These two work together Muscles and Skeleton These two work together

What does your skeleton do for you? Supports you as you stand and sit Protects your internal organs Allows you to move Makes new blood cells Stores calcium, phosphorus and fat

Let’s “dissect” a bone Compact bone is on the outside (the hard stuff)

Spongy bone is on the inside (more porous)

Bone marrow is at the center Red marrow makes blood cells Yellow marrow stores fat

What do you call the places where bones connect? joints

More physics: joints act like levers You would not be able to move without these

What holds your bones together at joints?

What connects your bones and muscles?

Exit Questions 1. How are COMPACT BONE and SPONGY BONE different? 2. What are 2 functions of bone marrow? 3. How are ligaments and tendons different? 4. What is a joint? Give 4 examples.

What do muscles do? Contract to help you move

Let’s “dissect” a muscle Muscles are made up of muscle fibers

Muscle fibers are made up of sarcomeres

Sarcomeres are composed of two types of protein Actin Myosin

Here’s what happens when muscles contract! A signal arrives from a nerve to the muscle Calcium is released inside the muscle (calcium is required for muscles to contract)

The myosin “heads” move dragging the actin with them

It looks like this

Thus, contracted muscles have shorter sarcomeres

Contracted sarcomere

When the muscle relaxes, The actin and myosin return to their normal positions

Cool animation http://www.blackwellpublishing.com/matthews/animate.html

There are three types of muscle 1. Cardiac in your heart

2. Smooth in your arteries and internal organs

3. Skeletal attached to your bones

Only one of these is voluntary which means you have to intentionally contract it Which one?

Exit Questions 1. Describe how muscles allow you to move. 2. What does voluntary mean? Involuntary? 3. Describe the three types of muscle. 4. What is a sarcomere? Which proteins make up the sarcomere, and how do they cause muscle contraction?