The Muscular System Unit Objectives: Be able to explain the differences between the 3 types of muscles in the human body Be able to describe common muscle actions and how muscle contractions are initiated Be able to name the major skeletal muscles of the body (human and cat) as well as their origin/insertion points

The Muscular System Muscles are responsible for all types of body movement Muscle Functions: Movement Maintain posture Stabilize joints Heat Three basic muscle types found in the body: 1-Smooth muscle 2-Cardiac muscle 3-Skeletal muscle

Characteristics of Muscles Muscle cells are elongated Contraction of muscles is due to the movement of microfilaments – many cells contracting at the same time All muscles share some terminology Prefix myo refers to muscle

1-Smooth Muscle Characteristics: How blood and food move No striations Spindle-shaped cells Single nucleus Involuntary – no conscious control Found mainly in the walls of hollow organs (blood vessels, intestines) Figure 6.2a

2-Cardiac Muscle Characteristics: What makes your heart beat? Striations Usually only one nucleus Cells joined to each other at an intercalated disc Involuntary Found only in the heart Figure 6.2b

3-Skeletal Muscle Characteristics: Moving your bones! Most are attached by tendons to bones Remember “tendons tug” Cells have more than one nucleus Striated – have visible banding Voluntary – subject to conscious control Cells are surrounded and bundled by connective tissue

Connective Tissue Wrappings of Skeletal Muscle Endomysium – around single muscle fiber Perimysium – around a bundle of fibers Epimysium – covers the entire skeletal muscle Fascia – on the outside of the epimysium Figure 6.1

Skeletal Muscle Attachments Epimysium blends into a connective tissue attachment; the tendon – a cord-like structure Sites of muscle attachment 1-Bones 2-Cartilages 3-Connective tissue coverings Animation: http://www.wisc- online.com/objects/index_tj.asp?objID=AP13904

Contraction of a Skeletal Muscle Video Muscle fiber contraction is “all or none” Within a skeletal muscle, not all fibers may be stimulated during the same interval Different combinations of muscle fiber contractions may give differing responses Graded responses – different degrees of skeletal muscle shortening Must have ATP in order to contract

Muscle Response to Strong Stimuli Muscle force depends upon the number of fibers stimulated More fibers contracting results in greater muscle tension Muscles can continue to contract unless they run out of energy (ATP) :(

Energy for Muscle Contraction Initially, muscles used stored ATP for energy – aerobic activities Bonds of ATP are broken to release energy Only 4-6 seconds worth of ATP is stored by muscles After this initial time, other pathways must be utilized to produce ATP – anaerobic activities and lactic acid build-up

Muscle Fatigue and Oxygen Debt When a muscle is fatigued, it is unable to contract The common reason for muscle fatigue is oxygen debt Oxygen must be returned to tissue to remove oxygen debt Oxygen is required to get rid of accumulated lactic acid Increasing acidity (from lactic acid) and lack of ATP causes the muscle to contract less

Muscles and Body Movements Movement is attained due to a muscle moving an attached bone Muscles are attached to at least two points Origin – attachment to an immoveable bone Insertion – attachment to a movable bone Figure 6.12

Ordinary Body Movements Flexion – decreases the angle between two adjacent body segments Extension – increases the angle between two adjacent body segments Rotation – the bone distal to the joint is moved either toward (medial) or away from (lateral) the midline Abduction – movement of a body part away from the midline Adduction – movement of a body part back toward the midline Circumduction – a combination of flexion, abduction, extension, and adduction http://www.med.umich.edu/lrc/hypermuscle/hyper.html

Body Movements Figure 6.13a–c

Body Movements

Body Movements Figure 6.13d

Naming of Skeletal Muscles 1-Direction of muscle fibers Example: rectus (straight) 2-Relative size of the muscle Example: maximus (largest) 3-Location of the muscle Example: many muscles are named for bones (e.g., temporalis) 4-Number of origins Example: triceps (three heads)

Naming of Skeletal Muscles 5-Location of the muscle’s origin and insertion Example: sterno (on the sternum) 6-Shape of the muscle Example: deltoid (triangular) 7-Action of the muscle Example: flexor and extensor (flexes or extends a bone)

Head and Neck Muscles Figure 6.15

Trunk Muscles ANTERIOR Figure 6.16

Deep Trunk and Arm Muscles POSTERIOR Figure 6.17

Muscles of the Pelvis, Hip, and Thigh Figure 6.19c

Muscles of the Lower Leg POSTERIOR ANTERIOR Figure 6.20

Superficial Muscles: Anterior Figure 6.21

Superficial Muscles: Posterior Figure 6.22

Movement Quiz: Standing on your toes as in ballet is (1) of the foot. Walking on your heels is (2) . Winding up for a pitch (as in baseball) can properly be called (3) . To keep your seat when riding a horse, the tendency is to (4) your thighs. In running, the action at the hip joint is (5) in reference to the leg moving forward and (6) in reference to the leg in the posterior position. When kicking a football, the action at the knee is (7) . In climbing stairs, the hip and knee of the forward leg are both (8) .

You have just touched your chin to your chest; this is. (9) You have just touched your chin to your chest; this is (9) of the neck. Using a screwdriver with a straight arm requires (10) of the arm. Consider all the movements of which the arm is capable. One often used for strengthening the upper arm and shoulder muscles is (11) . Moving the head to signify “no” is (12) . Action that moves the distal end of the radius across the ulna is (13) . Raising the arms laterally away from the body is called (14) of the arms.When you are cupping your hands in order to hold a bowl of soup, the position is called __(15)__.

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