Module 4A: Muscular System Terminology/Tissue/Mechanics Flashcards
what does myo/mys mean?
muscle
what is a muscle fiber?
a muscle cell (skeletal or smooth)
why are muscle fibers called “fibers”?
because they are elongated in appearance
why are cardiac muscle cells just called cardiac muscle cells and not fibers?
because they aren’t elongated
what converts chemical energy (ATP) into mechanical energy (to exert force)?
muscle tissue
what are the three types of muscle tissue?
- smooth muscle
- cardiac muscle
- skeletal muscle
where can smooth muscle be found?
internal organs (except heart) and blood vessels (unless it is very small)
where can cardiac muscle be found?
only the heart
- makes up our heart wall
where can skeletal muscle be found?
in muscles
what is smooth muscle?
- have relatively long muscle fibers that you can find in the walls of organs like bladder, intestines, as well as inside our blood vessels
what is skeletal muscle?
attaches to bones to move them or to resist the movement of those bones
why does our smooth muscles have sarcomeres?
because it needs to contract
what are the two layers of smooth muscle in the intestine?
- longitudinal layer (outermost layer)
- circular layer (under longitudinal layer)
what does the circular layer of smooth muscle in the intestine do when it contracts?
will restrict the lumen (extends the lumen when it is relaxed)
- longitudinal layers also help with this
what do the two layers of smooth muscle (longitudinal and circular) in the intenstine appear like?
- elongated
- have no striations
- uni-nucleated (one nucleus per cell)
what is smooth muscle controlled by?
autonomic nervous system (involuntary)
the two smooth muscle layers for the intestine work together, alternating contraction and relaxation to make a wave-like motion. what does this do?
this slow wave motion permits time for absorption while still squeezing the material through the organ (called Peristalsis)
what is peristalsis?
squeezing material through the organs
- allows us to absorb what we need and just move the rest of the material along
single-unit smooth muscle tissue have more generalized innervation to the cells whereas a multi-unit smooth muscle tissue would have?
more specific innervation to the cells
compared to skeletal muscles, the cells of smooth muscle are arranged how?
longitudinal (diagonally), and when they contract, the organelles shorten
when smooth muscle is arranged circularly, what happens when it contracts? vs longitudinal contracting?
circular: squeezes and constricts the lumen
longitudinal: the organelles shorten
how is smooth muscle organized?
diagonally; not striated
typically, single neurons reach more muscle fibers in smooth muscle than skeletal. what does this result in?
more cells contracting simultaneously
some smooth muscle cells have no innervation (no nerve supply), how do they contract?
from chemicals/hormones
is cardiac muscle elongated and striated?
no. it is not elongated but they are striated
what type of control is cardiac muscle under?
involuntary
- under autonomic nervous system control
what are the contractions of cardiac muscle controlled by?
local electrical and chemical controls of your pace maker
- cardiac muscle fibers display “autorhythmicity”
what is autorhythmicity?
the ability to repeatedly generate spontaneous action potentials for each beat of our heart
the cardiac muscles are highly interconnected. what does this allow the muscle to do?
allows the muscle to contract as one (more so than the other types of muscle)
what does skeletal muscle attach to?
bones
which type of muscle moves or resists the movement of bones?
skeletal muscle
what is the only type of muscle that is consciously controlled?
skeletal muscle
what is skeletal muscle attached to bone through?
the tendon
what is surrounding the whole muscle?
the epimysium
what is surrounding a fascicle (a bundle of muscle fibers)
the perimysium
what is a fascicle?
a bundle of muscle fibers
what surrounds muscle fibers that are make up of myofibrils (the filaments of the muscle)?
an endomysium
why do we need rich blood supply to skeletal muscle?
because when we work we need lots of nutrient and oxygen that blood will bring
true or false: only some fibers are supplied with a nerve ending
false
- each fiber is supplied with a nerve ending
— we cannot contract without nervous stimulation
what are sarcomeres?
contractile unit of skeletal muscle
- a single unit runs from Z-line to Z-line
- they have myofilaments
what shortens a sarcomere?
thick and thin filaments (MYOFILAMENTS) binds to each other
- the thick filament grabs the thin filament, pulling on it, to shorten the sarcomere. this makes the z-discs/lines come closer together
what is a myofilament?
the thick and thin filaments in a myofibril
what is a single contractile fiber in muscle fiber called?
myofibril
what is myosin?
the thick filament in a sarcomere
what is actin?
the thin filament in a sarcomere
what causes the striations (making the muscle look striped) in skeletal muscle?
the highly organized structure of thin and thick filaments
- because of the sarcomeres
the muscle fibers can each get larger and get more sarcomeres or also get more muscle fibers as well as more blood cells to supply the area when what happens?
when the muscle hypertrophes
which muscle type has the longest muscle cells?
skeletal muscle
true or false: skeletal muscle is elongated, smooth and involuntary controlled
false:
it is elongated, striated and voluntary controlled
what is a motor unit?
a single nerve (neuron) and all of the muscle fibers it innervates (supplies)
as the need for force increases, the firing rate of the active motor units will?
increase
- producing more force more often
- we will recruit additional motor units to add additional force in the output
what does innervation/innervates mean?
the nerves are connecting to something to depolarize or activate it
what is muscles PRIMARY function?
to produce movement
what are the functions of muscle?
- producing movement
- stabilizing joints
- maintain posture and body position
- generating heat
- protect organs
- regulate passage of substances
- constriction/dilation (eye (controlling amount of light), blood vessels (help to push the blood elsewhere))
what are the two types of attachments for muscles?
- direct - muscle fuses to the bone or cartilage - where epimysium of the muscle is continuous with the periosteum of the bone
- indirect - where epimysium of the muscle continues as a tendon or aponeurosis which then merges into the periosteum of the bone (more common)
what are the three types of muscle contraction?
- isometric
- concentric (isotonic)
- eccentric (isotonic)
what is an isometric contraction?
when the load is equal to the force of contraction
- there is no movement in the joints
- muscle contracts but does not shorten
what are the two types of isotonic contraction?
- concentric
- eccentric
what is an isotonic contraction?
when there is shortening or lengthening of the muscle during contraction
what is concentric contraction?
the tension in the muscle is generated as the muscle is shortening
- the force of the contraction is stronger than the load and the movement and muscle force are in the same direction
what is eccentric contraction?
tension is developed in the muscle while the muscle is lengthening
- often the force that causes the movement is gravity
- the force of contraction is less than the force of the load
- movement and muscle force are in opposite directions
what factors affect the force of contraction?
- NUMBER or muscle fibers RECRUITED
- SIZE of muscle fibers
- FREQUENCY of nerve stimulation
- degree of muscle stretch
- fibers have an optimal length for maximizing contraction
- ex. if muscle is stretched, thick filament cannot reach thin filament
true or false: muscle attachment occurs in one place
false:
muscle attachment occurs in more than one place
as a muscle shortens, which point moves closer to the origin?
the insertion point
- the action is what happens to one or more joints as a result of the muscle contraction
what is an “origin”?
the “fixed” point of attachment (or more fixed)
- typically the more proximal attachment
what is an “insertion point”?
attachment on moveable bone
- typically the more distal attachment
what does muscles produce or restrict when they cross a joint and are activated?
produce or restrict movement in that joint
muscles can only ____, never _____.
only pull, never push
- there is a muscle that “does” a movement and another that “undoes” it (usually a pair of muscles)
what is a prime mover? (AGONIST)
a muscle with the major responsibility of producing a specific movement of a bone or stabilizing it
what is a synergist?
secondary muscles which contribute to action of prime mover
what is an antagonist?
a muscle that opposes a specific movement (usually relaxed/stretched when agonist is active)
- typically they oppose the movement or action of prime mover
- tend to be the muscles on the opposite side of a joint to the prime mover
what do most skeletal muscles use to move?
leverage
what are the three components of a lever system?
- lever
- effort
- load
what is a lever?
- rigid bar (bone) that moves on a fixed point called fulcrum (joint)
- the point/joint around which all the movement will occur
what is effort in the lever system?
force (supplied by muscle contraction) applied to lever to move resistance (load) that is applied to the moveable bone in the system
what is load in the lever system?
resistance (bone + tissues + any added weight) that is moved by the effort
- the weight that needs to be moved
what are the two basic principles of levers?
- effort FARTHER than load from fulcrum = lever operates at mechanical ADVANTAGE
- effort NEARER the load to fulcrum = lever operates at mechanical DISADVANTAGE
what is the set up of a first class lever?
fulcrum between load and effort
what is the set up of a second class lever?
load between fulcrum and effort
what is the set up of a third class lever?
effort between fulcrum and load
what are examples of each class lever applied to anatomy?
1st class: nodding your head (Fulcrum is your C1, load is your chin)
2nd class: standing on your toes (fulcrum is your toes, load is body weight)
3rd class: flexion at the elbow (fulcrum is your elbow, load is your hand and effort is the force generated in your biceps)
what are the two ways of naming muscles by location?
- intercostal (rib)
- temporalis (temporal bone)
what are the two ways of naming muscles by shape?
- teres (round)
- trapezium (trapezoid)
what are the two ways of naming muscles by size?
gluteus maximum (big muscle) and minimus (small muscle)
what are the two ways of naming muscles by the direction of their muscle fibers?
- RECTUS femoris (straight)
- internal OBLIQUE (diagonal)
what are the two ways of naming muscles by number of origins?
- biceps brachii (two origins)
- triceps brachii (three origins)
what are the two ways of naming muscles by location of attachments?
sternocleidomastoid (sternum, clavicle, mastoid process)
what are the two ways of naming muscles by muscle action?
aDductor longus
