Notes 13-3

Muscular System has many functions:
 Movement
 Body temperature
 Posture
 Food source

Function: Movement





Work with skeletal system to move body contract = shorten/tighten
Muscles PULL bones, never push muscle cells are called muscle fibers
Often work in pairs/groups for one movement

Function: Body Temperature
 HOMEOSTASIS: Muscle contraction releases heat to keep your body the right temperature
 Shivers: fast muscle contractions to raise body temperature

Function: Maintain Posture


Most muscles always hold a little bit of contraction/tension
Tension = “muscle tone”
 Keep you standing up straight (posture)

Function: Food Source
 Meat that you eat is muscle!

Types of Muscle Tissue
1.
2.
3.
Skeletal Muscle
Smooth Muscle
Cardiac Muscle


Skeletal = you control it (called
VOLUNTARY)
Smooth/Cardiac = you don’t control it
(called INVOLUNTARY)

Skeletal Muscle
 Attached to your skeleton by tendons (CT)
 Voluntary
 Structure = bundles of fibers
 striated
 Examples: quadriceps, biceps, triceps, abs, etc.
 React quickly, tire quickly

Skeletal Muscle: Bundles of Fibers

Skeletal muscles cross joints
 And work in pairs by contracting and relaxing.

Muscles at Work
 Because muscle cells can only contract, not extend, skeletal muscles must work in pairs.
While one muscle contracts, the other muscle in the pair relaxes to its original length.

FUN Facts!
 There are more than 630 muscles in the body.
 On average, the body weight is 40% muscle.
 Out of the 630 muscles, 30 of them are facial muscles, which help to create all those different faces of happiness, surprise, joy, sorrow, sadness, fright, etc.
The biggest muscle in the body is the gluteus maximus (buttock)

Smooth Muscle
 Inside organs
 Involuntary (automatic movements)
 Shorter fibers than skeletal muscle
 React slowly, tire slowly
 Example: pushes food through stomach and intestines

Cardiac Muscle
 Fibers have branched shape (like tree branches) that form webs and layers
 Make up the heart <3
 Striated
 Involuntary
 Never tire

Cardiac Muscle: Branched Fibers

Muscle Types: Fiber Shapes

Tendons
 Attach muscles to bones


White skinny part of muscle
“Gristle”

Muscles and Exercise
 Soreness DURING exercise: chemicals buildup as you use up energy (lactic acid)
 Soreness AFTER exercise: tears and damage to muscle fibers
 Healing and replacement of damaged cells = muscle growth
 The muscle gets thicker and therefore stronger

Can Muscles get hurt?
 It is possible to hurt a muscle because they can become pulled, hence "pulled muscle."
 Can actually tear a muscle the same way that a ligament or tendon gets torn or a bone gets broke.
 And they can heal themselves with rest and time.
 Muscles can also cramp, which is when a muscle stays contracted

Skeletal Muscle Development


Skeletal muscles
“mature” and strengthen as you grow up

Increase coordination
Babies can’t lift head
(neck muscles still weak)

http://youtu.be/RsWNyqnHQ2I