MUSCLE TISSUE Flashcards
what is the function of skeletal muscle?
Skeletal movement Maintenance of posture Support of soft tissues Sphincter function Thermoregulation
what is skeletal muscle made of?
Large multinucleated cells (fibres)
what are Large multinucleated cells (fibres)?
fused myoblasts surrounded by loose CT containing collagen and elastin fibres, which merge into the tendon at sites of muscle attachment.
what are muscle fibres?
non-dividing cells surrounded by satellite cells
what is the cell memb of skeletal muscle called?
sarcolemma
what are satellite cells?
undifferentiated, muscle stem cells with regenerative potential
what is the function of satellite cells?
Function as a reserve that can be activated to replace or increase muscle as necessary
what is the appearance of skeletal muscle?
striated microscopic appearance and needs nervous innervation
what is skeletal muscle also known as?
striated voluntary muscle
what is the composition of skeletal muscle?
Muscle fibre
Bundles of 1 form muscle fascicle
Bundles of 2 form muscle
what is a muscle fibre surrounded by?
(fused myocytes)
by endomysium
what is a muscle fascicle surrounded by?
by perimysium
what is a muscle surrounded by?
by epimysium
what is found inside the muscle fibre?
myofilaments
Bundles of 1 form myofibrils
what are myofilaments made of?
thin filaments (actin, tropomyosin, troponin) thick filaments (myosin)
what are the myofibrils surrounded by?
sarcoplasmic reticulum
what are transverse tubules?
form tunnels through muscle fibre and encircle myofibrils. Conduct AP for the initiation of contraction.
what is a sarcomere?
Smallest functional unit of muscle
what are Z lines?
bound sarcomere; formed by protein that supports the thin filaments
what are I bands?
light in appearance; consist of thin filaments
what is the A band?
dark in appearance; consists of thick filaments (with or without thin filaments)
what is the M line?
consists of proteins supporting the thick filaments
what is the H zone?
contains thick filaments only
what does the zone of overlap of the sarcomere contain?
contains both thick and thin filaments
Contraction achieved by sliding motion between the thick and thin filaments
what is the appearance of cardiac muscle?
striated
what are the characteristic of cardiac muscle?
Only found in heart (cardiocytes)
Not fused (single nucleus); branched
Smaller than skeletal muscle fibres
what are found at the ends of cardiocytes?
intercalated discs
what is found in intercalated discs?
gap junctions and desmosomes
what does the stabilisation of tissue allow?
exchange of ions and small molecules allowing spread of AP
do the cardiocytes regenerate?
no, which is why heart muscle can slowly degenerate with age, leading to various medical problems
is there any reliance on nervous innervation wth cardiac muscle?
no, pacemaker cells stimulate contractions - nervous system can only alter rate of activity
what is cardiac muscle known as?
striated involuntary muscle
where is smooth muscle found?
Cardiovascular system (blood vessels) Skin (hair movement) Respiratory system Digestive Urinary Reproductive
what is the structure of smooth muscle?
Muscle cells small, slender, tapering Single nucleus (not fused)
are sarcomeres present in smooth muscle?
no, Actin & myosin filaments scattered throughout the cell
what are the thin filaments anchored to?
dense bodies, which are located underneath the cell memb
is smooth muscle capable of regeneration?
yes, Smooth muscle cells are capable of division
Either trigger own contractility or innervated
what is smooth muscle known as?
non-striated, involuntary muscle
