Flashcards in Skeletal Muscle Tissue Part 2 (tension) Deck (84):
Force exerted on a single muscle fiber
Opposing force exerted by weight of object
Isometric- muscle tension does NOT move load
Isotonic- muscle tension moves load & shortens muscle
Example of isometric vs isotonic?
Isometric- holding pencil
Isotonic- moving pencil
Example of muscle tension and a load?
Muscle tension- gripping pencil
Includes? Avg? Ex?
Includes: somatic motor neuron & the skeletal muscle fibers it stimulates
Avg. 150 muscle fibers per motor unit
Ex. Eye 10-20 fibers/motor unit
Biceps 2000-3000 fibers/motor unit
What is the "all or none" rule?
All muscle fibers in a motor unit contract & relax together
Total strength of contraction depend on? (2)
1) Size of motor units
2) # of motor units activated @ 1 time
Muscle twitch contraction
Brief contraction of all muscle fibers in a motor unit from a single action potential
(1 single muscle contraction)
Recorded pattern of a twitch
Parts of a muscle twitch (3)
Contraction period Relaxation period
When action potential is propagated
During cross bridging
(Myosin attach to actin and power stroke)
Calcium 2+ transported back into SR
Contractile force decreasing
Frequency of stimulation and muscle response
Increase rate of motor neurons firing creates greater force
What's wave summation
What does it create?
Sum of muscle twitches on muscle fibers
2nd twitch (contraction) begins before end of 1st twitch
2nd twitch is stronger
Creates a greater force bc motor units cannot relax between stimuli
What happens for muscles when there's constant stimuli?
Decrease? Increase? Leads to?
Relax time decreases
Ca 2+ concentration increases
Amount of wave summation increases
Tetanus leads to fatigue
Muscle shapes are affected by what?
Fascicles are arranged in patterns which affect function of muscle
6 muscle shapes (patterns) ?
Evenly spaced, attached to a tendon same width as muscle
Ex. Sartorius in thigh (long)
Broad muscle tapers to a single tendon
Ex. Pectoralis in chest (big & tapers down, traps, lats)
Muscle resembles a feather
Fascicles attached to tendon @ angle
Types: unipennate, bipennate, multipennate
Ex. Rectus femoris of thigh
Muscle encircles a structure
Ex. Orbicularis oculi of eye
Muscle wraps around bone or twisted appearance
Ex. Supinator in forearm (tight fit to bone)
Muscle thicker in middle, tapered at ends
Ex. Biceps brachii
Functional groups of muscles
Movements at joints involve several muscles
Each muscle has a specific job
List the functional groups of muscles (4)
Provides most force for movement
Usually the largest muscle
Lies on opposite side of a joint from agonist
Opposes & slows the motion
Work w/ agonist
Provides additional support to guide movement
Hold a bone in place
Makes movement more effective & reduces injury risk
(Not limpy bc this)
What are the diseases/disorders of the muscular system? (4)
Carpal tunnel syndrome
Carpal tunnel syndrome
Nerve damage due to irrational of median nerve in wrist
Numbness, tingling in fingers low blood circulation
Carpal tunnel syndrome
Anti inflammatory drugs
-immune system mistakenly produces antibodies that destroy ACh receptors
Weakness eyelid, face, neck, and extremity muscles
Droopy eyelids, double vision
Drugs to inhibit the enzyme that digest ACh
Cause- not precisely known
Pain, tenderness, & stiffness of muscles (all the time)
Inflammation of muscles
Common muscular conditions (5)
Sudden & involuntary muscle contraction
Seizure or convulsion
-multiple spasms of skeletal muscles
Strong, painful spasms of leg & foot
Stretching or tearing of muscle
Twisting of a joint- damaging muscles, tendons, ligaments, blood vessels
Example of antagonist and agonist on body
Biceps moves (agonist) and tricep slows it down (antagonist)
Example of functional groups of muscles on an object (cup)
Agonist-movement of cup to mouth
Antagonist- cup to mouth w/o being jerky
Synergists- directs cup to mouth
Fixators- holds movement in place
Amount of stimulus that will cause muscle contraction
(Not enough stimulus -> no muscle contraction)
Recruitment of motor units
Process where the number of active motor units increases
-as intensity of stimulation increases, more motor units in a muscle are activated (ex. Picking up stapler vs book)
What's a motor unit?
Where is it located?
Neuron and muscle fiber it innovates
(Neuron & all axon terminals that attach to muscle fibers)
IN A MUSCLE
Which contract first?
Strong vs weak contractions?
Smallest muscle fibers contract 1st
Larger muscle fibers contract 2nd
-weak contractions: posture muscles (like holding your head up)
-strong contractions: running
NOT ALL MOTOR UNITS OF A MUSCLE ARE CONTRACTING AT THE SAME TIME (ALTERNATE)
Force of muscle contractions?
Force depends on # of cross bridges activated (power stroke)
-# of fibers stimulated
-size of fibers
-frequency of stimulation
-degree of stretch
Velocity & duration of muscle contraction
Type of muscle fibers contracting
What type of ATP production used
Purpose? Leads to?
Small amount of tension in muscle due to weak, involuntary contractions of motor units
-established by neurons in brain & spinal cord
-keeps body posture
Flaccid- state of limpness where muscle tone is lost (weak)
How many Types of muscle fibers are involved in muscle contraction?
Characteristics of 2 types of muscle fibers involved in muscle contraction
-vary in myoglobin content
•white muscle fibers-white muscle
•red muscle fibers-dark muscle
•most muscles are a combination of both
-contract & relax at different speeds
-vary in the source of ATP production & fatigue rate
Type 1 of muscle fibers involved in muscle contraction
Slow oxidative fibers (SO)
Characteristics of type 1 (SO)
Fatigue? ATP? Location? Measure? Contraction?
Dark red muscle- large amounts of myoglobin & capillaries
ATP produced by aerobic respiration
Slow rate of contraction
Produce less force for a longer period of time
*very resistant to fatigue
Adapted for: maintaining posture & aerobic endurance activities
(Think turkey, dark on our body legs & arms) (last to fatigue)
Type 2 muscle fibers (3)
Fast oxidative glycolytic (FOG)
Fast oxidative (FO)
Fast glycolytic (FG)
Characteristics of type 2 muscle fibers
Example? Fatigue? Measure? Classified?
Categorized by energy production method
Less myoglobin & blood supply (white muscle)
Fast twitch fibers
Larger diameter fiber
Ex. Eye muscles
Fast oxidative glycolytic fibers (FOG)
Fatigue? Contraction? Adapted for?
-moderate resistance to fatigue
-fast rate of contraction
-adapted for: walking, jogging
Fast glycolytic (FG)
Fatigue quickly (first to fatigue)
Contract strongly & quickly (most force)
Adapted for: intense movements of short duration like weight lifting, throwing a baseball
Recruitment of the muscle fibers
Definition? Which forces are what fibers?
Different motor units recruited in specific order
-weak force needed: SO motor units activated
-more force needed: SO & FOG
-max force required: SO FOG & FG
What's is the way to remember what forces are which fibers?
Weak forces last longer than max, therefore, SO fatigue last
In skeletal muscle, ATP is required to...
POWER the NA+/K+ pumps involved in action potentials
RELEASE the myosin heads from actin active sites & RECOCK the heads in preparation for another power stroke
PUMP Ca2+ back into SR during relaxation
How is ATP generated/created? (3) depends on? Carried out how?
Immediate cytosolic reactions (ATP) (digestion, breaking down carbs)
Glycolytic catabolism in the cytosol (Glycolysis, Anaerobic)
Oxidative catabolism in the mitochondria (aerobic)
All 3 processes may occur simultaneously in muscle fibers during contractions, but used in DIFFERENT proportions, depending on the resources & needs of the cell
What's the main immediate energy during muscle contraction?
Stored ATP in the muscle fiber which is tepidly consumed during muscle contraction
(In our blood) Concentration in the cytosol 5-6 times higher than ATP
Can immediately regenerate enough ATP for about 10 secs of max muscle activity
Series of reactions that occur in all cells' cytosol to break glucose down into pyruvate; it provides energy for muscle contraction once immediate source of energy are depleted
What does glycolysis use?
Glucose found in the blood & stored in muscle (or liver) cells as glycogen
It can replenish ATP for 30-40 secs of sustained contraction
Leads to what?
Aka glycolysis which does not require oxygen directly but the amount of oxygen present leads to 2 possible outcomes
1) if oxygen abundant, pyruvate formed by glucose catabolism enters mitochondria for oxidative catabolism which then occur simulate royalty w/ glycolysis as long as glucose is available
2) if not abundant, pyruvate converts into 2 molecules of lactic acid which is either converted back into glucose by liver or taken up by mito. For oxidative catabolism
Aka oxidative catabolism which requires oxygen directly
Allows for longer lasting muscle contractions bc these reactions produce many MORE ATP than glycolysis
ATP production depends on?
Amount of ATP produced depends on the TYPE of fuel used by the fiber
What do muscle fibers prefer to use for oxidative energy sources?
Prefer to use glucose, but as it becomes unavailable, they will catabolism fatty acids & amino acids (protein, muscle itself)
(Glucose is easier to break down & use)
What is the predominant energy source after 1 minute of contraction? Why?
Provides nearly 100% of the necessary ATP after several minutes
Can provide ATP for hours, as long as oxygen and fuels are available
3 sources of energy for ATP are?
Glycolysis immediate (anaerobic catabolism) - no oxygen
Oxidative catabolism (aerobic catabolism) - oxygen
First class lever
Fulcrum is located btwn applied force & load to be moved
Force applied & load moved are in opposite directions (see saw)
Lever works @ mechanical advantage or disadvantage, depending on location of fulcrum
Pivot, or hinge point
Weight you're trying to move
Effort applied to lever
Second class lever
Fulcrum is located farther from applied force
Load moved is btwn fulcrum & force applied, & moves in same direction as force
Lever works at mechanical advantage to move large loads at short distance w/ little effort
Third class lever
Fulcrum is located closer to applied force
Force applied between fulcrum & load moved, & moves in same direction as force
Lever works at mechanical disadvantage to move small loads a greater distance w/ greater speed
Ex of all levers
First - dribbling basketball
Second- rising on tiptoe
Third- pulling up on a fishing rod
What does lack of ATP cause?
Causes the muscles to bc ridged bc no ATP causes muscle tension.
Power stroke wouldn't be able to occur as a result of the lack of ATP, which makes the muscle stay tense