Muscular System
Muscles are responsible for all types of body movement
Three basic muscle types are found in the bodySkeletal muscleCardiac muscleSmooth 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 terminologyPrefix myo refers to musclePrefix mys refers to musclePrefix sarco refers to muscle
Types of Muscle
Types of Muscle, cont.
Skeletal Muscle AttachmentsSkeletal Muscle Attachments
Slide 6.5Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Epimysium blends into a connective tissue attachment Tendon – cord-like structure
Aponeuroses – sheet-like structure
Sites of muscle attachment Bones
Cartilages
Connective tissue coverings
Microscopic Anatomy of Microscopic Anatomy of Skeletal Muscle cell (fiber)Skeletal Muscle cell (fiber)
Slide 6.9aCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The nuclei are pushed aside by ribbonlike myofibrils
Cells are multinucleate
Nuclei are just beneath the sarcolemma(plasma membrane)
Figure 6.3a
Microanatomy of Skeletal Muscle
Each muscle cell is called a muscle fiber. Within each muscle fiber are many myofibrils.
Slide 6.10aCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Myofibril
Bundles of myofilaments
Myofibrils are aligned to give two distinct bands:
I band = light band
A band = dark band
Figure 6.3b
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 stimulus2-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 respiration3-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
Action
Origin&
Insertion
ShapeNumber
OfOrigins
Size
Location
Direction ofMuscleFibers
SkeletalMuscle
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
LocationStructure near which
a muscle is foundMuscle near frontal bone =
FrontalisMuscle 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
Flexion – Movement that decreases angle between 2 bones.
Extension – movement that increases angle between 2 bones
Abduction – movement away from the midline of the body
Muscular System
Adduction – movement towards the midline of the body
Supination – occurs when palms rotate forward or upward
Opposition: moving the thumb to touch the tips of the other fingers
Pronation – occurs when palms rotate downward or posteriorly
Dorsiflexion – standing on heal
Plantar flexion – standing on toes
Axial and Appendicular Muscles
Figure 11–3a
Axial and Appendicular Muscles
Figure 11–3b
Divisions of the Muscular System
1. Axial muscles: position head and spinal column move rib cage 60% of skeletal muscles
2. 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
Figure 11–5c
Inferior rectusMedial rectusSuperior rectusLateral rectusInferior obliqueSuperior oblique
Muscles of Mastication
Figure 11–6
3 Muscles of Mastication
Masseter:the strongest jaw muscle
Temporalis: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 musclesTransversus abdominisRectus abdominis:
Diaphragmatic muscle or diaphragm:divides thoracic and abdominal
cavitiesperforms respiration
Pelvic Floor MusclesFunction
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 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 Limbs1. Muscles that move the thigh
2. Muscles that move the leg
3. 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 musclesrectus femoris muscle
Flexors of the kneeo Semitendinosiso Semimembrenosiso 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. Skeletal muscle fibers become smaller in diameter
2. Skeletal muscles become less elastic:
develop increasing amounts of fibrous tissue (fibrosis)
3. Decreased tolerance for exercise4. Decreased ability to recover from
muscular injuries