The Muscular System Chapter 11 Unit 6 The Muscular System There are approximately 600 muscles in the human body, about half of your body weight Muscles are composed of muscular tissue, which is constructed of bundles of muscle fibers about the size of a human hair The larger the muscles, the greater the fibers Muscles perform their duties by alternating contractions and relaxing
The Muscular System All muscle activity is influenced by the nervous system The Muscular System The group of cells and its motor neurons are called motor units A muscle contraction is a quick progression of events following a stimulus
When repeated stimulation occurs without a relaxation time, the muscle is maintained in a state of contraction called tetanus This happens when we experience muscle cramps and spasms Muscle Fuel All body tissues must have food and oxygen to survive The muscles receive an ample supply of both because of their importance to the bodys safety and well-being
The body stores carbohydrates in its muscles in the form of starch called glycogen When muscles function, they use the stored glycogen, changing it to glucose, as their source of energy Heat is released as this fuel is used, thereby warming the body Exercise burns glycogen Functions Of Muscles In addition to providing heat and the ability to move, muscles support the structures of the body and hold the body upright The muscles along the back, shoulders, and
neck hold the trunk and head erect while permitting great flexibility in movement Muscles also provide protective padding to shield delicate internal organs and structure form injury Muscles gives shape to the body Muscle Growth Muscle tissue changes slightly with age Muscles grow in relation to the structures to which they are attached, for example, muscles of the eye grow very little, whereas the large muscles of the lower extremities
grow considerably Types Of Muscle Tissue There are three types of muscle tissues -Skeletal muscle tissue -Smooth muscle tissue -Cardiac muscle tissue
Skeletal muscle tissue Skeletal, striated(striped) and voluntary or involuntary(next slide) Attached to bones, moves the skeleton, produces heat Essential to cause contraction These muscles are supplied with motor nerves for simple motions like extending the arm or breathing, to doing the highly coordinated movements like walking, swimming, or skiing 1Three
Skeletal(striated) names for this tissue: Skeletal- describes its location Striated(striped)describes its appearance Voluntary or involuntary - describes how it functions Specialized to contract and bring about movement 2 Smooth Muscle Tissue
Nonstraited, smooth, involuntary Found in walls of hollow organs such as blood vessels, intestines, and uterus Helps with peristalsis(to propel food through the digestive tract) 3 Cardiac Muscle Tissue
Have faint striations, involuntary Pumps blood Composes the walls of the heart Regulates the rate of the contraction Cardiac muscle contracts to squeeze blood out of your heart, and relaxes to fill your heart with blood.
Skeletal Muscle Action When muscle contract, they become shorter and thicker Example: when the biceps contract to bend at the elbow, the shorter and thicker muscle become, this causes a bulge in the upper arm
Skeletal Muscle Action The skeletal muscle that bends a joint is called a flexor muscle Whereas the action of straitening the joint is done by the extensor muscle The extensor muscle that straightens the elbow is the triceps
Skeletal Muscle Action Muscle also contract to move extremities away from the bodys center line, which is known as abduction, or toward the center line, which is known as adduction Muscle Tone
Loss of muscle tone can occur when muscles are not used, as with severe illness, elderly people, paralysis, or temporarily when an extremity has been immobilized in a cast With prolonged lack of use, muscles will atrophy(wasting away of a part of the body) Another condition that develops from lack of muscle use is called contracture, where the muscle become
paralyzed(fingers, elbows, knees, and hip joints) Muscle Attachment A tendon is known as a strong fibrous structure, are attached to rough surfaces on a bone, are extremely strong and do not stretch The thickest and strongest tendon in the human body is the Achilles tendon, which attaches the
gastrocnemius muscle in the calf of the leg to the heel bone Attached muscle to bone Muscle Attachment A similar type of connective tissue is called a ligament A ligament is flexible and supports organs and connects bone to bone
Remember: a tendon connects muscle to bone and a ligament connects bone to bone Major Skeletal Muscles The muscle most important in breathing divides the chest cavity from the abdominal cavity, this muscle is called the diaphragm
The sternocleidomastoid and the trapezius are the major muscles of the neck and the upper back that hold the head erect and assist with its movements Major Skeletal Muscles The pectoralis major is the main upper chest muscle, this enables us to flex the
arm across the chest The intercostal muscles lie beneath the pectoralis major, between the ribs, these enlarge the diaphragm during inspiration Major Skeletal Muscles The back is covered by a large muscle called the latissimus dorsi, its main function is to extend and
adduct the arm(as with swimming) The shoulders are protected by a triangle muscle called the deltoid, which abducts the arm The deltoid is used for small injections of medications, intramuscularly Major Skeletal Muscles(lower extremity) The lower extremities muscles involve half of the bodys total
muscle mass The buttock are formed by the large gluteus maximus muscles, which support the bodys weight and enable use to stand erect The upper outer quadrant(ventral gluteal) of the buttock is the site for intramuscular injections, especially for large amounts of a slowly absorbing medication
Major Skeletal Muscles(lower extremity) The front of the thigh has the longest muscle of the body, the Sartorius, this flexes the hip and knee joints to turn the thigh outward, making it possible to sit cross-legged on the floor
Major Skeletal Muscles(lower extremity) The quadriceps femoris, with four separate parts: Rectus femoris(vastus intermedius) Vastus lateralis(nest slide) Vastus medicalis Sartorius(last slide) It is a powerful extensor of the knee and is used when we rise from a sitting position, kick a ball, or swim
Vastus Lateralis The Vastus lateralis is the largest part of the quadriceps femoris This is an IM injection site, and is the standard for infants and young children because it is the safest and largest muscle for
children Major Skeletal Muscles(lower extremity) The gastrocnemius is the main muscle in the calf of the leg, this permits you to stand tiptoe It runs from its two heads just above the knee to the heel, and is involved in standing, walking,
running and jumping. Muscles Of Expression A number of muscles in the face enable us to show our feelings The frontalis(frontal) muscles can raise to express surprised The obicularis oris allows us to whistle, kiss, smile, grin
Muscle Strain And Cramps A strain is an injury to a muscle or tendon in which the muscle fibers tear as a result of overstretching Muscle cramps are unpleasant, often painful, caused by muscle contraction or over shortening, it can usually be relived by stretching the muscle or causing it to bear weight Disease And Disorders Tendonitis: This is a painful inflammation of the
tendon Epicondylitis(also called tennis elbow): This is inflammation of a forearm tendon at the attachment on the humerus at the elbow Fibromyalgia Syndrome: This is a chronic musculoskeletal condition characterized by widespread pain, it affects people of all ages Disease And Disorders Muscular
Dystrophy: This is a group of congenital disorder results in progressive wasting away of skeletal muscle There are several types of muscular dystrophy(listed on page 419) Disease And Disorders Torticollis: This
neck deformity bends the head to the affected side and rotates the chin toward the opposite side This caused by shorting or spasm of the strenocleidomastiod neck muscle
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