The Muscular SystemThe Muscular System

Muscles FactsMuscles Facts•Are there more muscles Are there more muscles or bones?or bones?– Muscles (around 640)Muscles (around 640)

•Each lb of muscle burns Each lb of muscle burns 75-100 calories a day 75-100 calories a day just by just by beingbeing

Muscles Facts Muscles Facts (cont.)(cont.)

•Approximately 40% of Approximately 40% of your body weight is your body weight is musclemuscle

•Largest muscle = Largest muscle = gluteus maximusgluteus maximus

Muscles Facts Muscles Facts (cont.)(cont.)

•Smiling Smiling uses 17 uses 17 musclesmuscles

•Frowning Frowning uses 43 uses 43 musclesmuscles

The Role of MuscleThe Role of Muscle

•muscle tissue muscle tissue contracts (shortens) contracts (shortens) and causes and causes movementmovement

Where are muscles?Where are muscles?

•attached to your attached to your skeletonskeleton (skeletal)(skeletal)

• in your heartin your heart (cardiac)(cardiac)• in your stomach and in your stomach and

intestinesintestines (smooth)(smooth)•called the MUSCULAR called the MUSCULAR

SYSTEMSYSTEM

Human MusclesHuman Muscles

Muscle Muscle BasicsBasics

•MMuscleuscles are made of s are made of bundles of protein bundles of protein fibersfibers

•The two main fibers are The two main fibers are actinactin (thin protein) and (thin protein) and myosinmyosin (thick protein) (thick protein)

Muscle BasicsMuscle Basics

•Remember: what moves Remember: what moves muscles?muscles?–Motor neuronsMotor neurons

•AcetylcholineAcetylcholine- a - a neurotransmitter released neurotransmitter released & moves across synapse & moves across synapse and contracts muscle. and contracts muscle.

Muscle BasicsMuscle Basics

Types of Types of MuscleMuscle1. Skeletal muscle•attached to bones of skeleton•Voluntary(we control them)

most of the meat we eat is this tissue

Skeletal Muscle Skeletal Muscle Continued:Continued:

•Microscope:Microscope:–Alternating Alternating light & light & dark bandsdark bands•StriationsStriations•Many Many nuclei nuclei

Types of Types of MuscleMuscle (cont.)(cont.)

2. Smooth muscle•Found in hollow structures:

stomach, blood vessels & intestines•involuntary

Smooth Muscle Cont’d:Smooth Muscle Cont’d:

•Spindle-shapedSpindle-shaped•One nucleusOne nucleus•Not striatedNot striated

Types of Types of MuscleMuscle (cont)(cont)

3. Cardiac muscle•found only in heart•not connected to bone•involuntary (we don’t control)

Cardiac Muscle Cont’d:Cardiac Muscle Cont’d:

•Striated like Striated like skeletal skeletal musclemuscle

•One nucleus One nucleus (may have 2)(may have 2)

• Involuntary Involuntary like smooth like smooth musclemuscle

•Muscles shorten Muscles shorten ((they they contract)contract)

•They are connected to They are connected to bones by tendons bones by tendons (achilles, forearm)(achilles, forearm)

Muscle ContractionsMuscle Contractions

•When one muscle When one muscle contracts, the opposite contracts, the opposite one must relaxone must relax–quadquadricepriceps / hamstrings / hamstringss–biceps / tricepsbiceps / triceps–tibialistibialis / / gastrocnemiusgastrocnemius

Muscles Work in PairsMuscles Work in Pairs

Nerves Activate MusclesNerves Activate Muscles

•Muscles contract when Muscles contract when sent a signal from the sent a signal from the nervous systemnervous system

•Signals may varySignals may vary– more muscle more muscle cells/fibers result in cells/fibers result in more force generatedmore force generated

Muscle FatigueMuscle Fatigue

•Results from oxygen Results from oxygen debtdebt

•Lactic acid builds up and Lactic acid builds up and muscle can’t contract muscle can’t contract effectivelyeffectively

•Recovery period “flushes Recovery period “flushes out” lactic acid and out” lactic acid and delivers oxygendelivers oxygen

MuscularMuscular SSystemystem ProblemsProblems

•SStraintrain:: tearing of fibers tearing of fibers•CCrampramp:: not enough not enough oxygen, overuseoxygen, overuse

•MMuscular uscular DDystrophyystrophy:: nerve messages to nerve messages to muscles are blockedmuscles are blocked

Steroids•Increase rate of Increase rate of muscle growthmuscle growth

•Stop bone growthStop bone growth•Side Effects:Side Effects: Heart attack, Heart attack, shriveled testes, etc.shriveled testes, etc.

Exercise & MusclesExercise & Muscles•When muscles are not When muscles are not used the cells become used the cells become smaller & weakersmaller & weaker

•Two main types of Two main types of exercise: exercise: aerobicaerobic & & anaerobicanaerobic

Aerobic ExerciseAerobic Exercise•Oxygen used rapidly Oxygen used rapidly by muscles by muscles

Uses Uses slow twitchslow twitch muscle muscle

•Glucose broken downGlucose broken down•Ex: swimming Ex: swimming & jogging & jogging

Anaerobic ExerciseAnaerobic Exercise•High intensity High intensity Uses Uses fast twitchfast twitch muscle muscle

•Glucose converted to Glucose converted to lactic acidlactic acid (muscle burn) (muscle burn)

•Ex: sprinting & Ex: sprinting & weight lifting weight lifting