muscular system notes

tendons

muscle to bone

periosteum strengthens connection with this

made of dense regular connective fibrous tissue

epimysia covers

ligaments

bone to bone

3 types of muscles

smooth, skeletal, cardiac

smooth muscle

involuntary

walls of hollow visceral organs

slow, sustained movements

layers of smooth muscle

circular: squeezes

longitudinal: ripples down

squeeze at top and then ripple downward

cardiac muscle

aka myocardium

intercalated discs are connections between the cells

skeletal muscle

multiple nuclei

• one really long cell with multiple nuclei

muscle fiber

= one long muscle cell with lots of nuclei

fibers are cells and fibers get packaged into fassicles and fassicles are bundled into muscles

fassicles

bundle of muscle cells

AKA bundle of fibers

what protects muscle fibers

connective tissue wrapping:

• endomysium: protects muscle fibers

• perimysium: protects fassicle

• epimysium: protects muscle

fassicle arrangements

diff shapes caused by how muscles are bundled

circular

convergent: come together

unipennate

parallel

bipennate

parallel fusiform

multipennate

pennate ones = many points of connection coming together

fusiform = come together

origin

point of attachment, anchor point, less moveable part

insertion

whichever bone has the most movement

what muscle naming is based off of

directional term, shape, points of attachment, etc.`

most body movements are the result of

2 or more muscles acting together or against each other

prime mover or agonist

muscle that produces a particular movement

antagonist

produces opposite effect on same bones

synergists

steady the area

stop from accidental movements

fixators

stabilizes the origin

for posture and balance

muscle cell membrane

aka sarcolema

fibers inside muscle cell

myofibrils

what are muscle cells stimulated by

electrochemical signals that travel along the sarcolemma (muscle cell membrane) AND THEN t-tubules carry signal to another muscle cell(fiber)

sarcomere explanation

actin and myosin are microfilaments that work together to contract and relax muscles

there can be lots of them in one fiber

causes striations in muscle

actin is blocked by tropomyosin which is held on by troponin; meanwhile, the myosin has an atp binded to it and whenever that atp releases its energy AND there’s a high enough calcium concentration for the troponin change shape and fall off of the actin, the myosin connects to the actin and pulls the actin closer to the midline which causes the muscle contraction

irritability

allows muscles to respond to a stimulus

more so neurological

losing it means you’re not responding

contractility

allows muscles to shorten

actual muscle issue

functions of muscle

movement, posture, heat generating, moving stuff

why can you bend partially

bc you don’t tell all your cells to move

bc if you tell one fiber to contract it will contract completely

motor unit

muscle cell + nerve cell

each muscle needs to be activated by a nerve but one can activate more than just one cell

neuromuscular junction

neuron forms a tiny space between it and the muscle fiber/cell which is called the synapse

the neuron releases neurotransmitters in vesicles in exocytosis which binds to receptor proteins and tells the muscle cell to move

acetylcholine

neurotransmitter that tells muscles to contract

acetylcholinesterase

breaks down ACh to prevent futher contraction of a muscle

not enough of this enzyme —> muscle cell keeps contracting

action potential

charge difference

signal that tells muscle cells to contract

this stimulates the sarcoplasmic reticulum to release calcium ions which attaches to troponin and allows myosin to attach to actin (which creates a crossbridge)

crossbridges

they’re the attachments of myosin heads to binding sites of actin

rigor mortis

example of it taking energy to release but not bind

• muscles let go (needs energy) and then it gains energy when it (myosin) releases

when you die, your muscle releases all the calcium so the troponin releases and allows the myosin to attach which causes your muscles to contract

sliding filament theory

filaments bind to each other and pull and overlap

creates contraction

steps to muscle contractoin

incomplete tetanus

muscle relaxes a little bit and then contracts some more

more time between signals

more jerking motions

what happens after a muscle contraction

everything goes back

• sodium potassium pump puts ions back (reabsorbed)

• troopomyosin covers actin binding sites so that myosin can’t form crossbridges anymore

muscle relaxes

graded responses

different degrees of shortening or contraction

more muscle cells = stronger response

can be produced by:

1. changing frequency of muscle stimulation

2. changing number of muscles stimulated

how to create atp

breaking creatine phosphate (from food)

aerobic respiration

anaerobic glycolysis

muscle fatigue

caused by not enough oxygen to create a complete contraction to release

if you’re anemic, you don’t have enough rbcs to carry oxygen

isotonic movements

muscle shortening

isometric

muscles don’t shorten, they are held in one place

ex. planlk

muscle tone

little contractions

muscles are always just ready to go

muscle atrophy

disuse of muscles

losing tone bc not using

aerobic exercise

increases endurance and becomes stronger

muscle size stays the same

more fatigue resistant

resistance training

grows muscle fibers and increases endurance

cramp

where you get a contraction and you just don’t let go

causes: overuse, dehydration, strain, staying in one position

muscle pull

strain, pull, or tear = damage to tendons by tearing muscle fibers

paralysis

nervous system not telling muscle to contract so it won’t

muscular dystrophy

defects in proteins that form filaments in muscle

• not structurally sound

caused by genes