Muscular System Flashcards
Muscle functions
Produce movement, maintain posture and produce heat.
Sarco-
Means flesh, but refers specifically to muscle.
Muscle fiber
Muscle cell. Threadlike and often run the length of the muscle.
Properties of muscle cells
Excitability, contractibility, extensibility and elasticity.
Excitability
Ability to respond to a stimulus.
Contractibility
Ability to shorten
Extensibility
Ability to lengthen or stretch.
Elasticity
Ability to return to precontraction length.
Sarcolemma
Muscle cell membrane.
Sarcoplasm
Intracellular fluid of a muscle cell.
Sarcoplasmic reticulum
System of interconnected hollow tubes surrounding myofibrils. Stores and releases calcium ions.
Epimysium
Thick outer connective tissue that surrounds the entire muscle or muscle group. Also called deep fascia.
Perimysium
Middle layer of connective tissue that surrounds each muscle fascicle.
Endomysium
The inner layer of connective tissue that surrounds individual muscle fibers. Continuous with tendons.
Muscle connective tissues, superficial to deep
Epimysium, perimysium, endomysium
Muscle component organization
Muscle, fascicle, muscle fiber, myofibril, myofilaments
Neuromuscular junction
Synaptic connection between a motor neuron and a muscle fiber.
Parts of a neuromuscular junction
Motor neuron, synaptic gap and motor end plate.
Motor neuron
Neuron that transmits impulses from the nervous system to muscle fibers.
Synaptic gap
Space between the motor neuron and the end plate. Acetylcholine crosses it.
Motor end plate
Folded sections of sarcolemma that contain receptors for acetylcholine.
Result of acetylcholine binding tot he motor end plate
The impulse travels through the T-tubules into the sarcoplasmic reticulum, causing calcium to be released.
Contraction
Myosin heads bind to actin, then the thick and thin filaments slide past each other.
Function of calcium ions in muscular contraction
They displace troponin and tropomyosin and allow for cross bridging and the subsequent power stroke.
Motor unit
A single motor neuron and all of the muscle fibers that it innervates.
Recruitment
More motor units are recruited to lift a heavier weight.
Myoglobin
Protein that delivers oxygen to muscles.
Muscle fatigue
A decline in a muscle’s ability to generate force.
Causes of muscle fatigue
Running out of ATP, oxygen or glucose or a lack of nerve impulses.
Isotonic contractions
The same weight is applied and the length of the muscle changes.
Concentric contractions
Type of isotonic contraction in which the muscles shorten.
Eccentric contractions
Type of isotonic contraction in which the muscles lengthen.
Isometric contractions
The length of the muscle does not change.
Slow twitch muscle fibers
Have lots of oxygenation and mitochondria. Have great capacity for long and slow contractions.
Fast twitch muscle fibers
Have less oxygen and mitochondria. Have capacity for fast contractions but are susceptible to fatigue.
Postural muscles
Are responsible for holding position.
Phasic muscles
Are responsible for generating movement.
Agonist
Prime movers which cause a desired action
Synergist
Muscles which assist the prime movers.
Fixators
Specialized synergists that stabilize a joint.
Antagonist
Muscle which lengthens while the agonist shortens.
