muscles and joints Flashcards
what type of tissue is muscle and what is its function
- contractile tissue
- essential for movement in animals
what are the three types of muscles
- smooth
- skeletal (also known as striated or voluntary muscle)
- cardiac
what is smooth muscle composed of
- small oval cells
- containing an irregular pattern of contractile protein fibres hence why it appears smooth under a microscope
how is smooth muscle function regulated
- by the autonomic nervous system and is capable of long sustained contractions eg. those in the visceral tissue
where is skeletal muscle found and what is often connected to
- it is widespread throughout the body and often connected to bones
what is skeletal muscle composed of
- composed of cells containing regular arrays of contractile proteins (mainly actin and myosin)
- this gives skeletal muscle its striated (stripy) appearance
what is the skeletal muscle controlled by
- the somatic nervous system and is capable fo short, vigorous contractions
what is the cardiac muscle composed of
- only found in the heart
- branched muscle fibres
- joined by intercalated discus (desmosomes and gap junctions) - allows movement of ions
- central placed nucleus
what are the length of contraction for cardiac muscle and what is it controlled by
- short duration contraction
- intrinsic contraction modified by autonomic nervous system - has its own rhythmic beat
what are the three layers of connective tissue in skeletal muscle
- epimysium - around entire bulk of muscle
- endomysium - around individual muscle fibres
- perimysium - around fascicles
endomysium fuses with tendon
tendon fuses with bone
what are muscle fibres largely composed of and what are they made up of
- composed of microfibrils
- made up of actin and myosin rich microfibrils
what is each microfibril made up of
- myofilament (form functional unit)
- myofilaments contain actin and myosin filaments in specific arraignments)
what are the thick and thin filaments
- myosin = thick filaments
- actin = thin filaments
what are the two types of muscle fibre
- type 1 (slow twitch)
- type 11 A and B (fast twitch)
properties of slow twitch fibres
- contains lots of mitochondria and capillaries
- produces large amounts of energy slowly by aerobic metabolism
- resistant to fatigue
- contains myoglobin
- slow contraction
properties of fast twitch fibres type 2A
- contain small amounts of myoglobin
- more extensive capillary network
- mixture of oxidative and glycotic (anaerobic metabolism)
- contract rapidly
- some resistance to fatigue
properties of type 2b fibres
- uses glycotic (anaerobic metabolism)
- few capillaries, mitochondria
- little myoglobin
- produces large amounts of energy quickly therefore rapid contractions
- early fatigue
how do muscles contract
- muscle contraction occur when actin and myosin fibres making up the sarcomere slide over each other causing the sarcomere to shorten and therefore the whole muscle fibre
- the shortening of the sarcomere form the striations
what are the dark bands called
- A bands (thick and thin filaments overlapping)
what are the light bands called
- I bands (made of actin)
what is one sarcomere
- z disk to z disk
what is found between the microfibrils
- mitochondria and sarcoplasmic reticulum
what is the M band
- myosin held together in centre
what type of muscle fibres make up the postural muscles
- mainly type 1
what type of muscle fibres make up the arms, jaws, muscle of the eye
- mainly type 2A and type 2B
what is a motor unit
- all muscle fibres innervated by a single motor neurone
what does the ratio of motor nerves to muscle fibres determine
- level of control
- high ratio will innervate lots of muscle fibres
what is the force of muscle contraction controlled by
- the number of activated motor units
how many types of muscle fibres does one motor unit contain
- only contains one type of muscle fibre - to meet the functional requirement, recruitment of different types of muscle fibres occur
are all motor units always in use
- no when some are fatigued, others can be recruited to maintain contraction
what control system do muscles have
muscle spindles
what detects change in length of a muscle
- sensory receptors within the belly
how do muscle spindles work
- muscle spindles - detects change in muscles
- muscle spindles contain intrafusal fibres that have their own innervation distinct from extrafusal fibres
- sensory neurones from muscle spindles send information to the spinal cord and cerebellum (proprioception)
as muscles acts what are there alterations in
- length
- tension
- strength of contraction
where is the synovial joint formed
- formed between two or more bones enabling movement
what does the shape of bone determine
- mobility and stability
what is good fit
- stable joint but loses some mobility
what is poor fit
- very mobile but unstable
what are the 5 characteristic features of synovial joints
- articular cartilage
- joint (synovial) cavity
- synovial fluid
- articular capsule
- reinforcing ligaments
why are boys covered by hyaline articular cartilage
- for cushioning and smooth movement
why is the synovial cavity filled with synovial fluid and where is secreted from
- lubricates the joints and role is shock absorption
- secreted by synovial membrane on non articular surfaces
where is the synovial fluid retained
- in joints by capsule of connective tissue
- capsule is strengthened by ligaments to limit movement and strengthen joints
what happens if a joint is moved too far in wrong position
- stretch receptors fire and position readjusted
- if position is not readjusted, pain endings will fire to reinforce warning
- if still nothing done ligaments may stretch to stop dislocation of joint
