The Muscular System

What does muscle do?

Shortens to create tension

What does muscles organization effect?

Power, range and speed of muscle movement

Fascicles

Muscle cells (Fibers) that are organized

How are skeletal muscles classified?

By fascicles and their relationships to the tendonds

What is the organization of skeletal muscle fibers?

Parallel, Convergent, Pennate and Circular muscle

Parallel muscle

Fibers parallel to the long axis of muscle, ex. Biceps brachii

Convergent muscle

Broad area that converges an attachment site, ex. tendon

Pennate muscle

Attatch slanted and can be in multiple angles1

Unipennate

A type of Pennate muscle, fibers on one side of the tendon, ex extensor digitorium

Bipennate

A type of Pennate muscle, Fibers on both sides of tendon, ex rectus femoris

Multipennate

A type of Pennate muscle, Tendon branches within muscle, ex deltoid

Circular muscles

Open and close to gaurd entrances in the body, ex orbicularis

Skeletal motion

Uses levers (bones), joints/fulcrum (a fixed point) muscle to provide applied force required to overcome loads

What are the three lever classes?

First class, Second class and Third class

First class lever

Like a seesaw, force and load are balanced

Second class lever

Like a wheelbarrow, small force moves a large weight

Third class lever

Most common, greater force moves smaller load, like a catapult

Origins

Fixed points of attachment

Insertion

One moving point of attachment

Actions

Movements produced by muscle contraction

How do the muscles interact?

Work in groups to maximize efficiency

What muscles reach maximum tension first?

Smaller muscles

Agonist

Prime mover, produces particular movement

Antagonist

Opposes movement of agonist

Synergist

Smaller muscle that assists agonist

Muscle opposition

Agonists and antagonists work in pairs

How does aging effect muscles?

Muscle fibers become smaller in diameter, less elastic, increased amount of fibrous tissue, decreased tolerance of exercise and decreased ability to recover

What are the three layers of connective tissue?

Epimysium, perimysium and endomysium

Epimysium

Separates muscle from surrounding tissues

Perimysium

Surrounds muscle fiber bundles (Fasicles)

Endomysium

Surround individual muscle cells (muscle fiber cells)

What do the ends of muscle become?

Tendons

Muscles have extensive v-

vascular systems

Are skeletal muscles voluntary or involuntary?

Voluntary

Sarcolemma

The cell membrane of a muscle fiber cell, a change in transmembrane potential begins contractions

Transverse tubules

Transmit action potential through cell, have same properties as sarcolemma

Myofibrils

Made of bundles of myofilaments

What are the types of myifilaments

Thin (Actin) and Thick (Myosin)

Sarcoplasmic reticulum

Membranous structure surrounding myofibrils, transmit action potential to myofibril, forms terminal cisternae attached to T tubules

Triad

T tubule and two terminal cisternae

Sarcomeres

Contractile units of muscle

Thin filaments

F-actin

Tropomyosin

Double strand that prevents actin-myosin interaction

Troponin

Globular protein that binds tropomyosin to G-actin

Initiation of thin filaments

Calcium binds to receptor and troponin molecule, troponin-tropomyosin complex change, exposes active site of F-actin

Thick filament

Contains myosin and titin

Titin

Strands that recoil after they stretch

Skeletal muscle contraction process

Neural stimulation by sarcolemma, muscle fiber contraction and tension is produced

Sarcoplasm

Cytoplasm of muscle fiber(cell)

Cisternae

Release calcium into sarcomeres to begin muscle contraction

Neuromuscular junction

Special intercellular connection of nervous system and skeletal muscle fiber, controls calcium ion release in sarcoplasm

Excitation-contraction coupling

Active site exposure, cross bridge formation, myosin head pivoting, cross bridge detachment, myosin reactivation

Relaxation depends on?

ATP, neural stimulus and number of free calcium ions

Rigor mortis

Fixed muscular contraction, ATP stops, calcium builds in sarcoplasm

Tension depends on

Pivoting cross-bridges, fibers resting length and frequency of stimulation

Twitch

One single contraction

Warmup latent period

Action potential moves through sarcolemma, causing calcium to releaseC

ontraction phase

Calcium ions bind, tension builds to peak

Relaxation phase

Calcium levels fall, active sites are covered and tension falls to resting levels

Tetanus

Maximum strength

Treppe

Wave

Incomplete tetanus

Complete tetanus

Motor units

Bundles of fibers attached to neurons, contract at the same time

Recruitment

Mutiple motor units stimulated

Muscle tone

Normal tension and firmness at rest

What does increased muscle tone increase?

Metabolic energy used even at rest

Elastic forces

The pull of elastic elements, expands the sarcomeres to resting length

Atrophy

Flaccid or weak

ATP

Active energy molecule

Creatine phosphate

Storage molecule for excess ATP energy in resting muscle

Creatine kinase

Enzymes that recharges energy

ATP generation

Produced by aerobic metabolism and anaerobic glycolysis

Aerobic metabolism

Primary energy source of resting muscles, breaks down fatty acids

Anaerobic glycolysis

Primary energy source for peak muscular activity, breaks down glucose from glycogen

Lactic acid

Low pH

Muscle fatigue

When muscles can no longer perform a required activity

Recovery period

The time required after exertion for muscles to return to normal

Oxygen debt/EPOC

After excercise the body needs more oxygen than usual to restabalize

Fatigue

Depletion of metabolic reserves, damage sarcolemma

Slow fibers

Slow to contract and fatigue

Fast fibers

Twitch fast muscle fibers