6.3 Muscles Flashcards
What attaches skeletal muscles to bones
Tendons
What is a pair of muscles called
An antagonistic pair
In an antagonistic pair, what happens to the muscles at the same time
-One muscle contracts
- One muscle relaxes
In an antagonistic pair, what is the muscle that’s relaxing called
Antagonist
When you bend your arm, what happens to the tricep muscle
It relaxes
When you straighten your arm, what happens to the tricep muscles
Contract
In an antagonistic pair, what is the contracting muscle called
Agonist
When you bend your arm, what happens to the bicep muscles
Contract
What are muscle fibres
Long, specialised cells
What is the membrane of muscle fibres called
The sarcolemma
What is the name of the ‘muscle fibre cytoplasm’
Sarcoplasm
The sarcolemma folds _______ to the ___________
- Inwards
- Sarcoplasm
What are the inwards folds of the sarcolemma called
Transverse (T) tubules
What does SR stand for
Sarcoplasmic reticulum
What does the SR store
Calcium ions
What are calcium ions important for
Muscle contraction
What organelle is densily concentrated in muscle fibres
Mitochondria
What are myofibrils the site of
Muscle contraction
What shape are myofibrils
Cylindrical
Where are myofibrils located
Along the length of muscle fibres
Skeletal muscles consists of bundles of what
Muscle fibres
Muscle fibres contain organelles that are the site of muscle contraction, what is the name of these organelles
Myofibrils
Myofibrils are made of multiple units, what are these units called
Sarcomeres
What is the end of a sacromere called
Z line
What are sarcomeres made from
2 types of myofilaments
What are the 2 types of myofilaments that make up a sarcomere
- Thick myofilaments
- Thin myofilaments
What protein are thick myofilaments made of
Myosin protein
What protein are thin myofilaments made of
Actin protein
Myosin and actin filaments are arranged in an _________ pattern in sarcomeres
Alternating
At the end of sarcomeres, what happens between the thick myosin filament and the thin actin filament
Overlap
What is the overlapping region of the filaments in a sacromere called
The A-band
In a sarcomere, what is the region with only myosin filament called
H-zone
Where does the thin actin filaments overlap with myosin filaments
Middle of the sacromere
What is the middle of the myosin known as
M line
What is the region with only actin filaments in a sacromere called
I-band
In a sarcomere, what filaments does not move
Myosin
Explain how actin and myoson produce contraction of a sacromere
- Myosin does not move
- When muscles contract, actin filaments slide over myosin towards the middle of the sacromere
What are the 2 myofilaments associated with actin
- Troponin
- Tropomyosin
What is the use of slow twitch muscles
Endurance
What is the use of fast twitch muscles
Burst of activity
List some examples of slow twitch muscles
- Back muscles
- Calf muscles
What is an example of a fast twitch muscle
Eye muscles
Do slow twitch muscles fatigue slowly or quickly
Slowly
Do fast twitch muscles fatigue slowly or quickly
Quickly
Do slow twitch muscles contract slowly or quickly
Slowly
Do fast twitch muscles contract slowly or quickly
Quickly
Do slow twitch muscles contract for a long time or contract and relax rapidly
Contract for long time
Do fast twitch muscles contract for long time or contract and relax rapidly
Contract and relax rapidly
Do slow twitch muscles have a high or low density of myofibrils
Low density of myofibrils
Do fast twitch muscles have a high or low density of myofibrils
High
Do slow twitch or fast twitch muscles have many mitochondria
Slow twitch muscles
Do fast twitch muscles have many or few mitochondria
Few mitochondria
How do slow twitch muscles respire
Aerobically
How do fast twitch muscles respire
Anaerobically
Do slow twitch or fast twitch muscles have a higher myoglobin concentration
Slow twitch
Is the glycogen storage in a slow twitch muscle high or low
Low
Is the glycogen storage in a fast twitch muscles high or low
High
In slow twitch muscles, is there a high density of capillaries or a low density of capillaries
High density
In fast twitch muscles, is there a high or low density of capillaries
Low density of capillaries
In slow twitch muscles is there a high or low lactate production
Low lactate production
In fast twitch muscles is lactate removed quickly or slowly
Quickly removed
What colour do slow twitch muscles appear
Dark
What colour do fast twitch muscles appear
Light
What is a neuromuscular junction
Synapse between motor neurone and muscle
At neuromusclar junctions, after the Ach has diffused across the cleft, where are the sodium gated channels located
In sarcolemma
In neuromusclar junctions, after the sodium ions have diffused in, what is now depolarised
The sarcolemma
Write the comparative statement: Neuromuscular junctions have excitatory only
Cholinergic synapes have excitory and inhibitory
Write the comparative statement: Cholinergic synapses link neurone to neurone or other effector organs
Neuromuscular junctions links neurones to muscle fibres
Write the comparative statement: Neutromuscular junctions involves motor neurones only
Cholinergic synapses involve all neurones, sensory, intermediate and motor
Write the comparative statement: Neuromuscular junctions are where action potential end
Cholinergic synapses may produce an action potential in the postsynaptic neurone
Write the comparative statement: Ach binds to receptors on membrane of postsynaptic neurone
In neuromuscular junctions Ach binds to receptors of the motor end plate
What type of molecule is Troponin
Proteins
What type of protein is troponin
Globular
What is tropomyosin
Protein that wraps around the actin filaments lying in groove between the 2 chains
What is actin filament
Globular proteins that are joined together into a long chain
How many chains of actin are in an actin filament
2
In a myosin molecule, what is the tail made of
Fibrous protein
In a myosin molecule, what is the head made of
Globular protein
In a myosin molecule, what enzyme does the head contain
ATP hydrolase
In a myosin filament, are the head of the myosin molecules at one end or both end
Both ends
When the actin filament slides, what happens to the length of the sarcomere
The length of the sarcomere shortens
When the actin filaments slide and the sarcomere shortens, what happens to the length of the I band
The I band shortens
When the actin filaments slide and the sarcomere shortens, what happens to the length of the H zone
It shortens and may even disappear
When the actin filaments slide and the sarcomere shortens, what happens to the length of the A band
Remains the same
Why does the A band remain the same length, even when the sarcomere shortens
Since the A band id determined by the myosin and the myosin doesn’t move
At a neuromuscular junction, what does the Acetylcholine bind to
The protein receptors on the motor end plate
In neuromuscular junctions, what happens after the Ach have bound to the protein receptor on the motor end plate
The sodium ion gated channels open and the sodium ions diffuse in
In a neuromuscular junction, what is the effect of the sodium ions moving in
The sarcolemma depolarised
In a neuromuscular junction, when the sarcolemma has depolarised, what then depolarises
The T tubules
In a neuromusclar junction, once the T tubules have been depolarised, what happens
The proteins in the T tubules are stimulated and the calcium ion gated channels in the sarcoplasmic reticulum open
After the calcium ions gated channels in the sarcoplasmic reticulum open, what happens
The calcium ions diffuse out of the sarcoplasmic reticulum and into the myofibrils
After the calcium ions have diffused out of the sarcoplasmic reticulum and go into the myofibrils, what do the calcium ions bind to
Bind to the troponin molecules on the actin filaments
What is the effect on troponin after calcium ions have bound to the troponin
The troponin changes shape
What is the effect on tropomyosin, when the troponin shape changes as a result of the calcium ions binding
Moving/ dislodging of tropomyosin which exposes the binding sites on the actin filament
What binds to the binding sites on tropomyosin
Myosin
What part of the myosin attaches to the actin binding sites
The myosin head
What is formed when the myosin head attaches to the acctin binding site
Actinomyosin cross bridge
When the myosin head attaches to the actin binding site, what is attached to the myosin head
ADP and Pi
Once the myosin head is attached to the actin binding site, what is released from the myosin head
ADP and Pi
When ADP and Pi are released from the myosin head, what does this do to the myosin head
Changes the angle of the myosin head
When ADP and Pi are released from the myosin head, and the angle of the myosin head changes, what do this do to the actin
Pulls the actin over myosin
What is the name of the process when actin is pulled over myosin
Power stroke
After the power stroke, what then attached to the myosin head
ATP molecule
When the ATP molecule binds to myosin head, what is the effect
Myosin head detaches from actin site
When the myosin head detaches from the actin binding site, what breaks
The actinomyosin cross bridges
After the myosin head detaches from the actin binding sites, what happens to the ATP molecule
ATP is hydrolysed into ADP and Pi by ATP hydrolase
What is released when ATP is hydrolysed
Energy
What is the energy that’s released from the hydrolysis of ATP used to do to the myosin head
The energy extends the myosin head
Once the myosin head has been extended again, by the energy released from the hydrolysis of ATP what is the myosin head ready to do
Ready to bind to the actin binding site
When the myosin head is ready to bind to the actin binding site, what is this stage called
Recovery stroke
Do muscle contraction or muscle relaxation move bones
Muscle contraction
What are the 2 sources of ATP for muscle contraction in anaerobic conditions
- The hydrloysis of creatine phosphate to phosphorlyse ADP
- Oxidation of triose phosphate to pyruvate and then lactate is produced
Explain the role of glycogen granules in skeletal muscles (2 marks)
- As a store of glucose
OR
To be hydrolysed to glucose; - For respiration / to provide ATP;
Describe the roles of calcium ions and ATP in the contraction of a myofibril (5 marks)
- Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum;
- (Calcium ions) cause movement of tropomyosin (on actin);
- (This movement causes) exposure of the binding sites on the
actin; - Myosin heads attach to binding sites on actin;
- Hydrolysis of ATP (on myosin heads) causes myosin heads to
bend; - (Bending) pulling actin molecules;
- Attachment of a new ATP molecule to each myosin head
causes myosin heads to detach (from actin sites).
ATP is an energy source used inn many cell processes. Give 2 ways in which ATP is a suitable energy source for cells to use (2 marks)
- Releases relatively small amount of energy / little energy lost as
heat; - Releases energy instantaneously;
- Phosphorylates other compounds, making them more reactive;
- Can be rapidly re-synthesised;
- Is not lost from / does not leave cells.
What is the role of ATP in myofibril contraction (2 marks)
- (Reaction with ATP) breaks/allows binding of myosin to actin/
actinomyosin bridge; - Provides energy to move myosin head;
Explain how a decrease in the concentration of calcium ions within muscle tissues could cause a decrease in the force of muscle contractions (3 marks)
- (Less/No) tropomyosin moved from binding site
OR
Shape of tropomyosin not changed so binding site not
exposed/available;
Ignore troponin.
Reject active site only once. - (Fewer/No) actinomyosin bridges formed;
Accept actin and myosin do not bind.
Reject active site only once. - Myosin head does not move
OR
Myosin does not pull actin (filaments)
OR
(Less/No) ATP (hydrol)ase (activation);
Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration (2 marks)
- Regenerates/produces NAD
OR
oxidises reduced NAD; - (So) glycolysis continues;
The scientist compared length of time that the control mice and the trained mice could carry out prolonged exercise. The trained mice were able to exercise for a longer time period than control mice. Explain why. (3 marks)
- (More aerobic respiration) produces more ATP;
- Anaerobic respiration delayed;
- Less or no lactate;
Explain the role of glycogen granules in skeletal muscle (2 marks)
- As a store of glucose
OR
To be hydrolysed to glucose; - For respiration / to provide ATP;
Suggest how a fall in pH leads to a reduction in the ability of calcium ions to stimulate muscle contraction (3 marks)
- Low pH changes shape of calcium ion receptors
- Fewer calcium ions bind to tropomyosin;
Accept troponin - Fewer tropomyosin molecules move away;
- Fewer binding sites on actin revealed;
- Fewer cross-bridges can form
OR
Fewer myosin heads can bind
Describe the role of calcium ions and ATP in the contraction of myofibrils (5 marks)
- Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum;
- (Calcium ions) cause movement of tropomyosin (on actin);
- (This movement causes) exposure of the binding sites on the
actin; - Myosin heads attach to binding sites on actin;
- Hydrolysis of ATP (on myosin heads) causes myosin heads to
bend; - (Bending) pulling actin molecules;
- Attachment of a new ATP molecule to each myosin head
causes myosin heads to detach (from actin sites).
What is the role of ATP in myofibrils contractions (2 marks)
- (Reaction with ATP) breaks/allows binding of myosin to actin/
actinomyosin bridge; - Provides energy to move myosin head;
Describe and explain how taking creatine supplements and carbohydrate-loading can improve performance of different types of muscle fibres during different types of exercise (5 marks)
- Fast (skeletal muscle) fibres used during
short-term/intense exercise; - Slow (skeletal muscle) fibres used during
long(er)-term exercise; - Creatine used to form phosphocreatine;
- (Phosphocreatine) combines with ADP to form
ATP; - (Carbohydrate/glucose) stored as glycogen
OR
Glycogenesis; - Glycogen hydrolysed to glucose
OR
Glycogenolysis; - Glucose for respiration;
Increased muscle activity causes an increase in heart rate, describe and explain how (4 marks)
- Increase in CO2 detected by chemoreceptors;
- Send (more) impulses to cardiac centre
OR
Send (more) impulses to the medulla; - More impulses (from centre/medulla) along
sympathetic pathway/neurones/nerves
OR
Fewer impulses (from centre/medulla) along
parasympathetic/vagus pathway/neurones
/nerves; - (To) SAN;
Explain the importance of muscle contraction in an organisms response to their environment
- Muscle contraction allows for movement, enabling the organism to respond to environmental stimuli
- Movement allows for taxis and kinesis responses
- Movement helps the organism find food, escape predators, or adapt to changing environmental conditions
Myasthenia gravis (MG) is an autoimmune disease caused when antibodies bind to box the sarcolemma (postsynaptic membrane) of neuromuscular junctions. This can
weaken contraction of muscles.
Suggest and explain how MG can weaken contraction of muscles. (2 marks)
- Less/no acetylcholine/neurotransmitter
binds to receptor/s; - Less/no depolarisation
OR
Fewer/no action potential(s)
OR
Fewer/no sodium ions enter to reach
threshold;
Mestinon is a drug that inhibits the enzyme acetylcholinesterase. Mestinon can help
in the treatment of MG.
Mestinon can help in the treatment of MG. Explain how. (3 marks)
- Less/no acetylcholine/neurotransmitter
broken down; - (More) acetylcholine attaches to
receptors; - Depolarisation (of sarcolemma) occurs
OR
Action potential(s) produced
OR
(Enough) sodium ions enter to reach
threshold
OR
Fewer/no antibodies attach;
