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Muscular System
Muscles are responsible for all types
of body movement
 Three basic muscle types are found in
the body

Skeletal muscle
 Cardiac muscle
 Smooth muscle

Characteristics of Muscle
All Muscle cells are elongated
(muscle cell = muscle fiber)
 All can contract 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 muscle

Types of Muscle
Types of Muscle, cont.
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
Characteristics of Smooth
Muscle





Has no striations
Spindle-shaped
cells
Single nucleus
Involuntary – no
conscious control
Found mainly in the
walls of hollow
organs
Cardiac Muscle
Characteristics





Has striations
Usually has a
single nucleus
Joined to another
muscle cell at an
intercalated disc
Involuntary
Found only in the
heart
Muscle Tissue
There are three types of muscle tissue
in the body.
 Skeletal muscle is the type that
attaches to our bones and is used for
movement and maintaining posture.
 Cardiac muscle is only found in the
heart. It pumps blood.
 Smooth muscle is found in organs of
the body such as the GI tract.
Smooth muscle in the GI tract moves
food and its digested products.
Skeletal Muscle
Skeletal muscle attaches to our skeleton.
 The muscle cells are long and cylindrical.
 Each muscle cell has many nuclei.
 Skeletal muscle tissue is striated. It has tiny
bands that run across the muscle cells.
 Skeletal muscle is voluntary. We can move
them when we want to.
 Skeletal muscle is capable of rapid contractions.
It is the most rapid of the muscle types.
 No rhythmic contraction.

Cardiac Muscle








Branching cells
One or two nuclei per cell
Striated
Involuntary
Medium speed contractions
Cardiac muscle tissue is only found in
the heart.
Its speed of contraction is not as fast as
skeletal, but faster than that of smooth
muscle.
IT has rhythmic contraction
Smooth Muscle








Fusiform cells (spindle-like shape)
One nucleus per cell
Nonstriated
Involuntary
Slow, wave-like contractions
Smooth muscle is found in the walls of
hollow organs.
The contractions of smooth muscle are
slow and wave-like.
Some has rhythmic contraction
Connective Tissue Wrappings of
Skeletal Muscle
 Endomysium –
around single
muscle fiber
 Perimysium –
around a
fascicle
(bundle) of
fibers
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 6.1
Slide 6.4a
Connective Tissue Wrappings of
Skeletal Muscle
 Epimysium –
covers the
entire skeletal
muscle
 Fascia – on the
outside of the
epimysium
Figure 6.1
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.4b
Skeletal Muscle Attachments
 Epimysium blends into (‫َ دَ َم ََج‬,
ََ ‫ج‬
ََ َ‫ ) َمز‬a
connective tissue attachment
 Tendon – cord-like structure
 Aponeuroses – sheet-like structure
 Sites of muscle attachment
 Bones
 Cartilages
 Connective tissue coverings
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.5
Function of Muscles
 Produce movement
 Maintain posture
 Stabilize joints
 Generate heat
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.8
Microscopic Anatomy of Skeletal
Muscle cell (fiber)
 The nuclei are pushed aside by
ribbonlike myofibrils
 Cells are multinucleate
 Nuclei are just beneath the sarcolemma
Figure 6.3a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.9a
Microscopic Anatomy of Skeletal
Muscle cell (fiber)
 Sarcolemma – specialized plasma
membrane
 Sarcoplasmic reticulum – specialized
smooth endoplasmic reticulum
Figure 6.3a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.9b
Microscopic Anatomy of Skeletal
Muscle cell (fiber)
 Myofibril
 Bundles of myofilaments
 Myofibrils are aligned to give distrinct bands
 I band =
light band
 A band =
dark band
Figure 6.3b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.10a
Microscopic Anatomy of Skeletal
Muscle
 Sarcomere
 Contractile unit of a muscle fiber
Figure 6.3b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.10b
Microscopic Anatomy of Skeletal
Muscle
 Organization of the sarcomere
 Thick filaments = myosin filaments
 Composed of the protein myosin
 Has ATPase enzymes
Figure 6.3c
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.11a
Microscopic Anatomy of Skeletal
Muscle
 Organization of the sarcomere
 Thin filaments = actin filaments
 Composed of the protein actin
Figure 6.3c
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.11b
Microscopic Anatomy of Skeletal
Muscle
 Myosin filaments have heads
(extensions, or cross bridges)
 Myosin and
actin overlap
somewhat
Figure 6.3d
Slide 6.12a
Microscopic Anatomy of Skeletal
Muscle
 At rest, there is a bare zone that lacks
actin filaments
 Sarcoplasmic
reticulum
(SR) – for
storage of
calcium
Figure 6.3d
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.12b
Microanatomy of Skeletal
Muscle
Each muscle cell is called a muscle fiber. Within
each muscle fiber are many myofibrils.
Neuromuscular Components
Neuromuscular junction- the point where a
motor neuron joins muscle fibers.
Motor unit- a motor neuron and all the
muscle fibers it innervates, may be few or
hundred
All or none law-with adequate stimulation,
a muscle cell will contract to its fullest
extent or not at all
Skeletal muscle activity
Muscles have special functions
 1-Irritability : the ability to receive and
respond to stimulus
 2-Contractility : the ability to shorten
 Muscle cell must be stimulated by
nerve impulse to contract
 There is a gap (synaptic cleft)
between the nerve &muscle cell

This gap is crossed by chemical
transmitter called Acetylcholine (Ach)
 Sarcolemma becomes temporarly
permeable to sodium
 This upset generates an electric
current called action potentiual which
is unstoppable leading to contraction

MUSCLE TONE

Relaxed skeletal muscles are always slightly
contracted
 This state is termed “muscle tone”

Stretch receptors in muscles and tendons are
activated




Spinal reflexes continually activate an alternating
subset of motor neurons
No active movement produced
Muscles kept firm, healthy, and ready to respond
to stimulation
Helps stabilize joints and maintain posture
MUSCLE CONTRACTIONS
 Isotonic
contraction
 Muscle length changes and
moves the load
 Once
tension is sufficient to
move load, tension remains
relatively constant
 Bending the knee, rotating the
arms and smiling are examples
ISOMETRIC CONTRACTIONS

Tension builds but muscle length
remains constant
Muscle attempts to move a load
greater than the force the muscle
is able to develop
 Try to lift your car or push against
immovable object or trying to lift
400kg are examples

Effect of exercise on Muscle
Muscles are no exceptions to the
saying –use it or lose it Regular exercise increases muscle
size, strength and endurance
 Aerobic exercise (isotonic
contraction)results in stronger muscle
with greater resistance to fatigue
 No increase in size but better heart &
lungs

Isometric (Resistance)
contraction
Require little time
 No special equipment
 Leads to enlargement of muscle cell
without increase in their number

Tetany
Sustained contraction of a muscle
 Result of a rapid succession of nerve
impulses delivered to the muscle.

Tetanus
This slide illustrates how a muscle can go into a sustained
contraction by rapid neural stimulation. In number four the
muscle is in a complete sustained contraction or tetanus.
Muscle fatigue.

Muscle fatigue occurs when an exercising
muscle can no longer respond to the same
degree of stimulation with the same degree of
contractile activity.
 Factors for this include an increase in
inorganic phosphate, accumulation of lactic
acid, and the depletion of energy reserves.
 Increased oxygen consumption is needed to
recover from exercise (paying off an oxygen
debt).
Naming Skeletal Muscle
Direction of
Muscle
Fibers
Location
Action
Skeletal
Muscle
Origin
&
Insertion
Size
Shape
Number
Of
Origins
Naming Skeletal Muscle

Direction of Muscle Fibers


Relative to the Midline
RECTUS means parallel
to midline
• Rectus Abdominus

TRANSVERSE means
perpendicular to midline
• Transversus Abdominus

OBLIQUE means
diagonal to midline
• External Oblique
• Internal oblique
Naming Skeletal Muscle
 Location
 Structure
near
which a muscle is
found
 Muscle near frontal
bone = Frontalis
 Muscle near the
Tibia = Tibialis
Naming Skeletal Muscle

Size


Relative Size of
Muscle
MAXIMUS means
largest
• Gluteus Maximus

MINIMUS means
smallest
• Gluteus Minimus

LONGUS means
longest
• Fibularis Longus

BREVIS means short
• Fibularis Brevis

Number of Origins


Number of tendons of
origin
BICEPS means two
• Biceps Brachii

TRICEPS means
three
• Triceps Brachii

QUADRICEPS
means four
• Quadriceps Femoris
Naming Skeletal Muscles

Shape



Relative Shape of
the Muscle
DELTOID means
having a
triangular shape
RHOMBOIDEUS
means having a
diamond shape
(Rhomboid Major)
Naming Skeletal Muscles

Origin & Insertion

ILIO COSTALIS
attaches to the
ilium & ribs
Naming Skeletal Muscles
Action:
NAME
FLEXOR
EXTENSOR
ACTION
EXAMPLE
Decrease angle at a joint
Flexor Carpi Radialis
Increase angle at a joint
Extensor Carpi Ulnaris
ABDUCTOR
Move bone away from
midline
Abductor Pollicis Longus
ADDUCTOR
Move bone toward midline
Adductor Longus
LEVATOR
Produces upward
movement
Levator Scapulae
DEPRESSOR
Produces downward
movement
Depressor Labii Inferioris
SUPINATOR
Turn palm
upward/anteriorly
Supinator
PRONATOR
Turn palm
downward/posteriorly
Pronator Teres
Types of Skeletal Muscle
Prime mover (Agonist) – muscle with
the major responsibility for a certain
movement
 Antagonist – muscle that opposes or
reverses a prime mover

Types of body movements
–
Movement that
decreases angle
between 2 bones.
 Flexion
–
movement that
increases angle
between 2 bones
 Extension
–
movement away
from the midline
of the body
 Abduction
 Adduction
–
movement
towards the
midline of the
body

Rotation – movement around a longitudinal axis

Circumduction-combination of flexion, extension,
abduction, and adduction. seen in ball and
socket joints as the shoulder
–
occurs when
palms rotate
forward or
upward
 Supination
– occurs
when palms rotate
downward or posteriorly
 Pronation
 Dorsiflexion
–
standing on
heal
flexion –
standing on
toes
 Plantar
Inversion
of the foot: turn the
sole medially.
Eversion of the foot: turn the
sole laterally
Axial and Appendicular
Muscles
Figure 11–3a
Axial and Appendicular
Muscles
Figure 11–3b
Divisions of the Muscular
System
1.
Axial muscles:



2.
position head and spinal column
move rib cage
60% of skeletal muscles
Appendicular muscles:



support pectoral and pelvic girdles
support limbs
40% of skeletal muscles
Here……………………………..
Muscles of the face
Figure 11–4a
Extrinsic Eye Muscles

Also called extra-ocular muscles
Figure 11–5a, b
Extrinsic Eye Muscles
Inferior rectus
Medial rectus
Superior rectus
Lateral rectus
Inferior oblique
Superior oblique
Figure 11–5c
Summary: Extrinsic Eye Muscles
Table 11–3
Muscles of Mastication
Figure 11–6
3 Muscles of Mastication

Masseter:


Temporalis:


the strongest jaw muscle
helps lift the mandible
Buccinator
flattens the cheek, holds the food
between the teeth
Muscles of the Vertebral Column
Figure 11–10a
Muscles of the Vertebral
Column
Spinal extensors or erector spinae
muscles (superficial and deep)
 Spinal flexors (transversospinalis)

Functions of Pelvic Floor
Muscles
1.
2.
3.
Support organs of pelvic cavity
Flex sacrum and coccyx
Control movement of materials
through urethra and anus
Perineum

Muscular sheet forming the pelvic floor,
divided into:
anterior urogenital triangle
 posterior anal triangle

Pelvic Diaphragm
Deep muscular layer extending to pubis:
 supports anal triangle

The Appendicular Muscles
Figure 11–13a
The Appendicular Muscles
Figure 11–13b
The Appendicular Muscles
Position and stabilize pectoral and
pelvic girdles
 Move upper and lower limbs

Divisions of Appendicular Muscles
1) Muscles of the shoulders and upper limbs:
 Position the pectoral girdle
 Move the arm
 Move the forearm and hand
 Move the hand and fingers
2) Muscles of the pelvis and lower limbs
Muscles that Position
the Pectoral Girdle
Figure 11–14a
6 Muscles that Position the
Pectoral Girdle

Trapezius:
superficial
 covers back and neck to base of skull
 inserts on clavicles and scapular
spines


Rhomboid and levator scapulae:
deep to trapezius
 attach to cervical and thoracic
vertebrae
 insert on scapular border

6 Muscles that Position the Pectoral
Girdle

Serratus anterior:




Subclavius:



on the chest
originates along ribs
inserts on anterior scapular margin
originates on ribs
inserts on clavicle
Pectoralis minor:

attaches to scapula
Muscles that Move
the Forearm and Hand
Figure 11–16a
Muscles that Move
the Forearm and Hand
Figure 11–16b
Muscles that Move the Forearm and
Hand
Originate on humerus and insert on
forearm
 Exceptions:

the major flexor (biceps brachii)
 the major extensor (triceps brachii)

Extensors and Flexors

Extensors:


mainly on posterior and lateral
surfaces of arm
Flexors:

mainly on anterior and medial
surfaces
13 Muscles that Move the Forearm and
Hand

Biceps brachii:



Triceps brachii:




flexes elbow
stabilizes shoulder joint
extends elbow
originates on scapula
inserts on olecranon
Brachialis and brachioradialis:



flex elbow
originates on scapula
inserts on radial tuberosity
Tendon Sheaths

Extensor retinaculum:
wide band of connective tissue
 posterior surface of wrist
 stabilizes tendons of extensor
muscles


Flexor retinaculum:
anterior surface of wrist
 stabilizes tendons of flexor muscles

The Intrinsic Muscles of the
Hand
Figure 11–18b
Muscles of the Pelvis
and Lower Limbs

Pelvic girdle is tightly bound to axial
skeleton:


permits little movement
has few muscles
Muscles that Position the Lower Limbs
1.
2.
3.
Muscles that move the thigh
Muscles that move the leg
Muscles that move the foot and toes
Muscles that Move the Thigh
Figure 11–19a, b
Muscles that Move the Thigh
Gluteal muscles
 Lateral rotators (obturator)
 Adductors

Gluteal Muscles (1 of 2)
Cover lateral surfaces of ilia
 Gluteus maximus:

largest, most posterior gluteal muscle
 produces extension and lateral
rotation at hip

Gluteal Muscles (2 of 2)

Gluteus medius and gluteus minimus:
originate anterior to gluteus maximus
 insert on trochanter

Adductors

Adductor magnus:


Adductor brevis:


hip flexion and adduction
Pectineus:


hip flexion and adduction
Adductor longus:


produces adduction, extension, and flexion
hip flexion and adduction
Gracilis:

hip flexion and adduction
Muscles that Move the Leg
Figure 11–20a
Extensors of the Knee

4 muscles of the quadriceps femoris:
3 vastus muscles
 rectus femoris muscle

Muscles that Move
the Foot and Toes
Figure 11–21a, b
Muscles that Move
the Foot and Toes
Figure 11–21c, d
Muscles that Move
the Foot and Toes

Extrinsic muscles that move the foot
and toes include:
muscles that produce extension at the
ankle
 muscles that produce flexion at the
ankle
 muscles that produce extension at the
toes
 muscles that produce flexion at the
toes

4 Muscles that Produce
Extension at the Ankle
Gastrocnemius
 Soleus
 Fibularis
 Tibialis posterior
The calcaneal tendon (Achilles tendon)

Muscles that Produce
Flexion at the Ankle

Tibialis anterior:

opposes the gastrocnemius
Muscles that Produce Flexion at the Toes
Flexor digitorum longum
 Flexor hallucis longus:


oppose the extensors
Muscles that Produce
Extension at the Toes
Extensor digitorum longum
 Extensor hallucis longus
 Extensor retinacula:


fibrous sheaths hold tendons of toes
as they cross the ankle
The Intrinsic Muscles of the
Foot
Figure 11–22a
The Intrinsic Muscles of the
Foot
Figure 11–22b, c
Effects of Aging
on the Muscular System
1.
2.
Skeletal muscle fibers become
smaller in diameter
Skeletal muscles become less
elastic:

3.
4.
develop increasing amounts of
fibrous tissue (fibrosis)
Decreased tolerance for exercise
Decreased ability to recover from
muscular injuries
Integration with Other Systems
Figure 11–24