Concept Check 27.5

Concept Check 27.5
1. Explain how muscles work in pairs in moving limbs.
Muscles cannot push, only pull; therefore they must work in pairs. For every skeletal muscle that contracts, there is another one that relaxes but can contract and pull the bone back in the opposite direction.
2. Identify the structures that make up a skeletal muscle.
Muscles consist of bundles of parallel muscle fibers along with a supply of nerves and blood vessels; and inside muscle fibers there are bindles of smaller structures called myofibrils; each one consisting of repeating units called sarcomeres. Each sarcomere is composed of two different filaments, the actin and myosin.
3. Identify at least three organ systems involved in a handshake. Describe what each system contributes to the handshake.
Eyes: Sense presence of another person and send info to brain.
Brain: Different brain regions send messages along nerves to the muscles.
Muscles: Muscles of your back, shoulder, upper arm, forearm, and wrist, stretch arm and perform shake.

4. Explain how actin and myosin interact as a muscle cell contracts.
Myosin heads attach to filament and contract it, ATP releases heads and they are free to attach to a new spot.