Histology - Muscle

Question 1

what are the steps to the contraction cycle?

Answer 1

1. ATP binds to myosin (high E state)
2. ATP hydrolyzed into ADP and P –> myosin is in “cocked” position
3. Ca2+ binds to troponin, exposing active site on actin
4. myosin head forms cross-bridge with actin
5. during power strike, myosin head bends, ADP and P released
6. new molecule of ATP attaches to myosin head –> cross-bridge detaches
7. ATP hydrolyzed to ADP and P, returning myosin to “cocked” position

Question 2

What causes rigor mortis?

Answer 2

no ATP –> unable to detach cross-bridge, so mucles lock up and don’t relax

Question 3

what is the role of calcium in smooth muscle?

Answer 3

activates calmodulin/myosin light chain kinase (MLCK)

Question 4

what is the role of calmodulin/myosin light chain kinase (MLCK) in smooth muscle?

Answer 4

activated by Ca2+, phosphorylation of individual myosin light chains allows binding and initiation of contraction

Question 5

what is the role of calcium in cardiac and skeletal muscle?

Answer 5

Ca2+ binds to troponin, displacing tropomyosin and exposes many actins at once for binding to myosin

Question 6

what is the sarcoplasm?

Answer 6

cytoplasm of muscle cells

Question 7

what are myofilaments?

Answer 7

threadlike substructures of the sarcoplasm

Question 8

what are myofilaments formed by?

Answer 8

actin and myosin

Question 9

what provides a muscle cell with the ability to contract?

Answer 9

the myofilaments (actin and myosin)

Question 10

what are muscle fibers?

Answer 10

muscle cells

Question 11

how are muscle cells typically arranged relative to one another?

Answer 11

parallel to one another in sheets or bundles

Question 12

is smooth muscle voluntary or involuntary?

Answer 12

involuntary

Question 13

is smooth muscle striated?

Answer 13

no

Question 14

what does the cytoplasm look like in smooth muscle?

Answer 14

uniform rather than striped

Question 15

what is the shape of smooth muscle?

Answer 15

spindle-shaped (fusiform)

Question 16

what does/do the nucleus/nuclei look like in smooth muscle?

Answer 16

single nucleus, elongated, located midway between ends of cell

Question 17

is skeletal muscle voluntary or involuntary?

Answer 17

voluntary

Question 18

is skeletal muscle striated?

Answer 18

yes

Question 19

what forms the cross-striations of skeletal and cardiac muscle?

Answer 19

precise registration of sarcometric bands

Question 20

what is the shape of skeletal muscle?

Answer 20

cylindrical, really long

Question 21

what is the sarcolemma?

Answer 21

cell membrane of a muscle cell

Question 22

what do/does the nuclei/nucleus look like in skeletal muscles?

Answer 22

multinucleated, located peripherally immediately below the sarcolemma

Question 23

what are fascicles?

Answer 23

bundles of skeletal muscle cells

Question 24

is cardiac muscle voluntary or involuntary?

Answer 24

involuntary

Question 25

is cardiac muscle striated?

Answer 25

yes

Question 26

what do/does the nuclei/nucleus look like in cardiac muscle?

Answer 26

one nucleus (sometimes 2) located centrally

Question 27

which type of muscle cell anastomoses with one another?

Answer 27

cardiac muscle cells

Question 28

what do intercalated discs do in cardiac muscle?

Answer 28

join muscle cells and increase speed of conduction of impulses

Question 29

what are intercalated discs made of?

Answer 29

desmosomes and gap junctions

Question 30

which cells are modified to function as a conducting system for heartbeats?

Answer 30

sinoatrial node, atrioventricular node, Purkinje fibers

Question 31

in brief, describe what happens when a smooth muscle cell contracts

Answer 31

the intermediate filaments and dense bodies come closer together

Question 32

what type of muscle is this?

Answer 32

smooth muscle

Question 33

what type of muscle is this?

Answer 33

smooth muscle

Question 34

what are the contractile protiens present in smooth muscle?

Answer 34

actin, tropomyosin, myosin II

Question 35

what are the intermediate filaments of smooth muscle made of?

Answer 35

desmin and vimentin

Question 36

what are the dense bodies of smooth muscle?

Answer 36

desmosomes

Question 37

what is the name for the gap junctions in smooth muscle?

Answer 37

connexons

Question 38

what are the high force-density muscles?

Answer 38

cardiac and skeletal muscles

Question 39

what structure is this?

Answer 39

sarcomere

Question 40

label the parts of the sarcomere

Answer 40

A: I band B: A band C: Z-line D: H-zone E: M-line F: actin thin-filaments G: myosin thick filaments

Question 41

what is the I band of a sarcomere?

Answer 41

section near the ends of the sarcomere where there is only actin thin filaments

Question 42

what is the A band in a sarcomere?

Answer 42

section where the actin thin filaments and the myosin thick filaments are overlapping

Question 43

what is the 3D structure of a sarcomere like?

Answer 43

quasi-crytstalline structure

Question 44

what is a syncytium?

Answer 44

single cell of cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei

Question 45

what is a myofiber?

Answer 45

single multinucleate skeletal muscle cell/syncytium

Question 46

what are myofibrils?

Answer 46

bundles of actin/myosin filaments found inside skeletal or cardiac muscle cells

Question 47

what is the sarcoplasmic reticulum?

Answer 47

found within muscle cells, stores Ca2+

Question 48

what is the result of having a sarcoplasmic reticulum?

Answer 48

quicker signal to entirety of cell because of stored Ca2+

Question 49

what are the T tubules in the sarcoplasmic reticulum?

Answer 49

extensions of the cell membrane

Question 50

what is the terminal cisterna of the sarcoplasmic reticulum?

Answer 50

primary site of Ca2+ release

Question 51

what is the longitudunal SR in sarcoplasmic reticulum?

Answer 51

location of ion channels for Ca2+ absorption

Question 52

label this sarcoplasmic reticulum

Answer 52

A: T tubule B: terminal cisterna C: triad D: longitudinal SR

Question 53

what is the yellow circled structure? what type of muscle is this?

Answer 53

fascia adherens cardiac muscle

Question 54

what type of muscle is this?

Answer 54

cardiac muscle

Question 55

what type of muscle is this?

Answer 55

cardiac muscle

Question 56

what is the structure being pointed to? what type of muscle is this?

Answer 56

intercalated disc cardiac muscle

Question 57

true or false: the myofibers in cardiac muscle are branching

Answer 57

true

Question 58

what part of the cardiac muscle cell anchors the cytoskeleton?

Answer 58

intercalated discs

Question 59

true or false: cardiac muscle is not rich in mitochondria

Answer 59

false. it is rich in mitochondria

Question 60

what type of muscle is this?

Answer 60

skeletal muscle

Question 61

what type of muscle is this?

Answer 61

skeletal muscle

Question 62

what type of muscle is this?

Answer 62

skeletal muscle

Question 63

true or false: there are lots of mitochondria in skeletal muscle

Answer 63

true

Question 64

what is the speed of Type 1 muscle? how does it get its E?

Answer 64

slow twitch oxidative

Question 65

what is the speed of Type 2a muscle? how does it get its E?

Answer 65

fast twitch oxidative

Question 66

what is the speed of Type 2b muscle? how does it get its E?

Answer 66

fast twich glycolytic (anaerobic)

Question 67

what is type 1 muscle used for?

Answer 67

long endurance

Question 68

what is type 2a/2b muscle used for?

Answer 68

brief, explosive power

Question 69

what is the diameter, capillary count, and mitochondria count of type 1 muscle?

Answer 69

d: smaller cap: lots mito: lots

Question 70

what is the diameter, capillary count, and mitochondria count of type 2 muscle?

Answer 70

d: larger cap: few mito: few

Question 71

what is dystrophin and where is it located?

Answer 71

protein located between the sarcolemma and outermost layer of myofilaments in myofiber

Question 72

what is the function of dystrophin?

Answer 72

supports muscle fiber strength, provides a scaffold

Question 73

what force does bundling provide?

Answer 73

flexibility

Question 74

what structure is being pointed to?

Answer 74

perimysium coalescing to form a tendon

Question 75

what makes up epi-, peri-, and endo-mysium? which structure is unique to endomysium?

Answer 75

vessels and nerves satellite cells only in endomysium

Question 76

what fuses to make a tendon?

Answer 76

collagenous fiber network

Question 77

what is a golgi tendon organ stretch receptor?

Answer 77

a type of proprioreceptor in the collagenous fibre network

Question 78

label the connective tissue elements

Answer 78

A: epimysium B: perimysium C: endomysium

Question 79

what are intrafusal fibers?

Answer 79

modified skeletal muscle fibers that serve as sensory structures

Question 80

what do intrafusal fibers sense?

Answer 80

proprioception, sense strength, length/position, reflex arc

Question 81

what are the types of sensory and motor nerves related to intrafusal fibers?

Answer 81

sensory: type IA motor: gamma

Question 82

what structure is being shown here?

Answer 82

intrafusal muscle fiber

Question 83

what type of structure is this?

Answer 83

intrafusal muscle fiber

Question 84

what is the function of satellite cells in skeletal muscle?

Answer 84

stem cell responsible for muscle growth, hypertrophy, and regeneration

Question 85

what structure is this?

Answer 85

satellite cell in skeletal muscle

Question 86

what is myostatin and what is its function?

Answer 86

protein secreted in muscle tissues negatively regulates muscle (demotes muscle growth)

Question 87

what happens when you have a mutation in the myostatin gene?

Answer 87

abnormal muscle growth --\> overgrowth