Muscle histology wk3 Flashcards
(26 cards)
what are muscle functions?
- survival (heart beat)
- movement
- moving substances through the body
- for speech/communication, chewing, posture, circulation, urination
overview of skeletal muscle
- voluntary, under conscious control - somatic nervous system
- specialised for rapid contraction of short duration
- striated
overview of smooth muscle
- found in vessels, GI tract, uterus and bladder
- involuntary
- non-striated
overview of cardiac muscle
- found only in heart (myocardium)
- involuntary
- rate and force of contraction regulated by ANS
- striated
how do you identify cardiac muscle?
central nuclei, broader, more dense areas that split up cardiomyocytes
what is the structure of skeletal muscle?
- muscle is made of several fascicles surrounded by a sense collagenous sheath - epimysium
- fascicles is surrounded by loose collagenous tissue - perimysium
- fascicles is made of many individual muscle cells/fibres
- these calls are held together by supporting tissue endomysium
histology of a muscle spindle
extrafusal muscle fibres - cause contraction
intrafusal muscle fibres (smaller) - surrounded by capsule
sensory nerve wraps around to detect amount of stretch
important in muscle tone and stretch reflexes
structures of inside muscles
muscles ==> fascicles ==> muscle fibres ==> myofibrils
what are dark and light bands in muscle fibres?
dark - both actin and myosin (thick filaments) present
light - only actin (thin filaments) present
what is the repeating functional unit of a myofibril?
sarcomere
what is sliding filament theory?
- under control of action potential
- sarcomere shortens so whole muscle shortens but filament does not
define sarcoplasm
cytoplasm of muscle cells
define sarcolemma
plasma membrane
what is sarcoplasmic reticulum?
derived from SER acts as a calcium reservoir. found between t tubules
what are t tubules?
- formed by invagination of sarcolemma and is around each myofibril
- forms internal network
- allows all myofibrils to contract at once as the depolarisation spreads rather than slowly travelling from area to area
what is the neuromuscular junction?
- presynaptic membrane filled with synaptic vesicles filled with ACh neurotransmitter
what is the structure of the tongue?
- tongue has muscle fascicles in different orientations
- transverse sections (chunks) and longitudinal sections (longggg)
- some perimysium between fasciculi
- other tissue includes adipose, glandular tissue, blood vessels and nervous tissue
what are mitochondrial assays?
- assays demonstrate the activity of mitochondria within muscle fibres
- dark:aerobic fibres, type 1 (slow twitch)
- grey: intermediate fibres type IIA (fast twitch)
- light: anaerobic fibres type IIB (fast twitch)
overview of type I/slow twitch (aerobic)
- large amounts of mitochondria and myoglobin
- smaller diameter, rich blood supply
- fibres maintain continuous contraction
- for muscles used all the time e.g. posture
overview of type IIB/fast twitch (anaerobic)
- contracts more rapidly due to faster myosin
- little mitochondria/myoglobin (white)
- glycogen - glycolysis
- for muscles for intense but sporadic contraction - extra-ocular muscles
overview of type IIA/fast twitch (intermediate)
- more mitochondria/myoglobin (red)
- aerobic and anaerobic respiration
where is nicleus in cardiac muscle ?
central position
what are intercalated discs?
- contains gap junctions, desmosomes, adhering junctions
- all rapid spread of contractile stimuli
- allow physical and electrical connections
- many mitochondria present
- when one cardiomyocyte contracts, so does the next one
What do smooth muscle cells have?
- single central nucleus
- spindle shaped
- non striated - arrangement of sarcomeres are in separate directions
- cells connected by gap junctions
