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