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Histology > Muscle Tissue > Flashcards

Muscle Tissue Flashcards

1
Q

Individual muscle cells are enveloped by ____

A

External lamina

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2
Q

Order of CT wrapping in skeletal muscle from big to small

A

. Epimysium (deep fascia)
. Perimysium (around fascicles)
. Endomysium (around muscle fiber)

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3
Q

Muscle fiber diameter and length

A

10-100 um in diameter

1mm-30cm in length

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4
Q

Embryology go muscle cell

A

. Myoblasts (progenitor cells) aggregate and fuse for multinucleated myotubes
. Myoblasts that don’t fuse become satellite cells (stem cells for skeletal muscle)

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5
Q

Myofibril

A

. Parallel array of cytoplasmic filaments within each muscle fiber
. Formed by thick myosin filaments and thin actin filaments

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6
Q

Sarcomeres

A

. Contractile units
. Consists of dark A band (anisotropic) and light I band (isotropic)
.Forms numerous junctions folds in region of neuromuscular junction

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7
Q

Myosin and actin organization in sarcomeres

A

. Myosin heads project from thick filaments to actin binding to acting forming transient bridges and ATP to catalyze energy release
. Actin associated w/ troponin and tropomyosin

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8
Q

Z discs

A

. Separate sarcomeres by divine I band

. Has alpha-actinin that attaches to thin filaments in I bands

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9
Q

T/F In I bands the thin filaments don’t overlap w/ thick elements

A

T

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10
Q

H zone

A

Center of A band void of any filaments

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11
Q

M line

A

Middle of H zone

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12
Q

How skeletal muscle contraction happens on microscopic level

A

. Sliding movement between thick and thin filaments
. Myosin head groups bind to actin then generate movement and pull thick filaments over the thin filaments shortening length of sarcomeres
. Energy generated by ATP hydrolysis by myosin heads

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13
Q

Sarcoplasm

A

. Cytoplasm of the muscle fiber

. Mitochondria and cisterna of sarcoplasmic reticulum (SER) in between fibrils

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14
Q

Sarcoplasmic reticulum

A

. Specialized for Ca sequestration and release (essential in muscle contraction)

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15
Q

Terminal cistern

A

. A-I Junction of each sarcomeres where tubules of SER coalesce to make larger tube

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16
Q

Transverse/T tube

A

. Deep invagination of the sarcolemma

. 2 terminal cisterns of SER contact this forming triad

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17
Q

What occurs at triad of skeletal muscle?

A

. Depolarization of sarcolemma from action potential causes Ca release from SER leading to muscle contraction

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18
Q

What are voluntary muscle innervated by?

A

Peripheral nervous system

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19
Q

nerve pathway to Neuromuscular junctions

A

. Myelinated motor nerves of PNS branch w/in perimysium to give rise to unmyelinated nerve terminals that pass via endomysium forming junctions w/ individual muscle fiber

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20
Q

Motor end plate

A

. Dilated terminal formed by axonal branch
. Located in trench on surface fo muscle fiber
. Contain Ach
. Only one per muscle fiber

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21
Q

Motor unit

A

. Group of muscle fibers innervated by single spinal nerve branches
. small in precisely controlled muscles
. Can have more than 100 fibers in muscles w/ less precision

22
Q

Muscle spindles

A

. Stretch detectors part of muscle proprioception system by detecting changes in length of the surrounding extrafusal muscle fibers caused from body movement
. Sensory nerves relay info from spindle to spinal cord

23
Q

Intrafusal fibers

A

. 2 mm long thin muscle fibers encapsulated by modified perimysium
. Get wrapped by several sensory nerve fibers that have penetrated muscle spindle

24
Q

Type I skeletal muscle

A

. Aerobic, slow, oxidative
. Small fibers
. Slow contractions for long periods of time but resistant to fatigue (true back muscles)
. Major source ATP is oxidative phosphorylation
. Numerous mitochondria
. High density of surrounding capillaries
. High levels myoglobin
. Low glycogen content

25
Q

Type IIa skeletal muscles

A

. Fast intermediate oxidative-glycolytic fibers
. Medium fibers
. Fast constrictions, less resistant to fatigue than type I
. Major source ATP is oxidative phosphorylation
. Numerous mitochondria
. High density surrounding blood capillaries
. High levels myoglobin (red fibers)
. Intermediate glycogen content

26
Q

Type IIb skeletal muscle fibers

A 
. Fast, white glycolytic
. Large fibers
. Fast contractions, suspect I’ll to fatigue
. Capable of fast, precise movements 
. ATP source anaerobic glycolysis 
. Sparse mitochondria 
. Lower density of surrounding blood capillaries 
. Low myoglobin levels (white fibers)
. High glycogen content
27
Q

T/F Fibers fo a single motor unit don’t have to be the same type

A

F, they are all the same type

28
Q

Hyperplasia vs. hypertrophy

A

Hyperplasia is increase in number of cells

Hypertrophy is increase in size of same muscle fibers

29
Q

Myopathies

A

. Innervation of muscle is intact
. Include hereditary muscular dystrophies
. Can be result of aging, malnutrition, and immobilization

30
Q

Muscle neuropathies

A

Innervation to muscle is lost

. Occurs in diseases caused by degeneration of motor neurons (ALS)

31
Q

Myasthenia gravis

A

. Autoimmune is ease where autoantibodies to neurotransmitter ACh receptors in muscle cells block binding of ACh

32
Q

Cardiac muscle location

A

. Found in myocardium of heart and at the proximal end of some large vessels entering and leaving heart

33
Q

Cardiac muscle structure

A

. Fibers cylindrical and shorter than skeletal fibers
. Single, centrally located nucleus
. Branching to connect fibers
. Have intercalated discs

34
Q

Intercalated discs

A

. Specialized intercellular junctions in cardiac muscle
. Appear as dark transverse lines that cross muscle cells
. Bind cardiac cells together and serve to anchor myofibrils
. Have many desmosomes and fasciae adherentes on transverse portion
. Longitudinally oriented portions have gap junctions

35
Q

Functional syncytium

A

Quick spread of ions between cells in cardiac muscles

36
Q

Cardiac cell thick and thin filaments

A

. Similar striated structure as skeletal muscle but branching makes it hard to see in LM

37
Q

T tubules and SER in cardiac muscles

A

. Present but less regularly arranged
. T tubules More numerous and larger
. SER less abundant

38
Q

Ca in cardiac muscle

A

. Slowly leaks from SER into cytoplasm after recovery from contraction
. Causes new automatic contractions independent of external stimuli

39
Q

Rate of inherent rhythm in cardiac muscle is modulated by ___

A

. External autonomic and hormonal stimuli

40
Q

T/F Mitochondria more numerous in cardiac muscle than skeletal muscle

A

T, 40% of cytoplasmic volume (2% of cell volume in muscle cell)

41
Q

Sources of energy in cardiac muscle

A

. Fatty acids major source stored as triglycerides in lipid droplets present in cardiac muscle
. Glycogen often present

42
Q

Difference between atrial cardiac cels and ventricle cardiac cells

A

. Atrial smaller w/ less T tubules than the cells of ventricles
. Release peptide hormone atrial natriuretic factor (ANF) that acts on target cells in kidney to affect Na excretion and H2O balance

43
Q

Innervation of cardiac cells

A

. ANS and punkinje cells

44
Q

Purkinje cells

A

. Modified cardiac cells that form pacemaker regions

. Makes coordinated contractions of myocardium as a while in each cardiac cycle

45
Q

Regeneration fo cardiac cells

A

Don’t have satellite cells and don’t regenerate

. Dead tissue replaced w/ fibrous scar tissue

46
Q

Smooth muscle cells contractions

A

. Continuous contractions of low force producing diffuse movements through contraction of whole muscle mass rather than of individual motor units

47
Q

Smooth muscle cell structure

A

. Small fusiform cells linked by gap junctions
. Single Centrally located nucleus
. SER not developed and no T tubules
. Not striated
. Thick and thin filament bundles criss cross obliquely
. Actin filaments attach to alpha-actinin in dense bodies in sarcoplasmic near sarcolemma
. Desmin also attaches to alpha-actinin

48
Q

Innervation of smooth muscle

A

. Involuntary contraction through autonomic nerves, hormones, and physiological conditions (stretch)
. Type of contraction depends on degree of autonomic innervation and density of gap junctions

49
Q

Autonomic smooth muscle innervation contraction type

A

. Iris of the eye type

. Muscle fibers contract as small group for precise action

50
Q

Peristalsis spontaneous contractions in smooth muscle

A

. Muscle cells generate own low level of rhythmic contraction
. ANS acts to inc. or dec. but doesn’t initiate

51
Q

Regeneration of smooth muscle cells

A

. Capable of regeneration

. Can undergo hyperplasia (uterus during pregnancy)

Histology (22 decks)

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