Anatomy- Muscular System (notes)

functions of the muscular system

movement of the body, maintaining posture, generates body heat, and plays a role in other body systems

types of muscle tissue

skeletal (striated/ voluntary), smooth (involuntary), cardiac (heart)

fascicles

many muscle fibers arranged in bundles

myocytes

muscle fiber and muscle cells

three different layers of connective tissue

1. epimysium 2. perimysium 3. endomysium

epimysium

outermost layer, surrounds entire muscle

perimysium

separated and surrounds the fascicles (bundles)

endomysium

surrounds each individual muscle fiber

sarcolemma

muscle fiber membrane

sarcoplasm

inner material surrounding fibers (like cytoplasm)

sarcoplasmic reticulum

transport and storage

myofibrils

parallel protein fibers within sarcoplasm

each myofibril is made of many

myofilaments

two types of myofilaments

myosin, actin

myosin

thick filaments, A Bands= dArk=thick= myosin

actin

thin filaments, bands=llght=thin=actin

Hierarchy:

muscles→ fascicles → myofibrils → myofilaments (actin & myosin)

neuromuscular junction

where a nerve and muscle fiber come together

motor end plate

folded area where muscle and neuron communicate

synapse

gap between the neuron and motor end plate (synaptic cleft)

synaptic vesicles

where neurotransmitters (NT) are stored

neurotransmitters

are hormones that only act in a small area (sympse)

acetylcholine

is the neurotransmitter that crosses the gap, which is stored in vesicles which is broken down by cholinesterase

the sliding filament theory

the theory of how muscle contracts, the contraction of a muscle happens as the thin filaments slide past the thick filaments, the theory involves five different molecules (actin, myosin, ATP, aceylchloine, cholinesterase???) and calcium ions

biomarkers

are substances that can indicate change to muscles

creatine kinase

is elevates in people who have suffered heart attacks and who have DMD

proteins (two rules)

1\. proteins like to change shape when stuff binds to them 2. changing shapes can allow proteins to bind or unbind with other stuff

trophonin and trypomyosin

are what blocks actin when a muscle fiber is at rest

calcium

is required to unblock the the tropohin and trypomyosin

muscle fatigue

muscle loses ability to contract after prolonged use

muscle cramp

a sustained involuntary contraction

oxygen debt

not have enough oxygen causes lactic acid

hypertrophy

muscles enlarge

atrophy

muscles become small and weak due to disease