Post on 11-Jan-2016
Skeletal MuscleSkeletal Muscle
Purposeful movement
Works withNervous
SystemOver 600 (657)40-50% body weightPrefix myo and mys= muscle
Prefix sarco=flesh
What do What do allall muscles have in muscles have in common?common?The contraction of muscles is
due to the movement of the microfilaments.
The function is movement, whether it’s◦Food, water, nutrients (peristalsis) ◦Fluid (blood) ◦Movement of bone for locomotion
FunctionsFunctions
Includes◦Moves bone-
locomotion◦Maintains
posture◦Stabilizes joints◦Generates heat◦Venous return of
blood to heart
Homeostasis- HeatHomeostasis- Heat
Generation of heat◦By-product of
muscle activity◦ATP powers
contractions but ¾ escapes as heat
◦Muscular system focus on skeletal muscle
Stabilization of JointsStabilization of Joints
With the contraction, muscles pull on bones for movement
Muscle ligaments for poor fitting joints- shoulder
PosturePosture
Work against gravity
Function continuously
Venous returnVenous return
Veins◦Have no
pressure◦Valves◦Helps with the
push of blood back to the heart
LocomotionLocomotion
With a contraction, brings bones closer together!
Walking, swimming, skiing
Manipulation◦Writing, tools!
Skeletal, Cardiac and Skeletal, Cardiac and SmoothSmooth
Muscle ArrangementMuscle Arrangement
Groups◦ Agonist (prime mover)
Directly performs specific movement◦ Antagonist
Oppose agonist◦ Synergist
Contract with agonist Stabilize joints
NomenclatureNomenclature
Direction of the muscle fibers
Size of the muscle
Number of originsLocations of
origin and insertion
Action of the muscle
Direction of the Muscle Direction of the Muscle FiberFiber
Named in reference to imaginary lines◦Rectus-straight-
parallel to the line Rectus femoris
◦Oblique- slant Internal/external
obliques
Relative SizeRelative Size
Maximus- largest◦Gluteus
maximusMinimus-
smallestLongus- long
Location of the muscleLocation of the muscle
Bone associated with◦Temporalis◦frontalis
Number of origins or Number of origins or ““headsheads””
BicepTricepQuadriceps
Location of the origin and Location of the origin and insertioninsertion
Attachment sites◦Sternoceidomas
toid Sternum Clavicle mastoid
Shape of the muscleShape of the muscle
Deltoid, trapezius◦Means
triangular
Action of the muscleAction of the muscle
Flexors, Extensors, adductor◦Adductor
muscles of the thigh cause, when they contract, its adduction
Homework for next classHomework for next classRead pg. 286-298:
◦Anatomy of muscles◦Muscle contraction◦Quiz on the notes
Anatomy of Skeletal MuscleAnatomy of Skeletal MuscleConnective tissue
◦ FasciaFibrous CT outside
◦ Endomysium Delicate CT covers each
fiber◦ Perimysium
Coarse CT Divides muscles into
bundles called fascicles Separates muscle into
bundles◦ Epimysium
Coarse sheath covering entire muscle
Gross Anatomy of Skeletal Gross Anatomy of Skeletal MuscleMuscle
Organelles◦Sarcolemma◦Sarcoplasmic
reticulum◦T-tubule
(transverse)◦Mitochondria◦Nucleus◦Sarcomere
Banding (z-line)
From inside outFrom inside out
Endomysium◦Each individual
fiber is wrapped in a delicate sheath
PerimysiumPerimysium
Each fiber is packaged into bundles-fasicle
Covering of that fasicle is perimysium
EpimysiumEpimysium
Tougher layer or topcoat on the fasicle
Blend into tendons or sheet-like aponeuroses
How do muscles contract?How do muscles contract?
Contractile unit –Sarcomere
Z-lines come in close contact
Sarcomere shortens, causing muscles to contract
Skeletal Muscle ContractionSkeletal Muscle Contraction
Functional properties◦Excitability/
responsiveness Receive/respond
◦Contractility Shorten when
stimulated
◦Extensibility Ability to stretch
◦Elasticity Recoil and
resume resting length after stretching
Skeletal Muscle is highly Skeletal Muscle is highly organized.organized.
Involved in a Muscle Involved in a Muscle ContractionContractionAch-acetylcholine-
neurotransmitterTropomyosin, troponin, actinMyosinCa2+
Nerve Stimulus and action Nerve Stimulus and action potentialpotentialMuscles must be
stimulated by nerve impulses
A motor neuron + muscles it stimulates is a motor unit
Neuromuscular JunctionNeuromuscular Junction
Site of muscle contraction
Synapse◦ separation between
nerve and muscle Neuromuscular
junctionMuscle fiber forms
◦ Motor end plate
Neuron AnatomyNeuron AnatomyAxon
◦ Long extension of a neuron
Axon terminals◦ Junctions with
sarcolemmaNeuromuscular
junction◦ Junctions with
sarcolemmaNeurotransmitter
◦ Ach-acetylcholine
Events of a muscle Events of a muscle ContractionContraction1. Action
potential reaches axon terminal of motor neuron
2. Stimulus for 2. Stimulus for ContractionContractionAcetylcholine
diffuses across the synaptic cleft
3. binds to receptors at the sarcolemma after an action potential is reached at the end of the neuron
Excitation Contraction Excitation Contraction CouplingCoupling4. Sarcolemma is
stimulatedImpulse travels
through to the T-tubulesmembrane◦ High concentration
calcium◦ Diffuses out into
the sarcoplasm of muscle fiber
5. Sarcoplasmic reticulum5. Sarcoplasmic reticulum
Action potential reaches SR
◦ Sarcoplasmic reticulum releases Ca2+
◦ Calcium channels open Binding sites on actin
exposed
6. diffused Ca2+
binds to troponin
7. Tropomyosin molecules7. Tropomyosin moleculesExpose specific sites
in actin8. Actin + myosin
form linkages9. Actin filaments
pulled toward center of sarcomere by myosin cross-bridges
10. Muscle fiber shortens and contracts
Contraction CycleContraction CycleMyosin heads
join to actin◦ Forms cross-
bridges◦ Cross-bridges pull
thin filament using ADP and P released from myosin
◦ ATP binds to myosin releasing linkages
Muscle Fiber RelaxationMuscle Fiber Relaxation
Acetylcholinesterase◦Enzyme that
decomposes acetylcholine
◦Muscle fiber is not stimulated
Muscle Fiber RelaxationMuscle Fiber RelaxationCa2+
◦ Reabsorbed into sarcoplasmic reticulum
◦ Concentration is reduced
Muscle Fiber RelaxationMuscle Fiber RelaxationATP breaks linkages
between actin and myosin, does not breakdown ATP itself
ATP heads are broken down
Troponin and tropomyosin inhibit interaction of actin and myosin
Muscle fiber relaxes
RememberRemember
ATP ◦Necessary for
both muscle fiber relaxation and contraction
Rigor MortisRigor MortisSkeletal muscles
◦ Partially contract◦ Up to 72 hours◦ Cross-bridging
with no ATP◦ Stay linked until
decomp begins
What does this mean?What does this mean?
A band- thick filaments stacked in a set and thin filaments that overlap on boath ends of thick
Thin=actin, thick=myosin
H zone◦ - thin filaments do not
reachM line/Middle
◦ -extends vertically down I band
◦ - thin filaments that do not project into the A band
Energy SourcesEnergy SourcesInitial source for
regeneration of ATP from ADP = creatine phosphate◦ Cannot directly supply
energy to the cell◦ Stores energy from
mitochondria-enzyme creatine phosphokinase
◦ Works for 10 seconds, then cellular respiration
InterrelationshipInterrelationshipWith the nervous
systemNo skeletal
muscle can contract unless stimulated
Muscle Contraction is “ALL or NOTHING’
What about Cross-What about Cross-bridging?bridging?Myosin cross-
bridging contains ATPase
ATP to ADPMore cross
bridging greater strength of the muscle contraction
Effects of Cross-bridgingEffects of Cross-bridging
Muscular ResponsesMuscular ResponsesThreshold
◦ Cannot contract the muscle until the threshold is reached
◦ Action potential is generated
Muscular ResponseMuscular ResponseMyogram
◦ Twitch Contractile
response of a single muscle fiber to an impulse
◦ Latent period Delay between
times of contraction Can be less than 2
milliseconds
Muscular ResponseMuscular ResponseSummation
◦ Period of incomplete relaxation before the next twitch
◦ Twitches combined and becomes sustained
Recruitment◦ Number of muscle
fibers in a motor unit varies
Gross Anatomy of Skeletal Gross Anatomy of Skeletal MusclesMuscles
Begin with the head and neck◦Frontalis,
obicularis oculi, obicularis oris, buccinator,
◦zygomaticus
Chewing muscles of the Chewing muscles of the faceface
Masseter◦Covers angle of
lower jaw◦Elevates mandible
Temporalis◦Fan shaped on
temporal bone◦Closes jaw,
synergist to the masseter
Muscles of MasticationMuscles of Mastication
Masseter◦ Front of ear with
clenched teeth, raises the mandible to close the jaw
Temporalis◦ Synergist to the
masseter in closing
Muscles of masticationMuscles of mastication
Chewing◦ Masseter◦ Temporalis◦ Medial pterygoid
closes the jaw, moves side to side
◦ Lateral pterygoid Opens the jaw,
protracts and side to side
TMJ- SyndromeTMJ- Syndrome
Kissing muscleKissing muscle
Orbicularis oris◦Protrudes the
lips for kissing◦Closes the lips
BuccinatorBuccinator
Chewing muscle◦ compresses the
cheek◦Allows mouth to
whistle or blow a trumpet
ZygomaticusZygomaticus
Smiling muscle◦Raises corner of
the mouth up
Little Fun Fact!!!!!Little Fun Fact!!!!!
It takes more muscles to frown (22-42) than it does to smile (17)
Neck Neck
Platysma◦ Sheetlike,
anterolateral to the neck
◦ Pulls corners of the mouth down
Sternocleidomastoid◦ Each side of the neck◦ Flex the neck, bowing,
called prayer muscle◦ One contracts the
head rotates to one side
Muscles that move the head and Muscles that move the head and spinespine
Sternocleiodomastoid◦Pulls head side to
sideSplenius capitis
◦Rotates the headSemispinalis capitis
◦Extends the headErector spinae
◦Keeps spine aligned
Muscles that move the Muscles that move the pectoral girdlepectoral girdle
Moving the scapula◦Trapezius◦Levator
scapulae◦Serratus
anterior◦Pectoralis minor
Muscles that move the armMuscles that move the arm
Pectoralis majorLatissimus dorsiDeltoidTeres
minor/minorSerratus anterior
Chest, Shoulder and Upper Chest, Shoulder and Upper limblimbTrunk muscles
◦Move the vertebral column
◦Anterior thorax-ribs, head and arms
◦Forms the abdominal girdle
Shoulder-Posterior Shoulder-Posterior musclesmusclesDeltoid
◦ Abduction of armTrapezius
◦ Form diamond or site shaped mass-elevate, depress scapula
Latissimus Dorsi◦ Extends and adducts
humerus, stroke in swimming
Erector Spinae-deep back
Injection siteInjection siteDeltoid
◦ Favored site◦ Fleshy, forms
rounded part of the shoulder
Muscles that move the Muscles that move the shouldershoulder
Serratus anterior◦Scapula to the
front and downPectoralis
minor/major
Muscles that move the Pectoral Muscles that move the Pectoral GirdleGirdle
Trapezius◦Triangle shaped
Rhomboideus major◦Adducts the
shoulderLevator Scapulae
◦Elevates the scapula
Serratus AnteriorPectoralis minor
Muscles that move the Muscles that move the upper armupper arm
All anterior muscles cause elbow flexion◦ Pectoralis Major
Flexes, adducts, rotates medially
◦ Latissimus dorsi Extends, adducts,
rotates◦ Deltoid
Abducts, extends and flexes
◦ Teres Major/minor Rotates arm laterally
Muscles that move the Muscles that move the lower armlower arm
Biceps brachii◦Flexes the
forearm and rotates laterally
Brachialis◦Flexes forearm
Brachioradialis◦Flexes forearm
Triceps brachii◦Extends forearm
Forearm movementForearm movementName of muscle
indicates what they are doing◦ Flexor carpi and
digitorum- wrist and fingers
◦ Extensor carpi and digitorum
Muscles that move the Muscles that move the fingersfingers
Flexor carpi radialis◦ Flex wrist, abducts hand
Flexor carpi ulnarisPalmaris longus
◦ Flex wristFlexor digitorium
superficialis◦ Flexes fingers and
writstExtensor digitorum
◦ Extends the fingers
Muscles of the TrunkMuscles of the Trunk
Trunk muscles◦Move the
vertebral column most posterior
◦Moves the ribs, head and arms-anterior
◦Abdominal wall
Anterior◦Pectoralis major
adducts/flexes the arm
◦Intercostals Between ribs Raises the rib
cage to breathe
Anterior Trunk MusclesAnterior Trunk Muscles
Muscles of the Abdominal Muscles of the Abdominal GirdleGirdleRectus abdominus
◦ Strap like, superficial
External oblique◦ superficial
Internal oblique◦ Deep, fibers rt.
Angle to externalTransverses
Abdominus◦ Compresses
abdominal contents
Nice!!!Nice!!!
Muscles of the thighMuscles of the thigh
Attached at the femur and some part of the pelvic girdle
Anterior◦Psoas major◦iliacus
Abdominal Girdle MusclesAbdominal Girdle Muscles
This is the core◦Contains ◦protects
Muscles of the Lower LimbMuscles of the Lower Limb
Do not need to stabilize the pelvic girdle◦Muscles can
span 2 joints◦Origin/insertion
interchangeable◦Resist gravity
Movement of:◦Hip ◦Knee◦Foot joints◦Longest◦Strongest◦Specialized
Walking, balance
Hip Joint MovementHip Joint Movement
Gluteus medius◦Hip abductor◦Site for IM injections
Iliopsoas◦Hip flexion,
prevents falled backward
Adductors◦Medial side of thigh
Gluteus MediusGluteus Medius
Superior/under the maximus◦Avoid sciatic
nerve◦Divide the
buttock into 4 equal quandrants
IliopsoasIliopsoas
Keeps you upright◦Keep you from
falling backwards
Muscles that move the Muscles that move the kneeknee
PosteriorHamstrings
◦Semimembranosus
◦Biceps femoris◦semitendinosis
Muscles that move the Muscles that move the kneeknee
Anterior◦Sartorius
Tailor’s muscle, cross-legs
◦Quads Rectus femoris 3 vastus
Lateralis, medialis, intermedius
Injection site on the thighInjection site on the thigh
Vastus Lateralis or rectus femoris
Muscles that move the Muscles that move the foot/anklefoot/ankle
PosteriorGastrocnemius
◦ Curve of lower leg◦ 2 bellied, dancer’s
leg, flexion of footSoleus
◦ Foot flexorAchilles tendon
◦ Calcaneal
Muscles that move the footMuscles that move the foot
AnteriorTibialis Anterior
◦Dorsiflex, invertExtensor
digitorium longus◦Toe extension
Fibularis muscle◦Longus, brevis and
tertius-flex, evert
TendonsTendons
Anchor musclesDurabilityConserving
spaceTough CollagenCan cross bony
projections which would tear
Stimulation and Stimulation and contraction contraction Special features
of skeletal muscle◦ Irritability
Receive and respond to stimulus
◦ Contractility Ability to shorten
(forcibly) when adequate stimulus is received
Why do we care about cross Why do we care about cross bridging?bridging?
When we work out, we build more crossbridges
The more the stronger the contraction
More Cross-bridges!!!!More Cross-bridges!!!!
Slow Twitch MusclesSlow Twitch Muscles
Type I◦Oxidative and
resistant to fatigue◦Red fibers- dark
meat◦High in myoglobin◦Many mitochondria◦Constantly used
muscles- muscles of the back
Slow twitchSlow twitch
Body building- repeated sets
Short period of time
Resistance and strength training
May have some increase in heart and pulse rate but not in the target zone
Red Muscle Anatomical Red Muscle Anatomical featuresfeatures
Type I- slow◦Oxygen rich
myoglobin◦Mitochondria◦Generate ATP to
keep up with the breakdown
◦Anaerobic
MyoglobinMyoglobin
In red muscle fibersStores some oxygen
for muscle useConsidered anerobic
exercise- use oxygen in the fiber itself
Important as blood flow might slow down
Fast Twitch-TypesFast Twitch-Types
We do both◦ So what about
Endurance, long distance?
Fast TwitchFast Twitch
Type IIa◦ Glycolytic, can be
fatigued◦ White fibers due to
glycogen in the muscle fiber
◦ No myoglobin◦ More sarcoplasmic
reticulums, reduced respiratory capacity
◦ Contract rapidly, quickly◦ Quick bursts of use
Fast Twitch Fatigue Fast Twitch Fatigue resistantresistant
Type IIB, intermediate fibers◦Combination of
white and red fibers
◦Combination of strength and endurance
Remember!!!!Remember!!!!
All muscles have a combination◦Speed and
aerobic capabilities Reflect function
Oxygen SupplyOxygen Supply
Aerobic allows glucose to be broken down
KrebsBlood carries
oxygen to the muscles
Where does the energy come Where does the energy come from?from?
ATP is in limited amounts
Creatine phosphate allows ADP to form ATP
4-6 X more abundant
Has high energy phosphate bonds
Oxygen DebtOxygen Debt
Shift from aerobic to anaerobic respiration
Lactic acid threshold
Lactic acid goes to the liver to convert glucose
Accumulate lactic acid
Types of ContractionsTypes of Contractions
Concentric◦Muscle
contracts◦Force greater
than the resistance
◦Muscle shortens◦Movement of
dumb bell is up
Muscle ContractionsMuscle Contractions
Eccentric Contraction◦Muscle contracts
with less force than resistance
◦Muscle lengthens◦Dumb bell moves
down
Isometric contractionIsometric contraction
Muscle contracts but does not change length
Muscle tensionNo movementPushing against a
wallDoing the “plank”
What about functions?What about functions?
Flexors◦Decrease the
angle of the joint
◦Parts become closer together
ExtensionExtension
Straightening the parts of the joint to increase the angle
Muscle fatigueMuscle fatigue
Peristant exercise over a long period of time◦ Decreased blood flow◦ Ion imbalances◦ Low pH◦ Cramps-sustained
involuntary contraction
Hyperextension◦ Excess extension
Sustained contractionSustained contraction
Responsible for muscle tone◦Muscle appears
at rest but some fibers are in a state of partial contraction
◦Posture◦Neck◦Tone is lost,
body collapses
AbductionAbduction
Moving a part away from the midline of the body
Measuring muscle Measuring muscle contractionscontractions
Myogram◦Measures the
response of a single muscle fiber to the Ach released by a single action potential- twitch
◦Contraction◦Relaxation◦All or none