Muscles and Tendons Flashcards
Name the 3 kinds of muscle in the body
What is each type - voluntary - where is it found?
- smooth (involutory) - visceral muscle
- striated (voluntary) - skeletal muscle
- cardiac - a type of striated muscle specific to the heart
Describe the structure of striated (skeletal) muscle
- Muscles consist of many fascicles which are enclosed in epimysium (connective tissue)
- Fascicles consist of many muscle fibres which are bound together in perimysium (connective tissue)
Describe muscle fibres structure
- Formed by fusion of many myoblast cells - so have many nuclei
- packed with contractile myofilaments in an interlocking arrangement - so nuclei also pushed to cell edge
- many mitochondria for energy needs
Myofilaments - Describe what myosin does
- binds to site on thin actin filament
- myosin heads flex and pull actin
- myosin heads release and bind to next site along
- in this way myosin ratchets along actin
What is a sarcomere?
- A sarcomere is the distance between the two z-disks
- the sarcomere is the functional unit of muscle
What tissues make up the fascia?
- the epimysium
- the perimysium
- endomysium
What does the perimysium cover?
- the fascicle
what does the epimysium cover?
- the muscle
What does the endomysium cover?
- the muscle fibre
where do arteries enter muscle?
- one or more may enter the muscle belly
What can the fascia do?
- they can merge at the end of the muscle belly and continue as tendon or aponeurosis which attaches bones or other muscle bellies
- muscles can also attach directly to bone (the periosteum) where collagen fibres continue as sharply fibres
What do muscle contractions do to veins and capillaries?
- muscle contractions massage capillaries and veins but sustained mass muscle contractions may inhibit circulation
Describe the nerve in the muscle?
- enters with the blood vessels and branches
- multiple neurone types - motor, vasomotor, sensory
- motor neurones generally from the ventral horn of spinal cord
- motor neuron + fibres it innervates - motor unit
What is the H-zone?
- just myosin on its own
What is the A-band?
- full length of myosin including overlapping actin
What is the I-band?
- just the actin filament on its own
What is the general pattern for muscles and tendons?
- muscle is proximal
- tenons are distal
- proximal tendons tend to be shorter and fatter, distal tendons are longer
Describe the structure of a tendon?
- composed of collagen fibre bundles in regular arrangement
- arranged in primary, secondary and tertiary collagen fibre bundles
- great tensile strength = transmit forces
- elastic energy store, crimped collagen microanatomy
- low metabolic needs - poor vascularisation but slow to heal
Roles of skeletal muscle?
- joint movement
- prevent joint movement - stabilisation
- postural control
- generating heat - shivering
Role of Cardiac Muscle?
- Maintaining a cardiac rhythm
Roles of smooth muscle?
- continence
- mastication
- swallowing
- digestion
- birthing
- vasodilation/ constriction
- bronchodilation / constriction
- pupil dilation / constriction
Name skeletal muscles that DON’T connect bones to bones!
- sphincters
- circular muscles (orbicularis around the eye)
- cutaneous muscles
- muscles joining other muscles
What force can muscle generate?
- can only generate pull (tension) forces
Muscle fibre contraction can occur as ..
- muscle shortens (concentric contract)
- muscle lengthens (eccentric contraction)
- muscle stays the same length (isometric contraction)
What can muscles act as?
- motors
- breaks
- springs
- stabilisers (sometimes called fixators or struts)
What is an agonist?
- An agonist or prime mover is responsible for a joint movement
What is an antagonist?
- an antagonist is capable of opposing that movement
what are synergists?
- other muscles that help or modify the action of an agonist without directly contributing to the action
- for example, eliminating unwanted side effects
what is a muscle origin?
- most proximal or central
what is a muscle insertion?
- distal or peripheral
Muscle design is closely linked with function what needs to be considered?
- size
- shape
- number of bellies
- tendinous origins or insertions
- architecture
What is force?
- the push or pull on an object with mass, that causes it to change velocity
what is work?
- the application of force along a displacement
Work equation:
force x change in distance
What is power?
- the rate of performing work
Power equation:
change in work / change in time
speed
change in distance /change in time
What is muscle force proportional to?
- muscle fibre cross- sectional area
Describe parallel-fibred muscles
- fibres run parallel to muscle line of action
- little to no external tendon
- sarcomeres are all in series in the fibres, so muscle can shorten more
- fewer fibres in cross section so lower force
- same potential for muscle work
- can move joints through larger range of motion
- potential to increase speed of joint movement
Describe pennate-fibred muscles
- shorter fibres attach at an angle to the muscles line of action
- often insert via an external tendon to the skeleton
- increased fibres in cross section so higher ability to generate force
- some loss in force transmission along the kind of action
- less muscle shortening overall (fewer fibres in series)
- to generate the same force, less energy is needed (better force economy)
Describe cardiac muscle
- only found in the heart
- striated
- short branching
- single central nucleus, many mitochondria
- connected by intercalated discs
- involuntary
describe smooth muscle?
- organ and vessel walls, iris
- no striations
- single nucleus
- long contractions, low energy, low force
- involuntary
Describe tendons
- dense regular connective tissue primarily composed of collagen
- connect muscle to bone
Describe ligaments
- dense regular connective tissue primarily composed of collagen
- connect bone to bone
What are the different types of ligaments?
- white ligaments, rich on collagen fibres, not very elastic, around the knee
- yellow ligaments, lots of elastic fibres ( spine, pelvis, nuchal ligament
What are the roles of tendons?
- transmit force to skeleton (joins muscle to bone)
- minimising distal limb mass
- elastic energy storage
- power amplification
- energy absorption
How can tendons be used in energy recovery?
- can store and release elastic energy (up to 93%)
- reduced mechanical work and cost of locomotion
How can tendons be used in force economy?
- long tendons allow for short muscle fibres
- less energy cost developing muscle force
How can tendons be used in power amplification?
- muscles can contract slowly and forcefully to load tendon
- stretched tendon can recoil faster that muscle can contract
