Download Chapter 7 The Muscular System

Chapter 7
The Muscular System
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 1
INTRODUCTION
• Muscular tissue enables the body and its parts to move
• Three types of muscle tissue exist in body
(see Chapter 3)
• Movement caused by muscle cells (called fibers):
shortening or contracting
• Muscle movement occurs when chemical energy
(obtained from food) is converted into mechanical
energy
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 2
MUSCLE TISSUE
• Types of muscle tissue (Figure 7-1)
• Skeletal muscle—also called striated or voluntary
muscle
• Microscope reveals crosswise stripes or striations
• Contractions can be voluntarily controlled
• Cardiac muscle—composes bulk of heart
• Cardiac muscle fibers are branched
• Has dark bands called intercalated disks
• Cardiac muscle fiber interconnections allow heart to contract
efficiently as a unit
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 3
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 4
MUSCLE TISSUE (cont.)
• Types of muscle tissue (cont.)
• Nonstriated muscle, or involuntary muscle—also called
smooth or visceral muscle
• Lacks cross stripes or striations when seen under
a microscope; appears smooth
• Found in walls of hollow structures, such as digestive tract,
blood vessels, etc.
• Contractions not under voluntary control
• Function—all muscle fibers specialize
in contraction (shortening)
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 5
STRUCTURE OF SKELETAL MUSCLE
• Muscle organs—mainly striated muscle fibers and connective
tissue



Connective tissue forms “wrappers” around each muscle fiber, around
fascicles (groups) of muscle fibers, and around the entire muscle; fascia
surrounds muscle organs and nearby structures
Most skeletal muscles extend from one bone across a joint
to another bone
Regions of a skeletal muscle (Figure 7-2)
• Origin—attachment to the bone that remains relatively stationary or fixed when
movement at the joint occurs
• Insertion—point of attachment to the bone that moves when a muscle contracts
• Body—main part of the muscle
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 6
STRUCTURE OF SKELETAL
MUSCLE (cont.)

Muscle organs (cont.)
• Muscles attach to bone by tendons—strong cords
or sheets of fibrous connective tissue that extend
from the muscle organ; some tendons enclosed
in synovial-lined tubes (tendon sheaths) and are
lubricated by synovial fluid
• Bursae—small synovial-lined sacs containing a small
amount of synovial fluid; located between some
tendons and underlying bones
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 7
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 8
STRUCTURE OF SKELETAL
MUSCLE (cont.)
• Muscle organs (cont.)
• Microscopic structure and function (Figure 7-3)
• Contractile cells are called muscle fibers; connective tissue holds muscle
fibers in parallel groupings
• Fibers of the cytoskeleton form cylinders that contain thick myofilaments
(containing myosin) and thin myofilaments (containing mainly actin)
• Basic functional (contractile unit called sarcomere
• Sarcomeres separated from each other by dark bands called
Z lines
• Sliding filament model explains mechanism of contraction
• Thick and thin myofilaments slide past each other to contract
• Contraction requires calcium and energy-rich ATP molecules (Figure 7-4)
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 9
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 10
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 11
FUNCTIONS OF SKELETAL MUSCLE
• Movement
• Muscles produce movement by pulling on bones
as a muscle contracts
• The insertion bone is pulled closer to the origin bone
• Movement occurs at the joint between the origin
and the insertion
• Groups of muscles usually contract to produce a single
movement
• Prime mover—mainly responsible for producing a given movement
• Synergist—helps the prime mover produce a given movement
• Antagonist—opposes the action of a prime mover in a given
movement
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 12
FUNCTIONS OF SKELETAL
MUSCLE (cont.)
• Posture
• A continuous, low-strength muscle contraction called
tonic contraction (muscle tone) enables us to maintain
body position
• Only a few of a muscle's fibers shorten at one time
• Produce no movement of body parts
• Maintain muscle tone called posture
• Good posture favors best body functioning
• Skeletal muscle tone maintains good posture by
counteracting the pull of gravity
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 13
FUNCTIONS OF SKELETAL
MUSCLE (cont.)
• Heat production
• Survival depends on the body’s ability
to maintain a constant body temperature
• Fever—an elevated body temperature—often a sign of illness
• Hypothermia—a reduced body temperature
• Contraction of muscle fibers produces most
of the heat required to maintain normal body
temperature
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 14
FUNCTIONS OF SKELETAL
MUSCLE (cont.)
• Fatigue
• Reduced strength of muscle contraction
• Caused by repeated muscle stimulation without adequate periods
of rest
• Repeated muscular contraction depletes cellular ATP stores and outstrips the
ability of the blood supply to replenish oxygen and nutrients
• Contraction in the absence of adequate oxygen produces lactic acid, which
contributes to muscle soreness
• Oxygen debt—term used to describe the metabolic effort required
to burn excess lactic acid that may accumulate during prolonged periods of
exercise
• Labored breathing after strenuous exercise is required to “pay the debt”
• This increased metabolism helps restore energy and oxygen reserves to preexercise levels
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 15
ROLE OF OTHER BODY SYSTEMS
IN MOVEMENT
• Muscle functioning depends on the functioning
of many other parts of the body
• Most muscles cause movements by pulling
on bones across moveable joints
• Respiratory, circulatory, nervous, muscular,
and skeletal systems play essential roles
in producing normal movements
• Multiple sclerosis, brain hemorrhage, and spinal cord
injury are examples of how pathological conditions in
other body organ systems can dramatically affect
movement
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 16
MOTOR UNIT
• Stimulation of a muscle by a nerve impulse
is required before a muscle can shorten and produce
movement
• A motor neuron is the specialized nerve that transmits
an impulse to a muscle, causing contraction
• Neuromuscular junction (NMJ)—point of contact
between a nerve ending and the muscle fiber
• Motor unit—combination of a motor neuron with the
muscle fibers it controls (Figure 7-6)
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 17
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 18
MUSCLE STIMULUS
• A muscle will contract only if an applied stimulus reaches a
certain level of intensity
• Threshold stimulus—minimal level of stimulation required
to cause a muscle fiber to contract
• Once stimulated by a threshold stimulus, a muscle fiber will
contract completely, a response called all or none
• Different muscle fibers in a muscle are controlled by different
motor units having different threshold-stimulus levels
• Although individual muscle fibers always respond all
or none to a threshold stimulus, the muscle as a whole
does not
• Different motor units responding to different threshold stimuli permit
a muscle as a whole to execute contractions of graded force
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 19
TYPES OF SKELETAL MUSCLE
CONTRACTION
• Twitch and tetanic contractions
• Twitch contractions are laboratory phenomena and not
normal muscle activity; they are a single contraction of
muscle fibers caused by
a single threshold stimulus
• Tetanic contractions are sustained muscular contractions
caused by stimuli hitting a muscle in rapid succession
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 20
TYPES OF SKELETAL MUSCLE
CONTRACTION (cont.)
• Isotonic contractions
• Contractions that produce movement at a joint because the
muscle changes length
• Concentric contractions—the muscle shortens at the insertion
end of the muscle to move toward the point of origin
• Eccentric contractions—the muscle lengthens under tension,
thus moving the insertion away from the origin
• Most types of body movements (walking, running, etc.) are
produced by isotonic contractions
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 21
TYPES OF SKELETAL MUSCLE
CONTRACTION (cont.)
• Isometric contractions
• Contractions that do not produce movement; the
muscle as a whole does not shorten
• Although no movement occurs, tension within
the muscle increases
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 22
EFFECTS OF EXERCISE ON
SKELETAL MUSCLES
• Exercise, if regular and properly practiced, improves
muscle tone and posture, results
in more efficient heart and lung functioning,
and reduces fatigue
• Muscles change in relation to the amount
of work they normally do
• Prolonged inactivity causes disuse atrophy
• Regular exercise increases muscle size, called
hypertrophy
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 23
EFFECTS OF EXERCISE ON
SKELETAL MUSCLES (cont.)
• Strength training is exercise involving contraction of
muscles against heavy resistance
• Strength training increases the number of myofilaments
in each muscle fiber, and as a result, the total mass of the
muscle increases
• Strength training does not increase the number of muscle
fibers
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 24
EFFECTS OF EXERCISE ON
SKELETAL MUSCLES (cont.)
• Endurance training is exercise that increases
a muscle’s ability to sustain moderate exercise over
a long period; it is sometimes called aerobic training
• Endurance training allows more efficient delivery of oxygen
and nutrients to a muscle via increased blood flow
• Endurance training does not usually result in muscle
hypertrophy
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 25
MOVEMENTS PRODUCED BY SKELETAL MUSCLE CONTRACTIONS
(Figures 7-7 through 7-9)
•
•
•
•
•
•
•
Flexion—decreases an angle
Extension—increases an angle
Abduction—away from the midline
Adduction—toward the midline
Rotation—around an axis
Circumduction—move distal end of a part in a circle
Supination and pronation—hand positions that result from
twisting the forearm
• Dorsiflexion and plantar flexion—foot movements
(upward and downward ankle movement)
• Inversion and eversion—foot movements (sideways)
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 26
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 27
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 28
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 29
SKELETAL MUSCLE GROUPS
(Table 7-1)
• Muscles of the head and neck (Figures 7-10
and 7-11)
• Facial muscles
• Orbicularis oculi
• Orbicularis oris
• Zygomaticus
• Muscles of mastication
• Masseter
• Temporal
• Sternocleidomastoid—flexes head
• Trapezius—elevates shoulders and extends head
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 30
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 31
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 32
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 33
SKELETAL MUSCLE GROUPS
(cont.)
• Muscles that move the upper extremities
•
•
•
•
•
Pectoralis major—flexes upper arm
Latissimus dorsi—extends upper arm
Deltoid—abducts upper arm
Biceps brachii—flexes forearm
Triceps brachii—extends forearm
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 34
SKELETAL MUSCLE GROUPS
(cont.)
• Muscles of the trunk (Figure 7-12)
• Abdominal muscles
•
•
•
•
Rectus abdominis
External oblique
Internal oblique
Transversus abdominis
• Respiratory muscles
• Intercostal muscles
• Diaphragm
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 35
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 36
SKELETAL MUSCLE GROUPS
(cont.)
• Muscles that move the lower extremities
•
•
•
•
Iliopsoas—flexes thigh
Gluteus maximus—extends thigh
Adductor muscles—adduct thighs
Hamstring muscles—flex lower leg
• Semimembranous
• Semitendinosus
• Biceps femoris
• Quadriceps femoris group—extend lower leg
• Rectus femoris
• Vastus muscles
• Tibialis anterior—dorsiflexes foot
• Gastrocnemius—plantar flexes foot
• Peroneus group—flex foot
Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 37