Download Muscular System

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 Attachments
 Epimysium blends into a 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
Microscopic Anatomy of
Skeletal Muscle cell (fiber)
 The nuclei are pushed aside by ribbonlike myofibrils
 Cells are multinucleate
 Nuclei are just beneath the sarcolemma(plasma
membrane)
Figure 6.3a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.9a
Microanatomy of Skeletal
Muscle
Each muscle cell is called a muscle fiber. Within
each muscle fiber are many myofibrils.
 Myofibril
 Bundles of myofilaments
 Myofibrils are aligned to give two
distinct bands:
 I band =
light band
 A band =
dark band
Figure 6.3b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 6.10a
Z line
Z line
The sarcomere is the functional unit of a muscle cell
Sarcomere Relaxed
The part of the sarcomere with only actin filaments is called the I band.
Sarcomere Completely
Contracted
The sarcomere is completely contracted in this slide. The I and H bands
have almost disappeared.
Neuromuscular Components
Neuromuscular junction- the point where a
motor neuron joins muscle fibers.
Motor unit is a motor neuron and all the muscle
fibers it innervates(may be few or hundreds).
All or none law : with adequate stimulation, a
muscle cell will contract to its fullest extent or
not at all .
So there is no partial contraction of muscle fiber
Skeletal muscle activity
Muscles have two 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 a chemical transmitter
called Acetylcholine (Ach)
 Sarcolemma becomes temporarly permeable
to sodium which enter the cell so leads to
depolarization of the cell.
 This upset generates an electric current called
action potentiual which is unstoppable
leading to muscle fiber contraction.

MUSCLE TONE

Relaxed skeletal muscles are always slightly
contracted
 This state is termed “muscle tone”
 Spinal reflexes continually activate an alternating
subset of motor neurons.
 No active movement produced but muscles are
kept firm, healthy, and ready to respond to
stimulation.
 Helps stabilize joints and maintain posture.
TYPES OF MUSCLE CONTRACTIONS
1-Isotonic contraction
Muscle length changes(shortens)
and moves the load.
 Once
tension is sufficient to
move a load, tension remains
relatively constant.
 Bending the knee, rotating the
arms and smiling are examples
2-ISOMETRIC CONTRACTIONS

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
- Isotonic contraction (Aerobic exercise) 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 equipments.
Leads to enlargement of muscle cell without
increase in their number
Energy for muscle contraction
ATP store in the muscle supplies
energy ONLY for 4-6 seconds
 ATP then comes from
1-direct phosphorylation of ADP

2-Anaerobic respiration
3-aerobic mechanism (oxidative
phosphorylation
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 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
 DELTOID means having a
triangular shape
 TRAPEZIUS means having
a trapezoid shape
 SERRATUS means having
a saw-toothed shape
(Serratus Ant.)
 RHOMBOIDEUS means
having a diamond shape
(Rhomboid Major)
Naming Skeletal Muscles

Origin & Insertion
STERNOCLEIDOMASTOID
attaches to the Sternum,
Clavicle, and Mastoid
Process
•Naming Skeletal Muscles
According to Function
NAME
ACTION
EXAMPLE
FLEXOR
Decrease angle at a joint
Flexor Carpi Radialis
EXTENSOR
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
Synergist – muscle that aids a prime mover
in a movement and helps prevent rotation
Fixator – stabilizes the origin of a prime
mover
Types of body movements
–
Movement
that
decreases
angle
between 2
bones.
 Flexion
–
movement
that
increases
angle
between 2
bones
 Extension
 Abduction
–
movement
away from
the midline
of the body
Muscular System
 Adduction
–
movement
towards the
midline of
the body
–
occurs when
palms rotate
forward or
upward
 Supination
Opposition: moving the thumb to touch the
tips of the other fingers
 Pronation
– occurs
when
palms
rotate
downward
or
posteriorly
 Dorsiflexion
–
standing on
heal
flexion –
standing on
toes
 Plantar
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
Muscles of the face
Figure 11–4a
Muscles of Facial xpression
Figure 11–4b
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
Muscles of Mastication
Figure 11–6
3 Muscles of Mastication

Masseter:


Temporalis:


the strongest jaw muscle
helps lift the mandible
Buccinator
flattens the cheek,hold the food
between the teeth
Anterior Muscles of the Neck
Figure 11–9
Oblique and Rectus Muscles
Figure 11–11a, b

Anterior abdominal wall muscles :
external oblique muscles
 internal oblique muscles
 Transversus abdominis
 Rectus abdominis:


Diaphragmatic muscle or diaphragm:
divides thoracic and abdominal
cavities
 performs respiration

Pelvic Floor Muscles
Function
1-Support organs of pelvic cavity
2-Flex sacrum and coccyx
3-Control movement of materials through urethra
and anus
 Divided into:
anterior urogenital triangle
 posterior 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
Muscles that Move the Arm
Figure 11–15a
Muscles that Move
the Forearm and Hand
Figure 11–16a
Muscles that Move
the Forearm and Hand
Figure 11–16b
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
Extensors of the Knee
4 the quadriceps femoris:
3 vastus muscles
 rectus femoris muscle

Flexors of the knee
o
o
o
Semitendinosis
Semimembrenosis
Biceps femoris
Muscles that Move the Leg
Figure 11–20b, c
Muscles that Flex the Leg (hamstring)
Figure 11–20a
Muscles that Move
the Foot and Toes
Figure 11–21a, b
Muscles that Move
the Foot and Toes
Figure 11–21c, d
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