Muscles Flashcards
What are the types of muscle tissues?
- Cardiac (found only in the heart and are involuntary)
- Smooth (walls of abdominal organs, blood vessels and airways and are also involuntary)
- Skeletal (moves the bones of the skeleton and are mostly voluntary)
What are muscle fibers?
- Muscle cells
- Elongated tubes that have incredible movement potential
- Could not create movement without other surrounding tissues and muscles
What are myofascial units?
- The “muscle” that is separate in whole from fibers and tissues
- If you were to build a myofascial unit, first a single muscle fiber needs to be placed onto fascia, then rolled up in connective tissue, then repeat this process several hundred times
- Tendons will form at either end, and then it will be sheathed in a final layer of fascia
- Lastly, nerves and blood vessels are added
What are muscle contractions?
- Muscles with the arrangement of 2 contact points can contract or shorten
- This action produces movement and maintains postural support
- Pulls fascial elements toward it’s center which includes its attaching tendons
- If the contraction is strong enough, the tendons pulling force will move the attaching bone and its general body part
- Muscle contracts, tendon is pulled, bone pivots around a joint, body part moves
- Overlapping of thick and thin filaments in the sarcomere of a muscle
What is the origin?
- The muscles attachment to the more stationary bone
What is insertion?
- The muscles attachment to the more mobile bone
What are the components of skeletal muscle?
- Muscle belly, fascia profunda, epimysium, perimysium, endomysium, tendon, fascicles, myofibrils, myofilaments, sarcomere
What is a muscle belly?
- Portion between tendons
- Bound together with neighboring muscles by a layer of fascia profunda (deep fascia)
- Composed of chunky fascicles which are formed by tubular muscle fibers
What is fascia profunda?
- Binds the muscle belly between tendons
- Type of dense, irregular connective tissue
- Also binds together muscle groups
- Allows movement of the muscles while providing space for nerves and blood/lymph vessels to pass and fill the space between muscles
What is epimysium?
- Layer of connective tissue beneath fascia profunda
- Outer fascial layer
- Found just beneath the deep fascia and swaths the entire muscle belly
What is perimysium?
- Layer of connective tissue beneath fascia profunda
- Middle fascial layer
- Separates the muscle belly into compartments (fascicles)
What is endomysium?
- Layer of connective tissue beneath fascia profunda
- Deepest fascial layer
- Within the fascicles of the muscle belly
What are myofibrils?
- Each muscle fiber contains cylindrical contractile organelles called myofibrils
- Contain myofilaments
What are myofilaments?
- Chain-like protein structures found in myofibrils
- Pull against each other to generate force in the muscle
What are sarcomeres?
- Where myofibrils are grouped into sections containing multiple adjacent myofilaments… forms a sarcomere structure
- The muscles base unit of contraction
- Made up of thick and thin myofilaments (to form these it needs myosin, actin, tropomyosin, troponin and titin)
What is the sliding filament theory?
- How the contraction unit functions
- Process by which the myosin heads at both ends of the thick filament attach to actin and progressively pull the thin filaments toward the M-line (middle of the sarcomere)
What are the general functions of muscles?
- Produce movement
- Stabilize posture
- Assist in circulation
- Produce body heat through thermogenesis
What is excitability?
- Capacity for muscles and nerve cells to respond to stimuli
- Chemical, electrical and mechanical stimuli can all lead to muscle activation
What is contractility?
- A muscle’s ability to develop tension when stimulated
What is extensibility?
- The capacity of muscle tissue to stretch without being damaged
What is elasticity?
- A muscles tendency to return to its original length after being stretched
What are parallel muscle bellies?
- Comprised of relatively long muscle fibers and are usually in a straightforward design
- 5 common types of parallel bellies: Flat, sphincter, fusiform, strap and triangular
- Usually have 2 short tendons
- Has a larger range of motion than pennate
What are pennate muscle bellies?
- Bird’s feather like design (fibers at an oblique angle to a central tendon)
- Requires one or more of the muscles tendons to extend most of the length of the muscle
- Unipennate (tibialis posterior), Bipennate (rectus femoris), Multipennate (deltoid)
- Need many muscle fibers, but of shorter length
- Is stronger than parallel
What is excursion?
- The degree that a muscle can change in length
What are muscle motor units?
- The attachment of a motor neuron to the muscle fibers it will innervate
- The quantity of muscle fibers to which a motor unit connects depends on the type of movement that is required of that muscle
What is the all-or-none law?
- When the motor neurons electrical stimulation is sufficient enough to engage its muscle fibers simultaneously and completely
- Total commitment within motor units is necessary so we can activate our muscles predictably and systematically
What is first recruitment?
- The number of a muscles motor units that are activated to generate enough tension to produce movement in the body
What is wave summation?
- The pace at which nerve signals are fired through a motor unit
What are slow contractile fibers?
- Constructed with endurance in mind
- Slower contractions but perform with greater efficiency
What are fast contractile fibers (Type IIA)?
- Larger and produce faster contractions than slow fibers
- Fatigue more rapidly
What are fast contractile fibers (Type IIB)?
- Biggest and most powerful fibers
- Flame out the quickest of all 3 types of fibers
What are isotonic contractions?
- When a muscle changes length, either shortening (concentric) or elongating (eccentric)
What are isometric contractions?
- When the length of the muscle does not change
- Works against the forces of gravity to hold and maintain contractions of “equal length”
- No joint movement occurs during this contraction
What is the difference between concentric and eccentric isotonic contractions?
- Concentric moves towards the body, shortening the muscle length
- Eccentric moves away from the body, elongating muscle length
What is reverse muscle action?
- When the origin and insertion of the muscle swaps roles
- Example: within the brachialis when doing a chin-up because the ulna (insertion) is stationary and the humerus (origin) must move towards the hand
What is a agonist muscle?
- Also known as prime mover
- Muscle that produces the main action
What is a synergist muscle?
- Any muscle that assists the agonist in producing the main action
- Less effective than agonist but still needed to produce movement
What is a antagonist muscle?
- Executes the action opposite of the agonist when it shortens
What is a neutralizer muscle?
- Stops the agonist from pulling both of its ends simultaneously (gives it direction)
- Is a fixating force to prevent undesired action and dictate which end of the agonist’s bony attachments will move
What is a supporter muscle?
- Often does not function near the main action, but supports another part of the body in position while the main action occurs
- Often neighboring muscles to the agonist are supporters
What factors affect a muscles role?
- Size affects its part in joint motion
- Shape and design of a joint determine the muscles role
- Muscles location in relationship to the joint axis
- The muscles line of pull (the direction of force exerted on a joint by a muscle)
What is passive insufficiency?
- When a bi- or multi-articular muscle is in a position of maximum length
- Example: can’t fully clench fist when maximally flexing your wrist
What is active insufficiency?
- Occurs when an action is weakened or incomplete due to excessive shortness of the multi-joint agonist
- Example: cannot fully flex your fingers back when extending your wrist
- Biarticular muscles (cross 2 joints) are more susceptible to active insufficiency
What are postural muscles?
- Designed to perform for long periods of time in a semi contracted state
- stabilize the body and keep it in an upright stance (for long term kinesiological health)
What are phasic muscles?
- Perform movement quickly and strongly
- Fatigue quickly and need more recovery time then postural muscles
What is the force-length muscle relationship?
- The length of a muscle, relative to its resting length during an isometric contraction, will determine the maximum force it can produce
What is the force-velocity muscle relationship?
- Asserts the speed of a muscles contraction will dictate its maximal force production
What does muscle length determine?
- It’s tension
What does a muscles contractile speed affect?
- The force it can generate
What is active tension?
- The muscle is actively producing tension by pulling itself toward its center
What is passive tension?
- The muscle is like a rubber band
- When stretched beyond its resting length it builds tension (wants to return to its original resting length)
