Muscular SystemsOverview

April 22, 2015Sutherlin ASTW. Crawford

Adapted from “The Anatomy of Domesticated Animals” and the Colorado Agriscience Curriculum

The Muscular System

Function:• locomotion or movement• life support– gathering food– reproduction– simple body functions

The Muscular System

Structure of muscles:– consist of mostly protein– found in bundles or sheets– connected to bones by tendons

The Muscular System

Classification of muscles:– Voluntary– Involuntary

The lean portion of animals carcass is what is used for food (muscles)

The Muscular System

• Voluntary– Under control of the animals will– All are straited (striped)– Flexor- decreases the angle between two bones

(biceps)– Extensor- opposite side and increases the angle of

two bones (triceps)

The Muscular System

• Involuntary– Not under the control of the animals free will– Heart– Secretory organs- force out secretions– Digestive system- movement of food– Respiratory system– Smoothed or straited

Let’s go further…

Muscular System Functions

• Body movement• Maintenance of posture• Respiration• Production of body heat• Communication• Constriction of organs and vessels• Heart beat

Properties of Muscle

• Contractility– Ability of a muscle to shorten with force

• Excitability– Capacity of muscle to respond to a stimulus

• Extensibility– Muscle can be stretched to its normal resting length and

beyond to a limited degree

• Elasticity– Ability of muscle to recoil to original resting length after

stretched

Muscle Tissue Types

• Skeletal– Attached to bones– Nuclei multiple and peripherally located– Striated, Voluntary and involuntary (reflexes)

Muscle Tissue Types

• Smooth– Walls of hollow organs, blood vessels, eye, glands, skin– Single nucleus centrally located– Not striated, involuntary, gap junctions in visceral smooth

Muscle Tissue Types

• Cardiac– Heart– Single nucleus centrally located– Striations, involuntary

Skeletal Muscle Structure

• Muscle fibers or cells– Develop from myoblasts– Numbers remain constant

• Connective tissue• Nerve and blood vessels

Embryologic origin

• Muscle cells are the result of the conjoining of embryo cells called myoblasts

• Explains multiple nuclei

Muscle Fibers

• Muscles are attached to bones by tendons– Tendon is the connective tissue– This tissue also encapsules the muscle and forms

the epimysium

Muscle Fibers

• Skeletal muscle is made up of bundles of subunits called fasicles (or fascicles)

• Fascicles are covered by connective tissue call perimysium

• Fascicles are made up of muscle cells– Muscle cells = muscle fibers

Muscle Fibers

• Muscle cells– Ensheathed in endomysium– Made up of long protein molecules call myofibrils– Myofibrils have two types of myofilaments• Thick myofilament• Thin myofilament

Muscle Fiber

Sarcomeres

• The myofibril is divided into chains of sarcomeres

• Sarcomeres are the sections of myofilaments that slide over one another as muscles contract and relax

• This is where the work happens

Organization of myofilaments I:

Sliding Filament Model

• Actin myofilaments sliding over myosin to shorten sarcomeres– Actin and myosin do not change length– Shortening sarcomeres responsible for skeletal

muscle contraction

• During relaxation, sarcomeres lengthen

Sliding filament model II:

Sarcomere Shortening

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http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__sarcomere_contraction.html

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