The Skeletomuscular System Flashcards
The Skeletomuscular system
What is responsible for all movement in the body?
Muscles
The Skeletomuscular system
What are the 3 basic types of muscle?
The Skeletomuscular system
Which type of muscle do we have voluntary control over?
Skeletal muscle
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Which type of muscle isnt striated?
Smooth
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Which type of muscle is the bodies energy converters?
Skeletal
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How many nuclei are in skeletal muscle?
Many
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How many nuclei are in cardiac muscle?
1
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How many nuclei are in smooth muscle?
1
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What prefixes refer to muscle?
Myo and mys
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Excitability
Ability to recieve and respond to stimuli
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Contractility
Ability to shorten when stimulated
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Exstensibility
Ability to be stretched
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Elasticity
Ability to recoil to resting strength
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Functions of skeletal muscle
Movement
Maintenance of posture and body position
Heat production
Store nutrient reserves
Protects bones and internal organs
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Skeletal muscle structure images
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What is a motor unit?
A motor neurone and all the muscle fibres that it invervates
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What affect does having fewer number of fibres per neurone have?
Allows finer movement
Requires more brain power
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Fascicles
Small bundles of muscle fibres
Group together to make up the muscle
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How long is a muscle fibre?
They go the length of the muscle
From tendon to tendon
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What surrounds each fascicle?
A connective tissue layer called the perimysium
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What surrounds the entire muscle?
An external connective tissue wrapping called the epimysium
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Endomysium
Connective tissue layer
Seperates and electrically insulates the muscle cells from each other
The Skeletomuscular system
What are the 3 connective tissue layers in the fascicle of muscles?
Starting from the inside going outwards?
Endomysium
Perimysium
Epimysium
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Sacromere
Contracile unit of the muscle fibre
From one Z line to another Z line
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What is the thick filament in the myofilament?
Myosin
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What is the thin filament in a myofilament?
Actin
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A band in the myofilament
Where thin and thick filaments overlap
Dark coloured
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H band in the myofilament
Just thick filaments
Thin filaments don’t reach that point
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I band in the myofilament
Just the thin filaments
Light coloured
The Skeletomuscular system
Z line in the myofilament
Marks boundries between adjacent sarcomeres
Connects thin filaments of each sarcomere
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Differences between sarcomere when contracted and relaxed
I band shortens
H zone shortens
A band stays the same
M line stays the same
Z lines get closer together
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Where does the actin filaments bind to?
The z line
The Skeletomuscular system
Which filament has the heads on them?
Thick myosin filaments
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What does muscle contraction require a lot of?
ATP
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Steps of sliding filament theory
Ca2+ bind to troponin
This causes tropomyosin to move and reveal actin binding sites
Myosin binds to actin
ADP released causing the myosin heads to change shape
Actin filament pulled along in rachet fashion by myosin heads
ATP binds to myosin head to detach it, giving off phosphate to become ADP
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What causes muscle contraction?
Stimulation from the motor neurone
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What does the energy from the ATP do in muscle contraction
Causes the myosin head to detach from the actin filament
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Explain why rigor mortis occurs
No more ATP
Therefore can’t make muscles relax
Myosin heads can’t detach from actin filaments
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Where does the Ca2+ come from for muscle contraction?
Calcium pumps in sarcoplasmic reticulem pumps them into the sarcomere
Creates a store of Ca2+
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Tropomyosin
Long fibrous molecule
Blocks the interaction between actin and myosin when muscle is relaxed
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Toponin
Binds reversibly with calcium
Then moves tropomyosin away from the actin binding site
The Skeletomuscular system
What are all the roles of ATP in muscle contraction?
Energises the power stroke of the myosin cross-bridges
Makes the myosin head detach from the actin binding site when the power stroke is finished
Actively transporting calcium ions into the sarcoplasmic reticulum
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In muscle contraction do all the myosin heads bind at once?
No
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What is the sarcolemma?
Muscle cell membrane
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What is the muscle cell cytoplasm called?
Sarcoplasm
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Sarcoplasmic reticulum
Smooth ER of myofibril
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Motor end plate
Contact surface with the axon terminal
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T tubule
Cell membrane extension into sarcoplasm
Allows the depolarising signal to contract to reach the myofibrils deep in the muscle fibre
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Cisternae
Areas of the ER dictated to Ca2+ storage
Found either side of the T-tubules
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What does the tension generated in skeletal muscle dependant on?
Frequency of action potentials transmitted along a somatic motor nerve
Amount of ACh released at neuromuscular junction
Frequency of action potentials across the skeletal muscle fibres
Amount of Ca2+ released from the sarcoplasmic reticulum
Number of cross-bridges formed between actin and myosin filaments
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What happens to relax the muscle?
Not just the muscle
ACh is removed from receptors
Ligand gated Na+ channels close
Na/K pumps reestablish resting membrane potential
Ca2+ ions leave troponin and are actively transported back to the cisternae
Tropomyosin moves back over the actin active site
Myosin heads release actin filament
Filaments move passively back to resting position
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The 3 phases of a muscle twitch
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What is the ratio of stimulation to muscle twitches?
1 : 1
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What happens during the latent stage of a muscle twitch?
Action potential generated up to myosin heads binding to actin
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What happens during the contraction stage of a muscle twitch?
Myosin heads slide along the actin filaments
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What happens during the relaxation stage of a muscle twitch?
Ca2+ ions moved back into the cisternae
Tropomyosin moves back over actin
Myosin heads release actin and go back to resting positions
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What causes what to move and expose the actin binding sites in muscle contraction?
Tropin moves tropomyosin
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What happens if the sarcomeres are stretched too far?
Cross-bridge interactions are reduced or cannot happen
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What happens if the sarcomeres have a resting length that is too small?
They cannot contract enough to produce tension
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Isometric contractions
Muscle contraction without movement
Muscle doesn’t shorten
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Isotonic contractions
Muscle contractions with movement
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What are the two types of isotonic muscle contraction?
Concentric - when the muscle shortens
Eccentric - when the muscle elongates
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Treppe
Gradual increase in contraction intensity during sequential stimulation
Might be due to Ca2+ ions accumalting in the cytosplasm with each stimulation
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Summation
Rapid sequence of stimuli
Muscle twitches fuse into each other
Makes the subsequent one stronger than the last
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Tetanus
Very rapid sequence of stimuli
No relaxation in the muscles
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Recruitment
Multiple motor units respond to stimulus
Therefore affects more muscle fibres
Creates a greater force then just one
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How is ACh removed?
Broken down by acetylcholinesterase
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If there is oxygen present how is ATP produced?
How much is produced?
Oxidative phosporylation
34 ATP per glucose
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If there is no oxygen present how is ATP produced?
How much is made?
Anaerobic glycolysis
2 ATP per glucose
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Muscle fatigue
A decline in the ability of the muscle to sustain the strength of contraction
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What are the causes of muscle fatigue?
Rapid build up of lactic acid
Decreased neurotransmitters at synapse
Decrease in oxygen supply
Decrease in energy supply
Psychological issues
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How is lactic acid formed?
During anaerobic glycoloysis
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What affects does aerobic (endurance) exercise have?
Promotes increased oxidative capacity of the muscle fiber
Increased blood vessel supply
Increased amount of mitochondria
Results in stronger, more flexible muscles with greater resitance to fatigue
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What affects does resistance exercise have?
Increased glycolytic activity
Increased synthesis of gylcolytic enzymes
Increased synthesis of myofibrils
Increased muscle size and strength
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How to make human growth hormone
Insert HGH gene into virus
Seed the virus into cultured human cells
Wait for the virus to reproduce
Extract HGH
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What is the muscle connective tissue?
Collagen fibres
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What type of collagen fibres are in the perimysium?
50% type I
50% type III
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What type of collagen fibres are in the endomysium?
Type I
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How does exercise/lack of exercise effect collagen fibres?
Inactivity cause the elastic properties to decrease
Exercise increases breakdown/synthesis to replace the old brittle collagen with new protocollagen
