histology Flashcards

1
Q

what x2 things are contained in the M line?

A

myomesin - holds thick filaments together

creatine kinase (CK/CPK)

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

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2
Q

single __ actin come together to form ___ actin

A

G (globular), F (filamentous)

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3
Q

what anchors the actin filaments at the Z line?

A

alpha-actinin

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4
Q

function of nebulin:

A

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

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5
Q

function of titin/connectin:

A

-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

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6
Q

what is a costamere?

A

connects the sarcomere of the muscle to the cell membrane

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7
Q

desmin function:

A

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

KEY PHRASE: connects myofibrils to EACH OTHER

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8
Q

dystrophin function:

A

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

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9
Q

function of dystroglycan complex:

A

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

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10
Q

where does desmin connect the myofibrils to the sarcolemma?

A

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

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11
Q

plectin function

A

connects desmin filaments to each other

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12
Q

function of alpha-beta crystallin

A

protects desmin

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13
Q

mutations in sarcoglycan complex lead to:

A

limb girdle muscular dystrophies

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14
Q

loss of dystrophin causes..

A

Duchennes muscular dystrophy

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15
Q

mutation of laminin causes…

A

congenital muscular dystrophy

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16
Q

mutations in desmin, plectin, or crystallins cause…

A

loss of myofibrils

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17
Q

Duchennes clinical features:

A

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

18
Q

T tubule arrangement in skeletal muscle:

A

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

19
Q

name of junction between muscle and tendon:

A

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

20
Q

development of myofibers

A

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

21
Q

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

A

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

22
Q

what are golgi tendon organs?

A

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

23
Q

components of a muscle spindle:

A

-capsule
-intrafusal muscle fibers
-stretch receptor

24
Q

what is a muscle spindle?

A

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

25
t tubules and SR terminal cisternae form a _____ in cardiac muscle
diad - one of each (unlike triad in skeletal) at the Z line (unlike at A-I in skeletal)
26
what are the vesicles surrounding the nucleus?
vesicles of atrial granules (atrial naturietic factor)
27
what lines are the gap junctions? the desmosomes?
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)
28
purkinje fibers stain more lightly than cardiac cells coordinate rhythmic contractions, located deep to endocardium high glycogen content
29
what are dense bodies?
act like Z discs in smooth muscle myofilaments anchor in them pull against to contract the cell
30
what is a corkscrew nucleus?
a nucleus that looks smooshed when the smooth muscle contracts using the dense bodies
31
what are submembranous dense bodies?
link adjacent smooth muscle cells together using cadherins (cell:cell)
32
what are calveolae?
invaginations in the sarcolemma of SM ~ T tubules
33
explain smooth muscle contraction:
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
34
regulatory protein complex of smooth muscle:
calmodulin-myosin light chain kinase
35
what are resident cells?
CT cells that make the CT (immigrant/transient)
36
what are the components of connective tissue?
1. resident cells 2. connective tissue 3. ground substance
37
types of embryonic CT:
-mesenchyme -mucous
38
vitamin C deficiency symptoms:
causes issues with collagen formation sx: bleeding gums and corkscrew hair
39
what is elastic laminae?
fenestrated sheets of elastin around blood vessels
40
what is the composition/structure of elastic fibers?
-mostly elastin and fibrillin -desmosine (and isodesmosine) cross links -allows for flexibility
41
what are the GAG types?
chondroitin dermatan heparan keratan heparin
42
types of core proteins:
syndecan perlecan lumican aggrecan