1. muscles
Chapter 8

2. 3 types of muscles:
skeletal: attached to bones, cylindrical, multinucleated, striated, voluntary
Cardiac: only in heart, branches, uninucleated, striations, involuntary
Smooth: hollow visceral organs, uninucleated, no striations, involuntary

3. Muscle functions Produces movement Maintains posture Stabilizes joints
Generates heat

4. Skeletal muscle activity
Skeletal muscles must be stimulated by nerve impulses to contract
One nerve cell can stimulate a few muscle cells or hundreds. The area where nerve cells branch into the muscle is called the neuromuscular junction.

5. Muscle activity continued…….
When a nerve transmitter reaches a muscle, it releases a chemical-acetylcholine
Sodiim ions rush into the muscle cell allowing it to contract—called action potential
Potassium ions will rush out of the cell to return cells to normal

6. Contraction of a muscle as a whole
“all or none” law applies to muscle contractions. A muscle cell will contract to its fullest when stimulated adequately. It will never partially contract.
Muscle twitches--- single brief, jerky contractions. Most muscle activity requires the nerve impulse to be sent rapidly and does not have a chance to rest.

7. Energy for muscle contractions
*ATP is the only energy source that can be directly used for muscle power.
There are 3 ways to generate ATP:
Creatine phosphate + ADP=ATP
Aerobic respiration-glucose is broken down to co2 + h2o with oxygen
Anaerobic glycolysis-without oxygen when activity is intense and oxygen is low, lactic acid will collect in muscles. --causes soreness in muscles

8. Skeletal muscles
Organ composed of several different types of tissues (vascular, nervous, connective tissues)
They pull on tendons, which in return pull on bones
Origen: the attachment of muscle (by means of tendon) to the stationary bone
Insertion: the other end of the muscle is attached to the movable bone.
Belly: fleshy portion of the muscle between the origin an insertion
Example: spring on a screen door-----Origen/door frame, insertion/door, spring/belly

9. Isotonic
Muscle shortens and movement occurs.
Most familiar type of contraction
Example: arm curl, lifting a box

10. Isometric
Muscles do not shorten, but tension increases
Example: lifting a heavy weight and it doesn’t move/holding it in place, pushing on a wall

11. Effect of muscles on exercise:
Endurance-jogging, biking, aerobics that result in stronger, more flexible muscles with greater resistance to fatigue
Resistance- enlargement of individual muscle cells by making more contractile filaments

12. 5 rules of muscle activity
Cross at least 1 joint
The bulk of muscle lies proximal to joint that is crossed
All have at least 2 attachments
They pull only---never push
Insertion moves toward origin during contraction