Biomechanics Midterm Flashcards
What is the arrangement of fusiform muscles (spindle shaped)?
How does their range of motion compare?
fibers arranged parallel and with large cross section diameter
produce a greater range of movement than similar sized muscles with pennate arrangement
What are parallel muscles?
fibers arranged parallel to the length of the muscle
Pennate muscles
Have shorter fibers
Unipennate muscle
attached to main tendon; fibers come in at an angle
ex. ext. digitorum
bipennnate musclle
ex. rectus femoris
pulls on centraltendon ith fibers on both sides
multipennate
multiple groups of fibers converge on one tendon in various directions
ex. deltoid
Convergent muscles (fan shaped)
broad origin, pointed insertion
the direction of the pull can be varied –> versatile
ex. pectoralis major –> different parts can be active at different times
Circular muscles
sphincters, eyes, mouth
closes down round areas
Muscle Actions
Strength, power and torque
Muscle action: strength
the max force a muscle can produce for a single max effort
the amt of tension a muscle produces
muscle action: power
work done over a given period of time (work/time)
a muscle contracting in a very brief amount of time (high power)
muscle action: torque
muscle force causing rotary movement of a body around an axis; a turning or twisting force
Muscle action: Contraction
What can they be used for?
tension developed in a muscle as a result of a stimulus
Used for: cause, control and prevention of joint movement
- initiate or accelerate movement of a body segment (usually contraction)
- slow down or decelerate movement of segment (usually stretching/lengthening –> controlling)
- prevent movement of a body segment
What are the main types of muscle contraction?
Isometric (same measure): muscles do not shortern/lengthen, but still produce tension
Isotonic: (same tone) lengthen or shorten, but maintain a consistent tone
- Concentric: to the center; bring together
- Eccentric: away from the center; bring apart
Isometric contraction
tension developed within a muscle without joint motion –> static contractions
Occurs when the tension a muscle develops is the same as the force applied to that muscle
USED TO STABILIZE JOINTS
Isotonic contractions
muscle contraction without appreciable change in the force contraction –> maintains tension under a constant load
- tension is developed within a muscle
FINISH
Concentric contraction
muscle develops tension as it shortens
occurs when a muscle develops enough tension to overcome the resistance appllied to it
used to initiate movement against gravity or resistance
Eccentric contraction (away)
muscle lengthens unders tension (gradual lowering under high weight)
muscle tensions is less than the resistance applied to it
- results in controlled joint motion
USED TO DECELERATE BODY SEGMENT MOVEMENT
**produce the most tension out of all types of contraction; most demanding type of contraction
Line of pull
direction of movement produced by the contracting muscle
- the pull of a muscle from its rigin to insertion
change can occur with change in joint position
Line of pull is a function of what/
the muscles attachment
the plane of joint motion
the muscles distance from the joint’s axis of rotation
What happens when the line of pull is altered from its optimal position due to muscle weakness or poor posture?
the muscle will be inefficient, work harder and have more strain put upon it.
This can lead to muscle and/or joint injury.
Angle of pull**
the angle betewen the line of pull of the muscle and the bone on hich it inserts
- a muscles angle of pull changes with every degree of joint motion
- a vertical component of the angle is always perpendicdular to the lever (attachment) and causes rotational movement at the joint axis (90* –> 100% rotational)
- a horizontak component of the angle of pull is always parallel to the lever and causes non-rotational movement at the joint axis (angle or 45*
What is muscle action is dependent upon?
# of motor units activated type of motor unit activated size of the muscle initial muscle length angle of the muscle and joint speed of muscle contraction
Reverse action of concentric muscle contractions
when a muscle contracts it pulls both ends toward the center of the muscle
- if neither of the bones attachments are stabilized, then bones are puled toward another
- usually, one bone is more stabilized and the less stabilized bone usually moves toward the more stabilized (ex. biceps curl - open chain; chin up - closed chain)
Range of motion
depends on length of muscle fibers (long = large range; parallell and fusiform muscles)
What does power depend on?
total number of muscle fibers
many fibers = great power
(convergent, unipennate, bipennate, multipennate muscles)
4 Properties of muscle force production and movement
irritability or excitability
contractility
extensibility
elasticity
Irritability (excitability)
property of muscle being sensitive or responsive to chemical, electrical or mechanical stimuli
Contractility
ability of muscle to contract and develop tensions (innternal force) against resistance when stimulated
Extensibility
ability of muscle to be passivle streatched beyond its normal resting length
Elasticity
ability of muscle to return to its original length following stretching
Interdigitation
a muscle may be innervated by more than one nerve and a particular nerve may innervate more than one muscle
What roles doe muscles work in?
Prime mover (Agonist)
Antagonist
Synergist
Stabilizer (fixator)
Prime movers (Agonists)
muscles that assume the major responsbilioty for producing a specific movement
Antagonists
muscles that oppose or revers the movement by prime mover
- if the prime mover is active, antagonist is released
- antagonist also help regulate the action of the prime mover by partially contracting to provide some resistance or to slow or stop
Synergist
a musclle which performs or assists the same same join motion as the agonist
- two muscles are callded synergeists that act to control morion of the prime mover
- immovbilizw the origin of the prime mover so that the prime mover can act more efficiency
STabilizers (fixator)
synergists that act to control motion of the prime mover
- immobilize the origin of the prime mover so that the prime mover can act more efficiently
- tends to be continuous low-level muscle activity with either isometric or eccentric pull
(ex. deltoid is the prime mover of arm abduction)
Mechanical Levers
Purely physical
LEver
a riigid bar that moves on a fixed point (bones)
Fulcrum
a fixed point of leverage (joint)
Effort
force appllied to move a resistance (tension/torque)
Load
resistance to be moved (bone, tissue mass and objects to be moved)
Mechanical advantage lever 9power lever)
load is close to fulcrum
effor applied far from the fulcrum
small effort appllied over a relatively long distance can be used to move a large load over a small distange
* such a leverl operates as a mechanial advantage and is commonly caled a power lever
Mechanical Dsiadvantage (speed leverage0
load is far from fulcrum
efost is applied new the fulcrum
The force exerted must be great ha the moved moved
- useful because they allow the load to move rapidly through a larger range of motion
Mechanical Muscke
A lever allows
1st class levers
dvvd
Second class levers
the load (resistance) lies between fulcrum and effort * we dont have many of these
Third class levers *Most of what we have in the body
effort is applied at t apoint between the load and the fulcrum
great speed with mechanical disadvantage
Functional Organization of Skeletal Muscles
Muscles –> fascicles –> muscle fibers (cells) –> myofibrils –> Thick and thin filaments
Each layer is wrapped with fascia
Sarcomere
Contains Thick and Thin Filaments
Make up a Myofibril
Myofibrils
Surrounded by: Sarcoplasmic Reticulum
Consists of: Sarcomeres
Muscle Fiber
Surrounded by: Endomysium
Contains Myofibrils
Types: Fast, ballistic (glycolytic fuel source); postural;
* Can contain multiple types of fibers
Muscle Fascicle
Surrounded by: Perimysium
Contains: Muscle Fibers
Skeletal Muscle
Surrounded by: Epimysium
Contains: Muscle Fascicles
Neuromuscular Juntion
What are the 5 basic components?
The site where the axon and muscle fiber communicate
- Motor Neuron
- Motor end plate
- Synaptic Cleft
- Synaptic Vesicles
- Neurotransmitters
What is the motor stimulation mechanism for muscle contraction?
Motor impulses cause the release of acetylcholine (ACh) from synaptic vesicles which bind to receptors on the motor end plate and generate muscle contraction
What is the process of muscle relaxation?
acteylcholinesterase breaks down acetylecholine
motor neuron impulses stop
calcium moves back into sarcoplasmic reticulum
myosin and actin binding prevented
What is a motor unit?
a single motor neuron and all the muscle fibers it controls
- the functional connection between the nervous system and the muscular system
- when a motor unit fires, all the muscle fibers contract together
- one neuron may innervate several muscle fibers
- one muscle fiber may be innervated by several motor neurons
- this creates both large and small motor units
- One muscle fiber may act with several motor units depending upon demand (interdigitation)