Download 1 - UTCOM Class of 2016

Muscle 1 Objectives
Dr. Chiaia
1. Categorize the three types of muscles according to their functions, structural
requirements, nuclear patterns, mechanism of conscious control.
Type/location of
nuclei
VOLUNTARY
INVOLUNTARY
STRIATED
SKELETAL MUSCLE
•
MULTIPLE
NUCLEI
•
PERIPHERAL
CARDIAC MUSCLE
•
1-2 NUCLEI
•
CENTRAL
NON-STRIATED
SMOOTH MUSCLE
•
1 NUCLEUS/
CELL
•
CENTRAL
(TWISTED)
2. Compare the three types of muscle according to sarcomeres, nuclei, cell
junctions, contraction, regeneration and mitosis.
*sarcomere = Striations
Muscle 1 Objectives
Dr. Chiaia
3x types of Skeletal Muscle Fibers: (based on Mb content)
3. Describe the three types of connective tissue in a skeletal muscle, and know
other structures present in these regions.
Types of CT:
a) Epimysium: (Type 1 Collagen) Irregular CT that surrounds many groups of
muscle fibers (i.e. Muscle)
b) Perimysium: (Type 1 Collagen) CT that surrounds Fascicles (a group of
muscle fibers )
c) Endomysium: (Type 1 Collagen) Loose CT that surrounds a Muscle Fiber
(an individual muscle cell) along with the Basal Lamina (Type IV Collagen)
Each Muscle Fiber has:
Myofibrils: structural units inside the M.cell sarcoplasm made of myofilaments
actin and myosin (thin and thick protein chains, respectively)
IFs: Desmin, vimentin and dystrophin hold myofibrils in alignment.
Sarcolemma (plasmalemma)= specialized invaginations, T-tubules
Cytoplasm: Sarcoplasm
Endoplasmic Reticulum: Sarcoplasmic Reticulum, Ca2+ reservoir
Mitochondria: Sarcosomes (usually encircle the myofibrils near the I-band)
Muscle 1 Objectives
Dr. Chiaia
4. Know the limits of Light and Electron Microscopy as they apply to skeletal
muscle fine structure.
- At LM level: The A band, I band and Z line can be observed
- At EM level: In addition to I, A and Z you can see H-Zone & M-Line “H&M”
5. Understand the structural components of a “Triad”, and the banding patterns of
a sarcomere.
Sarcomere Banding:
A Band: LM Region of overlapping thick and thin filaments
I Band: LM Thin filaments only
H Band: EM Thick filaments only (Light staining region @ center of A band)
M Line: EM Thick filaments and crossbridges (dark staining line at center of H
zone)
Z Line:
LM Alternately spaced thin filaments from adjoining sarcomeres
anchored by protein cross bridges
“Triad”: 2 x terminal cisternae + transverse T- tubule
Detailed text and picture from:
http://cwx.prenhall.com/bookbind/pubbooks/martinidemo/chapter10/medialib/CH10/html/ch10_3_3.html
This site is very helpful at filling in some of the sparse blanks.
Muscle 1 Objectives
Dr. Chiaia
6. List the proteins that are associated with the Z-line and describe each of their
functions.
 Z Line Protein: Anchoring Protein – shape of Z
 Alpha Actinin: Binding Protein for Actin – actin to Z line
 Cap-Z: Caps the + ends of the thin filaments at Z line
7. List the proteins that are associated with the thin filament and describe each
of their functions. What is the major protein? What are the specific functions of
the “minor” proteins?
3x major proteins: Z-line Protein, Alpha Actinin, Cap-Z
5x minor proteins:
 Actin: (polar has + end that is attached and an – free end)
o Helical Dimer
o Has Myosin binding site
 Tropomyosin: Regulates availability of myosin binding sites
o At rest covers myosin binding sites on actin filament
 Troponin: Ca+ regulation of contraction
o 3 globular subunits
o TnT = Tn Tropomyocin Binds to tropomyosin strand and one G actin,
holding Tn-Tropomyocin complex in position.
o TnI = Tn inhibit Binds to tropomyosin locking them together as a
troponin–tropomyosin complex
o TnC = Tn calcium Binding site for Ca2+ during initiation of muscle
contraction. In a resting muscle, intracellular Ca2+ concentrations
are very low and this binding site is empty.
o A contraction cannot occur unless the position of the troponin–
tropomyosin complex changes, exposing the active sites on F actin.
The necessary change in position occurs when calcium ions bind to
receptors on the troponin molecules.
 Nebulin: Anchored at Z line, runs the length of each actin filament.
o Nebulin holds the F actin strand together: back bone
o As thin filaments develop, the length of the nebulin molecule runs
the length of the F actin strand.
 Tropomodulin: cap protein for – end of actin filaments.
8. List the proteins that are associated with the thick filament and describe each
of their functions.
 Myosin: Major structural protein
o Dimer
 M-Line Proteins:
o Myomesin: holds myosin bundles apart to allow for overlap of thin
filaments
o Creatine kinase: catalyzes the conversation of ADP to ATP
 C-Protein: binds myosin strands together into a thick filament
 Titin: anchors the tail regions of the myosin dimers
Muscle 1 Objectives
Dr. Chiaia
9. List the proteins that are associated with the M-line and describe each of their
functions.
See number 8 for answer.
10. Understand the 3-dimensional aspects of a sarcomere. Know what a
sarcomere looks like in longitudinal section and in cross section. Know the cross
section patterns associated with trans-sections in different band regions.
Transverse EM view:
 Each Actin Filament is associated with 3 adjacent myosin filaments.
>> Actin: Myosin = 1:3
 Each myosin filament contacts 6 adjacent actin filaments.
>> Myosin: Actin = 1:6
11.Understand the requirement for actin cap proteins.
Cap Z is one of the 3x major Z-line proteins, and it truncates actin filament at Zline, without a cap protein, actin continues polymerization at the + end.