the muscular system: the cell & muscle contraction

tendons vs ligaments

tendons attach muscles to bones — ligaments attach bones to bones

body composition varies among ppl, but muscles make up approx. __ of the body’s weight

1/3

functions of the muscular system

movement, maintaining posture, stabilizing joints, & generating heat (when ATP is used)

3 types of muscle tissue

1. Cardiac

2. Skeletal

3. Smooth

define striated muscle tissue (+ examples)

muscle tissue w/ a striped appearance from sarcomeres—organized arrangement of actin & myosin muscle filament into repeating units

• ex. cardiac & skeletal muscles

Sarcomeres

muscle contraction units in organized arrangement of actin & myosin muscle filament into repeating cycles of relaxed & contracted muscle fiber — present in striated muscle tissues such as cardiac & skeletal

cardiac muscle tissue

branch-shaped cell tissue that pumps blood

1. involuntary controlled

2. located near the heart

3. mononuclear

4. striated

smooth muscle tissue

diamond-shaped cells that aid body functions by surrounding internal passages & pathways to regulate flow of substances (ex. air, food, blood)

1. involuntary control

2. located in hollow organs

3. mononuclear

4. not striated

skeletal muscle tissue

cylinder-like cells responsible for movement

1. voluntarily controlled

2. attached to bones

3. multinuclear

4. striated

myofilaments (types?)

proteins that myofibrils are made of; 2 types are thick myofilaments (myosin) & thin myofilaments (actin)

myofibrils

tube-like structures within a muscle fiber containing myofilaments such as myosin & actin that aid in muscle contraction w/ ATP — image: the red small bundles parallel to one another

myosin

thick myofilaments that work w/ actin (thin) for muscle contraction

actin

think myofilament anchored to Z-Lines acting as boundaries for sarcomeres giving muscle a striped appearance

Sliding Filament Theory

explains muscle contraction as the process of synchronized shortening of sarcomeres —> muscle fibers (myosin & actin) sliding past each other —> muscle contracts

neurotransmitter needed to initiate a muscle contraction

acetycholine

steps of muscle contraction according to the Sliding filament theory

GRAB —> PULL —> RELEASE & RESET

1. calcium released from sarcoplasm reticulum binds w/ Tropomyosin (changing the shape of the actin), pulling tropomyosin off from covering the binding sites —> connects w/ myosin

2. GRAB: Myosin head forms cross bridges b/w actin & myosin

3. PULL: Power stroke causes sarcomere shortening actin filament like rowing motion (muscle contracts)

4. RELEASE & RESET: ATP breaks cross-bridge & resets myosin to original

5. calcium is repumped back into SR (can’t function w/o) OR cycle continues as long as calcium is present

label & define*: nucleus, sarcolemma*, sarcoplasmic reticulum*, t-tubes (transverse tubule system), mitochondria, myofibril*, sarcoplasm

1. sarcolemma - cell membrane of muscle cell

2. SR - specialized endoplasmic reticulum that releases Ca

3. T-tubes - network of tubes that act as calcium releasing channels from the SR & ensuring myofibrils contract simultaneously

4. myofibril - small tube-like structure containing the contractile filaments

label & define muscle fiber, perimysium, fascicle, epimysium, endomysium, muscle cell

inner to outer

1. muscle cells (4)

2. muscle fiber (4) - bundle of individual muscle cells

3. endomysium (6) - connective tissue covering each muscle fiber

4. fascicle (5) - bundle of muscle fibers

5. perimysium (2) - connective tissue covering each fascicle

6. epimysium (3) - protective layer over the whole muscle (the clusters of fascicles)