Muscle Flashcards
what are the 5 muscle functions?
heat production
Production of body movements
Stabilisation of body positions - posture
Regulation of organ volume
Movement of substances internally
muscle includes what parts in the body?
muscle fibres, connective tissue, nerves & blood vessels
what is muscle skeletal wrapped in?
epimysium
what is the difference between perimysium and endomysium?
perimysium surrounds fibre bundles called fascicles.
endomysium surrounds each individual fibre.
what type of cell are muscle fibres made up of?
elongated cylindrical cells.
what is the muscle sarcolemma known as?
the plasma membrane.
what is the sarcoplasm in muscle?
cytoplasm - contains myoglobin which is related to haemoglobin
what is the endoplasmic reticulum known as in muscle?
sarcoplasmic reticulum. - stores calcium ions.
what are myofibrils and where can you find them in muscle?
Thick (myosin) and thin (actin) protein filaments. Found along entire length of cell.
what is the H-zone in sarcomere?
middle zone, only thick filaments.(myosin)
what is the l-band in sarcomere.
inner parts bside z disc, only thin filaments. (actin)
what is the a band in sarcomere?
the whole length of thick filaments (myosin)
thick filaments (myosin) in myofibril are composed of what?
a myosin tail and myosin heads (moveable).
thin filaments (actin) found in myofibril are composed of what?
actin (yellow bobbles), troponin (grey double bobbles), tropomyosin (stems)
what does myosin binding site on thin filament (actin) bind to?
the myosin head on thick filament. (during contraction)
what are thin filaments (actin) binded to?
z-discs.
what does tropomyosin on thin filament (actin) do?
tropomyosin blocks binding site at rest.
what happens during muscle contraction?
actin molecules and z discs are pulled and slide towards H- zone. both h and I zones narrow.
what triggers muscle fibres?
a motor neuron. neuron + triggered fibres = motor unit.
what is a neuronal ending to a muscle fibre called?
neuromuscular junction.
between the synaptic end bulb and motor end plate (muscle area) is what?
synaptic cleft.
what happens at the neuromuscular junction?
Release of the neurotransmitter, acetylcholine (ACh)
Diffuses across cleft
Activation of ACh receptors on sarcolemma
Generation of Muscle Action Potential
Repeats with each nerve action potential
Breakdown of ACh by the enzyme acetylcholinesterase
how is muscle contraction initiated?
Muscle action potential
Ca2+ released from Sarcoplasmic Reticulum (SR)
4 Ca2+ bind to troponin
Moves tropomyosin off actin sites
Myosin binds to actin and starts contraction cycle
explain contraction cycle.
Myosin binds to actin & releases phosphate group (forming crossbridges)
Crossbridge swivels releasing ADP & shortening sarcomere (power stroke)
ATP binds to Myosin => release of myosin from actin
ATP broken down to ADP & Pi => activates myosin head to bind and start again
Repeats as long as Ca2+ concentration is high
during muscle relaxation calcium ions are transported back to SR, what does this process involve?
active transport and use of ATP. Tropomyssin covers actin binding site.
Describe aerobic respiration
Production of ATP in mitochondria
Requires oxygen and carbon substrate
Produces CO2 and H2O and heat.
limiting factors of muscle fatigue include:
Ca2+
Creatine Phosphate
Oxygen
Build up of acid
Neuronal failure
what happens to muscles after exercise.
Lactic acid converted back to glucose in liver
Creatine Phosphate and ATP resynthesised
Oxygen binds to deoxymyoglobin
what are the 3 types of muscle fibre.
Slow oxidative (SO)- small diameter & red
large amounts of myoglobin and mitochondria
ATP production primarily oxidative
Fatigue resistant
Fast oxidative- glycolytic (FOG)
Large diameter = many myofibrils
Many mitochondria and high glycolytic capacity
Fast glycolytic fibres (FG)
white, fast & powerful and fast fatiguing
For strong, short term use
Ties of muscles contraction
If force is constant and the muscle shortens = Isotonic Contraction
If length is constant and the force varies = Isometric Contraction
The latter is often a postural muscle activity
what does strength exercise do for fast glycolytic fibres
increases size and strength of them.
