KINE 433 exam 2 Woodman summer

muscular system

Which muscle types are voluntary and which are involuntary and what are they regulated by?

• Cardiac and smooth muscle are involuntary, regulated by the ANS

• Skeletal muscle is voluntary, regulated by the central nervous system (CNS)

the basic structure of skeletal muscle- what are the layers

endomysium- connective tissue around individual muscle fibers

Perimysium- connective tissue around bundles of fibers

Epimysium- connective tissue that surrounds entire muscle

what is muscle composed of (think cells) and what properties do these cells vary in?

1.) many muscle fibers

2.) muscle fibers vary in contractile and metabolic properties

structure of a single muscle fiber (think organalles- what is the contractile element, what conducts ATP, what contains glycogen and myoglobin, what are T-Tubules, and what stores calcium)

1.) Muscle fibers are multi nucleated: large cell size so more nuclei, and the size development starting as from myoblasts

2.) mitochondria density (varies within diff types of fiber for ATP production)

3.) Myofibril= contractile element composed of actin and myosin

4.) plasmalemma= membrane surrounding a muscle fiber and conducts ATP

5.) sarcolemma= intracellular fluid containing glycogen and myoglobin

6.) T-Tubules: transverse tubules- extensions of plasmalemma that transmits action potential to individual myofibrils.

7.) sarcoplasmic reticulum (SR)= store calcium!!

What is a sarcomere, what are the protein filaments?

Sarcomere= contractile unit of a muscle fiber

Myosin: thick filament (dark band)

Actin: thin filament (light band)

where does contraction originate from? what does this activate?

the central command - originates in the brain

CC activates muscle, CV system and resp. system simultaneously

What is a motor unit? the α-motor neuron carries the action potential from where to where?

1.) Motor unit: a α-MN and all the muscle fiber it innervates (think of those sticky hands and you pick up ~3 pencils with it- that’s one motor unit)

2.) the α-MN carries the AP from the CNS to muscle fibers (then starts to recruit muscle fibers…)

Excitation-contraction coupling (electrical+mechanical response)(neuromuscular junction)- what are the 7 steps from CC to contraction

1.) Action potential start in brain

2.) α-MN releases ACh

3.) ACh binds to nicotinic receptors

4.) AP travels down T-Tubules

5.) SR releases Ca²⁺

6.) Ca²⁺ binds to troponin and pulls tropomyosin off active sites (tropomyosin is like a thick band covering troponin, once calcium bind to troponin, troponin changes shapes to make this shift then allowing myosin to bind to actin)

7.) myosin heads bind to actin and tilts

cross bridge formation and process from relaxed to contracting to fully contract (remeber the role of ATP)