muscles Flashcards
what are the three types of muscle in the body
cardiac (heart muscle) moderate
skeletal muscle (attached to bones) rapid
smooth muscle/ involuntary muscle (walls of hollow organs, respiratory passageways) slow
give details of cardiac muscle
myogenic - they contract without the need of a nervous impulse
light striated
involuntary (autonomic nervous system)
single nucleus
give details on smooth muscle
walls of hollow organs, respiratory passageways
involuntary part of the autonomic nervous system
contracts and relaxes slowly
non striated
give details on skeletal muscle
voluntary - somatic nervous system
heavily striated
multiple nucleus’
rapid contraction
no branching
describe how you would distinguish between the three types of muscle
skeletal is unbranched and multiple nucleus’
smooth muscle is tampered (pinched at each end) has the most gaps/ is the thinnest. not striated
cardiac muscle is branched and striated
describe the structure of a muscle
made of bundles of muscle fibres which are covered in a membrane called sarcolemma (some folds inwards forming T tubules) and shared cytoplasm is called sarcoplasm. each muscle fibre contains many microfibrils, long cylinder organelles made of protein ie actin (thin filament and myosin which is the thick filament which are lined in parallel for maximum force.
what is the job of T tubules
they carry an action potential down towards the muscle so that the whole fibre receives the impulse to contract at the same time.
muscle fibres have a modified endoplasmic reticulum. what is it called and what does it do
sarcoplasmic reticulum. it extend throughout the muscle fibres and contains Ca2+ ions which are needed for muscle contraction.
what two types of protein filaments are myofibrils made up of
actin - thin filaments 2 strands wrapped round one another
myosin - thick filament long rod shaped fibres
during contraction of the muscles what happens to the muscle structure
the sarcomere, H band and light band becomes smaller and the dark zone stays the same length as the myosin filaments have not changed length.
describe the structure of myosin
has a globular head which is hinged allowing movement backwards and forwards. on the head there is a binding site for ATP and actin. the myosin head align forming myosin filaments
actin has a binding site for myosin which is usually blocked by another molecule. what is this molecule called? and what is it held in place with
tropomyosin which is help in place with troponin.
when at a resting site the actin myosin site is
blocked by tropomyosin so the filaments cannot slide past each other
what happens when a muscle is stimulated to contract
myosin heads form bonds with actin filaments known as actin myosin cross bridges. the myosin head flex and pull the actin filament along the myosin filament. it detaches from the actin filament using ATP.
describe how the sarcolemma becomes depolarised.
muscle contraction is triggered when an action potential arrives at a NT junction (point where the motor neurone and skeletal muscle meets) calcium ions channels open and calcium diffuses into the synaptic knob causing vesicles to fuse with presynaptic membrane secreting acetylcholine across the synaptic cleft. it bind with ligand gated Na+ channels and causes them to open. Na+ ions move into sarcolemma leading to depolarisation.
how do the muscle fibres all contract at the same time and strongly.
there are many motor junctions along the muscle fibre to ensure that the muscles contract simultaneously and strongly.
how do you prevent the muscle being over stimulated
acetylcholinesterase breaks down acetylcholine into ethanoic acid and choline which diffuse back into the neurone and recombine forming acetylcholine. this stops depolarisation of the sarcolemma.
define sarcomere
the sarcomere is the basic functional unit of a muscle fibre
define sarcolemma
plasmic membrane around fibres
define sarcolemma
plasmic membrane around fibres
what is the sarcoplasm
shared cytoplasm within fibres
what is the sarcoplasmic reticulum
endoplasmic reticulum in sarcomere.
name the two proteins in actins structure
troponin - bind to calcium2+ ions
tropomyosin - wraps round the actin filament and blocks the actin -myosin binding site
describe stimulation
action potential arrives, depolarise the sarcolemma and sarcoplasmic reticulum opening the Ca2+ voltage gated channels on SR so Ca2+ ions enter sarcoplasm and bind to troponin. this pulls tropomyosin and expose the actin myosin binding site.
describe attachment
myosin binds to the A-M binding site. this cause the myosin filament to flex (power surge) pulling the actin filament along it releasing ADP.
Describe detachment
ATP binds to the myosin head causing it to detach from the AM binding site. calcium activates the ATPase in myosin head so ATP on the myosin head is hydrolysed to ATP and Pi providing energy for the myosin head to return to its original position.
