muscles Flashcards
smooth muscle
found in places where there is regulation (arteries)
- unstraited
- long and spindle line muscle fibres
- under involuntary control
- myofibrils are arranged irregularly
cardiac muscle
- straited in apperance
- involuntary control
- it has its own ability to contract does not need nervous system
- somatic and autonomic nervous system
skeletal muscle
- straited
- logitudinal bundles of muscle fibres
- involuntary and volunatry control
micro view of skeletal muscle features
sacrolemma: cell membrane
myfibrils: muscle fibres that make up the muscle fibres
sacromere: energy of the myofibril
z-line: seperate each of the sacromere
actin (thin) and myosin (thick)
sliding filament theory
- as the mysoin and actin slide it gives rise to light or dark area
- contraction: actin is pulled together over the myosin (creates overlap)
- extension: actin is pulled away from the myosin (increase 2 disc line)
what are the different shapes of muscle
- fusiform (muscles that run longitudinaly to the tendon)
- penniform (fibres that run on an angle to the skeleton tendon)
- unipennate (fibres that come off an angle of the tendon)
- bipennate (fibres that come of the sides of the tendon)
- mutipennate (fibres that come off either side of multiple tendons)
white muscle fibre types
- Large diameter
- Good for power and speed activities
- Fast contraction speed (ie “fast twitch” – FT)
- Fatigue rapidly
red muscle fibre types
Small diameter
• Good for endurance activities & continuous contractions
• Slow contraction speed (ie “slow twitch” – ST)
• Fatigue resistant
silding filament theory 6 steps
- Influx of Ca++ ions to expose the actin binding sites
- Binding of myosin to actin
- Power stroke – causing filaments to “slide”
- Binding of ATP to myosin to cause disconnection from actin
- Hydrolysis of ATP to re-energise and replenish the crossbridge
- Transport of Ca++ ions back to the sarcoplasmic reticulum
(via calcium pump)
concentric contraction
tension developed in the muscle is sufficent to overcome any load (muscle shorten)
eccentric contraction
tension developed in the muscle is insufficent to overcome the load (muscle lengthens)
isometric contraction
the tension matches the load and there is no change in the muscle length
head and neck muscles strengh exercises:
- head curls
- lateral raise
- shoulder shrugs
- neck stretches
- neck rotation
trunk extensor strengthening
- erector spinae muscles
- curl the trunk to train the smaller parts of the muscles
(back extension) - romanian deadlift
trunk rotation strengthening exercises
- trunk rotation (superman one leg one arm)
- abdominal crunch with a twist
trunk flexion
- abdominal crunches
special considerations
- Use of isometric exercises in preference to isotonic exercises
- neck rolling, only roll half the way not 360 degrees
- preventing lower back pain: strong abdominals & hamstrings+ flexible iliopsoaslimit APT
- Problem - invoking psoas major m. during some exercises
what does a motor unit comprise of
- a motor neuron, plus
* all the attached muscle fibres
recruitment of muscle fibres difference
- Small motor units produce precise movements
- Large motor units produce gross movements
muscle tone
Asynchronous motor unit contraction causes a constant
state of low-level tension on the muscle.
3 factors affecting tension in the muscle
1- frequency of stimulation (single/mutiple stimultions)
2- number of motor units recruited
3- the length of the muscle (length/tension)
treppe
increase in tension without summation
temporal summation
increase frequency of stimulation we do no allow the muslces to relax the tension
incomplete tetancy
tension is high however muscles can sill relax
complete tetanus
no relaxation of muscle those binding sites are continusly open
fatigue
muscles runs out of ATP and the body needs to replensih the ATP decrease frequency
3 phase of a muscle twitch
1- latent period
2- contraction phase
3- relacation
number of motor units recruited
Stimulation voltage is to:
- recruit motor units
- Sub threshold stimulus
- Threshold stimulus
- Recruitment
- Maximal stimulus
degree of muscle stretched
- Unstretched muscle:
- Mod. stretched muscle:
- Overstretched muscle:
latent period
- sacrolemma and t-tubules depolarize
- Calcium released into the cytosol
- crossbridges begin to cycle but no visible shortening of muscle
contraction period
- sacromeres shorten result of myosin crossbridges cycyling and continues into the peak of developing tension
- speed depends on weight being lifted and fibre type
relaxation period
Calcium activley transported back into terminal cisterneae
- cross bridges cycling decreases and ends
force production is affected by
- Temporal summation
- Motor unit recruitment
- The length of the muscle
temporal summation
Force production is affected by the firing rate of the MN. As the rate of firing increases, so also does the tension developed in the attached muscle fibres, as well as the whole muscle.
motor unit recruitment
Stronger stimuli cause multiple motor unit recruitment. Red (ST) fibres tend to be recruited first, followed by white (FT) fibres, which require higher threshold voltages.
length tension relationship
Force production is affected by the length of the muscle at any given moment. This is determined by the number of cross bridge links that can be made within each sarcomere
early improvments in strength are due to
• tug of war analogy: Changes in the involvement of motor units
• co-contraction of antagonist muscles
(muscles that oppose the action of the prime mover)
• Disinhibition of the agonist
(the body’s protective mechanism).
the rate at which force is produced is due to a number of factors
- The number of sarcomeres in series
* The rate at which cross bridges work.
the rate that cross bridges work is dependant on what
• ST fibres (Red) - cross bridges work at a slower rate - useful for sustained contractions. • FT fibres (White) - cross bridges work at a fast rate - but fatigue more quickly.
what muscles fibres does the gastrocnemius and soleus have
gastrocnemius m. • high FT fibres • power muscle • explosive actions soleus m. • high ST fibres • endurance muscle • postural actions
aggregrate muscle actions
When a group of muscles are contracting on one
side of a joint, it usually means that another
group is lengthening on the opposite side.
modes of contraction
CONCENTRIC CONTRACTION tension > resistance muscle shortens • ECCENTRIC CONTRACTION tension < resistance muscle lengthens • ISOMETRIC CONTRACTION tension = resistance muscle length remains unchanged
