Skeletal Muscle Tissue Part 2 (tension) Flashcards
Muscle tension
Force exerted on a single muscle fiber
Load
Opposing force exerted by weight of object
Isometric contractions
Isotonic contractions
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
Load-pencil
Motor units
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)
Myogram?
Recorded pattern of a twitch
Parts of a muscle twitch (3)
Latent period
Contraction period Relaxation period
Latent period
2 milliseconds
When action potential is propagated
(No force)
Contraction period
10-100 milliseconds
During cross bridging
(Myosin attach to actin and power stroke)
Relaxation period
10-100 milliseconds
Calcium 2+ transported back into SR
Contractile force decreasing
Frequency of stimulation and muscle response
Aka? Definition?
Increase rate of motor neurons firing creates greater force
-wave summation
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 Sustained contractions-tetanus Tetanus leads to fatigue
Muscle shapes are affected by what?
Fascicles are arranged in patterns which affect function of muscle
6 muscle shapes (patterns) ?
1) parallel
2) convergent
3) pennate
4) circular
5) spiral
6) fusiform
Parallel
Evenly spaced, attached to a tendon same width as muscle
Strap-like appearance
Ex. Sartorius in thigh (long)
Convergent
Broad muscle tapers to a single tendon
Ex. Pectoralis in chest (big & tapers down, traps, lats)
Pennate
Muscle resembles a feather
Fascicles attached to tendon @ angle
Types: unipennate, bipennate, multipennate
Ex. Rectus femoris of thigh
Circular
Muscle encircles a structure
Ex. Orbicularis oculi of eye
Spiral
Muscle wraps around bone or twisted appearance
Ex. Supinator in forearm (tight fit to bone)
Fusiform
Muscle thicker in middle, tapered at ends
Ex. Biceps brachii
Functional groups of muscles
Involves? Purpose?
Movements at joints involve several muscles
Each muscle has a specific job
List the functional groups of muscles (4)
Agonist
Antagonist
Synergists
Fixators
Agonist
Provides most force for movement
Usually the largest muscle
Antagonist
Lies on opposite side of a joint from agonist
Opposes & slows the motion
Synergists
Work w/ agonist
Provides additional support to guide movement
Fixators
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
Muscular dystrophy
Myasthenia gravis
Fibromyalgia
Carpal tunnel syndrome
Cause? Symptoms?
Nerve damage due to irrational of median nerve in wrist
Numbness, tingling in fingers low blood circulation
Carpal tunnel syndrome
Treatment?
Surgery
Anti inflammatory drugs
Myasthenia gravis
Cause?
Autoimmune disease
-immune system mistakenly produces antibodies that destroy ACh receptors
Myasthenia gravis
Symptoms ?
Weakness eyelid, face, neck, and extremity muscles
Droopy eyelids, double vision
Myasthenia gravis
Treatment?
Drugs to inhibit the enzyme that digest ACh
Fibromyalgia
Cause? Symptoms?
Cause- not precisely known
Pain, tenderness, & stiffness of muscles (all the time)
Inflammation of muscles
Common muscular conditions (5)
Spasm Cramp Facial tics Strain Sprain
Spasm
Sudden & involuntary muscle contraction
Seizure or convulsion
-multiple spasms of skeletal muscles
Cramp
Strong, painful spasms of leg & foot
Facial tics
Periodic spasms
Strain
Stretching or tearing of muscle
Sprain
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
Threshold stimuli
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
Muscle recruitment
Which contract first?
Strong vs weak contractions?
Contract how?
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?
Depend on?
Affected by?
Force depends on # of cross bridges activated (power stroke) Affected by: -# of fibers stimulated -size of fibers -frequency of stimulation -degree of stretch
Velocity & duration of muscle contraction
Depends on?
Type of muscle fibers contracting
What type of ATP production used
-aerobic respiration
-anaerobic respiration
Muscle tone
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?
2
Characteristics of 2 types of muscle fibers involved in muscle contraction
Similarities? Differences?
-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?
Smallest diameter
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 *fatigue quickly 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
Creatine phosphate
(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
Glycolysis
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
Anaerobic catabolism
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
Aerobic catabolism
Aka oxidative catabolism which requires oxygen directly
Allows for longer lasting muscle contractions bc these reactions produce many MORE ATP than glycolysis
Oxidative catabolism
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?
Oxidative catabolism
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?
Digestion 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
Fulcrum
Pivot, or hinge point
Load
Weight you’re trying to move
Force
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
Muscular dystrophy cause and treatment?
Progressive degeneration & weakening of muscles
Muscle fibers die & replaced by fat & connective tissue
Can be genetically inherited
Duchenne muscular dystrophy- don’t produce protein dystrophin
Inject muscles w/ immature muscle cells that produce dystrophin
