Bio-the muscular system

What are the two main mechanisms used to produce ATP?

• aerobic respiration

• anaerobic fermentation

ex. both processes are used throughout the body

Aerobic respiration

• uses oxygen to create ATP

• yields 26-32 ATP per glucose

• requires usage of mitochondria

ex. not used during intense exercises when the body can’t deliver enough oxygen 

ex. running and swimming are types of aerobic exercise

Anaerobic fermentation

• no usage of oxygen 

• yields 2 ATP per glucose 

• excess glucose is converted to lactate

ex. used during short and intense exercises

Axon terminal 

bulbous swelling at the end of a nerve fiber, separated by the synaptic cleft 

ex. contains the synaptic vesicles 

Neuromuscular junction

where a nerve fiber meets a muscle fiber

Synaptic vesicles

sacs in the synaptic knob that contain the neurotransmitter acetylcholine

Acetylcholine 

the neurotransmitter that is released by the nerve fiber in synaptic vesicles that bind to ACh receptors on the muscle fiber, stimulating muscle contraction 

ex. ACh = contraction; no ACh = no contraction 

Acetylcholinesterase 

enzyme found on muscle fiber and synaptic cleft that breaks down excess ACh to stop muscle stimulation 

What are the five functions of the muscular system?

• movement

• stability

• control of openings and passages

• heat generation

• glycemic control

What are the different types of myofilaments?

• thick filaments

• thin filaments

Thin filament 

• half as wide as thick filaments

• made of intertwined strands of protein actin

• also contains tropomyosin and troponin proteins  

Actin

protein strands on thin filaments than contain myosin binding active sites or depressions

Troponin

protein on thin filaments that attracts calcium (Ca)

Tropomyosin

thread like structure that prevents myosin from reaching actin

How does myosin end up reaching actin?

after calcium channels open in the sarcoplasmic reticulum, Ca floods the cytosol of the muscle fiber and binds to troponin molecules on thin filament which changes the shape of tropomyosin and reveals the myosin binding active sites of actin

Isometric contraction

contraction of a muscle without a change in length when the muscle produces tension but does not shorten

ex. important in stabilizing joints and maintaining posture

Isotonic contraction

contraction of a muscle with a change in length

two types: concentric and eccentric contraction

Concentric contraction 

muscle shortens as it maintains tension

ex. bicep curls

Eccentric contraction

muscle lengthens as it maintains tension

ex. more likely to cause injury

Endomysium

thin layer enclosing each muscle fiber that separates muscle fibers and allows room for blood capillaries and nerve fibers

Perimysium

surrounds bundles of muscle fibers (fascicles)

ex. thicker than the endomysium

Epimysium 

the layer surrounding the muscle as a whole 

Fasciae

fibrous sheets separating muscles from each other that may separate functionally related muscles into compartments

Fascicles

bundles of muscle fibers or nerves

ex. help organize muscle fibers for contraction

Compartment syndrome 

when the fasciae binds the muscles

ex. causes problems

Slow twitch (red) muscle fibers

• filled with blood vessels

• rely on aerobic respiration

• long, slow twitches

• have good endurance

ex. marathon runners

Fast twitch (white) muscle fibers

• have few blood vessels 

• rely on anaerobic fermentation

• fast twitches

• fatigue easily

ex. basketball players