Muscular System

Muscular System

Series of tissues throughout thebody that act to move bones or organs• Divided into:• Skeletal• Smooth• Cardiac

Divisions of the System

Skeletal- “striated”- found pullingskeleton, arranged in stripes

Smooth- found lining digestive andparts of circulatory system

Cardiac- in heart only, constantlycontracting

Muscle Contraction

Nerve impulse travels to nerve tellingit to contract

Must receive enough signal that itreaches its threshold, which tells themuscle to contract

- threshold is point at which muscle will contract

Muscle Contraction

Muscle contraction is all-or-none response, much like nerve• If muscle gets enough signal,

it will contract. If not, it willnot react at all.

Chemical Energy

When it is time for your cells tocontract, they must use chemicalenergy in the form of ATP

Adenosine TRIphosphate- one P isremoved making ADP (adenosineDiphosphate). The energy from theP bond results in energy for movement

Process of Contraction

Actin and myosin are proteins withina muscle

Actin attaches to the myosin’s “head”,and gets pulledATP is used, causing myosin to rebindfurther down the actin and pull again

Sliding Fillament Model

The myosin contraction causes theactin to “slide” along the myosin strands, pulling the muscle

This is a muscle contraction

Muscle Contraction

As myosin pulls, the muscle becomesshorter, or contracts

There are two types of muscle-Flexors- shorten causing a twobones to bendExtensors- shorten pulling the bones straight

Muscle Structure

Origin- The non-moveable point towhich the muscle is attached

Insertion- the attachment to the bonethat is moved by the muscle

Muscle Issues

• Sprain vs. Strain• Muscular Dystrophy

Sprain vs. Strain

Sprain- stretch/tear of ligament

Strain- stretch/tear of tendon

Graded I-III• I- ice• II- immobilize, limit movement• III- immobilize, may need surgery

Muscular Dystrophy

Sex-linked inherited degenerativedisease

Results in loss of muscle tissue, oftenresults in death at a young age

*commomly- Recessive, inherited on X chromosome, so only affects males