The Muscular system

Only Skeletal & voluntary muscles/organs

            Maintains posture – due to tonus

                        Tonus - continuous contraction of muscle

            Stabilizes articulations

            Red meat of the body

            Functions for locomotion

            Produces heat

            Interdependent system

            Contractible irritable extensible elastic

            Usually attached to bone

            Fatigues Fast

            Responds to Stimuli Faster

            Less Extensible

            Supports Nervous & Vascular system

                        Muscle movement can act as a pump (especially vascular system – lymph)

            Has both Sensory and Motor Neurons

            Lots of Mitochondria

Muscle Belly

            Fibers & tendon(s)

                        Tendon of Origin – attaches to less moveable structure

                        Tendon of Insertion – attaches to more movable structure

            May have 2 or more tendons of Origin

            May have Single origin and Several insertions

           

Aponuerosis à broad flat tendonous sheet, mainly serving to connect a muscle with the parts it moves

Deep Fascia

Each fiber has a sarcolemma

Endomycium surrounds sarcolemma

Fasiculus is a bundle of fibers

Perymycium surrounds each fascicle

Epimycium surrounds the all fasicles as a whole

NueroMuscular Junction

            Muscles and nerves actually don’t touch

            Synaptic bulb is the end of the nerve that begins the synaptic cleft

            Synaptic Cleft is just the space between the nerve and the muscle

            Motor End Plate is the sarcolemma of the muscle

In the Synaptic Cleft

            Several Mitochondria

            Several Synaptic vesicles

                        Containing ACh acetylcholine

                                    ACh  causes change in permeability that causes muscles to contract

                        Or contains AChE acetylcholinesterase

                                    AChE causes change in permeability that causes muscles to relax

                                                By removing ACh

Arrangement

            Nuclei lies under the sarcolemma

            Myofibril arrangement causes light and dark bands

                        Also directly responsible for muscle contraction

            Actin = thin band

                        Filaments anchored in Z line

            Myosin = Thick band

                        Filaments anchored near M line

Sarcomere

            Distance between 2 adjacent Z lines

           

I Band – Thin Actin ONLY

H Zone – Thick Myosin ONLY

A Band - location where Actin and Myosin overlap

M Line – Down the middle of thick myosin

Sliding Filament Theory

The sliding filament theory is the explanation for how muscles produce force (or, usually, shorten).  It explains that the thick and thin filaments within the sarcomere slide past one another, shortening the entire length of the sarcomere.  In order to slide past one another, the myosin heads will interact with the actin filaments and, using ATP, bend to pull past the actin

All or None Law

If the stimulus is any strength above threshold, the nerve or muscle fiber will give a complete response or otherwise no response at all

            Motor units

                        Controls anywhere from 3 – 150 fibers

                        # of motor units determines Total amount of force used

Roles of Muscle

            Prime Mover – Main muscle involved in desired action

            Antagonist – Counteracts action of prime mover

            Synergist – Steadies movement or removes unwanted movement

            Fixator – Maintains same position

            Coordination – Cooperation Between muscles

                        Controlled via cerebellum

A muscle that is closer to a joint has greater range of motion but losses leverage

A muscle that is away from a joint has less range yet more leverage

Muscle Arrangement

            Longitudinal (Parallel) all fibers arranged parallel fashion

                        Can shorten by 1/3 or ½ length of muscle belly

                        Weak

            Unapenate – Muscle fibers attach laterally along 1 side

            Bipenate – muscle fibers attach laterally 2 sides – Powerfull

            Radiate --Combined arrangement of flat and fusiform

muscles, orginate on brad aponeurosis and

converge onto a tendon

            Orbicularis -- a muscle encircling an orifice