Discover Activity How Do Muscles Work? 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. 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.
Discover Activity How Do Muscles Work? After 2 minutes 1 min after resting Other hand- 1 min after resting Other hand- after 2 minutes # of times open & close clothespin Time
muscles Under your control Not under your conscious control Smiling Walking Breathing Digesting food voluntary muscles involuntary muscles
striated heart Quickly-does not get tired involuntary Cardiac Not striated Internal organs Slowly- tires slowly involuntary Smooth striated Attached by tendons to bones Quickly-tires quickly voluntary Skeletal appearance location how it reacts voluntary or involuntary muscle types
Skeletal muscle cells appear banded, or striated.
Unlike skeletal muscles, smooth muscle cells are not striated.
found only in the heart Skeletal, Smooth or Cardiac cardiac
found in internal organs Skeletal, Smooth or Cardiac smooth
attached by tendons Skeletal, Smooth or Cardiac skeletal
does not get tired Skeletal, Smooth or Cardiac cardiac
involuntary Skeletal, Smooth or Cardiac cardiac & smooth
voluntary Skeletal, Smooth or Cardiac skeletal
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?