8th grade ch. 1 sec. 4 the muscular system

Ch. 1 Ch. 1 Sec. 4Sec. 4

Muscular Muscular SystemSystem

Discover Activity How Do Muscles Work?

1. Grip a spring-type clothespin with the thumb and index finger of your writing hand. Squeeze the clothespin open and shut as quickly as possible for two minutes. Count how many times you can squeeze the clothespin before your muscles tire.

2. Rest for one minute. Then, repeat Step 1.• Think It Over• Predicting What do you think would happen if

you repeated Steps 1 and 2 with your other hand? Give a reason for your prediction. Then, test your prediction.

Time # of times open & close clothespin

After 2 minutes1 min after restingOther hand- after 2 minutesOther hand- 1 min after resting

Discover Activity How Do Muscles Work?

involuntary muscles voluntary muscles

Not under your conscious control

Under your control

Breathing

Digesting food

Smiling

Walking

muscles

muscle types

voluntary or

involuntary

how it reacts

location appearance

Skeletal voluntary Quickly-tires quickly

Attached by tendons to bones

striated

Smooth involuntary Slowly- tires slowly

Internal organs

Not striated

Cardiac involuntary Quickly-does not get tired

heart striated

Skeletal muscle cells appear banded, or striated.

Unlike skeletal muscles, smooth muscle cells are not striated.

Cardiac muscle cells are striated.

skeletal muscles must work in pairs

• muscle cells can only contract- not extend

• while 1 muscle contracts other muscle returns to original length

As the biceps contract, the triceps on the back of the upper arm return

to its original length.

Muscular strength & flexibility

Warm up before exercising

Muscle strain can still occur

Tendons can tear

Muscles can cramp

skeletal muscle

smooth muscle

cardiac muscle

found only in the heart

found in internal organs

attached by tendons

does not get tired

involuntary

voluntary

Dissecting a Chicken Wing• Put on a pair of latex gloves. • Take a chicken wing, a paper plate, and a dissecting kit. • Put the chicken on the table. • Examine the wing. • How many bones are there? • How many joints? • What kind of joints? • Carefully remove the skin. Discuss the questions below with your

partner and record your answers in your journal. • How many muscle groups are there? • Are the muscle groups in pairs? • What bones does each group connect? • Try to use a muscle to move another part of the wing. • Remove the muscles and tendons carefully. Locate ligaments. • Look for the cartilage & bone marrow. • There must also be veins and nerves here. How could we speculate

about which parts are veins or nerves?

Hold wing in place with pinsHold wing in place with pins

Remove the skin with the Remove the skin with the scissors and tweezers.scissors and tweezers.

Chicken TibiaChicken Tibia

Bone MarrowBone Marrow

Bone MarrowBone Marrow

Cartilage and spongy bone

ligaments

ligaments

Connects bones in movable joints

Tendon

• Connects muscle to bone