L1, L2, L3

list four functions of the muscular system

• moves body

• maintains posture

• assists with respiration

• produces body heat

OTHER ACCEPTABLE ANSWERS

• constricts organs and blood vessels

• contracts heart to circulate blood

describe the cardiac muscle according to the: voluntary/involuntary, nuclei, location, cell shape, function and any specialisations

• involuntary

• single, central

• heart

• branched cells

• contracts heart to generate pressure and move blood around

• intercalated disks (

describe the smooth muscle according to the: voluntary/involuntary, nuclei, location, cell shape, function

• involuntary

• single, central and elongated

• spindle cells

• blood vessels, inner lining of organs, glands, iris of eye

• vasoconstriction/dilation, peristalsis, pupil size

describe the skeletal muscle according to the: voluntary/involuntary, nuclei, location, cell shape, function and any specialisations

• voluntary (sometimes involuntary)

• multinucleated, peripheral

• connected to bones via tendons

• cylindrical cells

• posture, locomotion, facial expression

• striated

what type of CT is epimysium and what does it cover

• dense CT

• covers entire skeletal muscle

what does perimysium cover and explain what that thing is made of

• covers a fasicle

• fasicles are a group of skeletal muscle fibres/cells/myofibres

what does endomysium cover

the individual myofibres

what is the sarcolemma and its function

• plasma membrane of skeletal muscle fibres

• propagates action potentials

what is the sarcoplasm

myofibres’ cytoplasm

what are myofibrils and what does it contain

• cylindrical organelles within myofibres

• contains: sacromere (microfilaments: actin and myosin) and titin

what is the sarcoplasmic reticulum and its function?

• smooth ER

• holds Ca2+ and releases it

what is the terminal cisternae?

enlarged SR on either side of T-tubule

what is the purpose of tranverse tubules, or T-tubules

transmits AP from the surface of cell to deep intracellular

what is titin and what is its purpose

• giant elastic protein from Z disk to M line

• passive elastic recoil

where are myofilaments found and what does it contain?

• found inside myofibrils

• contains thin filaments (actin, troponin, tropomyosin) and thick filaments (myosin)

the myofibril has a striation pattern due to different bands. what is the I band?

• the light band

• contains only part of actin molecules

the myofibril has a striation pattern due to different bands. what is the A band?

• the entire length of myosin

• there are some overlapping of myosin and actin

the myofibril has a striation pattern due to different bands. what is the H zone?

• central area of A band

• contains only myosin

the myofibril has a striation pattern due to different bands. what is the Z disk?

• anchors actin

• boundary of sacromere

the myofibril has a striation pattern due to different bands. what is the M line?

• the exact middle of sacromere

• anchors the myosin

what is the sacromere and its function?

• causes the striations in skeletal muscle; repeating myofilaments

• function: the unit of contraction for skeletal muscle via the sliding filament model of contraction

what are the components of the actin molecule

• troponin

• G actin

• F actin

• tropomyosin

where does each component of troponin attach to?

• G-actin

• Ca2+

• tropomyosin

what happens when Ca2+ attaches to troponin?

troponin changes shape and moves tropomyosin to expose the G-actin’s binding site

explain the process of when ATP attaches to a myosin molecule

1. ATP is attracted to the bent myosin molecule at resting stage

2. this causes the myosin to erect at 90 degrees and cause energy to be released by breaking down ATP to ADP + P

3. ADP + P is removed while the myosin molecule swivels back into its original position, bringing the actin molecule towards M line

explain the resting, erected and swivelling stages of myosin

1. resting - myosin at a 45 angle with ATP attached

2. erected - breakdown of ATP → ADP + P causes myosin to “erect” at a 90 degree angle

3. swivelling - ADP + P is removed and a new ATP attaches, causing the myosin to swivel back to its original position

describe the sliding filament model of contraction

• at relaxed muscle, all the zones are shown, ATP is attracted to myosin but no nerve impulse

• once a nerve impulse comes and causes the muscle to contract, A band stays still except for the myosin heads, which is moving actin towards the M line

• H zone and I band narrows as it is it pulled towards the M line

• at fully contracted muscle, H zone completely disappears and I band is even narrower

An action potential arrives at the neuromuscular junction. Describe the following steps that occur for a muscle to contract (6) - AKA excitation-contraction coupling

1. nerve impulse propagates along sarcolemma and into the T-tubules

2. this transmits into sarcoplasmic reticulum and stimulates the release of Ca2+ into the sarcomere of myofibrils

3. Ca2+ attaches to troponin

4. troponin changes shape and moves tropomyosin away from binding site of G actin (G-actin is now exposed)

5. cross-bridge cycle occurs when myosin has ATP

6. muscle shortens and contracts (H zone disappears, I band is narrow)

describe the 5 steps of cross-bridge cycle

1. active sites are exposed via Ca2+ binding with troponin

2. myosin head attaches to binding site of G-actin by breaking down ATP → ADP + P

3. myosin head pivots and pulls actin filament towards M line while releasing ADP + P

4. new ATP attaches to myosin and causes it to release actin

5. myosin head hydrolyses (ATP → ADP +), returns to original position, ready for another stimulus

what is the termination of the excitation-contraction coupling?

• Ca2+ is actively pumped back into SR by falling off troponin

• troponin returns to original shape

• tropomyosin returns and covers binding/active sites

what decides the movement in the body?

the positioning of the bone, joint and muscles

what are the three ways a muscle can attach to a bony feature

tendon, aponeurosis, direct attachment to periosteum