Lecture A7, A8 Flashcards by Tami Ojewole

Muscles are formed from this type of cell?

myoblasts

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Myoblasts (def.)

embryonic precursors of myocytes

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myocytes (a.k.a ____ )

muscle cells

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Differentiation of myoblasts into muscle cells is called ______

-myogenesis

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During myogenesis of skeletal muscle, myoblasts do what?

-fuse into multinucleated myotubes, which are combined into muscle fibers

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Myoblasts arise from ______ called _____

-blocks of mesodermal cells
-somites

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Somites are found where?

-lateral to the neural tube in the embryo that is derived from the neural crest.

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Somites also give rise to tissues other than muscle like: ______

-skeletal tissue and CT in skin

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where myoblasts will form in developing somite is determined by ______

specific signals from surrounding tissue including neural tube and the lateral ectoderm

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early somite differentiates into ______

dermomyotosome & sclerotome

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dermomyotosome differentiates into ______

dermotome & myotome

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sclerotome gives rise to ____

skeletal structure

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dermotome gives rise to ______

connective tissue of skin

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____ induce myogenesis

Wnt, Hh and BMP

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In myogenesis, there are multiple types of ______

Wnt proteins and Frizzled receptors

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BMPs act similarly to _____ and act as _____

-TGFB proteins
-morphogens

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BMPs organize what?

several parts of human body including bones

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In myogenesis, Wnt 1/3a from ____ , Wnt6/7a from _____ , BMP4 from _____ and HH act on early somite

-neural tube
-surface ectoderm
-lateral mesoderm plates

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Like other progenitor cells, myoblasts ______ to increase cell number.

-proliferate

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In the correct environment, (signalling proteins), myoblasts will further ______

differentiate into muscles

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Myoblasts also migrate via cell movement through ______ to the sites where muscles will form (aka _____)

-the developing embryo
-premuscle masses

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_____ are transcription factors that direct myoblast
differentiation

-MEFs and MRFs

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MRF stands for _____

muscle regulator factor proteins

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MRF is expressed where?

-only in muscle

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Types of MRF: _____

MyoD, Myf5, Myogenin (MyoG) and Mrf4 (in order of activation)

MRF is ____ (type of TF) that does what? (2)

-a bHLH TF -binds a DNA motif called the E-box, interacts with MEFs

MRF binds to ____ as co-factors

E-proteins

MEF stands for _____

muscle enhancer factor proteins

MEF is expressed where?

-in several cell linages

MEF does what?

-interacts with MRFs -binds DNA motif called MADS box (MEF-box)

MEF often binds DNA as _____

a dimer

The myogenic program is split into two parts: _____

-determination -differentiation

Determination of myogenic program has two parts: ____

-induction -maintenance

Maintenance of myogenic program involves _____

steady state of MRFs and MEFs

Differentiation of myogenic program involves _____

muscle differentiation genes

Expressing MyoD (a MRF) does what in cell?

-turns cell into a myoblast cell

MyoD expression induces muscle cell fate in this lineage?

-mesodermal

MyoD expression does not induce muscle cell fate in these lineages?

-endodermal + ectodermal

MRFs are required at ______ of the myogenic lineage

-multiple stages

MRF transcription factors directly regulate _____ in myoblasts and are degraded after _____

-the cell cycle -associated phase

MRF associated with G1

-MyoD

MRF associated with M

-Myf5

Myocytic stem cell (aka ____)

satellite cell

Myoblasts fusion (uninucleated) form ___ which differentiate to form _____

-myotubes (multinucleated) -muscle fiber/myofiber (multinucleated)

committed satellite cell does this to contribute to muscle regeneration and repair?

symmetric division (horizontal plane)

satellite stem cell does this to contribute to muscle regeneration and repair?

symmetric division (horizontal plane) asymmetric division (vertical plane)

3 types of muscle cells

1) Skeletal muscle 2) Cardiac muscle 3) Smooth muscle

Multiple myoblasts fuse together to form _______

skeletal muscle

The dermomyotome (DM) is derived from the ______

-dorsal part of the somite

A myotome is ____ (def.)

- the group of muscles innervated by a single spinal nerve

Primary myogenesis (def.) + happens at what stage?

-cell fusion (somitic stem cell -> fetal stem cell) -embryonic

Secondary myogenesis (def.) + happens at what stage?

-basal lamina assembly + innervation/NMJ formation (fetal stem cell -> myocytes) -fetal

General structure of skeletal muscle

- myofiber (muscle cell) has multiple myofibrils which has sarcomere units

Sarcomere: I band

thin filaments

Sarcomere: A band

-thin and thick filaments -doesn't change length during contraction

Sarcomere: H zone

-thick filaments only -shortens during contraction

Sarcomere: Z disk

-border between two sacromeres

General structure of smooth muscle cells

-thick and thin filaments -dense bodies + attachment plaques

dense bodies + attachment plaques in smooth muscle cells are analogous to _____ of skeletal and cardiac muscle fibers

Z-discs

Parts of skeletal myofibrils + function

-actin (filamentous and globular)- thin filament -myosin - thick filament -tropomyosin - covers myosin-binding site on actin -troponin - attaches to tropomyosin with Ca++ binding site

Sliding-filament Contraction is dependent on ____

ATP, Ca++

The sarcoplasmic reticulum does what?

-release Ca++ upon depolarization with nerve signals through Ca++ release channel

Ca++ recovery in sarcoplasmic reticulum

-Ca++ renters SR through Ca++ ATPase

T tubules are found in what type of cells?

striated muscle cells (cardiac and skeletal )

Transverse tubules do what?

permit rapid transmission of the action potential into the cell

Nerve that synapses on neuromuscular junction releases _____

acetylcholine (ach)

neuromuscular junction (def.)

chemical synapse between a motor neuron and a muscle fiber

ACh (def.)

neurotransmitter secreted from parasympathetic neurons

Skeletal muscle contraction steps

1) nerve triggers release of ach from synaptic knob into cleft 2) ach binds to ach receptors on NMJ (starts impulse in sarcolemma of muscle fiber) 3)impulse spread through T tubules 4) Ca++ ions released from terminal cisternae into sarcoplasm 5) Ca binds to troponin which changes shape, moving tropomyosin = open active sites 6)myosin heads of thick filament attaches to open sites = crossbridges 7) myosin moves thin fila. toward center then ATP binds myosin heads 8) ATP broken into ADP & P 9) repeating movement until Ca++ removed (active transport) 10) tropomyosin covers active sites = relaxation of filaments

smooth muscle cells have this characteristics: ____

single nuclei (mononuclear), not organized myofibrils

adjacent smooth muscle cells were physically couplied at ____

dense bodies

caveolae function

regulate cell signaling and uptake and release of Ca2+ from sarcoplasmic reticulum

characteristics of cardiac muscle

-mononuclear -gap junctions + desmosomes -intercalated discs

Cardiomyocyte lineage from ____

cardiac mesoderm (further differentiation activates/repressed by Wnt)

Myoepithelial cells are _____ to muscle cells

-similar

Myoepithelium are part of secretory glands: _____

* Sweat * Mammary * Lacrimal (tear) * Salivary

Myoepithelial cells lineage

stem cell -> luminal progenitor + basal progenitor luminal progenitor -> ductal luminal + alveolar basal progenitor -> myoepithelial

Mammary gland epithelium cell lineages

ectoderm => mesenchymal stem cell => endothelial precursor cell => ductal precursor cells (puberty) + alveolar precursors cells (pregnancy) => (both produce) myoepithelial cells + luminal cell

Lecture A7, A8 Flashcards

(78 cards)