histology

Question 1

what x2 things are contained in the M line?

Answer 1

myomesin - holds thick filaments together

creatine kinase (CK/CPK)

no thin filaments here because it’s only myosin tails, no heads to bind actin

Question 2

single __ actin come together to form ___ actin

Answer 2

G (globular), F (filamentous)

Question 3

what anchors the actin filaments at the Z line?

Answer 3

alpha-actinin

Question 4

function of nebulin:

Answer 4

-helps anchor actin
-runs laterally from the Z line along the actin length
-acts as a template and regulates actin length

Question 5

function of titin/connectin:

Answer 5

-extends from Z disc to M line
-associates with myosin and maintains its position at the middle of the sarcomere
-an elastic scaffold for myosin

Question 6

what is a costamere?

Answer 6

connects the sarcomere of the muscle to the cell membrane

Question 7

desmin function:

Answer 7

surrounds myofibrils at the Z line and interconnects multiple myofibrils to the sarcolemma

KEY PHRASE: connects myofibrils to EACH OTHER

Question 8

dystrophin function:

Answer 8

-helps link the sarcolemma/matrix to the myofibrils
-“dystroglycan complex”
-“sarcoglycan complex”

Question 9

function of dystroglycan complex:

Answer 9

connects dystrophin to laminin-2
alpha subunit binds laminin 2 on the membrane
beta subunit binds dystrophin intracellularly

Question 10

where does desmin connect the myofibrils to the sarcolemma?

Answer 10

at the costamere (wraps around the Z lines of the fibrils)

Question 11

plectin function

Answer 11

connects desmin filaments to each other

Question 12

function of alpha-beta crystallin

Answer 12

protects desmin

Question 13

mutations in sarcoglycan complex lead to:

Answer 13

limb girdle muscular dystrophies

Question 14

loss of dystrophin causes..

Answer 14

Duchennes muscular dystrophy

Question 15

mutation of laminin causes…

Answer 15

congenital muscular dystrophy

Question 16

mutations in desmin, plectin, or crystallins cause…

Answer 16

loss of myofibrils

Question 17

Duchennes clinical features:

Answer 17

loss of dystrophin
loss of myofibrils
loss of myofibers
increasing adipose tissue to fill in atrophied areas

Question 18

T tubule arrangement in skeletal muscle:

Answer 18

triads
SR terminal cisternae - T tubule - SR terminal cisternae
at the A-I junction

Question 19

name of junction between muscle and tendon:

Answer 19

-myotendinous junctions
-dense regular CT
-tendons connect muscle fibers to bone, skin, or other muscles
-continuous with CT (deep fascia) around muscle (epimysium)

Question 20

development of myofibers

Answer 20

-single nucleate - myoblasts (nucleus at center)
-fuse to form skeletal myotube (numerous nucleus at center)
-myotubes differentiate into myofibers (peripheral nuclei)

Question 21

fate of myoblasts that don’t fuse into the myotube:

Answer 21

satellite cells
in basal lamina outside of sarcolemma
proliferate and replace injured muscles

Question 22

what are golgi tendon organs?

Answer 22

encapsulated bundles of type 1 collagen
receive sensory innervation only (no motor!)
-collagen has no mechanism for contraction itself
contraction compresses the collagen
compresses afferent nerve fiber
relays to CNS

Question 23

components of a muscle spindle:

Answer 23

-capsule
-intrafusal muscle fibers
-stretch receptor

Question 24

what is a muscle spindle?

Answer 24

sensory AND motor innervation
intrafusal muscle fibers in between extrafusal
surrounded by a capsule
propioception - senses stretch and tension (stretch receptors)

Question 25

t tubules and SR terminal cisternae form a _____ in cardiac muscle

Answer 25

diad - one of each (unlike triad in skeletal)
at the Z line (unlike at A-I in skeletal)

Question 26

what are the vesicles surrounding the nucleus?

Answer 26

vesicles of atrial granules (atrial naturietic factor)

Question 27

what lines are the gap junctions? the desmosomes?

Answer 27

lines parallel to the Z and M lines are transverse component (desmosomes, fascia adherans)

lines perpendicular to Z and M lines are longitudinal component (gap junctions)

Question 28

Answer 28

purkinje fibers
stain more lightly than cardiac cells
coordinate rhythmic contractions, located deep to endocardium
high glycogen content

Question 29

what are dense bodies?

Answer 29

act like Z discs in smooth muscle
myofilaments anchor in them
pull against to contract the cell

Question 30

what is a corkscrew nucleus?

Answer 30

a nucleus that looks smooshed when the smooth muscle contracts using the dense bodies

Question 31

what are submembranous dense bodies?

Answer 31

link adjacent smooth muscle cells together using cadherins (cell:cell)

Question 32

what are calveolae?

Answer 32

invaginations in the sarcolemma of SM
~ T tubules

Question 33

explain smooth muscle contraction:

Answer 33

thin filaments anchored to dense bodies via alpha-actinin which interact with thick filaments. intermediate filaments (desmin) also attach to dense bodies

*adjacent cells can share the same dense body - movement is coupled

Question 34

regulatory protein complex of smooth muscle:

Answer 34

calmodulin-myosin light chain kinase

Question 35

what are resident cells?

Answer 35

CT cells that make the CT (immigrant/transient)

Question 36

what are the components of connective tissue?

Answer 36

1. resident cells
2. connective tissue
3. ground substance

Question 37

types of embryonic CT:

Answer 37

-mesenchyme
-mucous

Question 38

vitamin C deficiency symptoms:

Answer 38

causes issues with collagen formation
sx: bleeding gums and corkscrew hair

Question 39

what is elastic laminae?

Answer 39

fenestrated sheets of elastin around blood vessels

Question 40

what is the composition/structure of elastic fibers?

Answer 40

-mostly elastin and fibrillin
-desmosine (and isodesmosine) cross links
-allows for flexibility

Question 41

what are the GAG types?

Answer 41

chondroitin
dermatan
heparan
keratan
heparin

Question 42

types of core proteins:

Answer 42

syndecan
perlecan
lumican
aggrecan