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28 Cards in this Set
- Front
- Back
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What are the three types of muscle?
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Smooth, cardiac (unconscious control) and skeletal (conscious control)
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What is the name of the muscle fibres that make up muscles?
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Myofibrils
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To aid strength, muscle fibres are said to be _____________ and share a __________
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multinucleate, sarcoplasm
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What is special about what the sarcoplasm contains?
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It has a large concentration of mitochondria and ER
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Thinner, consists of two strands twisted around one another
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Actin
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Thicker, consists of long rod-shaped fibres with bulbous heads that project to the side
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Myosin
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What is the name for the striped effect of muscle?
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Striations
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Isotropic band (2)
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Lighter
Actin - no overlap |
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Darker
Actin and myosin overlap |
Anisotropic band
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What is at the centre of the anisotropic band?
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H-Zone
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What is in the centre of the isotropic band?
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Z-Line
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What is the distance between adjacent Z-lines?
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Sarcomere
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Tropomyosin
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Fibrous strand around the actin filament
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Troponin
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Globular protein
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Features of slow-twitch fibres (8)
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Contract more slowly
Less powerful contractions Longer period Large myoglobin store (red) Glycogen supply --> metabolic energy Rich supply of blood vessels to deliver oxygen and glucose Many mitochondria --> ATP Endurance work (common in calf) |
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Features of fast-twitch fibres (8)
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Contract rapidly
Powerful contractions Short period Intense exercise Common in said muscles e.g. biceps Thicker and more numerous myosin filaments High conc of enzymes involved in anaerobic respiration Phosphocreatine store - molecule that rapidly generates ATP from ADP in anaerobic conditions to provide energy for muscle contraction |
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What is a neuromuscular junction?
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The point where a motor neurone meets a skeletal muscle fibre
Many along the muscle (smoother contraction) |
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What is a motor unit?
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All muscle fibres supplied by a single motor neurone that act together as a single functional unit
Groups of motor units often work together to coordinate the contractions of a single muscle |
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What controls the strength of muscle contraction?
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How many motor units are innervated! :)
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When a nerve impulse is received at the neuromuscular junction...
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Synaptic vesicles fuse with presynaptic membrane and release their acetylcholine
Acetylcholine diffuses to postsynaptic membrane - Increase permeability to sodium ions which enter rapidly and DEPOLARISE the membrane Acetylcholine broken down by acetylcholinesterase Choline and ethanoic acid (acetyl) diffuse back into the neurone Combined using energy provided by mitochondria |
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Why is acetylcholine broken down by acetylcholinesterase?
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To ensure the muscle is not over-stimulated
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During contraction, what changes occur to the sarcomere? (3)
What remains the same? |
H-zone becomes narrower
I-band becomes narrower Z-lines move closer together (HIZ) Anisotropic band remains the same width (A band = myosin) |
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Outline the process of muscle stimulation
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AP reaches neuromuscular junction
Ca ion channels open and Ca IONS move into synaptic knob Ca ions cause synaptic vesicles to fuse with presynaptic membrane and release ACh into synaptic cleft ACh diffuses across and binds with receptors in postsynaptic membrane, causing DEPOLARISATION |
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You need to learn the process of muscle contraction!
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!
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Outline the process of muscle relaxation
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When nervous stimulation ceases, CA ions are actively transported into sarcoplasmic reticulum USING ENERGY from hydrolysis of ATP
Reabsorption allows tropomyosin to block actin Myosin heads unable to bind to actin filaments |
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What is ATP needed for in muscle contraction? (2)
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Movement of the myosin heads
Reabsorption of Ca ions in sarcoplasmic reticulum by AT |
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Very active muscles require instant ATP - this is done anaerobically. What is used to rapidly generate ATP?
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Phosphocreatine
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How does phosphocreatine work?
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It regenerates ATP. Essentially it is a reserve supply of phosphate which is immediately able to combine with ADP to reform ATP
The store is replenished using phosphate from ATP when the muscle is relaxed |
