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ANATOMY & PHYSIOLOGY I
LECTURE NOTES FOR CHAPTER (UNIT II)
BIO-220
LECTURE 7: MUSCLES AND MUSCLE TISSUE
Winter 2007
(Ch. 9)
I. Three types of muscle tissue: skeletal, cardiac, smooth.
II. Functions of muscle tissues: producing movement, maintaining posture, stabilizing joints, heat production.
III. Gross structure of skeletal muscle.
A. Epimysium – covers entire muscle; made of dense irregular C.T., separates the muscle from surrounding
tissues; part of the deep fascia (broad band of dense irregular C.T. beneath around muscle & organs)
B. Perimysium – surrounds bundle of muscle fibers called fascicles, contains dense irregular C.T., blood
vessels & nerves. Do not confuse with Paramecium.
C. Endomysium – delicate loose areolar tissue covering individual muscle fibers
D. Tendons & aponeuroses: extensions of epimysium, perimysium & endomysium; attach the muscle to bones
or other muscles; are not contractile & are not very vascular (heal poorly)
IV. Microanatomy of muscle cells
A. Muscle cells (= muscle fibers):
1. 100 μm in diameter, very long (as long as the muscle)
2. Cell membrane = sarcolemma, cytoplasm = sarcoplasm (contains myoglobin), multiple peripheral nuclei
3. T (transverse) tubules (extensions of the sarcolemma that penetrate cell): transmit electrical impulses from
sarcolemma inward, so electrical impulses penetrate deeply into cell.
B. Each cell contains hundreds to thousands of myofibrils (account for 80% of cellular volume), which are
bundles of thin & thick protein chains called myofilaments, they are the contractile elements of skeletal
muscle. Each thick filament is surrounded by a hexagonal array of thin filaments. Each thin filament is
surrounded by a triangular array of thick filaments.
1. Thin myofilaments are composed of 3 proteins: actin, tropomyosin, troponin. These are the units that
actually move to make a contraction.
2. Thick myofilaments consist of bundles of myosin molecules; each molecule contains two myosin heads at
both ends. Myosin heads project out from thick filaments, allowing them to bind to the thin filaments
during contraction.
C. Sarcoplasmic reticulum (SR):
1. A tubular network around each individual myofibril, stores calcium which is released into sarcoplasm
during muscle contraction
2. On either side of a T tubule, SR enlarge, fuse & form expanded chamber called terminal cisternae
D. Sarcomeres:
1. The repeating functional units of myofilaments (separated from one another by Z lines); interactions b/w the
thin & thick filaments of sarcomeres are responsible for muscle contraction
2. A band – dark band, width of thick filament
a) H zone – central region of A band, where no thin filament overlap with thick filaments
b) M line – proteins connecting all the thick filaments in the central region of A band
3. I band – light band, region where only thin filament exist
a) Z disc – proteins connecting all the thin filaments in the central region of I band
V. Muscle Contraction
A. Sliding Filament Theory: “the filaments are sliding toward the center of the sarcomere, alongside the thick
filament” (during muscle contractions, because of sliding of thin filaments over thick filaments, H zones &
I bans disappear; A bands do not change in width)
B. Sequence of events in a muscle contraction:
1. Nerve impulse reaches axonal terminal, causing the release of acetylcholine (ACh) into synaptic cleft via
exocytosis
2. Ach binds to Ach receptors on motor end plate and generates nerve impulses in sarcolemma
3. Action potential propagates along the membrane lining the T-tubules, entering the muscle cell and causing
SR to release Ca++ into sarcoplasm
4. Ca++ causes thin filaments to slide toward the centers of the H zone. End result - muscle shortens.
5. Muscle relaxation: release of acetylcholinesterase (AChE), an enzyme in the neuromuscular junction,
destroys ACh and stops the generation of a muscle action potential. Ca++ is taken back in the SR, which
results in the separation of thin/thick filaments cross bridges. (ATP is required to separate myosin-actin
cross bridges).
6. The muscle fiber resumes its resting state but does not uncontract (stretch).
VI. Motor Units:
A. A motor nerve is a bundle of axons; it conducts nerve impulse away from central nerve system; each axon
branches 4 to over 200 times
B. Each separate branch supplies a separate muscle cell; thus if an axon has 10 branches, it supplies 10 muscle
fibers
C. Motor unit = all the muscle fibers controlled by a single motor neuron
D. Recruitment = the steady increase in muscular tension produced by increasing the number of active motor
units; peak tension is produced when all the motor units in the muscle are recruited.
VII. “Uncontracting”:
A. Muscles may release from contraction in only two ways -1. After ATP releases myosin heads from actin, the resting muscle may be pulled back to its stretched state
by the contraction of antagonists (muscles that operate the opposite side of a joint).
2. Gravity may pull a muscle back into stretched position if the muscle is relaxed and there is little
resistance.
VIII. Effect of exercise on muscle cells
1. Aerobic exercise (= endurance exercise, e.g., jogging, distance swimming): causes the following changes
(mostly in slow fibers): increased capillaries into muscles; increased mitochondria; increased myoglobin
synthesis in muscles; more efficient metabolism; muscle fibers do not hypertrophy
2. Anaerobic exercise (= resistance exercise, e.g., short distance dash & swim, weight-lifting, pole vault):
causes fast fiber hypertrophy; develops more mitochondria; higher concentration of glycolytic enzymes;
larger glycogen reserve
3. A skeletal muscle that is not stimulated by nerve on a regular basis loses muscle tone & mass, results in
muscle atrophy
IX. Myotoxic Effects
1. Tetanus is a term describing the full and sustained contraction of a muscle. It may occur when –
a. A muscle is fully contracted under voluntary control, such as when you are lifting heavy weight
b. Myotoxins (muscle poison) that mimic acetylcholine bind to motor end plates but cannot be
removed by the cell’s enzymes
c. Invasive Myotoxic ions, such as Fe+++, enter the muscle and cause rapid, permanent exocytosis of
Ca+ from SR (result of rusty nail wounds)
d. Sarcomeric ATP is depleted, making the release of myosin heads from actin filaments impossible.
In life, this is the action of many plant poisons. In death, the condition is called rigor mortis (“the
stiffness of death”).
2. Myotoxic effects are life threatening. Vaccines may prevent or severely limit toxic effects; if the patient
has not been vaccinated, administration of vaccine must occur very shortly after injury. Once symptoms
occur, likelihood of full recovery is limited.
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BIO-220
LAB: MUSCULAR SYSTEM
(Ch. 10)
A. Skeletal muscles produce movement by exerting force on tendon, which in turn pull on bones or other
structures such as skin
B. Most muscles cross at least one joint and are attached to the articulating bones that form the joint
C. When such a muscle contracts, it draws one articulating bone toward the other
1. the attachment to the stationery bone is the origin
2. the attachment of the movable bone is the insertion
MUSCLES OF FACIAL EXPRESSION:
Muscle Name
Origin
Insertion
Orbicularis oris
maxillae & mandible
lips
Orbiculair oculi
Zygomaticus
(major & minor)
medial margin of orbit
skin around eyelids
skin & muscles at angle of
mouth
mandible, skin of chin &
cheek
skin of eyebrow & bridge of
nose
galea aponeurotica
closes eyes
Insertion
Action
increases size of thoracic
cavity for breathing
Platysma
Frontalis
Occipitalis
zygomatic bone
fascia of chest (over pectoral
& deltoid muscles)
galea aponeurotica
superior nuchal line of
occipital line
MUSCLES USED IN BREATHING:
Muscle Name
Origin
xiphoid process, costal
Diaphragm
cartilages of last 6 ribs,
lumbar vertebrae
External intercostals
inferior border of each rib
superior border of each rib
Internal intercostals
MUSCLES THAT MOVE THE HEAD:
Muscle Name
Origin
central tendon
Action
closes lips, protrudes lips
(kissing muscle)
raises angle of mouth (smile)
depresses mandible, tenses
skin of neck
raises eyebrow, winkles
forehead
draws scalp backword
superior border of next rib
inferior border of the
previous rib
elevates rib
Action
flexes neck if both sides
contract; rotates head towards
the opposite side if one side
contracts
contracts both sides extend
head; contracts one side
rotates head to the same side
as the contracting muscle
Sternocleidomastoid
sternum & clavicle
Insertion
mastoid process of temporal
bone
Splenius capitis
ligamentus nuchae & spines
of C7-T4
occipital bone & mastoid
process temporal bone
depress ribs
MUSCLES OF MASTICATION:
Muscle Name
Origin
Insertion
Action
Masseter
zygomatic arch
angle & ramus of mandible
elevates mandible
Temporalis
temporal lines
coronoid process of mandible
elevates & retracts mandible
3
MUSCLE THAT MOVE THE SHOULDER:
Muscle Name
Origin
Insertion
Action
abduct scapula
Serratus anterior
anterior margins of ribs 1-8
(or 1-9)
anterior surface of vertebral
border of scapula
Pectoralis minor
anterior surfaces of ribs 3-5
coracoid process of scapula
dedpresses scapula, pulls
scapula anteriorly
Rhomboideus minor & major
spinous processes of C7-T5
vertebral border of scapula
adducts scapula
Trapezius
occipital bone, ligamentum
nuchae, spines of C7-T12
clavicle, acromion, spine of
scapula
elevates scapula (upper
portion), depresses scapula
(lower portion), adducts
scapula, extends head
MUSCLES THAT MOVE THE FORARM:
Muscle Name
Origin
above glenoid fossa, coracoid
Biceps brachii
process of scapula
Insertion
radial tuberosity
Action
flexes forearm, supernates
forearm
Brachialis
coronoid process of ulna
flexes forearm
olecranon process of ulna
extends forearm
lateral surface of proximal
radius
middle of the lateral surface
of radius
supinates forearm
distal radius
pronates forearm
Insertion
greater tubercle of humerus
intertubercular groove of
humerus
Action
flexes, adducts and medially
rotates arm
extends, adducts and
medially rotates arm
deltoid tuberosity of humerus
abducts arm
greater tubercle of humerus
abducts arm
Trceps brachii
anterior surface of humerus
long head – below glenoid
fossa; lateral head – lateral &
posterior shaft of humerus
proximally, medial head –
posterior surface of humerus
distally
lateral epicondyle of humerus
Supinator
Pronator teres
medial epicondyle of
humerus, cornoid process of
ulna
Pronator quadrtus
distal ulna
MUSCLES THAT MOVE THE ARM:
Muscle Name
Origin
clavicle, sternum, costal
Pectoralis major
cartilages of ribs 2-6
spinous processes of T7
Latissmus dorsi
through all lumbar through
sacrum, posterior iliac crest,
lumbodorsal fascia
Clavicle, acromion & spine
Deltod
of scapula
supraspinous fossa
Supraspinatus
pronates forearm
Infraspinatus
infraspinous fossa
greater tubercle of humerus
rotates arm laterally
subscapularis
subscapular fossa
lesser tubercle of humerus
Teres major
inferior angle of scapula
lesser tubercle of humerus
rotates arm medially
medial rotates, adducts &
extends arm
Teres minor
lateral border of scapula
greater tubercle of humerus
rotates arm laterally
4
MUSCLES THAT MOVE THE WRIST & FINGERS:
Muscle Name
Origin
medial epicondyle of
Flexor carpi radialis
humerus
medial epicondyle of
Flexor carpi ulnaris
humerus; upper dorsal border
of ulna
medial epicondyle of
Palmaris longus
humerus
medial epicondyle of
Flexor digitorum superficialis humerus
anterior medial surface of
Flexor digitorum profundus
ulna
Extensor carpi radialis
lateral epicondyle of humerus
(longus)
lateral epicondyle of humerus
Extensor carpi ulnaris
lateral epicondyle of humerus
Extensor digitorum
MUSCLES THAT MOVE THE THIGH:
Muscle Name
Origin
iliac crest, sacrum, coccyx
Gluteus maximus
iliac crest
Gluteus medius
lateral surface of ilium b/w
Gluteus minimus
inferior & anterior gluteal
lines
Insertion
ventral surface of
metacarpals II & III
pisiform, hamate &
metacarpal V
Action
palmar aponeurosis
ventral surface of middle
phalanges 2-5
ventral surface of middle
phalanges 2-5
dorsal surface of metatarsal
III
metacarpal V
flexes wrist
flexes & abducts wrist
flexes & adducts wrist
flexes phalanges
flexes phalanges
extends & abducts wrist
extends & adducts wrist
middle & distal phalanges of
each finger
Insertion
gluteal tuberosity of femur
greater chochanter of femur
greater chochanter of femur
extends phalanges
Action
extends thigh (hip jt),
laterally rotates thigh
abducts & medially rotates
thigh
abducts & medially rotates
thigh
Tensor fasciae latae
anterior part of iliac crest
lateral fascia of tibia
flexes & abducts thigh (hip
jt)
Adductor longus
linea aspera of femur
abducts thigh
Adductor magnus
inferior ramus of pubis
inferior ramus of pubis,
ischium, ischial tuberosity
linea aspera of femur
abducts thigh
Adductor brevis
inferior ramus of pubis
linea aspera of femur
abducts thigh
MUSCLES THAT MOVE THE FOOT & TOES:
Muscle Name
Origin
lateral condyle & proximal
Tibialis anterior
shaft of tibia
lateral condyle of tibia,
Extensor digitorum longus
anterior surface of fibula
lateral condyle of tibia,
Peroneus longus
lateral surface of fibula
lateral & medial condyle of
Gastrocnemius
femur
Insertion
metatarsal I,
medial cuneiform
dorsal surfaces of phalanges
2-5
ventral surface of metatarsal,
medial cuneiform
calcaneus via Achilles tendon
(calcaneal tendon)
Action
Flexor digitorum longus
distal phalanges 2-5
posteromedial surface of tibia
dorsiflexion & inversion
extends toes, dorsiflexion &
eversion
plantar flexion, eversion
plantar flexion, flexes knee
flexes toes, palntar flexion,
inversion
5
MUSCLES THAT ACT ON THE LEG:
Muscle Name
Origin
Quadriceps femoris (includes
the following 4 muscles):
Insertion
Action
tibia tuberosity via patellar
ligament
tibia tuberosity via patellar
ligament
tibia tuberosity via patellar
ligament
tibia tuberosity via patellar
ligament
extends leg
lateral condyle of tibia &
head of fibula
medial surface of proximal
tibia
medial condyle of tibia
medial surface of tibia
inferior to medial condyle
medial surface of tibia near
tibia tuberosity
flexes leg, extends thigh
MUSCLES OF THE ABDOMINAL WALL:
Muscle Name
Origin
Insertion
External abdominal oblique
lower 8 ribs
linea alba & iliac crest
Internal abdominal oblique
iliac crest, inguinal ligament,
thoracolumbar fascia
linea alba & lower 4 ribs
Action
compresses abdomen,
contraction of one side alone
bends spine laterally
compresses abdomen,
contraction of one side alone
bends spine laterally
1) Rectus femoris
anterior inferior iliac spine
2) Vactus lateralis
greater trochanter & lateral to
linea aspera of femur
medial to linea aspera of
femur
anterolateral surface of femur
3) Vactus medialis
4) Vastus intermedius
extends leg
extends leg
extends leg
Hamstrings (includes the
following 3 muscles):
1) Biceps femoris
2) Semitendinosus
ischial tuberosity & linea
aspera
ischial tuberosity
3) Semimembranosus
ischial tuberosity
Gracilis
inferior ramus of pubics
Sartorius
anterior superior iliac spine
Transversus abdominis
Rectus abdominis
iliac crest, inguinal ligament,
lumbar fascia & costal
cartilage of last 6 ribs
superior surface of pubis
around symphysis
flexes leg, extends thigh
flexes leg, abducts thigh
flexes leg, abducts thigh
flexes thigh & leg, rotates
thigh laterally
linea alba & pubis
compresses abdomen
xiphoid process & costal
cartilages of ribs 5-7
compresses abdomen, flexes
vertebral column
MUSCLES THAT MOVE THE VERTEBRAL COLUMN:
Muscle Name
Origin
Insertion
Action
Erector spinae
1) Iliocostalis
iliac crest & ribs
ribs
2) Longissimus
transverse processes of
lumbar, thoracic & lower
cervical vertebrae
transverse processes of
vertebrae above the vertebra
of origin, plus the mastoid
process of the temporal bone
spinous process of upper
thoracic vertebrae
3) Cervical vertebrae
4)
Spinalis
spinous process of lumbar &
lower thoracic vertebrae
extends vertebral column &
bends it laterally
extends vertebral column
extends vertebral column
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