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Muscular System Vocabulary
Aer – air; aerobic
An – not; anaerobic
Bi – two; biceps
Caput – head
Di – two
Ergon – work; synergist
Fasciculus - a bundle; fascicle
Gaster – stomach
Iso – equal; isometric
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Muscular System Vocabulary
Kneme – knee
Lemma – husk; sarcolemma
Metron – measure; isometric
Mys – muscle; epimysium
Platys – flat; platysma
Sarkos – flesh; sarcoma
Syn - together; synergist
Tetanos – convulsive tension; tetnus
Muscular System Vocabulary
Tonos – tension; isotonic
Trope – a turning; tropomyosin
-trophy – nourishing; atrophy
What do YOU know about the muscular
system?
Overview of Muscular System
Types of Muscle Tissue
1. Skeletal - Under voluntary control
* muscular system
2. Cardiac - Under involuntary control
* heart wall
3. Smooth - Under involuntary control
* visceral organs
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Skeletal Muscles
Skeletal muscles attach to bones directly or
indirectly
Perform five functions
1. Produce movement of skeleton –
contractions pull on tendons to
produce movement
2. Maintain posture and body position –
continuous muscle contractions
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Skeletal Muscles
3. Support soft tissues
4. Guard entrances and exits – encircle
openings to the digestive and urinary
tracts
5. Maintain body temperature – heat released
by energy produced during contractions
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Anatomy of Skeletal Muscles
Gross Anatomy: Connective tissue organization
Three Layers
• Epimysium
• Fibrous covering of whole muscle
• Separates the muscle from surrounding tissue
• Perimysium
• Fibrous covering of fascicle (bundle)
• Contains blood vessels and nerve cells
• Endomysium
• Fibrous covering of a single cell (a muscle fiber)
Contains stem cell
• Tendons (or aponeurosis)
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Anatomy of Skeletal Muscles
The Organization of a Skeletal Muscle
Figure 7-1
Anatomy of Skeletal Muscles
Microanatomy of a Muscle Fiber
• Much fiber different than a “typical”
cell
 can be very long (60 cm or 24”) /
equal to the entire length of that
specific muscle
multinucleated (can have hundreds of
nuclei)
Anatomy of Skeletal Muscles
The Organization of a Single Muscle Fiber
Figure 7-2(a)
Anatomy of Skeletal Muscles
Microanatomy of a Muscle Fiber
• Transverse tubules (T tubules)
• narrow tubes filled w/extracellular fluid which form
a passageway through a muscle fiber
• Myofibrils (contraction organelle) cylindrical
structures encircled by T-tubules
• hundreds to thousands
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Anatomy of Skeletal Muscles
Microanatomy of a Muscle Fiber
Sarcolemma
• Muscle cell membrane surrounding the
cytoplasm
Sarcoplasm
• Muscle cell cytoplasm
Sarcoplasmic reticulum (SR)
Like smooth ER
Contains high concentration of Ca+ ions which
are actively pumped in
Contraction begins when Ca+ is released into
the sarcoplasm
Anatomy of Skeletal Muscles
Sarcomere — Repeating structural unit of the
myofibril
Are responsible for muscle contraction by
shortening the entire cell
• Components of a sarcomere
• Myofilaments made of the proteins actin &
myosin arranged in thin and thick bands
• Thin filaments (actin with an active site
capable of interacting w/ myosin)
• Thick filaments (myosin)
Anatomy of the Muscular System
An Overview
of the Major
Skeletal
Muscles
Figure 7-11(a)
Anatomy of the Muscular System
An Overview
of the Major
Skeletal
Muscles
Figure 7-11(b)
Anatomy of the Muscular System
Origins, Insertions, and Actions
• Origin (where it begins)
Muscle attachment that remains fixed
• Insertion (where it ends)
Muscle attachment that moves
• Action (what it does)
What joint movement a muscle produces
Almost all skeletal muscle either originate or
insert on the skeleton
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Anatomy of the Muscular System
Primary Action Categories – Muscles in Action!
• Agonist (Prime mover)
• Main muscle whose contraction produces a
movement in an action
• Antagonist
• Opposed muscle to a muscle in action
• Synergist
• Helper muscle to a muscle in action
Anatomy of the Muscular System
Muscle Terminology
• Names of muscles provide clues to
location, orientation, or action
• Axial musculature—Muscles with origins
on the axial skeleton that position and
move head, spine, rib cage
• Appendicular musculature—Muscles that
stabilize or move appendicular components
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Anatomy of the Muscular System
The Axial Muscles
•
Four groups of axial muscles
1.
2.
3.
4.
Head and neck
Spine
Trunk
Pelvic floor
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Anatomy of the Muscular System
Axial Muscles of the Trunk
Thoracic region
• External intercostals (costal = ribs)
• Origin - inferior border of rib
• Insertion - on superior border of next rib
• elevates ribs
• Internal intercostals
• Origin - superior border of each rib
• Insertion - inferior border of preceding rib
• Depresses the ribs
• Diaphragm
• separates the thoracic cavity from the abdominal
cavity
• Important in respiration
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Anatomy of the Muscular System
Abdominal region
• Rectus abdominis (rectus= straight, parallel)
• depresses ribs and flexes vertebral column
• External oblique
• compresses abdomen, depresses ribs, flexes or
laterally vertebral column
• Internal oblique
• compresses abdomen, depresses ribs, flexes or
laterally vertebral column
• Transversus abdominis
• Compresses abdomen
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Anatomy of the Muscular System
Oblique and Rectus
Muscles and the
Diaphragm
Figure 7-15(a)
Anatomy of the Muscular System
Oblique and Rectus Muscles and
the Diaphragm
Figure 7-15(b)
Anatomy of the Muscular System
Oblique and Rectus Muscles and
the Diaphragm
Figure 7-15(c)
Anatomy of the Muscular System
Selected Muscles of the Head
• Frontalis
• Raises eyebrows, wrinkles forehead
• Orbicularis oris
• Compresses lips
• Buccinator
• Compresses cheeks
• Masseter
• Elevates mandible
• Temporalis
• Elevates mandible
• Pterygoids
• Elevate, protract, and/or move mandible
side to side
Anatomy of the Muscular System
Muscles of the Head and Neck
Figure 7-12(a)
Anatomy of the Muscular System
Muscles of the
Head and
Neck
Figure 7-12(b)
Anatomy of the Muscular System
Muscles of the Head and Neck
Figure 7-12(c)
Anatomy of the Muscular System
Selected Muscles of the Neck
• Platysma
• Origin - from cartilage on 2nd rib to scapula
• Tenses neck of skin and depress mandible
• Digastric
• Depresses mandible and/or elevates larynx
• Mylohyoid
• Elevates floor of mouth and hyoid, and/or
depresses mandible
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Anatomy of the Muscular System
• Stylohyoid
• Elevates the larynx
• Sternocleidmastoid
Lets break it down!
sterno = sternum
cleido = clavicle
mastos = breast
oid = breast-like
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Anatomy of the Muscular System
Sternocleidmastoid
Based on the definition where might it
originate and insert
origin = superior margins of sternum and
clavicle
insertion = mastoid region of the skull
• Both sides together flex the neck; alone
one side bends the head towards the
shoulder and turns the face to the
opposite side
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Anatomy of the Muscular System
Muscles of the Anterior Neck
Figure 7-13
Anatomy of the Muscular System
Selected Muscles of the Spine
• Splenius capitis
• Two sides work together to extend the neck:
either alone rotates and laterally flexes head
to that side
• Semispinalis capitis
• Two sides work together to extend the neck:
either alone rotates and laterally flexes head
to that side
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Anatomy of the Muscular System
Selected Muscles of the Spine
• Erector spinae groups (Spinal Extensors)
• Spinalis group
Two sides work together to extend vertebral column;
either alone extend neck and laterally flexes head or
vertebral column to that side
• Longissimus group
Two sides work together to extend vertebral column;
either alone rotates laterally flexes head or vertebral
column to that side
• Iliocostalis group
Extends vertebral column or laterally to that side:
moves ribs
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Anatomy of the Muscular System
Selected Muscles of the Spine
Spinal Flexor
• Quadratus lumborum
Together they depress ribs, flex vertebral column;
one side acting alone produces lateral flexion
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Anatomy of the Muscular System
Muscles of
the Spine
Figure 7-14
Anatomy of the Muscular System
The Appendicular Muscles
•
Two functionally distinct groups
1. Muscles of the shoulder and
upper limbs
2. Muscles of the pelvic girdle and
lower limbs
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Anatomy of the Muscular System
Selected Shoulder Muscles
Trapezius
• Origin = occipital bone and spinous
processes of thoracic vertebrae
• Insertion = clavicle and scapula
• Action = depends on active region
May elevate, adduct, depress, or rotate
scapula and/or elevate clavicle
Can also hyperextend neck
Rhomboid
• Action = Adducts and laterally rotates
scapula (downward)
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Anatomy of the Muscular System
Selected Shoulder Muscles
• Levator scapulae
• Action = elevates scapula
• Serratus anterior
• Origin = anterior and superior margins of ribs 1-9
• Action = Protracts shoulder, abducts and medially
rotates scapula (upward)
• Pectoralis minor
• Origin = anterior of ribs 3-5
• Action = Depresses and protracts shoulder, rotates
scapula laterally (downward); elevates ribs if scapula is
stationary
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Anatomy of the Muscular System
Muscles of the Shoulder
Figure 7-17(a)
Anatomy of the Muscular System
Muscles of the Shoulder
Figure 7-17(b)
Anatomy of the Muscular System
Muscles the Move the Arm
• Deltoid
• Origin = clavicle and scapula
• Insertion = humerus
• Action = abducts the shoulder
• Supraspinatus (rotator cuff muscle)
• Origin = scapula
• Insertion = humerus
• Action = abducts the shoulder
• Subscapularis (rotator cuff muscle)
• Origin = scapula
• Insertion = humerus
• Action = medial rotation of the shoulder
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Anatomy of the Muscular System
• Teres major
• Origin = scapula
• Insertion = humerus
• Action = adduction and medial rotation of the shoulder
• Infraspinatus (rotator cuff muscle)
• Origin = scapula
• Insertion = humerus
• Action = medial rotation of the shoulder
• Teres minor (rotator cuff muscle)
• Origin = scapula
• Insertion = humerus
• Action = lateral rotation of the shoulder
as Benjamin Cummings
Anatomy of the Muscular System
• Pectoralis major
• Origin = cartilage of ribs 2-6, body of the
sternum, and clavicle
• Insertion = humerus
• Action = abducts the shoulder
• Latissimus dorsi
• Origin = spinous process of lower thoracic
vertebrae, ribs, & lumbar vertebrae
• Insertion = humerus
• Action = flexion, adduction, and medial
rotation of the shoulder
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Anatomy of the Muscular System
Muscles that Move the Arm
Figure 7-18(a)
Anatomy of the Muscular System
Muscles that Move the Arm
Figure 7-18(b)
Anatomy of the Muscular System
Muscles That Move the Forearm - flexors
• Biceps brachii
• Origin = scapula
• Insertion = radius
• Action = flexion at shoulder and elbow,
supination
• Brachialis
• Origin = anterior, distal surface of humerus
• Insertion = ulna
• Action = flexion at elbow
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Anatomy of the Muscular System
Muscles That Move the Forearm - extensors
• Triceps brachii
• Origin = humerus at the scapula
• Insertion = ulna
• Action = extension at elbow
• Pronators
• Origin = ulna
• Insertion = humerus
• Action = pronation
• Supinator
• Origin = scapula
• Insertion = humerus
• Action = supination
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Anatomy of the Muscular System
Muscles That Move the Forearm and Wrist
Figure 7-19
Anatomy of the Muscular System
Muscles That Move the Wrist
• Wrist flexors
• Flexor carpi ulnaris
• Flexor carpi radialis
• Palmaris longus
• Wrist extensors
• Extensor carpi radialis
• Extensor carpi ulnaris
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Anatomy of the Muscular System
Muscles That Move the Forearm and Wrist
Figure 7-19
Anatomy of the Muscular System
Muscle of the Pelvis and Lower Limbs
Three functional groups
1. Thigh movement
2. Leg movement
3. Ankle, foot, and toe movement
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Anatomy of the Muscular System
Muscles That Move the Thigh
• Gluteal muscles
• Action: generally move the hip (extend, lateral
and medial rotation as well as abduction and
flexion)
• Thigh adductors
• Adductor magnus
• Adductor brevis
• Adductor longus
• Thigh flexors
• Iliopsoas (psoas major + iliacus)
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Anatomy of the Muscular System
Muscles That Move the Thigh
Figure 7-20(a)
Anatomy of the Muscular System
Muscles That Move
the Thigh
Figure 7-20(b)
Anatomy of the Muscular System
Flexors of the Knee
1. Biceps femoris (hamstring muscle)
• Insertion = tibia
• Action = flexion at knee, extension and lateral
rotation of the hip
2. Semimembranosus (hamstring muscle)
• Insertion = tibia
3. Semitendinosus (hamstring muscle)
• Insertion = tibia
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Anatomy of the Muscular System
Extensors of the Knee
• Quadriceps femoris group
1. Rectus femoris
2. Vastus lateralis
3. Vastus intermedius
4. Vastus medialis
All insert into the tibial tuberosity by way of
patellar ligament
Action: extension at knee (all)
Rectus femoris also has flexion at hip
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Anatomy of the Muscular System
Muscles That Move the Leg
Figure 7-21
Anatomy of the Muscular System
Muscles That Move the Foot
• Plantar flexion
• Soleus
• Gastrocnemius
• Eversion and plantar flexion
• Fibularis
• Dorsiflexion
• Tibialis anterior
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Anatomy of the Muscular System
Muscles That Move the Foot and Toes
Figure 7-22(a)
Anatomy of the Muscular System
Muscles That Move
the Foot and Toes
Figure 7-22(b)
Anatomy of the Muscular System
Muscles That Move
the Foot and Toes
Figure 7-22(c)
Anatomy of the Muscular System
Muscles That
Move the Foot
and Toes
Figure 7-22(d)
Aging and the Muscular System
Age-Related Reductions
• Muscle size: fibers become smaller in diameter
With the cardiac muscle becoming smaller blood flow to
active muscle does not increase as rapidly with
exercise
• Muscle elasticity: develop more fibrous
connective tissue making muscle less flexible
• Muscle strength: decreases
• Exercise tolerance: decreases in part to
reduced thermoregulatory ability
• Injury recovery ability : repair is limited and
scar tissue usually forms
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Sliding Filaments and Cross Bridges
Sliding Filaments: where Sarcomeres
Contract
Z Line – made of proteins
• Boundaries of each sarcomere
• Zone of overlap
• Move closer together during contraction
M Line - made of proteins
• Connect thick filaments to its neighbors
A Band
• Area containing thick filaments
I Band
• Light region between two successive A bands
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Sliding Filaments and Cross Bridges
Cross Bridges – myosin heads which connect
thick and thin filaments
• When a cross bridge binds to an active site it
pivots (moves) towards the center of the
sarcomere pulling thin filaments in that direction
• After it pivots it returns to its original position
• It can then repeats the cycle of: attach, pivot,
detach, and return (like a person pulling a rope
one –handed)
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Anatomy of Skeletal Muscles
The Organization of a
Single Muscle Fiber
Figure 7-2(b)
Anatomy of Skeletal Muscles
The Organization of a Single Muscle Fiber
Figure 7-2(cde)
Anatomy of Skeletal Muscles
Changes in the
Appearance of
a Sarcomere
During
Contraction of
a Skeletal
Muscle Fiber
Figure 7-3 (1 of 2)
Anatomy of Skeletal Muscles
Changes in the
Appearance of
a Sarcomere
During
Contraction of
a Skeletal
Muscle Fiber
Anatomy of Skeletal Muscles
The Organization of a Single Muscle Fiber
Figure 7-2(a)
Control of Muscle Contraction
Steps in Neuromuscular Transmission
Motor neuron (nerve cell) with action potential
• Fine branches with expanded ends called
synaptic terminals
Acetylcholine (ACh): neurotransmitter
• Triggers muscle contraction
Action potential: electrical impulse in sarcolemma
• T tubule action potential
• Calcium release from SR
Control of Muscle Contraction
The Structure and Function of the
Neuromuscular Junction
Action potential
Arrival of an action potential
at the synaptic terminal
Axon
Arriving action potential
Synaptic terminal
Sarcolemma
Vesicles
ACh
Synaptic
cleft
Sarcolemma of
motor end plate
AChE molecules
ACh
receptor
site
ACh binding at the
motor and plate
Release of acetylcholine
Vesicles in the synaptic terminal fuse
with the neuronal membrane and dump
their contents into the synaptic cleft.
Muscle
fiber
The binding of ACh to the receptors
increases the membrane permeability to
sodium ions. Sodium ions then rush
into the cell.
Appearance of an action
potential in the sarcolemma
An action potential spreads across the
surface of the sarcolemma. While this
occurs, AChE removes the ACh.
Action
potential
Na+
Na+
Na+
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Anatomy of Skeletal Muscles
The Contraction Process
• Actin active sites and myosin cross-bridges
interact
• Thin filaments slide past thick filaments
• Cross-bridges undergo a cycle of movement
• Attach, pivot, detach, return
• Troponin-tropomyosin (proteins) control
interaction
• Prevent interaction at rest
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Resting sarcomere
ADP
+
P
Tropomyosin
Myosin head
Troponin
Actin
ADP
P +
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Figure 7-5
2 of 7
Resting sarcomere
ADP
+
P
Myosin head
Active-site exposure
ADP
+ P
Sarcoplasm
Troponin
Ca2+
Tropomyosin
Actin
Active site
ADP
P +
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Ca2+
ADP
P +
Figure 7-5
3 of 7
Resting sarcomere
ADP
+
P
Myosin head
Active-site exposure
ADP
+ P
Sarcoplasm
Troponin
Actin
ADP
+
Ca2+
Tropomyosin
Cross-bridge formation
P
Ca2+
Active site
ADP
P +
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Ca2+
ADP
ADP Ca2+
P +
P +
Figure 7-5
4 of 7
Resting sarcomere
ADP
+
P
Myosin head
Active-site exposure
ADP
+ P
Sarcoplasm
Troponin
Actin
ADP
+
Ca2+
Tropomyosin
Cross-bridge formation
P
Ca2+
Active site
ADP
P +
Ca2+
ADP Ca2+
P +
ADP
P +
Pivoting of myosin head
ADP + P
Ca2+
Ca2+
ADP + P
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Figure 7-5
5 of 7
Resting sarcomere
ADP
+
P
Myosin head
Active-site exposure
ADP
+ P
Sarcoplasm
Troponin
Actin
ADP
+
Ca2+
Tropomyosin
Cross-bridge formation
P
Ca2+
Active site
ADP
P +
Ca2+
ADP Ca2+
P +
ADP
P +
Cross bridge detachment
Pivoting of myosin head
ATP
ADP + P
Ca2+
Ca2+
Ca2+
ATP
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Ca2+
ADP + P
Figure 7-5
6 of 7
Resting sarcomere
ADP
+
P
Myosin head
Active-site exposure
ADP
+ P
Sarcoplasm
Troponin
Actin
ADP
+
Ca2+
Tropomyosin
Cross-bridge formation
Ca2+
Active site
ADP
P +
Myosin reactivation
P
Ca2+
ADP Ca2+
P +
ADP
P +
Cross bridge detachment
Pivoting of myosin head
ATP
ADP
+ P
ADP + P
Ca2+
Ca2+
Ca2+
ADP
P +
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Ca2+
Ca2+
ATP
Ca2+
ADP + P
Figure 7-5
7 of 7
Control of Muscle Contraction
Summary of Contraction Process
Table 7-1
Control of Muscle Contraction
Key Note
Skeletal muscle fibers shorten as thin
filaments interact with thick filaments and
sliding occurs. The trigger for contraction
is the calcium ions released by the SR
when the muscle fiber is stimulated by its
motor neuron. Contraction is an active
process; relaxation and the return to
resting length is entirely passive.
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Muscle Mechanics
Some Basic Muscle Definitions
• Muscle tension—The pulling force on the
tendons that muscle cells generate when
contracting
• Muscle twitch—A brief contractionrelaxation response to a single action
potential
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Muscle Mechanics
The Twitch and Development of Tension
Figure 7-6
Muscle Mechanics
Motor Units
• Motor Unit —A motor neuron and all the
muscle cells it controls
• Recruitment—To increase muscle tension by
activating more motor units
Small motor units provide finer control
 Motor units are intermixed in the
muscle to pull evenly on the tendon
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Muscle Mechanics
Motor Units
Figure 7-8
Muscle Mechanics
Key Note
All voluntary (intentional) movements
involve the sustained contractions of
skeletal muscle fibers organized into
distinct motor units. The force
generated can be increased by
increasing the frequency of action
potentials or by recruiting additional
motor units.
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Muscle Mechanics
• Muscle tone —Tension in a “resting”
muscle produced by a low level of
spontaneous motor neuron activity.
• Function of muscle tone
• Stabilizes bones, joints
• Prevents atrophy (muscle wasting)
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Muscle Mechanics
Types of Contractions
Isotonic contraction
The tension (load) on a muscle
stays constant (iso = same, tonic =
tension) during a movement.
(Example: lifting a baby)
Isometric contraction
The length of a muscle stays constant
(iso = same, metric = length) during a
“contraction” (Example: holding a baby
at arms length)
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Muscle Mechanics
Muscle Elongation
• Muscle contract actively
• Muscles can only pull
• Muscles never push
• Muscle elongates passively
• Elastic forces
• Contraction of opposing muscles
• Effects of gravity
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Energetics of Muscle Contraction
ATP and Creatine Phosphate Reserves
• Muscle contraction consumes much
ATP
• ATP transfers energy directly to cycling
cross-bridges and calcium pumping
• CP stores energy and regenerates ATP
• CP transfers its energy to ADP
• Creatine phosphokinase (CPK) catalyzes
• ADP (2 “P”s) becomes ATP(3 “P”s)
• CP levels greatly exceed ATP levels
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Energetics of Muscle Contraction
ATP Generation
• Light activity
• Aerobic metabolism of fatty acids
• Storage of glucose as glycogen
• Moderate activity
• Breakdown of glycogen to glucose
• Glycolysis of glucose
• Peak activity
• Anerobic breakdown of glucose
• Production of lactic acid
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Energetics of Muscle Contraction
Muscle Fatigue—When a muscle
loses ability to contract due to a low
pH (lactic acid buildup), low ATP
levels, or other problems
Recovery Period—Time after muscle
activity that it takes to restore preexertion conditions
Oxygen Debt—Amount of excess
oxygen used during the recovery
period
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Energetics of Muscle Contraction
Key Note
Skeletal muscles at rest metabolize
fatty acids and store glycogen. During
light activity, muscles can generate
ATP through the aerobic breakdown of
carbohydrates, lipids, or amino acids.
At peak levels of activity, most of the
energy is provided by anaerobic
reactions that generate lactic acid.
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Muscle Performance
Two Types of Skeletal Muscle Fibers
• Fast fibers: Large diameter, abundant
myofibrils, ample glycogen, scant
mitochondria. Produce powerful, brief
contractions
• Slow fibers : Smaller diameter, rich
capillary supply, many mitochondria,
much myoglobin. Produce slow, steady
contractions
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Muscle Performance
Physical Conditioning
• Anaerobic endurance
Time over which a muscle can contract
effectively under anerobic conditions.
• Hypertrophy
Increase in muscle bulk. Can result from
anerobic training.
• Aerobic endurance
Time over which a muscle can contract
supported by mitochondria.
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Muscle Performance
Key Note
What you don’t use, you lose. When
motor units are inactive for days or
weeks, muscle fibers break down their
contractile proteins and grow smaller
and weaker. If inactive for long periods,
muscle fibers may be replaced by
fibrous tissue.
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Cardiac and Smooth Muscle
Cardiac Muscle Tissue
•
•
•
•
Small cells
Single nucleus/cell
Aerobic metabolism
Intercalated discs – double
membrane between cells that aids
adjacent cell communication
• Long contraction time
• Self-exciting (automaticity)
• No tetanic contraction
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Cardiac and Smooth Muscle
Cardiac
Muscle
Tissue
Figure 7-10(a)
Cardiac and Smooth Muscle
Smooth Muscle Tissue
• Nonstriated cells (no sarcomeres)
• Calcium control of contraction different
from striated muscle
• Wide range of operating lengths
• Involuntary muscle
• Under hormonal or local control
• Pacesetter cells
• Motor neurons often unneeded
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Cardiac and Smooth Muscle
Smooth Muscle Tissue
Figure 7-10(b)