MUSCULAR SYSTEM

7TH GRADE

Prentice Hall textbook

CH 1/Section 4

Muscular System•There are about 600 muscles in your body

•Muscles make up about 40% of your body weight

WHAT ARE SOME FUNCTIONS OF MUSCLES? 1. Muscles move the bones of the skeleton, allowing us to be mobile (ex. biceps/triceps pulls on forearm bones)

2. Muscles keep your heart beating (ex. cardiac muscle contractions)

3. Muscles allow our chest to expand for breathing (ex. diaphragm contracts or relaxes)

4. Muscles hold your organs in place & helps protect them (ex. abdominal muscles protect vital organs under them)

5. Muscles help move materials throughout the body (ex. smooth muscles in digestive system move food along, & muscles in blood vessels move blood cells)

Many layers of muscles allow us to move in many different ways!

Skeletal muscles in the human body….

Take a closer look at what muscles help our body to do!!!

TWO TYPES OF MUSCLE• Muscles can be either voluntary or involuntary – what is the

difference?• Involuntary Muscle – Muscles that are not under our

conscious control (we are not aware of their movement- ex. cardiac & smooth muscles)

• Voluntary Muscle – Muscles we have conscious control of (such as all skeletal muscles)

Muscles are made up of three kinds of muscle tissue:

1. Skeletal muscle tissue 2. Smooth muscle tissue

3. Cardiac muscle tissue

SKELETAL MUSCLES:

1.Skeletal muscles are attached to bones by tendons. These muscles pull on bones to move them!

(Tendon: Strong connective tissue that attaches a muscle to a bone)

***Skeletal muscles provide the force that moves your bones … so we can move our bodies!!!

TENDON VERSUS LIGAMENT

Both are connective tissue, but where and what they connect are different!

“Bind”means to attach!!

2. Skeletal muscles are:

• Voluntary (we can control them!)

• Striated (muscle looks striped or banded)

**Skeletal muscles react very quickly (think sudden movement) BUT they also tire very quickly (exhausted after exercising hard!)

SMOOTH MUSCLES:

1.Smooth muscles are involuntary muscles that work automatically to control certain movements inside your body.

-Smooth muscles are NOT striated (not banded)

-They react slowly but do not get tired quickly (slow movement…work over a long time)Examples of where smooth muscles are found:

1.Inside lining of your internal organs

2.Walls of your digestive tract (walls of stomach)

3.Walls of your blood vessels (veins, arteries, capillaries)

Peristalsis

Involuntary waves of muscle contraction that keep food moving down through the digestive tract.

The process of breathing requires a lot of work by several involuntary, smooth muscles…like your rib muscles and the diaphragm…..

Whew! Who knew it was so complicated just to breathe??

CARDIAC MUSCLE

- Found only in the heart!!! Cardiac = heart

- Cardiac muscle works to contract & relax the heart each time it beats…every second of every day!

- Has characteristics that are similar to both skeletal and smooth muscles

Like skeletal muscles, cardiac muscle is striated

Like smooth muscles, cardiac muscle is involuntary

-Cardiac muscle never gets tired!! And, it reacts quickly!

COMPARISON OF THE 3 TYPES OF MUSCLE TISSUE

SKELETAL MUSCLES MUST WORK IN PAIRS!Because muscle cells can only contract (or shorten), not extend (stretch), skeletal muscles must work in pairs to allow for movement.

One muscle of the pair contracts, at the same time, the other muscle relaxes to its original length!

Movement of bones at a joint:

1.Nerves in brain send electrical message to muscles.

2.One muscle contracts (shortens), while other muscle relaxes to normal length.

3.Contracted muscle pulls on a tendon.

4.Tendon pulls on the bone.

5.Bone moves!!

Click on link to see a step-by-step animation of joint movement!!http://kidshealth.org/kid/interactive/muscles_it.html

MUSCULAR STRENGTH AND FLEXIBILITY

-Regular exercise maintains a muscle’s strength and flexibility

-The thicker the muscle fibers are, the stronger the muscle becomes

-A proper warm-up and stretching helps prepare your muscles for exercise.

Muscle Injuries-Most injury to muscle occurs when they are overworked or overstretched…this is called muscle strain.

-Connective tissue like tendons and ligaments can also become overstretched or tear (One common sports injury is an ACL tear….ouch!)

-Muscles cramp when the entire muscle contracts strongly & quickly and stays contracted (feels tight)

Skeletal Muscle Injuries- strains…ouch!

Appearance of the muscle of a rabbit following a strain injury (overuse of a muscle)… Note the small hemorrhage (bleeding) at the tip of the injured muscle on the left

WhiplashInjury

HUMAN BODY SYSTEM INTERACTIVE WEBSITES:The list of websites below is a combination of references for additional information on the body systems, as well as interactive games for you to practice what we are learning. Some websites are focused on only one

body system, others cover several body systems. HAVE FUN LEARNING

http://kidshealth.org/kid/htbw/htbw_main_page.html (the “Best” kid-friendly body site!)http://www.edheads.org/ (#1 student favorite!! Go to “Choose an Activity” to begin)http://www.prongo.com/human/game.html (human body quiz game)http://www.sciencenetlinks.com/interactives/systems.html (structure-body parts matching for systems)http://www.bbc.co.uk/schools/podsmission/bones/annie02.shtml (skeletal system matching)http://www.vtaide.com/png/assess.htm (online quiz...scroll down to Human Body section)http://www.sciencekids.co.nz/ (various games…easy peasy games!)http://www.gamequarium.org/dir/Gamequarium/Science/Human_Body/ (links to tons of cool games)http://www.kineticcity.com/controlcar/activity.php?virus=nastro&act=4 (structure-body parts matching)http://www.neok12.com/diagram/Respiratory-System-01.htm (practice labeling parts of respiratory system)http://www.anatomyarcade.com/games/gamesRespiratory.html (lots of great games on all systems- page opens to respiratory system, but you can choose another system too!)http://kidshealth.org/kid/htbw/lungs.html (one of the best kid friendly body system websites- go to main page to pick the system)http://sciencereviewgames.com/srg/games/hs.php?id=137 http://education.jlab.org/vocabhangman/index.html (play vocab hangman or “millionaire”http://www.toxrap.org/36_kids_game1intro.html (travel through the circulatory system)