Muscle Flashcards
Esophageus 3 different portion. Skeletal is…
First portion
Can you detect striations in skeletal muscle cross section?
No
Skeletal muscle…nuclei?
Multi nucleated. Syncytial - beneath plasmolemma
Origin of skeletal muscle?
Myoblasts - mononuclear, undifferentiated, no myofibrils
Form myotubes - differentiate - organelles expressed
Satellite cells in muscle fibres?
And in cardiac muscle
Surround muscle fibre. Quiescent myoblasts - fuse - myoblasts - myotubes - replace lesions
No satellite cells - not repair after dmg
What surrounds groups of muscle fibres?
CT
Sarcomere proteins?
Titin - thick fil correct arrangement at m line
Nebulin - maintain correct length of actin
Actinin - attach actin fil to z line
G actin to f actin
Req atp and mg2+ and k+
Polymerisation
Troponin tic
T - bind to torpomyosin
I - bind to actin
C - bind to calcium
Myosin head(2)
2 peptides
Active site - attach to actin filament
Desmin, plectin, ab crystallin, a-actinin
Desmin - int filament inserted into costameres
Plectin - connect adjacent desmin
Ab-crystallin - heat shock protein - protect desmin from stress related damage
A-actinin - anchor actin to z-disk
Dystrophin and mutation
Linked sarcolemma to actin
Mutation - muscular dystrophy
Vital in cell stability
M line protein function and names? And em line?
Maintain correct arrangement of myosin filament
Myomesin, m protein, schlemin
Electron dense line
Sliding filament mech
Atp bind to myosin head, break cross bridge.
Atp hydrolysis myosin head 90
Myosin bind to actin. Release adp + pi 45* angle
Rigor mortis?
And why?
Stiffening muscle after death.
24/48 hr muscle after muscle proteins broekn down. Allows muscle to relax.
No oxy, no atp. Atp not bind to myosin head
Smooth muscle contains specifically different from skeletal and cardiac muscle?
Dense bodies.
Greater elasticity.
Larger tension curve
Sarcoplasmic reticulum. Triad? And where is central portion of triad?
Where located?
2 terminal cisternae of sarcoplasmic reticulum 1 t tubule
H band central portions between 2 triads
Triad located at a-i junction
Depolarisation of pm of t tubule pm
Ca2+ channels move. Calcium released. High to low conc gradient. Ca bind to TnC. Cause tropomyosin to move. Expose myosin head binding sites
Nmj and toxins(4)
Neuron + muscle cell - synapse.
Large no of infoldings on post synaptic membrane
Toxins (4)-botulinum - block rel of ach
Curare - ach receptor block
Neostigmine - prevent removal of ach - used against curare
Neurotoxins - ach receptor block
Disease of nmj?
Myasthenia gravis - autoimmune attack ach receptors - lost
Different types of skeletal muscle fibres?
Red slow twitch - type one
Intermediate - pink type 2a
White - type 2 b fast twitch
Which stain to differentiate between skeletal muscle fibres?
Succinate dehydrogenase. Stains mito. Slow twitch - greater amount of mito
Red slow twitch muscle fibres
High no of mito. Low glycogen store - completely borken down due to aerobic. Large no of capp. Myoglobin. Resistance to fatigue. Slow sustained contractions.
Found in postural and axial muscle of skeleton
Pale fast twitch muscle fibres?
Low myoglobin. Low mito. Low capp. High glycogen. Easy fatigue due to lactic acid production. Upper limps, digit muscle, extrinsic ocular muscles.
Fastest level of myosin head hydrolysis
Intermediate
Lower limbs. Contract similar to fast twitch. High no. Mito, myoglobin. Store glycogen and anaerobic respiration
Hypertrophy and stimulated by(3)
Increase in muscle size. Increase in no of filaments.
Resistance training. Testosterone. Anabolic steroids
Atrophy and how occur!
Muscle cells smaller - reduction in muscle size
Pathology - removal of nerve, immobility, lack of use
Cardiac muscle tissue. Innervation? What cells and what Connect by?
Autonomic nervous system
Myocardium - heart contraction (cardiomyocytes) - joined by junctions (intercalated disks)
Numerous cylindrical cells arranged from end to end
Heart layers?
Pericardium - serosa cavity - epitcardium - myocardium - endocardium
Nuclei of cardiac?
Central, maube multiple
Cross section of cardiac muscle
Some nucleus seen
Striated
Granules
Presence of myofibrils
Cardiac cells, biconical juxtanuclear region contains
Mito, lipofuscins, golgi, glycogen, grangles
Cardiac muscle granules contain?
Atrial natriuretic factor
Brain natriuretic factor
Effect sodium secretion in kidney. Response to high blood bp.
Inhibit renin by kidney and Aldesterone by adrenal cortex
Inhibit sm contraction
What happens during heart failure of levels of BNP
Increase
Cardiomyocytes 2 features?
Elongated (100um) Rounded nucleus (maybe multiple)
What tissue surrounds cells and contains?
Connective tossue.
Bv provide vascularisation to avascular cardiac bundle
Transverse and lateral portion of intercalated disks?
Transverse - mascula adherens(desmosomes), fascia adherens (cadherin and catenins) strong adhesion
Longi - gap junction - ca2+ movement
Intercalated disks connect cells mechanically, electrically, chemically - contracts cell like single mass
Cardiac muscle - what does adherens junction do?
Bind actin at z lines
Cardiac muscle - endomysium?
Rich capl network - ct bv cardiomyocytes
How to differentiate between sm and cardiac muscle in cross section?
Different morphology of cytoplasm.
Sm cyto - homogenous
Cardiac - granules/myofibrils
Cardiac and skeletal muscle nucleus?
Skeletal periphery
Cardiac at nucleus
Diads in cardiac muscle?
1 t tubule 1 sr larger than in skeletal muscle
At z lines and no AI junctuon
Heart contraction?
Purkije fibres - modified muscle cells (less abundant contractile myofibre) not specialised for contraction. SAN AVN VENTRICLES
Between myofibrils?
Inaddition to juxtanuclear mito, large mito between myofibrils and glycogen granules
Diads less numerous in?
Cardiac atrial muscle
Cardiac muscle cells injury and repair
Injury to cardiac muscle. Loss of cells - replaced by fibrous ct - cardaic function lost at injury - myocardial infarction
Cardiac cells divide?
0.1% of cardiac cells are able to divide
Smooth muscle thin filaments
Actin, troponin, calponin, caldesmon
Sm thick filaments
Myosin.
Side polar thick filament.
No central bare zone.
Bare zone at ends form tapered ends.
Calponin and caldesmon are?
Actin binding proteins (ABP)
Block myosin binding site
Sm. Innervation. Shape of cells. Any striations, why? When do actin and myosin interact?
Autonomic nervous system
Elongated and fusiform
No transverse striations - fewer myofibril
Actin and myosin only interact when contract
Sm cells surrounded by?
Basal lamina and supported by ct
Relation of sm cells?
Thinner aspect of one cells with thicker aspect of another cell
Cross section of sm cells?
Depending on where cut.
Centre -> able to see nucleus.
Where diameter largest
Where sm found?
Muscularis externa of Hollow organs.
Ovary medulla. Gi tract. Cillary process of eye. Wall of arteries and veins. Pre-capp sphincters, iris of eye.
Si, li - innner circ outer longi
Urinary tract - inner longi outer circ.
Urinary bladderr, ureter 3 layers - inner longi, middle circ, outer longi
Dense bodies are located?
Sm. Below sarcolemma, a-actinin binds actin and tropomyosin
No troponin.
Dense bodies act as sm z-lines
Sm int. Filaments
Vimentin and desmin
Help with contraction
Pulling cell ends
Shortening cell
Sm has no?
However does have? And where found? And what function?
No myofibrils, no striations,
However many infoldings of sarcolemma - caveolae -> in cardiac and sm.
Act as t tubules.
Sm - calveolae (5)
Integral membrane proteins. Sm cardiac muscle membrane - caveolin 3 Non receptor endocytosis Closely associated with ser Regulation of contraction and ca
In terms of innervation.
2 types of sm
Single unit - one axon innervates all sm in area. Therefore spread via gap junctions
Multiple unit - group of sm cells - innervated by many axons.
Autonomic neuron varicosity?
Contains NET
Sm contraction steps?
Ca released. Bind to calmodulin. Activates myosin light chain kinase. Phosphorylation of light chain on myosin head. Expose heavy bind - therefore exposed actin filament binding site
Actin myosin form crosslink-> contraction -> shortening of cell
Sm Descrease in ca
Ca not bind to calmodulin. MLCK deactivated. Myosin phosphatase activates. Dephosphorylation of myosin light chain. Covers myosin head. Therefore actin unable to bind.
Skeletal muscle cells - morphology in cross section and lngi section?
Polygonal cells
Peripheral nucleus
Z lines - h band - a i bands - nucleus at periphery
