Muscles Flashcards
What are muscles made up of
Microfibrils
What is actin
Thin two stranded layer twisted around eachother
What is myosin
Thicker consists of long rod shapes tails with bulbous heads that project to the side
What parts of myosin are important for muscle contraction
Myosin heads and tails
What are the three bands
A I and H
What is sarcoplasm
Surrounds muscles
What is sarcomere
Plasma membrane
What do myosin heads contain
Adp
What moves out the way to allow myosin heads to bind to actin
Tropomyosin
What colour are the bands
I = light
H = grey
A = dark
What is contained in the different bands
I = only actin
H = part of A band (thats only myosin)
A = actin and myosin
What happens when there is no action potential
Calcium channels close
NO more Ca diffuses in
Continues being actively transported out
No more calcium in sarcoplasm, troponin will move back into binding sites (no muscle contraction)
What are thick filaments and thin filaments made up of
Thick = myosin
Thin = actin
What protein molecules are myosin and actin made from
Myosin = fibrous protein molecules with globular heads
Actin = globular protein molecules
What is tropomyosin made of
Two actin chains twisted together
Describe the sliding filament model of muscle contraction process
1) Action potential arrives from the sarcoplasmic reticulum
2) Ca+ bind to troponin molecules stimulating them to change shape
3) Troponin and tropomyosin proteins to change position on actin filaments
4) Myosin binding sites are exposed on actin molecules
5) Globular heads on myosin bind with sites, forming cross-bridges between two types of filament
6) Cross bridge formation causes myosin heads to spontaneously bend releasing ADH pulling actin filaments towards the centre of the sarcomere
7) ATP binds to myosinn heads causing it to change shape so myosin heads release from actin filaments
8) Enzyme ATP hydrolase to hydrolyse ATP -> ADP, inorganic phosphate moves myosin heads back to their original position
9) Myosin heads bind to new binding sites on actin filament moving close to Z disc
10) Pulls the actin filaments closer to the centre of the sarcomere so the sarcomeres shorten
11) ATP binds to myosin heads to detach again
Why is ATP needed for muscle contraction
To return myosin heads to their original position that causes actin filaments to slide
Return Ca+ back into sarcoplasmic reticulum (active transport)
Explain the sliding filament model simply
1) Action potential reaches muscle cell
2) Ca+ diffuse in and bind to troponin
3) Troponin move out the way of myosin binding sites on actin
4) Myosin heads bind to the binding sites on action using ADP
5) Myosin heads change angle causing te actin and myosin to slide past each other
6) ADP is swapped out for ATP so myosin heads detach from the binding site
7) ATP hydrolysed into ADP releasing energy change the angle of myosin heads back to their original position
8) Cycle continues as long as there is an action potential
When do muscles only have a small amount of atp
At rest
Mitochondrisa function in muscle fibres
Aerobically respire to produce ATP but this is slow
Use phosphorylation to produce ATP from ADP + Pi
What is phosphocreatines use
Stored by muscles used for rapid production of ATP
Equation for the production of ATP from phosphocreatine
ADP + phosphocreatine -> ATP + creatine
Phosphate ion from phosphocreatine transferred to ADP
Two types of muscle fibres
Fast and slow fibres
Fast muscles contraction
-Contract rapidly
-Myosin heads bind and unbind from actin binding sites faster than slow
-Rapid contraction-relaxation cycle = need large amounts of Ca+ ti stimulate contraction
Fast muscles ATP
Use a-naerobic respiration for ATP
Fast muscles respiration
Suited for short bursts of high intensity activity because they fatigue quickly -> produce lactic acid from anaerobic respiration
Fast muscles blood supply
Fewer capillaries
Blood containing glucose and oxygen flow through capillaries
So have slow O2 and glucose supply for aerobic resp
Fast muscle fibres myoglobin and what myoglobin is
Lower amounts of myoglobin
Myoglobin = similar to haemoglobin
Myoglobin stores O2 in muscles and increases rate of O2 absoprtion in capillaries
Slow muscles respiration
Aerobic respiration for ATP
Fatigue less = less lactate produces so easier for endurance
Muscle examples of slow fibres
Human back muscles = contract for long periods in order to keep skeleton erect when standing or sitting
Wings in geese/ legs of wolves
Slow muscle fibres blood supply
Denser network of capillaries
Blood containing glucose and oxygen flow through capillaries
Short diffusion distance and good supply of O2 and glucose for aerobic resp
Myoglobin in slow muscle fibres
High amounts of myoglobin, haemoglobin and mitochondria
Increase rate of O2 supply, O2 absorption and aerobic respiration
Proportions of muscle fibres
Most have equal amount of slow and fast
Some have higher of certain type enhancing performance on specific sport
Athletes train for short burst high intensity activities = higher proportion of fast muscles than slow in arms and legs
Endurance activities = high slow than fast fibres in arms and legs
What gets larger when someone trains their muscles
Size of fibres increase not number of fibres
What happens to calcium ions after long period of exercise
Decrease in availability of Ca+
Why are Ca+ essential in exercise
Move tropomyosin away from actin-binding sites
Activating ATPase
When is lactate produced
After repeated contractions
Anaerobic respiration provides supply of ATP for muscle contract, producing lactate as a waste
What affect does lactate have on muscles
Lowers PH affecting contraction of fibres
what microscope is used to observe skeletal muscles
Optical microscope
How does an optical microscope work
Light directed through thin layer of biological material supported on a glass slide
Light focused through several lenses so an image is visible
Magnifying power of microscope can be increased by rotating the higher power objective lense into place
What word is used to describe muscle action and why
Antagonistic = muscle pulls in one direction at a joint and the other muscle pulls in the opposite direction
How do muscles maintain posture
By isometric contraction
Antagonist muscles both contracting at joints to keep joint at a certain angle
What is a striated muscle made of
Muscle fibres
How are muscle fibres specialised
Each muscle fibre contains:
-arrangement of contractile proteins in cytoplasm
-surrounded by cell surface membrane
-many nuclei
Name the different parts of the muscle fibre
Cell surface membrane = sarcolemma
Cytoplasm = sarcoplasm
Endoplasmic reticulum = sarcoplasmic reticulum
Name of sarcolemme that folds in from its outer surface
T-tubules that run close to the SR
What does the sarcoplasm contain
Mitochondria = atp for contraction
Myofibrils = bundles of actin
Membrane of sarcoplasmic reticulum
Contain protein pumps to transport calcium ions into lumen of sr
Adaptions of slow twitch fibres
-Large myoglobin store
-Rich blood supply of blood vessels to deliver oxygen and glucose for aerobic respiration
-Numerous mitochondria = atp
Fast twitch fibres adaptations
-Thicker and more numerous myosin filaments
-High concentration of enzymes = anaerobic respiration’s production of ATP
-Store of phosphocreatine = ATP from ADP in anaerobic resp
Whats a neuromuscular junction
Motor neurone meets skeletal muscle fibre
What happens when a nerve impulse is received at the neuromuscular junction
1) Synaptic vesicles fuse with the presynaptic membrane and release acetylcholine
2) Acetylcholine diffuses into postsynaptic membrane (muscle fibre) altering its permeability to Na+
3) Na+ enter rapidly depolarising the membrane
What happens to the acetylcholine at neuromuscular junctions
1) ACh is released by synaptic vesicles and diffused into the postsynaptic membrane
2) Acetylcholine then broken down by acetylcholinesterase to ensure that the muscle is not over-stimulated
3) Resulting choline and ethanoic acid (acetyl) diffuses back into the neurone where its recombined into acetylcholine using ATP from mitochondria
Similarities between neuromuscular junction and cholinergic synapse
Neurotransmitters transported by diffusion
Receptors that on binding cause influx of Na+
Use sodium potassium pumps to repolarise axon
Use enzymes to breakdown the neurotransmitter
What changes to the sarcomere when muscles contract
I band = shorter
Z line = move closer together
H zone = shorter
