HBS 1.2 test

tendons

Flexible, but inelastic cord of strong fibrous collagen tissue attached a muscle to a bone.

skeletal muscle

striated, voluntary, limbs, movement

smooth muscle

no striated, no voluntary, intestines, digestiong

cardiac muscle

striated, no voluntary, chest, breathing

involuntary muscle contraction

moves without you willing it too move

skeletal, cardiac, smooth pic

just look at em!

requirements for muscle contraction

ATP & salt

when the muscle fibers “shorten” what happens?

the muscle contracts

step 1

motor neuron fires an action potential. neurotransmitter acetylcholine is released at muscular junction. Acetylcholine binds to receptors on muscle fibers sarcolemma, causing depolarization.

step 2

depolarization spreads along sarcolemma. travels into the fiber via T.tubules. This triggers the gated calcium channels on the SR to open.

step 3

Ca2+ stored in the SR flood into the sarcoplasm.

step 4

Actin’s myosin binding sites are blocked by tropomyosin protein which troponin complex holds in place. calcium ions bind to the troponin which causes a conformational change and exposes the binding sites.

step 5

myosin heads powered through ATP hydrolysis bind too actin and pulls the thin filament towards the center of the sarcomere. This pulls the z discs closer together and the sarcomere shortens.

why do muscle cramps happen?

calcium stays in the muscle cell and there is not enough ATP for the head to deattach

why do muscles contract involuntarily to maintain homeostasis?

contractions release heat helping body maintain homeostasis

Your friend tried to convince you that the only reason to make sure you get enough calcium is so you can build strong bones. Can you offer them another reason? 

calcium is also needed for muscle contraction because it binds to troponin and exposes binding sites

Explain how it is that actin and myosin in the sarcomere never actually shorten and yet the muscle as a whole does.

actin and myosin dont shorten but slide past eachother which shortens the sarcomere

muscle fiber diagram!!

know them!

do muscles work alone?

• An abundant supply of blood vessels brings nutrients and oxygen to muscles while also removing wastes.

• Nerves control when muscles contract and how strong those contractions are.

muscle rules

• muscles always cross at least one joint

• muscles have origin and insertion. origin is not moveable and insertion is moveable

• muscles always pull in the direction of the fibers

• muscles work in opposing fibers

pectoralis major

origin = sternals

insertion = proximal to humerus

moves arm rotating medially, adduction

pectoralis minor

origin = ribs

insertion = scapular

pulls scapula forward and down

brachialis

origin = anterior brachial

insertion = ulnar side of antecubital

flexes forearm at elbow

intercostals

elevate and depress ribs for breathing

left psoas major

origin = vertebrae

insetion = trochanter of femur

action = hip flexion

activities = climbing/marching

left gluteus medius

origin = gluteal lines

insertion = trochanter of femur

action - abduction of hip

neither flexor extensor

activities: walking

what happens after cast removal?

muscle fibers shrink because they’re not being stimulated to contract or support weight (muscle atrophy)