Mod 4 Musculoskeletal system 3 Flashcards
What influences force?
skeletal muscle contraction influence force
How to produce force?
Produces force to power movement (converts ATP into mechanical energy)
What are the three types of muscle tissue?
1) skeletal
2) cardiac
3) smooth
What are the functions of the skeletal muscle
1) Produce movement: responsible for locomotion and balance
2) maintain posture and body position
3) stabilize joints
4) generate heat (contract) (maintain body temp)
The ORDER
Muscle –> fascicle –> fiber –> myfibrils –>sacromeres –> basic contractile unit of skeletal muscles
What do muscles recieve?
a nerve, artery and vein
What are the three levels of muscle tissue?
1) Epimysium, 2) Perimysium 3) Endomysium
Epimysium?
dense irregular, the connective tissue surrounding the entire muscle, may blend with fascia
Perimysium?
Fibrous dense connective tissue surrounding fascicles (groups of muscle fibers)
Endomysium?
Fine areolar connective tissue surrounding each fibre
How do muscles attach to the skeleton?
Muscles span joints (attach to bones at least 2 places, but origin and insertion, they can be direct and indirect
Origin?
The attachment that is relatively fixed (typically proximal)
Insertion?
The attachment that is more moveable, usually distal
Direct attachment?
Fleshy: epimysium fused to the periosteum of bone or perichondrium of cartilage
Indirect attachment?
Indirect: connective tissue wrapping extend beyond muscle as rope-like tendon/sheet-like aponeurosis
Tendon?
Tendons are rope-like bands of connective tissue
What makes up a muscle?
Together a muscle and its tendon made up a muscle-tendon pair
What can muscles do?
Muscles can only pull on tendons or skeletal (never push)
What are the muscle action, functional groups?
1) Agonist
2) Antagonist
3) Synergist
(antagonist and agonist are located on the opposite sides of joint)
The muscle that is contracting is called the agonist and the muscle that is relaxing or lengthening is called the antagonist. One way to remember which muscle is the agonist – it’s the one that’s in ‘agony’ when you are doing the movement as it is the one that is doing all the work.
What is individual muscle force influenced by?
Influenced by muscle architecture and function
What are the different types of muscle arrangements (architecture)
1) parallel 2) Pennate 3)circular
What is meant by parallel?
Fascicles lie in parallel to muscles line of action: strap and fusiform
- long muscle fascicles mean more muscle shortening =larger ROM at joint (lower PCSA)
What is meant by pennate?
Fascicles at an angle relative to the line of action
- uni-pennate
- bi- pennate
- multi-pennate
(PICTURE)
Short angle fibres (smaller ROM)
- more fibre packed within a given volume = higher forces are more power (higher PCSA)
What is the muscle’s physiological cross-sectional area?
Different muscles have different force- muscle physiological cross-sectional area
What is the greatest predictor of force?
The greatest predictor of force is the muscle’s physiological cross-sectional area ( the cross-sectional area of the muscle is perpendicular to its fiber direction)
PCSA?
muscle volume/fiber length
How does sarcomere length influence force?
some overlap or actin and myosin in ‘relaxed muscle’, the greater the overlap in actin and myosin with active and passive shortening of the muscle – the more possible actin and myosin cross-bridges available
Influences the amount of force that can be developed, length-tension and force-length relationship
What makes up the muscle-tendon unit and why are these components important when considering muscle force?
- Contractile component (CC)- muscle fibers actin, myosin cross-bridges
- series elastic component (SEC) intracellular titin, tendon
- parallel elastic component (PEC) connective tissue (epimysium), perimysium, endomysium, passive cross-bridge connections
Passive force?
parallel elastic component (PEC) connective tissue within the muscle- epimysium, perimysium and endomysium
Why is connective tissue important?
it is important for generation of passive force and limits overstretch
What is the motor unit?
A single motor unit is the smallest functional unit in the musculoskeletal system, 1 motor unit= 1 motor neuron, its motor axon and all of the muscle fibers it innervates
Degree of excitatory influences recruitment
lots of excitatory input in a motor neuron= many motor neurons being recruited
What is force influenced by?
Force is influenced by the discharge rate of active motor units and the fibre type of the motor units
what are slow types of fibres?
Oxidative fibres rely on aerobic respiration, oxygen is the energy source
Slow type 1 fibres: cinderella fibres (long and fatigue), the high proportion in postural muscle, smaller force magnitude and longer force duration.
Glycolytic fibers?
use glycolysis for energy source, break down of glucose into ATP
Types glycolytic fibres?
Fast-twitch, type 2B fibers, larger force, shorter duration, and faster fatigue
What are the intermediate fibers?
Intermediate fibers use oxygen as an energy source (ATP), uses aerobic respiration, use many mitochondria and have high myoglobin
Types of intermediate fibers?
Fast-twitch type 2A fibers, a larger force than type 1, fatigue faster than type 1
Order of fibers?
slow-twitch, low force, fatigue resistant, intermediate, fast-twitch, more force, fatigues more quickly
What is Henneman’s size principle
the smaller the units are usually recruited first, the larger units are recruited later
Types of contraction?
Static –> isometric (same length) and
dynamic
- concentric (shortening) movement up
- eccentric (lengthening) movement down
Notes
the maximum force that can be produced is dependent on the direction such that eccentric is > isometric >concentric
Why does the contraction type matter?
- the absolute force produced depends on the motor task
- an eccentrically contracting muscle can produce more force at the same muscle length than a concentrically muscle
- you can hold more load than you can lift, and the lower more load, than you can hold steady
What is a parallel fascicle length?
Where fibers are parallel to the force-generating axis
What is a uni-pennate fascicle length?
Where fibers at an angle to the force-generating axis
What is a multi-pennate fascicle length
where fibers are at multiple angles to the force-generating axis
