muscles Flashcards
what is a muscle
a muscle is a tissue as it is composed of many similar cells working together collectively
what is the function of a muscle
contraction
how to describe contraction
comparatively fast, fatigues rapidly and is under conscious control.
skeletal muscles is under the control of the somatic nervous system (voluntary)
information of skeletal muscles
made up of bundles of fibres, have striped appearance (also called striated muscle).
each fibre contains many myofibrils running the length of the fibre.
what are myofibrils made of
made of multinucleate cells
myofibril structure consists of….
I band made of Actin (shortens during contraction)
A band made of actin and myosin (stays same during contraction)
sarcomere - z line to z line (shortens during contraction)
what are actin
thin filaments, globular protein
- many link together to form a chain
- 2 chains twist together to form actin filament
what are myosin
thick filaments, fibrous protein
- has a tail attached to M line
- several lie in a bundle to form a myosin filament
- heads form cross bridges between actin and myosin
what does the neuromuscular junction do
- it is the point at which the motor nuerone synapses with msucle
- neurotransmitter acetylcholine produced at axon terminals
- acetylcholine diffuses through gap and fuses with receptors on post-synpatic membrane
- post-synaptic membrane is highly folded to form motor end plate - large surface area
- this causes depolarisation of membrane at motor-end plate
- depolarisation goes down t-tubules causing calcium ions to move out of sarcoplasmic reticulum
- therefore causing a CONTRACTION OF MYOFIBRILS
examples of other fibrous proteins
typomyosin - twists around actin chains
troponin - attaches to actin chains at regular intervals
what is the muscular-ratchet mechanism
- myosin heads stick out and they contain ATPase (hydrolyses ATP to ADP + Pi)
- action potential arrives, myosin heads engage into binding sites on actin filaments
- ATP hydrolyses to ADP + Pi and energy is released causing the heads to swivel, rowing the actin past myosin.
- heads release, return to original position and rejoin and repeat action.
- when muscle relaxes, heads disengage.
what is oxygen debt
when exercising, oxygen is needed for aerobic respiration. there is a limit to the volume of oxygen that can be taken in.
during intense exercise, muscles will not receive enough oxygen so will have to respire anaerobically.
during anaerobic respiration, pyruvate is reduced to lactate using hydrogen from reduced NAD. meaning a build up of lactic acid.
whe oxygen is available again, the lactate can be oxidesed back into pyruvate by liver.
this extra oxygen needed is called the oxygen debt.
what does a build of lactic acid cause
cramps, muscle fatigue
what is the main energy source used during exercise
glycogen, a branched molecule made up of alpha glucose with 1-4 glycosidic linkages. stored in muscle and liver
information about glycogen
may become limiting, if used up the fat reserves will be used. body will always respire some fat to conserve glycogen.
What is carbohydrate loading?
increasing the glycogen content of the liver and muscle.
7 days before event, perform exhaustive exercise to all but deplete your energy stores
next 2-3 days cut back on carbs and do low exercise to keep carb level low.
3-4 days before event, eat very high car diet. glycogen stores in muscle will become full as possible
info about muscle types
2 fibre types occuring together in varying combinations depend on
- genetics of person
- training
- location of muscle
what are slow twitch fibres
used largely in aerobic (endurance) exercises.
more efficient at using oxygen (oxidative phosphorylation) to generate more ATP
used for continuous extended muscle contraction over a long time
e.g marathon running, aerobics, jogging
What are fast twitch fibres
used largely in anaerobic metabolism - depends on glycolysis and anaerobic respiration to create ATP
generates short burst of strength/speed
e.g sprinting, high jump, javelin throw.
differences of slow and fast twich fibres
slow twitch - - ATP via aerobic respiration - lots of mitochondria -many capillaries -smaller diameter - contains myoglobin fast twitch - - ATP via anaerobic respiration - few mitochondria - little myoglobin - few capilarries - larger diameter to slow twitch.
