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)