, or stabilize part of the body

2. MUSCLE CONTRACTIONS Muscle Tone In order to function, muscles should always be slightly contracted and ready to pull. Whatever a person is doing – moving, standing, or sitting – the brain makes tiny adjustments to the tone of individual muscles so posture is always preserved. Only during sleep does muscle tone diminish and the body relax completely

3. Muscle contractions may be isotonic or isometric. ISOTONIC CONTRACTION When muscles contract and shorten. (Walk, talk, etc.)

4. ISOMETRIC CONTRACTION When the tension in a muscle increases but the muscle does not shorten. (exercises such as tensing the abdominal muscles.)

5. MUSCULAR SYSTEM Nearly half our weight comes from muscle tissue. There are 650 different muscles in the human body. Muscles give us form and shape. Muscles produce most of our body heat.

6. THREE MAIN FUNCTIONS Responsible for all body movement. Responsible for body form and shape (posture) Responsible for body heat and maintaining body temperature.

7. TYPES OF MUSCLES SMOOTH SKELETAL CARDIAC

8. Skeletal Muscle Attached to bone Striated (striped) appearance VOLUNTARYcaused by a person’s conscious decision to do something Multinucleated muscle cell bundles (muscle cells = muscle fibers) SARCOLEMMA = cell membrane ***Contract quickly, fatigue easily, can’t maintain contraction for long period of time

9. Smooth Muscle Visceral (organ) muscle Found in walls of digestive system, uterus and blood vessels Cells small and spindle-shaped INVOLUNTARY Controlled by autonomic nervous system Act slowly, do not tire easily, can remain contracted for long time

10. Cardiac Muscle Found only in the heart Striated and branched Involuntary Cells are fused – when one contracts, they all contract

11. SPHINCTER = special circular muscles in openings of esophagus and stomach, stomach and small intestine, anus, urethra and mouth.

12. CHARACTERISTICS OF MUSCLES CONTRACTIBILITY – the ability of a muscle to reduce the distance between the parts of its contents or the space it surrounds. EXCITEABILITY (IRRITABILITY) – the ability to respond to certain stimuli by producing impulses.

13. EXTENSIBILITY – the ability to be stretched. ELASTICITY – ability of muscle to return to its original length when relaxing.

14. MOVEMENT 1. Muscles move bones by pulling on them. As a muscle contracts, it pulls the insertion bone closer to the origin bone. Movement occurs at the joint between the origin and the insertion.

15. MOVEMENT Muscles pull the bones, to which they are attached by tendon, across a joint When a muscle contracts, one of the bones to which it is attached – the insertion – moves, while the other attachment point – the origin – remains fixed.

16. Since they can only pull and not push, muscles work in antagonistic pairs to produce opposing movements. Ex: flexor muscles in the forearm, bend fingers, while their antagonists, the extensor muscles, straighten them.

17. Ex: The biceps muscle pulls the forearm upward toward the shoulder to bend the arm. Its antagonist, the triceps, pulls the forearm downward to straighten the arm. The brachioradialis acts as a synergist to the biceps, helping it bend the arm. Muscles that work together to produce the same movement are called synergists

18. Rule: A muscle’s insertion bone moves toward its origin bone. 2.Groups of muscles usually contract to produce a single movement

19. MOTOR UNIT – a motor neuron plus all the muscle fibers it stimulates. The nerve impulses that stimulate contraction are carried in nerves by bundles of wire-like motor neurons. As a motor neuron nears a muscle, it divides into several branches called axon terminals, each serving a different muscle fiber. TOGETHER, each motor neuron and the muscle fibers it stimulates are called a MOTOR UNIT

21. NEUROMUSCULAR JUNCTION – the junction between the motor neuron’s fiber which transmits the impulse – and the muscle cell membrane. ACETYLCHOLINE – chemical neurotransmitter, diffuses across the synaptic cleft (carries impulse across synaptic cleft)

23. MUSCLE FATIGUE – caused by the accumulation of lactic acid in the muscles. If too little O2 reaches the muscles during strenuous exercise, waste lactic acid builds up, causing the muscles to ache.

24. OXYGEN DEBT – after exercise, the amount of oxygen needed by the muscle to change lactic acid back to glucose. An athlete pants after a race because his body needs to get extra oxygen to its cells – over & above their resting oxygen consumption- In order to “pay off” an “oxygen debt.”

25. This “debt” is generated during hard exercise by anaerobic respiration, when muscle fibers obtain energy without using oxygen. The waste product of this process – lactic acid – must be disposed of by aerobic respiration, a process that requires extra oxygen, before muscles can work normally again

26. MUSCLE TONE - When muscles are slightly contracted and ready to pull. DIAPHRAGM – Dome-shaped muscle that separates the abdominal and thoracic cavities, aids in breathing

27. Disorders and Related Terminology ATROPHY – wasting away of muscle due to lack of use. HYPERTROPHY – an increase in the size of the muscle cell.

28. STRAIN – tear in the muscle resulting from excessive use. Bleeding inside the muscle can result in pain and swelling. Ice packs will help stop bleeding and reduce swelling.

29. MUSCLE SPASM (cramp) – sustained contraction of the muscle, usually because of overuse. MYALGIA – muscle pain HERNIA – organs can protrude through this weak muscle.

30. FLAT FEET (TALIPES) – weakening of leg muscles that support the arch, downward pressure on the foot eventually flattens out the arches. Condition can be helped by exercise, massage and corrective shoes.

31. TETANUS (lockjaw) – Infectious disease, continuous spasms of voluntary muscles, caused by a toxin from the bacillus clostridium tetani, enters the body through puncture wound. Prevented by an anti-toxoid vaccine.

32. TORTICOLLIS (wry neck) – may be due to an inflammation of the trapezius and/or sternocleidomastoid muscle.

33. MUSCULAR DYSTROPHY – group of diseases in which muscle cells deteriorate. Most common is Duchenne Muscular Dystrophy, caused by a genetic defect.

34. MYASTHENIA GRAVIS – progressive muscular weakness and paralysis, sometimes death. Cause unknown. Fatal when respiratory muscles are paralyzed.

35. TENDONITIS – inflammation of a tendon CONTRACTURE – tightening or shortening of a muscle.

36. NAMING MUSCLES Every skeletal muscle is given a Latin name according to one or more of its features and some cover several features.

37. MUSCLE FEATURES & DESCRIPTIONS LOCATION: Example: the frontalis runs over the frontal bone of the skull RELATIVE SIZE: using terms such as maximus (largest), minimus (smallest), longus (long), and brevis (short). Example: the gluteus maximus is the biggest gluteal

38. SHAPE- Example: the two trapezius muscles form a trapezoid (four sided) shape ACTION – using terms such as flexor (bends a joint) and extensor (straightens a joint). Example: the flexor carpi ulnaris bends the hand at the wrist.

39. ORIGIN & INSERTION Ex.: the sternocleidomastoid has origins (where bones do not move) on the breast bone (sternum) and collar bone (clavicle – cleido) and insertions (where bones do move) on the mastoid process of the skull’s temporal bone.

40. NUMBER OF ORIGINS Using terms such as biceps (two heads) Ex: the biceps brachii (arm) has two origins on the scapula (shoulder blade)

41. Deltoid – mean triangular – which is named after its shape Gastrocnemius - fleshy calf muscle whose name means “belly of the leg” Orbicularis oculi – forms a ring around the eye (means “circular” and “of the eye”