Muscle Tissue

Question 1

types of muscle

Answer 1

1. skeletal
2. cardiac
3. smooth

Question 2

contraction mediated by

Answer 2

thin and thick myofilaments

Question 3

thin filaments

molecular comp

Answer 3

globular actin monomers (G-actin) > polymers> double helix filamentous actin

troponin complex (3 subunits)

tropomyosin molecule

Question 4

troponin complex

Answer 4

TnC - bind calcium
TnT- attach tropomyosin
TnI- inhibit actin/myosin interaction, binds troponin complex to actin molecules

Question 5

tropomyosin molecule

Answer 5

alpha helix of 2 polypeptide chains
each molecule covers 7 G-actin active sites
head to tail assembly of molecules = tropomyosin filament

Question 6

thick filaments

composition

Answer 6

myosin II (200 molecules)

Question 7

myosin molecule

components

Answer 7

2 heavy chains + 4 light chains

heavy chain = alpha helix tail w/ globular heads
light chain = small chunks/golf balls on globular heads

Question 8

trypsin + myosin molecule

Answer 8

trypsin breaks myosin molecule into 2 segments
heavy meromyosin- 4 light chains, 2 globular heads, short twisted tail
light meromyosin- long twisted tail

Question 9

heavy meromyosin + papain

Answer 9

papain further breaks down heavy
two S1 (2 light chains + 1 head)
one S2 (short twisted tail)

Question 10

thin + thick filaments

Answer 10

= sarcomere
contracting unit of skeletal/cardiac muscle
cylindrical shape

thin and thick alternate/overlap

Question 11

myofibril

Answer 11

combo of bands (A/H + I/Z), assembly of sarcomeres

enclosed in skeletal muscle cell (fiber) > fasciculus (bundle)

assembly of sarcromeres

Question 12

A band

Answer 12

thin and thick
bisected by H band (thick only)

dark and wide

Question 13

I band

Answer 13

thin only
bisected by Z (attachment for thin filaments)

light

Question 14

sarcomere accessory proteins

purpose

Answer 14

attach, space, algin myofilaments for even, precise, orderly arrange

Question 15

alpha actinin

Answer 15

attach thin filaments to Z disk

Question 16

nebulin

Answer 16

thin filaments to Z disk
2 molecules / 1 thin

nonelastic

Question 17

titin

Answer 17

thick to Z
elastic so produce tension/force generating

4 titin/ 1 thick

Question 18

midline proteins

M line

Answer 18

myomesin
C protein
thick to M band (middle of H)

Question 19

endomysium

skeletal muscle

Answer 19

surrounds each muscle fiber/cell

retiuclar fibers + external lamina

Question 20

perimysium

skeletal muscle

Answer 20

thin collagenous CT
surround each bundle/fascicle

Question 21

epimysium

Answer 21

aka deep fascia (dense, irregular collagenous CT)
surrounds gross muscle
nerves and vessels

Question 22

skeletal muscle

appearance

Answer 22

banding/striated longitudinal

mulitnuclei pushed to periphery- euchromatic, oval shape

uniform size of cells cross section

in LM only see A (dark) and I (light) bands

Question 23

cardiac muscle

appearance

Answer 23

weak striated/banded but branched so different size (cross sections)

have intercalated discs and capillaries, and atrial granules (hormones inside)

Question 24

smooth muscle

appearance

Answer 24

spindle shape
1 nucleus in middle
different size cells (cross section)
no striations/sarcomeres

sardines, little extracellular space

Question 25

skeletal muscle | composition

Answer 25

T tubules- invaginations of sarcolemma, continuous w/ ECS, carry nerve impulses SR- elaborate sER meshwork surrounding myofibrils terminal cisternae- part of sER, next to T tubules, store Ca in lumen

Question 26

triad of skeletal muscle

Answer 26

one T-tububle + two terminal cisternae

Question 27

motor unit

Answer 27

neuron + all skeletal muscle fibers it innervates have end plates aka myoneural junction - 1 per/fiber, have axon terminal (Ach) + synaptic cleft + skeletal muscle cell sarcolemma/post synaptic membrane

Question 28

myasthenia gravis

Answer 28

acetylcholine (Ach) antibodies attach to receptors so Ach can't bind = muscle weakness

Question 29

atrial granules | cardiac muscle

Answer 29

have atrial natriuretic peptide and brain natriuretic factor (diuretics, act on kidneys to lower BP or loss of water/sodium) most numerous in R atrium fibers

Question 30

intercalated discs

Answer 30

specialized junctions of cardiac muscle transverse portion: fascia adherens (transmit contractile forces cell to cell) and desmosomes (bind cells together) lateral portion: gap junctions, allow ion flow

Question 31

purkinje fibers

Answer 31

specialized cardiac muscle like batteries to ignite regular cells to contract conducting system | @ endocardium (inner most layer heart)

Question 32

dystrophin | accessorry protein

Answer 32

cytoplasmic binds thin to laminin (external lamina surrounding fiber) if absent = muscular dystrophy aka weakness and wasting/ atrophy

Question 33

caveolae | smooth muscle

Answer 33

pinocytotic vesicles bubble like on inner surface of cell membrane release Ca into cell for contraction

Question 34

myofilament bundles

Answer 34

criss cross to form dense bodies points of attachment on internal suface of cell membrane to anchor

Question 35

presynaptic events

Answer 35

1. nerve transmitted down axon 2. impulse reaches presynaptic membrane 3. Ca2+ ions enter terminal 4. synaptic vesicles attach to inner surface of presynaptic membrane 5. synaptic vesicles release Ach into cleft | start with nerve down axon end w/ Ach release

Question 36

postsynaptic events

Answer 36

1. Ach binds to receptors on postsynaptic membrane 2. Na+ ions enter skeletal muscle cell 3. K+ ions exit skeletal muscle cell 4. sarcolemma becomes depolarized 5. depolarization spreads to T-tubule opening | start Ach binding receptors end at T-tubules

Question 37

events inside skeletal muscle cell

Answer 37

1. depolarization spreads to T-tubule membrane 2. nerve impulse carried deep into muscle cell 3. depolarized T-tubule trigger change in permeability of terminal cisternae of SR @ each side of T-tubule 4. Calsequestrin from SR releases Ca2+ ions into cytoplasm 5. Ca ions attach to TnC of troponin = conformational change 6. TnT pushes tropomyosin filaments deeper into groove of actin to uncover active sites 7. myosin head associates w/ active site of actin monomer using ATP 8. head and rod of myosin bend to pull actin filament over myosin filament = sliding of thin filament towards midline