Chapter 7 The Muscular System

The Muscular System Muscles are responsible for all types of body movement – they contract or shorten and are the machine of the body Three basic muscle types are found in the body Skeletal muscle Cardiac muscle Smooth muscle

Characteristics of Muscles Muscle cells are elongated (muscle cell = muscle fiber) Contraction of muscles is due to the movement of microfilaments All muscles share some terminology Prefix myo refers to muscle Prefix mys refers to muscle Prefix sarco refers to flesh Slide 6.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Skeletal Muscle Characteristics Most are attached by tendons to bones Cells are multinucleate Striated – have visible banding Voluntary – subject to conscious control Cells are surrounded and bundled by connective tissue = great force, but tires easily Slide 6.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Connective Tissue Wrappings of Skeletal Muscle Endomysium – around single muscle fiber Perimysium – around a fascicle (bundle) of fibers Figure 6.1 Slide 6.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Connective Tissue Wrappings of Skeletal Muscle Epimysium – covers the entire skeletal muscle Fascia – on the outside of the epimysium Figure 6.1 Slide 6.4b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Skeletal Muscle Attachments Epimysium blends into a connective tissue attachment Tendon – attach muscle to bone Ligaments – attach bone to bone Sites of muscle attachment Bones Cartilages Connective tissue coverings Slide 6.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Smooth Muscle Characteristics Has no striations Involuntary – no conscious control Found mainly in the walls of hollow organs Push food along digestive tract Contract uterus during childbirth Control diameter of blood vessels Slow, sustained and tireless (can remain contracted for long periods) Slide 6.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Cardiac Muscle Characteristics Has striations Involuntary Found only in the heart Requires continuous oxygen supply Steady pace! Figure 6.2b Slide 6.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Function of Muscles Produce movement Maintain posture Stabilize joints Generate heat Slide 6.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Microscopic Anatomy of Skeletal Muscle Cells are multinucleate Nuclei are just beneath the sarcolemma (cell membrane) Figure 6.3a Slide 6.9a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Microscopic Anatomy of Skeletal Muscle Sarcolemma – specialized plasma membrane Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum Figure 6.3a Slide 6.9b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Characteristics of Muscles Contractility – ability to shorten in response to a suitable stimulus Excitability/Irritability – ability to receive and respond to a stimulus (produces electric signals/impulses) Extensibility – ability to be stretched Elasticity – ability to return to original length when relaxing Slide 6.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Muscle Attachments & Functions Muscles are attached to bones by tendons Bones are connected to bones by ligaments

Muscle Attachments & Functions When a muscle attaches to an immoveable bone, it is called the origin. Attachment to the moveable bone is called the insertion. Sternocleidomastoid Origin: sternum & clavicle Insertion: mastoid process

Example: Origin of the shoulder muscle (deltoid) is by the clavicle and scapula. Its insertion is on the humerus. When the deltoid contracts, the area by the scapula remains stationary, but the area by the humerus moves and abducts the arm away from the body.

Types of Body Movements Adduction – moving a body part toward the midline Abduction – moving a body part away from the midline Flexion – decreasing the angle between two bones, or bending a body part Extension – increasing the angle between two bones, or straightening a body part Rotation – turning a body part around its own axis (head from side to side)

Body Movements Slide 6.33 Figure 6.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Effects of Exercise on Muscle Results of increased muscle use Increase in muscle size Increase in muscle strength Increase in muscle efficiency Muscle becomes more fatigue resistant Slide 6.31 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Muscle Fatigue Caused by accumulation of lactic acid in the muscles During period of vigorous exercise, the blood is unable to transport enough oxygen to meet demand This causes the muscles to contract anaerobically lactic acid builds up in muscles. Results in muscle fatigue and cramping

Types of Muscles Prime mover – muscle with the major responsibility for a certain movement Antagonist – muscle that opposes or reverses a prime mover Synergist – muscle that aids a prime mover in a movement and helps prevent rotation Slide 6.35 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Naming of Skeletal Muscles Location of the muscle Example: many muscles are named for bones (e.g., temporalis) Number of origins Example: biceps (two headed muscle on humerus) Slide 6.36b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Naming of Skeletal Muscles Direction of muscle fibers Example: external abdominal oblique – edge of lower rib cage Size of the muscle Example: gluteus maximus (largest muscle in buttock) Slide 6.36a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Naming of Skeletal Muscles Shape of the muscle Example: deltoid (triangular) Action of the muscle Example: flexor and extensor (flexes or extends a bone) Slide 6.37 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Head and Neck Muscles Slide 6.38 Figure 6.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Trunk Muscles Slide 6.39 Figure 6.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Deep Trunk and Arm Muscles Figure 6.16 Slide 6.40 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Muscles of the Pelvis, Hip, and Thigh Figure 6.18c Slide 6.41 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Muscles of the Lower Leg Figure 6.19 Slide 6.42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Superficial Muscles: Anterior Figure 6.20 Slide 6.43 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Superficial Muscles: Posterior Figure 6.21 Slide 6.44 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings