Muscles 1

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  • Created by: Hindleyc
  • Created on: 10-04-19 15:10
What are the 3 main types of muscles
Cardiac- fires own AP, Smooth- lines tubes (involuntary), Striated(skeletal used for voluntary movements such as walking
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What is skeletal muscles
muscle attached to bones- not under control of brain
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Tendons
Binds muscle to bone
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Ligaments
Binds bone to bone
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What can the heart muscle be
Parasympathetic and sympathetic (autonomic)
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Where is most impulse from
Heart itself- myogenic, striated but smaller
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What is smooth muscle
Lines some of internal organs, important in digestive system, rhythmic contractions help to move food along- autonomic
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What shapes are cells
Spindle shaped-short and thin with single nucleus (mono nucleated) unstriated
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What is skeletal
Multi-nucleated cells elongated and contains multiple nuclei- very large,
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What is it
Striated - distinctive pattern of light and dark bands when viewed under a microscope
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Muscles cannot
Push
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What can they do
only pull- must be 2 of them to make a bone move into position and back again
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contracting creates a
pulling force
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What are they arranged into
Antagonistic pairs
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What is there
one on each side of a joint so 1 contract and 1 relaxes so only pulling
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What does the movement depend on
muscles bones and joints
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what generally happens to bring about movement
groups of muscles work together
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What is skeletal muscle constantly used for
Maintaining posture, covers skeleton and allows bones to be moved relative to one another
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What does voluntary nervous system control
Skeletal muscle by sending messages from CNS to muscle tissue
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What do nerves do
transmit impulses between muscles and the CNS
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What do muscles do
Pull on bones to which they are attached to by tendons
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What are muscles
effectors (Create an effect like movement)
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As muscles contract what happens
tendons pull on bones
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Why are tendons good
don't stretch or break because of the presence of the fibrous protein collagen which is inelastic and very tough
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What does collagen in bones make them
slightly bendy and less brittle
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At joints between bones what are present and what does it contain
Ligaments containing elastin- protein with branched fibres that can stretch to 1.5x their length and back again
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What does elastin in ligaments allow
Joints to move slightly but prevents dislocation
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What does skeletal muscle look like and how is each muscle attached to skeleton
Stripy (striated muscle), tendons
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Why is it important it has elastic
force of contraction is entirely transmitted to the bone
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What are skeletal muscles under
Voluntary control
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What does it consist of
Overlapping, elongated cells called muscle fibres held together by connective tissue with a tendon at each end
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When the fibres contract what happens
the muscle shorten pulls the tendons and move the bones
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What do the muscle fibres look like under a microscope (light)
striped along their length (stripes formed by a regular pattern of protein filaments which are lined up to form dark and light bands
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What does muscle consist of
2 proteins- actin and myosin that are responsible for the contraction of muscle
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What do these form
Thin and thick strands of/or filaments
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What are myosin filaments compared to actin
About 2x as thick as actin (thin)
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Therefore what are the cells which make up skeletal muscles called
Muscle fibres
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What causes a muscle twitch
Hydrolysis of ATP providing the energy required for muscle contraction
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ATP=
ADP + Pi =33kj/mol
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What do most muscle fibres store
phosphocreatine
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What is it
A Chemical that phosphorylates ADP into ATP
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What does the reaction maintain
the muscles supply of ATP during vigorous exercise
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ADP + phosphocreatine =
ATP + creatine
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What do muscles do and have
contract and relax- twitch, many mitochondria
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What are M tissue made up of
Cells that can contract creating a pulling force, makes up to 40% body mass
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What are the muscles used for
Maintaining posture, covers skeleton and allows bones to be moved relative to one another, voluntary nervous system controls skeletal muscle by sending messenger from CNS to muscle tissue
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What is a NMJ
Motor N to muscle fibre
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What are muscles under
Nervous control
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Where is contraction initiated
At NMJ
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What do muscle fibres surround
The end of the neurone to increase area over which signals are received
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STEPS
1.Action potential arrives at motor neurone Ca^2+ channels open and flood in, Increase conc of Ca^2+ in cells stimulates vesicles which contain neurotransmitter acetylcholine - moves towards presynaptic membrane and fuse with it
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then
Acetyl choline diffuses across synaptic cleft binding to receptors on post synaptic membrane =sarcolemma, Na channels open and Na+ floods into muscle cell
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then
Post synaptic membrane depolarised (muscle cell)
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If threshold is reached what happens
depolarises
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then what does is do
Travels along Muscle cells membrane and into T-tubule
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What is a T tubule
Deep infold of sarcolemma which is muscle fibre membrane on the post synaptic membrane
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What is the sarcoplasmic reticulum
made of membranes with small wave of depolarisation
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What is needed
it to twitch (not just AP)- set up muscle contraction
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Inside sarcoplasmic reticulum what was happening while at rest
pumping Ca^2+ into sarcoplasmic reticulum by AT (AP in other)
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What does the arrival of AP do
Extend across MC membrane into T-tubules -all depolarised spread to other
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Then
Ca^2+ released asa has been building up a while at rest- calcium switch Ca2+ released into sarcoplasm of muscle cell
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What is stripy structure of protein due to
Actin and myosin
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What does muscle fibre do
Contract (twitch)
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Many motor neurones=
larger contraction
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Simplified steps
1 Impulse arrives at NMJ (motor end plate) causes vesicles to fuse with the pre s m and release acetyl choline into gap 2. AC binds to receptors on the muscle fibre membrane (sarcolemma) casting depolarisation
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then what happens
3.Depolariation wave travels down tubule ( t systems) 4.T system depolarisation leads to Ca2+ release from stores in sarcoplasmic reticulum (specialised ER)- wave 5. Ca2+ binds to proteins in the muscle which leads to contraction
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then
6.Acholinerase in the gap rapidly breaks down AC so that contraction only occurs when impulses arrive continuously 7. Muscle fibre only able to generate a force while it is contracting- unable to push-
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what is it
not elastic to make arm move brings about movement muscle has initiated and tendons pull on bone
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What are T tubules
Close to sarcoplasmic reticulum to depolarise then Ca2+ been going in released
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Structure of skeletal muscles- muscle=
Muscle=bundle of fibres
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What are bundles of fibres
Fibres
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What are fibres
groups of myofibrils
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What are myofibrils made of
Filaments
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Other cards in this set

Card 2

Front

What is skeletal muscles

Back

muscle attached to bones- not under control of brain

Card 3

Front

Tendons

Back

Preview of the front of card 3

Card 4

Front

Ligaments

Back

Preview of the front of card 4

Card 5

Front

What can the heart muscle be

Back

Preview of the front of card 5
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