The Muscular System

Chapter 19, section 3

Click on the image to play a movie

Parts of the Muscular System

Muscle cells working together (muscle tissue)

Connective tissue that attaches the muscle to the bone (tendons)

What system controls your muscles?

When a muscle fiber is electrically excited what happens?

Click on the image to play a movie

3 types of muscle tissue

Smooth: Allows hollow organs to contract

(“contractility”)

Involuntary (with few exceptions) Digestive tract, blood vessels One nucleus/cell Slower to contract,

but does not tire easily

Cardiac muscle

Cardiac muscle: in the heart only Uninucleated, striated, and branched Have intercalated disks: locks fibers together

so heart may contract quickly Relax completely between contractions, which

prevents fatigue Involuntary.

Skeletal muscle

Skeletal muscle: Attach to the bones for movement, help

protect internal organs Under voluntary control Multinucleated Have “striations”

Which type of muscle is slow to contract?

Which type of muscle is found only in the heart?

Which type of muscle is usually voluntary (controlled by your conscious mind)?

Connecting muscles to bones

Connective tissue attaches muscles to bones “tendons”

Contraction occurs in pairs:

http://biology.clc.uc.edu/courses/bio105/muscles.htm Flexor: muscle which bends a part of the body Extensor: muscle which straightens a part of the body Example:

Click on the image to play a movie

Click image to go to website clip.

Exercise Types Resistance:

Most effective in developing size and strength of skeletal muscles

Overcome resistance (weight) of another object

Aerobic: Steady, moderate

intensity activity Strengthens the skeletal

muscles somewhat, but most effective in developing the heart

Click on the image to play a movie

Which type of muscle has different columns of molecules lined up in it’s cells so that there are alternating colored bands or striations?

Which kind of exercise would you want to do to strengthen the heart?

Levers click on the word “levers” to go to a website clip

A bar that moves around a fixed point (“fulcrum”)

Three types of levers: 1st, 2nd and 3rd class

First Class Levers (head)

Fulcrum is between the effort and the load.Which way will the load move?

Second Class Levers (on toes)

This time the load is betweenThe fulcrum and the effort.

Which way will the load move?

Third Class Levers (your arm)

Now the effort is between the fulcrum and the load.Which way will the load move?

Mechanical Advantage Mechanical advantage is how much the lever

magnifies the force

MA (mechanical advantage) = load/effort

Pushing down with 10 N of force.

Pushing down with only 5 N of force.

According to the formula what is the mechanical advantage of the lever if the load is 10 N and the force is only 5 N to move the load?

Did the lever help do some work?