muscle tissue Flashcards
what does the cytoplasm of muscle cells and fibres contain
actin and myosin - contractile proteins
what are the properties of muscle tissue
- excitability
- contractibility
- extensibility
- elasticity
what are the functions of muscle tissue
- body movements
- stabilising body positions - posture
- moving substances within the body
- generating heat
what are the cytoplasmic organelles of muscle fibres
- plasma membrane - sarcolemma
- cytoplasm - sacroplasm
- smooth ER - sarcoplasmic reticulum
- mitochondria - sarcosomes
what ate the types of muscle tissue
- striated - skeletal and cardiac
- smooth
what is the organisation of skeletal muscle
- each muscle fibre surrounded by endomysium
- groups of muscle fibres form fascicles
- muscle fascicle surrounded by perimysium
- entire muscle surrounded by epimysium
what is perimysium made from
sheath of connective tissue
what is epimysium composed of
dense irregular connective tissue
what is the function of skeletal muscle
moves bones
- moves in voluntary manner - except diaphragm
what are the components of muscle fibres
muscle fibres —> myofibrils —> myofilaments
what is the structure of muscle fibres
- morophofunctinal unit
- long cylindrical mulinucleated syncytium
- nuclei is oval and along cell periphery
- surrounded by basal lamina
what cells differentiate into skeletal muscle
mesenchyme cells - myoblasts
what forms myofilaments
myotubes synthesise the proteins to make myofilaments
how are muscle satellite cells
when part of myoblast population doesn’t fuse and differentiate
what does satellite cells do
proliferate and produce new muscle fibres
where are satellite cells found
external surface of muscle fibres and external lamina
what does the sarcoplasm of muscle fibres contain
general organelles, speical organelles and inclusion
what does the myosyncitium contain
myofibrils creating the biggest part of the sarcoplasm
what are myofibrils composed of
thin actin and thick myosin
what is myosin
fibrillar protein with numerous globular heads
- 15nm thick
- located in dark A band
what is actin
made of G-actin, troponin complex and tropomyosin
what is the function of globular heads of myosin
bind to specific actin binding sites causing a chemical reaction leading for ATP hydrolysis and energy release
what is tropomyosin
a protein of fibrillar structure wound around F actin and binds to troponin
what does TnT do
mediates the connection of troponin to the tropomyosin molecule
what does TnC do
binds the calcium released from sarcoplasmic reticulum at the beginning of contraction
what does Tnl do
if no calcium is bound to TnC the Tnl covers the binding site for myosin on the actin fibre and contraction cannot occur
describe the sliding filament theory
- mutual sliding of actin and myosin filaments
- movement force if given by flexion of head of myosin induced by ATP hydrolysis
- before contract the binding site of actin is covered by troponin-tropomyosin complex
what does the conducting system do
regulation of contraction in skeletal muscles
what are T-tubules
deep tubular invaginations of plasma membrane surrounding myofibrils
- provide fast transfer of stimulus to surface of muscle fibres
what does the sarcoplasmic reticulum do
calcium storage and surrounds each myofibril
where is the terminal cisternae located
flat region of SR addicted to T-tubules
what forms a traids
t- tubules and 2 cisterns of SR
how is calcium involved in muscle contraction
1) membrane of SR depolarises and Ca channels open
2) CA2+ pump is activated which consumes ATP and actively absorbed calcium back into the SR
what supplies muscle fibres
alpha-efferent fibres from multipolar anterior horn neurones of the spinal cord or brainstem
what is a motor unit
single nerve fibre and all its muscle
what is the neurotransmitter at the neuromuscular junction
acetylcholine
what is the motor end plate
chemical synapse where the terminal branch or the axon contact a target muscle cell
what is the enlarged knob of the axon terminal end called
terminal button
that is the system of energy production for muscle tissue
- mitochondria - ATP
- glycogen - storage of energy
- myoglobin - oxygen binding protein, emergency supply
what causes the red colour of the muscle
myoglobin
when there is higher amounts of myoglobin what occurs
longer period of contraction
what are the types of muscle fibres
- type 1 - red oxidative fibres
- type 2a - fast, intermediate oxidative glycolytic fibres
- type 2b - fast, white glycolytic fibres
what are slow, red oxidative fibres
- slow, continuous contractions
- energy from aerobic oxidative phosphorylation
- many mitochondria and abundant myoglobin
what are fast, intermediate oxidative glycolytic fibres
- many mitochondria and myoglobin
- has glycogen
- oxidative metabolism and anaerobic glycolysis
- rapid contractions in short bursts
what are fast, white glycolytic fibres
- few mitochondria and myoglobin
- abundent glycogen
- depended on glycolysis for energy
- rapid contraction but fatigue quickly
what are muscle spindles
stretch receptors in skeletal muscle that detach and change length in muscle
what do stretch receptors do
1) convey length information to CNS via afferent nerve fibres
2) processed by brain as proprioception
3) response of muscle spindles change in length - regulating muscle contraction
what is the structural and function unit of skeletal muscle
muscle fibres
where is involuntary strained muscle found
walls of the heart - myocardium
what is a cardiomyocyte
morphofunctional unit of the cardiac muscle
- long, cylindrical shape - centrally located nucleui
what is the function of the sarcoplasm in cardiac muscle
- contractile system
- conducting system
- supporting system
- system of energy production
describe the contractile system
- end of cardiomyocyte split into branches forming 3D cytoplasmic network
- between cells loose CT has capillary network
what is the conducting system in cardiac muscle
- SR is not well developed
- transverse tubules are wide and forms dvads with sacroplasmic reticulum
what is the supporting system of cardiac muscle
ends of ajacent cardiac cells connect through intercellular junctional complex forming intercalated disks
- provide anchoring for myofibril and permits rapid spread of contractile stimuli
what are the 3 types of intercalated discs
- transverse portion - fascia adherens and desmosomes
- lateral portion - gap junctions
what are the types of cardiomyocytes
- contractile
- conducting
- secretory
what does the conductive system consist of
Sinoatrial node
Atrioventricular node
Atrioventricular bundle (bundle of His)
Purkinje fibers.
what is the cardiac conductive system
collection of nodes and specialised conductive cells that initiate and co-ordinate contraction of heart muscle
where is involuntary non-striated muscle found
- tunica media layer of arteries (except large elastic arteries) and veins
- urinary bladder
- male and female reproductive tracts
- gastrointestinal tract
- respiratory tract,
- ciliary muscle and iris of the eye
- glomeruli of the kidneys - mesangial cell
what is the morophofunctional unit of smooth muscle tissue
smooth myocyte
what are the smooth muscle cells
myocytes - nonstraited and fusiform cells
what is the function of sarcolemmal vesicles/ caveolae
- present along periphery of smooth muscle
- uptake and release calcium
