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Histology > Muscle Tissue > Flashcards

Muscle Tissue Flashcards

(51 cards)

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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

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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

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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

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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

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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
Type IIa skeletal muscles
. 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
Type IIb skeletal muscle fibers
``` . 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
T/F Fibers fo a single motor unit don’t have to be the same type
F, they are all the same type
28
Hyperplasia vs. hypertrophy
Hyperplasia is increase in number of cells | Hypertrophy is increase in size of same muscle fibers
29
Myopathies
. Innervation of muscle is intact . Include hereditary muscular dystrophies . Can be result of aging, malnutrition, and immobilization
30
Muscle neuropathies
Innervation to muscle is lost | . Occurs in diseases caused by degeneration of motor neurons (ALS)
31
Myasthenia gravis
. Autoimmune is ease where autoantibodies to neurotransmitter ACh receptors in muscle cells block binding of ACh
32
Cardiac muscle location
. Found in myocardium of heart and at the proximal end of some large vessels entering and leaving heart
33
Cardiac muscle structure
. Fibers cylindrical and shorter than skeletal fibers . Single, centrally located nucleus . Branching to connect fibers . Have intercalated discs
34
Intercalated discs
. 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
Functional syncytium
Quick spread of ions between cells in cardiac muscles
36
Cardiac cell thick and thin filaments
. Similar striated structure as skeletal muscle but branching makes it hard to see in LM
37
T tubules and SER in cardiac muscles
. Present but less regularly arranged . T tubules More numerous and larger . SER less abundant
38
Ca in cardiac muscle
. Slowly leaks from SER into cytoplasm after recovery from contraction . Causes new automatic contractions independent of external stimuli
39
Rate of inherent rhythm in cardiac muscle is modulated by ___
. External autonomic and hormonal stimuli
40
T/F Mitochondria more numerous in cardiac muscle than skeletal muscle
T, 40% of cytoplasmic volume (2% of cell volume in muscle cell)
41
Sources of energy in cardiac muscle
. Fatty acids major source stored as triglycerides in lipid droplets present in cardiac muscle . Glycogen often present
42
Difference between atrial cardiac cels and ventricle cardiac cells
. 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
Innervation of cardiac cells
. ANS and punkinje cells
44
Purkinje cells
. Modified cardiac cells that form pacemaker regions | . Makes coordinated contractions of myocardium as a while in each cardiac cycle
45
Regeneration fo cardiac cells
Don’t have satellite cells and don’t regenerate | . Dead tissue replaced w/ fibrous scar tissue
46
Smooth muscle cells contractions
. Continuous contractions of low force producing diffuse movements through contraction of whole muscle mass rather than of individual motor units
47
Smooth muscle cell structure
. 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
Innervation of smooth muscle
. 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
Autonomic smooth muscle innervation contraction type
. Iris of the eye type | . Muscle fibers contract as small group for precise action
50
Peristalsis spontaneous contractions in smooth muscle
. Muscle cells generate own low level of rhythmic contraction . ANS acts to inc. or dec. but doesn’t initiate
51
Regeneration of smooth muscle cells
. Capable of regeneration | . Can undergo hyperplasia (uterus during pregnancy)

Histology (22 decks)

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