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Flashcards in Muscle Deck (64):
0

Can you detect striations in skeletal muscle cross section?

No

1

Esophageus 3 different portion. Skeletal is...

First portion

2

Skeletal muscle...nuclei?

Multi nucleated. Syncytial - beneath plasmolemma

3

Origin of skeletal muscle?

Myoblasts - mononuclear, undifferentiated, no myofibrils
Form myotubes - differentiate - organelles expressed

4

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

5

What surrounds groups of muscle fibres?

CT

6

Sarcomere proteins?

Titin - thick fil correct arrangement at m line
Nebulin - maintain correct length of actin
Actinin - attach actin fil to z line

7

G actin to f actin

Req atp and mg2+ and k+
Polymerisation

8

Troponin tic

T - bind to torpomyosin
I - bind to actin
C - bind to calcium

9

Myosin head(2)

2 peptides
Active site - attach to actin filament

10

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

11

Dystrophin and mutation

Linked sarcolemma to actin
Mutation - muscular dystrophy
Vital in cell stability

12

M line protein function and names? And em line?

Maintain correct arrangement of myosin filament
Myomesin, m protein, schlemin
Electron dense line

13

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

14

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

15

Smooth muscle contains specifically different from skeletal and cardiac muscle?

Dense bodies.
Greater elasticity.
Larger tension curve

16

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

17

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

18

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

19

Disease of nmj?

Myasthenia gravis - autoimmune attack ach receptors - lost

20

Different types of skeletal muscle fibres?

Red slow twitch - type one
Intermediate - pink type 2a
White - type 2 b fast twitch

21

Which stain to differentiate between skeletal muscle fibres?

Succinate dehydrogenase. Stains mito. Slow twitch - greater amount of mito

22

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

23

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

24

Intermediate

Lower limbs. Contract similar to fast twitch. High no. Mito, myoglobin. Store glycogen and anaerobic respiration

25

Hypertrophy and stimulated by(3)

Increase in muscle size. Increase in no of filaments.
Resistance training. Testosterone. Anabolic steroids

26

Atrophy and how occur!

Muscle cells smaller - reduction in muscle size
Pathology - removal of nerve, immobility, lack of use

27

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

28

Heart layers?

Pericardium - serosa cavity - epitcardium - myocardium - endocardium

29

Nuclei of cardiac?

Central, maube multiple

30

Cross section of cardiac muscle

Some nucleus seen
Striated
Granules
Presence of myofibrils

31

Cardiac cells, biconical juxtanuclear region contains

Mito, lipofuscins, golgi, glycogen, grangles

32

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

33

What happens during heart failure of levels of BNP

Increase

34

Cardiomyocytes 2 features?

Elongated (100um)
Rounded nucleus (maybe multiple)

35

What tissue surrounds cells and contains?

Connective tossue.
Bv provide vascularisation to avascular cardiac bundle

36

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

37

Cardiac muscle - what does adherens junction do?

Bind actin at z lines

38

Cardiac muscle - endomysium?

Rich capl network - ct bv cardiomyocytes

39

How to differentiate between sm and cardiac muscle in cross section?

Different morphology of cytoplasm.
Sm cyto - homogenous
Cardiac - granules/myofibrils

40

Cardiac and skeletal muscle nucleus?

Skeletal periphery
Cardiac at nucleus

41

Diads in cardiac muscle?

1 t tubule 1 sr larger than in skeletal muscle
At z lines and no AI junctuon

42

Heart contraction?

Purkije fibres - modified muscle cells (less abundant contractile myofibre) not specialised for contraction. SAN AVN VENTRICLES

43

Between myofibrils?

Inaddition to juxtanuclear mito, large mito between myofibrils and glycogen granules

44

Diads less numerous in?

Cardiac atrial muscle

45

Cardiac muscle cells injury and repair

Injury to cardiac muscle. Loss of cells - replaced by fibrous ct - cardaic function lost at injury - myocardial infarction

46

Cardiac cells divide?

0.1% of cardiac cells are able to divide

47

Smooth muscle thin filaments

Actin, troponin, calponin, caldesmon

48

Sm thick filaments

Myosin.
Side polar thick filament.
No central bare zone.
Bare zone at ends form tapered ends.

49

Calponin and caldesmon are?

Actin binding proteins (ABP)
Block myosin binding site

50

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

51

Sm cells surrounded by?

Basal lamina and supported by ct

52

Relation of sm cells?

Thinner aspect of one cells with thicker aspect of another cell

53

Cross section of sm cells?

Depending on where cut.
Centre -> able to see nucleus.
Where diameter largest

54

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

55

Dense bodies are located?

Sm. Below sarcolemma, a-actinin binds actin and tropomyosin

No troponin.

Dense bodies act as sm z-lines

56

Sm int. Filaments

Vimentin and desmin
Help with contraction
Pulling cell ends
Shortening cell

57

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.

58

Sm - calveolae (5)

Integral membrane proteins.
Sm cardiac muscle membrane - caveolin 3
Non receptor endocytosis
Closely associated with ser
Regulation of contraction and ca

59

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.

60

Autonomic neuron varicosity?

Contains NET

61

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

62

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.

63

Skeletal muscle cells - morphology in cross section and lngi section?

Polygonal cells
Peripheral nucleus

Z lines - h band - a i bands - nucleus at periphery