Muscular SystemChapter 8

Poke a Muscle

Learn your muscles

The 3 Muscle Types

• The job of all muscles is to contract

• They are all fibrous because cells are elongated

• The 3 Muscle Types Are:

–Skeletal Muscle

–Cardiac Muscle

–Smooth Muscle

OverviewOf

Muscle

Skeletal Muscle

• Cigar Shaped• Multinucleated• Striated• Voluntary• Can Be Involuntary When Reflexes Are

Involved• Very Strong and Fast But Need Rest• Most Attached to Bone• Do not undergo mitosis. Once dead, dead.

Skeletal Muscle Cell

Cardiac MuscleDo not undergo mitosis. Once dead, dead.

Smooth Muscle

Long thin nuclei and no striations

How are Muscles Structured?

• Muscle Cells have a plasma membrane called a Sarcolemma.

• The muscle fiber is enclosed in Endomysieum. (Endo= , Mys= )

• Many Muscle fibers bound together make a Fascicle.

• The Fascicle is wrapped in a membrane called the Perimysieum (Peri= ). Pg. 174 Tortora

Muscle Structure Continued

• Many fascicles are wrapped together by an Epimysium. (Epi= )

• Epimysia attach to tendons or Aponeuroses. (pg. 192: Tortora)

• Tendons: Strong, Thin, and made up of collagen (dense connective tissue). Aponeuroses are sheet-like tendons.

Skeletal Muscle (pg. 174)

QuizYourself

What is the major Organelle of the Muscle Cell? Pg. 176

• Myofibril(s)=Working unit of the muscle cell. Made of Subunits called sarcomeres.–Give muscles the striped or striated

appearance–The light band is the I-band–The dark band is the A-band–Between the I-bands is the Z-line–Between the A-bands is the H-zone

Match theTerms

Mechanism of muscle contraction

• The above micrographs show that the sarcomere gets shorter when the muscle contracts

• The light (I) bands become shorter• The dark bands (A) bands stay the same length

Relaxedm uscle

Contractedm uscle

relaxed sarcom ere

contracted sarcom ere

Take a long deep breath, its not that bad.

• And remember a bicycle cannot stand alone, because it is two tired.

• Now lets go on.

• But lets first watch this short video clip.

Overview of the Job of the Bands

So how do these bands work?

• The myofibrils are surrounded by the sarcoplasmic reticulum, a specialized form of smooth endoplasmic reticulum that releases calcium.

• They are made of bands of– Actin (the thin filaments) that make up the I-

bands – Myosin (the thick filaments) that make up the

A-bands

So what is the Molecular Basis of Muscle Contraction? (pg. 176)

• 1) Nerve sends out Acetylcholine or ACh

• 2) Motor Unit= All muscles triggered by nerve. (1 nerveTriggers 100’s of cells)

• 3) The Sarcolema becomes permeable to Na+

• 4) Na+ causes an action potential because it disturbs the electrical conditions of the sarcolema (pg.178)

How does ACh stimulate the muscle?

• ACh causes the sarcolema to release Calcium (Ca+)

• Ca+ binds to the actin causing it to change shape.

• Myosine finds actin’s new shape attractive and grabs hold.

What happens after the Myosin grabs hold? (pg. 179)

• Myosin’s head snaps towards the H-band of the sarcomere.

• ATP releases and re-cocks the myosin

• Only some myosin heads move at one time.

• Over all: Pg. 181

Description of Muscle movement

How does the muscle relax?

• When the action potential ends:

–Sarcomere absorb Ca+

–ATP releases myosin heads

–Actin takes on its former and less attractive shape.

–Muscle Cells can relax Best Movie on Muscle Contraction

RevisitedBest Movie review

of the muscle

Write one paragraph explaining how a muscle works.

Do this from memory.

This will help you learn.

Paul AndersonReview

So, What is this Action Potential?

• Action Potential– Electrical Current or Charge– In order to return the cell to its original

condition, K+ is pumped into the cell by the sodium potassium pump.

Sodium/Potassium

Pump

How do muscles work together?

• Prime Mover: Major muscle doing the bulk of the work contracting.

• Synergist: Group of muscles working together to contract.

• Antagonist: Muscle that works against the prime mover and or synergists.

How do Muscles work Together?

Summation and Tetanus

• Twitch: a single action potential causing the muscle to contract for a millisecond and then relax. Latent...Contraction...Relaxation period

• Summation effect: a second action potential arrives before the first is over. The contraction is larger. Wave summation

• Tetanus: multiple summation effects causing a smooth sustained contraction.

• Fatigue will set in and forces relaxation.

What is Recruitment?

• Motor unit recruitment: various motor neurons in a whole muscle do not fire at the same time. Some are relaxed some are contracted.

• Why?– Creates smooth muscle units not jerky

movements. – Put your hand out and hold it still…..

Types of Skeletal Muscle Fibers

• Slow…Slow Oxidative Fibers (SO)– Red, Make ATP Aerobiclatly, Fatigue

resistant. Marathon runners getting out of a chair when old.

• Fast– Fast oxidative –glycolytic Fibers (FOG).

• Red, ATP by anaerobic Medium fast

– Fast glycolytic Fibers (FG)• White. Anaerobic. Short, Fast, circuit trainers

Why can you crack your joints?

Click here to find out!

Muscle Movements

• http://www.healthchecksystems.com/exercise1.htm#hyper

Types of Muscle Movements

Flexion: decrease in the angle between articulating bones.

Extension: increase in the angle between articulating bones.

Abduction: movement of bone away from the midline

Adduction: movement of bone towards from the midline

To exercise the:

Quadriceps: straighten the knee

To exercise the: Gastrocnemius. Stand on your toe.

To exercise the:

Hamstring GroupBend the knee. Flexes thigh. Includes the bicepts femoris

Exercise the:Trapezius : rotates shoulder., shoulder shrugs. Extends head.

Exercise for:Latissimus Dorsi: moves arm down and backwards.

Exercise for:Deltoid: abducts, flexes, extends & rotates arm at shoulder joint.

Exercise For: Gluteus Maximus extends and rotates thigh laterally at hip joint.

Exercises for: Oblique: Flexes vertebral column, contracts sides, rotates.

Exercises for: Rectus Abdominis: flexes vertebral column / compresses abdomen (think crunches)

Exercise for : Pectoralis Major Adducts and rotates arm medially. Extends arm at shoulder

Push up: Works Pecs on The Up-Motion

Exercises for: Bicepcontracts arm into L shape

Exercises for: Triceps…extends arm at shoulder and elbow

Now Quiz Yourself!

See if you know your muscles…

Another goodQuiz site

Interesting Aspects:

• Some of us may have a spare muscle: the Plantaris muscle 1 in 10 don’t.

• Want to see it? Click the link.

• Groin pull? Here is the problem:

Groin PullOr strain.

PlantarisIn

Action