deck_8220383

Question 1

defining characteristic of muscle tissue

Answer 1

ability to contract!- shortening/lengthening of skeletal muscle- contraction of smooth muscle

Question 2

skeletal muscle

Answer 2

• voluntary movement- striated- covered by thin layer of fascia- parallel arrays of muscle fibers- external basal lamina

Question 3

skeletal muscle histology

Answer 3

• longitudinal eosinophilic fiber filled with myofibrils- multiple nuclei per cell; all pushed to the edges- striations perpendicular to length of myocyte- in cross-section: striations not visble but individual myofibrils are

Question 4

sarcomeric unit

Answer 4

• gives skeletal muscle striated appearance- Z lines = boundaries- I band = actin myofilaments- A band = myosin overlapping with actin- H band = isolated mysoin- M band = cross linked myosin (middle)

Question 5

nerve stimulation of a skeletal muscle fiber

Answer 5

occurs via somatomotor neurons in spinal and cranial nerves1. nerve impulse causes Ach release from end plate synaptic vesicles into synaptic cleft of sarcolemma2. opening of ACh gated Na+ channels causes local depolarization of sarcolemma3. depolarization spreads to T tubules4. at the triad, depolarization enters the cell through T tubules at the junction of A and I bands5. depolarization activates voltage sensitive Ca channels on the T tubule membrane6. Ca released from sarcoplasmic reticulum into sarcoplasm7. initiation of muscle contraction

Question 6

subdivisions of muscle (small -> large)

Answer 6

• myofilament = complex of actin and myosin- myofibril = bundle of myofilaments = back to back sarcomeres- muscle fiber = cell = bundle of myofibrils surrounded by endomysium- muscle fascile = made of fibers surrounded by perimysium- skeletal muscle = made of fasciles and covered by epimysium

Question 7

thin filaments

Answer 7

• actin, troponin, and tropomyosin- present in Z, I, A bands

Question 8

thick filaments

Answer 8

• myosin- present in A, H, M bands

Question 9

contraction of skeletal muscle

Answer 9

0. relaxed state: troponin/tropomyosin bind myosin1. muscle stimulation = Ca release2. Ca binds to troponin on thin filaments, freeing myosin3. myosin binds actin4. power stroke: myosin pulls actin, pulling thin filaments towards M-line5. ATP binding allows for myosin release of actin

Question 10

structural elements of a muscle fiber

Answer 10

• sarcolemma = plasma membrane- myofibrils surrounded by layer of sarcoplasm containing mitochondria and sarcoplasmic reticulum- T tubules = entrances through sarcolemma- Triad = t tubule adjacent to two terminal cisternae of the sarcoplasmic reticulum

Question 11

cardiac muscle histology

Answer 11

• also striated- shorter, branching myofibrils- central nuclei- cells attach at ends via intercalated disks (junctions that propagate depolarization)

Question 12

cardiac muscle contraction

Answer 12

• similar to skeletal muscle (also dependent on Ca ions)

Question 13

smooth muscle

Answer 13

• involuntary movement- no striations- actin and myosin connected by dense bodies (a-actinin + IFs (desmin and vimentin))

Question 14

smooth muscle histology

Answer 14

• eosinophilic cytoplasm- cigar shaped nuclei

Question 15

smooth muscle contraction

Answer 15

1. initiation of contraction by nerve impulse, stretch, or hormones2. intracellular Ca increase3. calcium binds calmodulin, which activates myosin light chain kinase4. phosphorylation of myosin5. myosin-P binds actin (no troponin involved)6. with ATP, myosin head will bend and induce contraction

Question 16

initiation of smooth muscle contraction

Answer 16

1. autonomic nerve impulses from nerves terminating in adjacent connective tissue open voltage-gated Ca channels (After 10-20 µM diffusion of NTs)2. smooth muscle stretching opens mechanosensitive Ca channels3. surface receptors of hormones trigger 2nd messengers that act on gated ER channels to release Ca