Histology - 514-8 Flashcards
What is the connective tissue component that surround a muscle cell?
Endomysium
What is the specialized plasma membrane of muscle cells called?
Sarcolemma
What is the cytoplasm of a muscle cell called?
Sarcoplasm
What is the specialized series of interconnected tubules throughout the sarcoplasm connected to storage sacs of Calcium called?
Sarcoplasmic Reticulum
Myofibrils are made up of…
myofilaments
Myofilaments are made of…
Actin and Myosin
What protein anchors myofibrils inside a muscle cell?
Dystrophin
What is a disease caused by abnormalities in dystrophin?
Muscular Dystrophy
What are T-tubules?
Perpendicular invaginations of the sarcolemma.
What connective tissue fibers surround the sarcolemma and connect muscle cells together?
Endomysium
What type of CT is continuous with the ends of a muscle cell to tendon?
Dense Regular
What type of cells are found between the Endomysium and Sarcolemma?
Satellite Cells.
A resting muscle cell membrane is______ and has a ______ charge
Polarized
Net postitive outside the cell
What defines a sarcomere?
Z- lines
Where does depolarization of a cell occur after it leaves the NMJ?
Sarcolemma and T-tubules
What are A bands?
The entire length of Myosin
What is the H band?
Myosin without actin overlap
What is the I band
Only actin with no myosin overlap
At rest, what covers the active site on the actin filaments?
Tropomyosin
What begins at the ACh receptors at the terminal button?
Depolarization
Upon depolarization, what do T-tubules induce the sarcoplasmic reticulum to release?
Calcium through channels.
What does Calcium bind to release tropomyosin from the actin filament?
Troponin
What is the key process of anabolic steroid use?
Stimulation of satellite cells. (Incorporation in fibers)
What is the functional unit of a muscle?
Sarcomere
Where is the calcium reservoir in sarcoplasmic reticulum?
Terminal Cisternae
Where are terminal cisternae positioned?
Over actin/myosin overlap
What structure is located between two terminal cisternae?
T-tubule
What does the t-tubule combined with lateral cisternal structures comprise?
Triad
Where are triads found in an transmission electron micrograph?
On border of myosin/actin, often next to mitochondria
What are the two regulatory proteins on Actin?
Tropomyosin (big)
Troponin (small - Ca binding site)
How many heads does one myosin contain?
Two
How many actin subunits make up an actin filament?
6 or 7
What is the elastic component in a sarcomere?
Titin - aka connectin
Where is Titin found?
Z-disk to M-line
How many muscle fibers can a small motor unit innervate?
Large motor unit?
3-6 fibers per nerve
1000 fibers per nerve
What is the synapse between a nerve fiber and muscle cell called?
NMJ
What is the folded and specialized region of sarcolemma under the terminal bouton called?
Motor End Plate
What enzyme breaks down ACh in the synaptic cleft?
Acetylcholinesterase
What is a cell membrane potential?
0.06 volts / 60 millivolts
What main ion is outside the cell?
Inside the cell?
Na
K
What helps create negative charge inside the cell?
Anionic proteins
What ion enters the synaptic bulb (bouton)
Calcium
What does entry of Calcium trigger?
ACh release
What moves more in depolarization, Na or K?
Na
Is the motor end plate ligand gated or voltage gated?
Ligand (ACh)
What do ACh receptors allow?
binding of ACh, opening of channel, which allows Na to rush into the cell
What does Calcium bind?
What does this do?
Troponin
Exposes Actin active site
What breaks the cross-bridge between actin and myosin?
ATP
What removes calcium from the sarcoplasmic reticulum?
Active transport pumps (use ATP)
What causes rigor mortis?
Sarcoplasmic reticulum breaks down - releases Calcium
Ca activated actin/myosin cross bridging
No ATP to remove myosin heads
How does botox work?
blocks ACh release
How does curare work?
blocks ACh receptors
How does tetrodotoxin work?
blocks Na movement in nerves
How does Black Widow venom work?
causes mass release ACh
How does Tetanus work?
blocks glycine (inhibitor preventing overstimulation)
How do many pesticides work?
By inhibiting acetylcholinesterase
What is Myasthenia Gravis and how does it work?
Autoimmune
Degrades ACh receptors - muscles no longer work
What are 2 ways to regenerate ATP from ADP?
Myokinase
Creatine kinase
What type of muscle fiber is fast twitch?
White
IIb
What is the main difference between cardiac and skeletal muscle?
Intercalated disks
also gap junctions and desmosomes
Is smooth muscle multi-nucleated?
No
What are the neurotransmitters for smooth muscle?
Norepinepherine and ACh
What to dense bodies do in smooth muscle?
create triangulation contraction between thin and thick filaments.
How are calcium channels often stimulated in smooth muscle?
Mechanically
What is a primary regulatory protein in smooth muscle?
Calmodulin
What does Calmodulin activate?
MLCK
Why is smooth muscle contraction slow?
ATPase act slowly
Ca pumps also slow
