the muscular system Flashcards
involuntary muscle tissue
not controlled consciously
bodily functions such as digestion, urination, circulation
voluntary muscle tissue
under conscious control
also referred to as ‘skeletal muscles’ - via levers and joints can produce movement
skeletal muscles
'striated muscles' some are flat and sheet-like some are short and fat some are long and slender 75% water, 20% protein 5% salts
functions of skeletal muscles
movement circulation energy storage shape and structure upright posture heat production
structure of skeletal muscle
external wall = fascia (sheath) ~ surrounding entire muscle is layer of connective tissue called ‘epimysium’
‘bundles of muscle fibres’ = bound together by fascia
‘myofibrils’/’myofilament’ = smaller fibres in each individual muscle fibre
‘sarcomeres’ = what each myofibril is made up of - form contractile units of the muscle
sarcomere
formed by 2 types of protein filament called actin and myosin
actin - thinner and lighter filament
myosin - thicker and darker
their overlapping nature allows sarcomeres to shorten - how muscles contract
when muscle is relaxed has a striped appearance
tendon
referred to as an ‘origin’ or ‘insertion’
when the muscle shortens the insertion moves towards the origin
when it lengthens the insertion moves away from the origin
connects muscle to the bone - sometimes also attach to other connective tissues
ligaments
connect bone to bone - provide stability
made from densely packed inelastic regular collagen fibres
the motor unit
made from a nerve or neuron and all of the muscle fibres of that nerve
when the muscles need to generate large forces (eg heavy strength training) the brain signals the muscles to recruit more motor units
all or nothing principle
when a muscle fibre is stimulated, every contractile unit within that fibre will contract
types of muscle fibre
fast twitch = larger, stronger more explosive fibres
slow twitch = slender and more enduring fibres
mitochondria
located inbetween muscle fibres - predominantly slow twitch
possess the unique ability to burn oxygen with other nutrients - generate energy in form of ATP
‘aerobic power house’ of the muscle cell
regular cardiovascular and endurance exercise stimulates increase in these cells = more aerobic energy
myoglobin
oxygen carrying protein located within muscle tissue
moves oxygen from blood vessel to mitochondria
primary oxygen carrier
regular cardiovascular and endurance exercise stimulates increase in these cells = more oxygen transported
muscle glycogen
formed from chains of glucose - in muscle and liver for energy
glycogen is broken down and deposited into blood as glucose - then used for energy - esp brain
combination of regular endurance and high level of carbs enhances muscles ability to store glycogen
when a muscle contracts, movement will occur if
1) the muscle crosses a joint
2) the opposing muscle relaxes
isotonic contractions
most common 2 phases = concentric, eccentric concentric = usually first stage, occurs when muscle becomes shorter and fatter insertion moves towards origin eccentric = muscles lengthens and is under tension 'negative phase' insertion moves away from origin eg leg extension, bench press
DOMS
delayed onset muscle soreness
linked with eccentric muscles
results in microscopic tears along length of the muscle fibre - repaired by protein during the hypertrophy process
advantages of isotonic contractions
develops strength or endurance through the joints
more relevant to daily activities
can develop motor skills
develops oxygen delivery mechanisms within the muscle
isometric contractions
the length of the muscle does not alter - distance between insertion and origin remains constant
eg - isometric contraction of bicep = holding a weight in the hands with elbow at a 90 degree angle
exert a ‘Valsalva effect’ because of their effect on internal pressure, esp blood pressure - done with caution
advantages of isometric contractions
requires little or no equipment/space
good in rehabilitation when only a small ROM is permitted
can be functional in things like developing strength of joint stabilisers
disadvantages of isometric contractions
not suitable for those with primary heart disease risk factors - rapid increase in blood pressure
only strengthens the joint at angle held - limits crossover benefits
can be tedious and boring
prime mover
muscle(s) responsible for creating the movement
eg pectorals for bench press
fixator
the muscle contracts isometrically to resist movement
eg medial and posterior deltoids, and latissimus dorsi during bench press
synergist
assistant muscle working with prime mover
eg in bench press - triceps assist pecs by extending elbow, anterior deltoid assists by flexing the shoulders
antagonist
the muscle(s) that must relax for the movement to take place
for one muscle to contract the opposing one must relax
eg during barbell curl triceps relax so biceps can flex
muscle contractions are governed by 2 factors
1) energy availability
2) nervous impulses
momentary muscle failure
when there is insufficient energy to fuel contraction. in the latter stages of heavy resistance training when muscles become exhausted - prevents contraction from continuing
