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