What are the functions of muscle?
The functions of muscle are:
Generate force and movement
Allow us to express and regulate ourselves
What are the 3 types of muscle?
The 3 types of muscle are:
What kinds of muscle is striated?
Skeletal and cardiac muscle is striated
What can you say about the nucleus of skeletal muscle?
Skeletal muscle is multinucleated
What do myoblasts not do?
Myoblasts do not replace cells if they are damaged
What does skeletal muscle form from?
Skeletal muscle forms in utero from mononucleate myoblasts
What happens to skeletal muscle during growth?
During growth skeletal muscle increases fibre size
What is muscle?
Muscle is bundles of fibres enclosed in connective tissue sheaths
What are muscles attached to the bone by?
Muscles are attached to the bone by tendons
What do satellite cells do?
Satellite cells replace cells during injury
What cell replaces cells during injury?
Satellite cells replace cells during injury
How do satellite cells replace cells during injury?
Satellite cells differentiate to form new muscle fibres
What can muscle fibres that cannot completely recover undergo?
Muscle fibre that cannot completely recover can undergo hypertrophy to compensate
What is hypertrophy?
Hypertrophy is the increase in size of skeletal muscles due to the growth of its component cells
What is striated muscle?
Striated muscle is muscle tissue that is marked by transverse dark and light bands
What does the structure of striated muscle look like?
What are the compartments of myofibril?
Myofibril is split into:
What is a sacromere?
A sacromere is the basic unit of striated muscle, between the Z lines
What is the sarcomere composed of?
The sarcomere is composed of:
Myosin filament (thick)
Actin filament (thin)
What does the structure of a sacromere look like?
What are the thick myosin filaments surrounded by?
The thick myosin filaments are surrounded by a hexagon of thin actin filaments throughout the structure
What is contraction caused by?
Contraction is caused by sliding filaments
What happens when the muscle is shortened compared to relaxed?
When the muscle is shortened:
A band is unchanged
I band is reduced
H zone is reduced
What causes the muscle to contract?
The cross bridge causes the muscle to contract
What does the cross bridge contain?
The cross bridge contains:
Actin binding sites
ATP binding sites
Describe the process of the cross chain cycle?
The process of the cross chain cycle is:
- Cross bridge binds to actin
- [Ca2+] rises
- Cross bridge moves
- ATP binds to myosin causing the cross bridge to detach
- Hydrolysis of ATP energizes the cross bridge
Why does an increase in [Ca2+] cause the cross bridge to move?
An increase in [Ca2+] causes the cross bridge to move because:
Tropomyosin partially covers myosin binding site, which is held in position by troponin
Calcium binds to troponin, changing conformation pulling tropomyosin away
ATP can bind to myosin
What is tropomyosin partially covering myosin binding site and being held in position by troponin known as?
What happens when calcium is removed?
When calcium is removed the myosin binding site becomes blocked by tropomyosin again
What is excitation/contraction coupling?
Excitation/contraction coupling is the conversion of electrical stimulis into a mechanical response
What is the process of excitation/contraction coupling?
The process of excitation/contraction coupling is:
- Muscle action potential propogated
- Ca2+ released
- Binds to troponin, removing blocking action by tropomyosin
- ATP binds to the myosin of the cross bridge
- Ca2+ taken up
- Tropomyosin blocking action restored
What is a motor unit?
A motor unit is a motor neuron and a collection of muscle fibres working together
How may muscle fibres within a motor uni be arranged?
Muscle fibres within a motor unit may be scattered throughout the muscle
What is tension?
Tension is the load exerted by a muscle
What is load?
Load is the force exerted on a muscle
What is isometric?
Isometric is a contraction with a constant contraction length
What is an example of a sport that uses isometric contraction?
Weightlifting is an example of a sport that uses isometric contraction
What is isotonic?
Isotonic is a contraction with a shortening muscle length
What is an example of an isotonic contraction?
An example of an isotonic contraction is running
What is lengthening?
Lengthening is a contraction with increasing length
What is an example of a lengthening contraction?
An example of a lengthening contraction is sitting down
What are twitch contractions shown by?
Twitch contractions are shown by:
Single AP → Muscle fibre → Twitch
What is the latent period?
The latent period is the time before excitation contraction starts
What is the contraction time?
Contraction time is the time between the start of tension and the peak of the tension
What does muscle fibre contraction time depend on?
Muscle fibre contraction time depends on:
Which type of contaction has the shorter latent period but the longer contraction event?
Isometric contraction has the shorter latent period by the longer contraction event
What happens as load increases?
As load increases:
Contraction velocity decreases
Distance shortended decreases
What is tetanus?
Tetanus is muscle spasms because AP is only 1-2ms long but the twitch lasts for up to 100ms so more APs may occur in this time, causing summation of APs
Why is tetanus tension greater than twitch tension?
Tetanus tension is greater than twitch tension because [Ca2+] never gets low enough to allow reblocking of myolin binding sites
What does the length-tension relationship look like?
Why does the length-tension relationship look the way it does?
The length-tension relationship looks like this because:
Less overlap of filament is less tension
Too much overlap and filaments interfere with each other
What is the optimal length (lo)?
The optimal length is the muscle length for the greatest isometric tension
What does movement around a limb require?
Movement around a limb requires 2 antagonistic groups of muscles:
Why are muscles arranged in a lever system?
Muscles are arranged in a lever system to amplify muscle shortening velocity to produce increases maneuverability
Do muscles exert or support muscle force?
Muscles tend to exert more force than they support