Week 8-Muscular Tissue Flashcards
Functions of Skeletal Muscle
1) Move the body
2) Maintain posture
3) Protect and support
4) Regulate elimination of materials
5) Produce heat
Characteristics of Skeletal Muscle
1) Excitability
2) Conductivity
3) Contractility
4) Extensibility
5) Elasticity
Excitability
Ability of cell to respond to stimulus
Conductivity
Involves electrical signal that is propagated along the plasma membrane as voltage gated channels open sequentially during an action potential
Contractility
Enables muscle cells to cause body movement and to perform other functions (contractile proteins within skeletal muscle slide past one another)
Extensibility
Lengthening of muscle cell
Elasticity
Ability of muscle cell to return to original length following either shortening or lengthening of muscle
Gross Anatomy of Skeletal Muscle
Skeletal muscles fibers, connective tissue layers, blood vessels, and nerves
Fascicle
Bundles of muscle fibers
Three Layers of Connective Tissue Components
1) Epimysium
2) Perimysium
3) Endomysium
-together they extend past muscle fibers to form tendon or aponeurosis
Epimysium
-Layer of dense irregular connective tissue that surrounds the whole skeletal muscle
-Provides protection and support
Perimysium
-Layer of dense irregular connective tissue around each fascicle
-Protection and support to bundles of muscle fibers
Endomysium
-Areolar connective tissue that surrounds each muscle fiber
-Electrically insulate muscle fibers
Tendon
Cordlike structure composed of dense regular connective tissue that connects muscle to bone
Aponeurosis
Thin, flattened sheet of dense regular connective tissue that connects muscle to skeletal component (bone/ligament) or to fascia
Deep fascia
-Expansive sheet of dense irregular connective tissue that is external to epimysium
-Separates individual muscles, binds muscles with similar functions, and fills spaces between muscles
-contains nerves, blood vessels, and lymph vessels
Superficial fascia
Areolar and adipose tissue that separates muscle from skin
End-plate Potential
Minimum voltage change that can trigger opening of voltage gated channels in sarcolemma to initiate action potential
Action potential
Depolarization and repolarization
Refractory period
-Period of time that includes depolarization and repolarization
-muscle cannot be restimulated during this time
Triad
T tubule flanked by terminal cisternae of sacroplasmic reticulum
Changes to Sarcomere During Contraction
-H zone disappears
-I band narrows in width and may disappear
-Z discs move closer
Sliding filament theory
Repetitive movement of thin filaments sliding past thick filaments
Oxygen Debt
Amount of additional oxygen that is consumed following exercise to restore pre-exercise conditions
Oxygen Debt
Amount of additional oxygen that is consumed following exercise to restore pre-exercise conditions
Power
Related to diameter of muscle fiber (large diameter=more powerful)
Speed
Slow or fast genetic variant of myosin ATPase
Fast twitch fibers
-have fast variant of myosin ATPase
-initiate contraction faster and contraction is shorter
Slow twitch fibers
-have slow variant of myosin ATPase
-initiate contraction slower and contraction is longer
Oxidative fibers
-provide ATP by aerobic respiration
-extensive capillary network, many mitochondria, lots of myoglobin (gives them red color)
-fatigue resistant
Glycolytic fibers
-provide ATP by glycolysis
-less extensive capillary network, fewer mitochondria, less myoglobin
-white color
-fatigable
Muscle Tension
Force generated when skeletal muscle is stimulated to contract
Muscle Twitch
A single, brief contraction period and then relaxation period of skeletal muscle in response to a single stimulation
Threshold
Minimum voltage needed to stimulated muscle to generate a twitch
Recruitment
Increase in muscle tension that occurs with an increase in stimulus intensity
Wave/Temporal Summation
Stimulation occurs so rapidly that complete relaxation of skeletal muscle does not occur before next stimulation event (summation of contractile forces)
Incomplete tetany
-further increases in stimulation frequency allows less time for relaxation between contraction cycles
-Tension tracing continues to increase and distance between waves decreases
Tetany
Continuous contraction
Fatigue
A decrease in muscle tension that occurs from repetitive stimulations
Muscle Tone
Resting tension in skeletal muscle generated by involuntary somatic nervous stimulation of muscle
Resting Muscle Tone
Random contraction of small numbers of motor units causes muscle to develop tension
Isometric contraction
Skeletal muscle tension is insufficient to overcome resistance and there is no movement of muscle
Isotonic contraction
Skeletal muscle tension results in movement of muscle
Concentric contraction
Shortening of muscle length
Eccentric contraction
Lengthening of muscle
Length-tension relationship
Amount of tension a skeletal muscle can generate when stimulated is influences significantly by amount of overlap of thick and thin filaments within muscle fibers when muscle begins its contraction
