ELM 8.1 Flashcards
The nAChR is a _________ transmembrane protein
pentameric
The nAChR is made up of what
2 alpha, 1 beta, 1 delta, and 1 epsilon
the nAChR has ____ instead of ____ in fetal receptors
gamma subunit
epsilon subunit
most of the antibodies in nAChR target the same part of the nAChR which is what?
MIR -main immunogenic region
in MG, the number of ___ is greatly reduced
nAChRs
sarin is what?
An irreversible inhibitor of AChE.
In skeletal muscle, the I band is formed by:
a. the attachment site for thin filaments b. the overlap of thin and thick filaments c. thick filaments d. thin filaments
d
The I band is formed primarily by actin (thin filaments) though there are other proteins contained within the Z line, and proteins such as nebulin, which is associated with actin, and titin, which stretches from the Z line to the M line. The I band is the portion of the thin filament that does not overlap with the thick filaments (myosin)
During contraction of skeletal muscle, the following structures shorten:
a. A band b. A and I bands c. H zone d. H zone and I band
d
The H zone and the I band are, respectively, the areas of the thick filaments that do not overlap with the thin filaments, and the areas of the thin filaments that do not overlap with the thick filaments. Overlap of the thick and thin filaments, and hence the length of the H zone and I bands, changes during muscle contraction.
In skeletal muscle, the function of titin is to:
a. cover actin sites b. maintain structure and elasticity c. regulate access to the myosin heads d. sequester calcium after contraction
b
Titin is the largest known mammalian protein and is a key structural component of muscle. It helps in muscle assembly and structural maintenance and its elasticity allows it to act as a kind of “molecular spring”.
Which of the following types of protein binds calcium and regulates the contraction of skeletal muscle?
a. actin b. myosin c. tropomyosin d. troponin C
d
In skeletal and cardiac muscle, the binding of calcium by troponin C is critical in the regulation of muscle contraction. Smooth muscle does not have troponin C. Instead, the regulation of contraction is mediated by myosin light chain kinase.
In skeletal muscle the calcium required for contraction enters the cytoplasm from/via the:
a. end-plate membrane b. sarcolemma c. terminal cisternae d. t-tubules
c
The terminal cisternae (also known as lateral sacs) are the portion of the sarcoplasmic reticulum adjacent to the t-tubules. The terminal cisternae contain ryanodine receptors (also known as the SR release channel). These are calcium channels whose opening is triggered via a physical linkage to voltage gated L type calcium channels (also known as dihydropyridine receptors) in the T tubules. Opening of the ryanodine receptors releases the Ca2+ that is accumulated in the SR by the Ca2+ ATPase.
At the neuromuscular junction acetylcholine signalling is terminated by the actions of:
a. acetyl coenzyme A
b. acetylcholinesterase
c. choline acetyltransferase
d. reuptake systems
b
AChE cleaves the ester bond between acetate and choline and thus ends the synaptic action of ACh.
In myasthenia gravis, the main immunogenic region is located in the nicotinic acetylcholine receptor:
a. alpha subunits b. beta subunit c. delta subunits d. epsilon subunit
a
The MIR is located at amino acids 67-76 of the alpha subunits (2 per receptor). This is at the top of the receptor and allows for easy access of antibodies.
The electroplaque of the Torpedo electric ray is embryologically related to:
a. connective tissue b. muscle c. neurones d. the adrenal medulla
b
The electrocytes in electric fish as specialized muscle tissue. They contain similar nicotinic acetylcholine receptors to those found in vertebrate muscle, but in much greater quantities. This has made the electroplaque very important to scientists studying the nicotinic receptor.
A drug that restores the enzymatic activity of acetylcholinesterase following exposure to sarin is:
a. atropine b. edrophonium c. pralidoxime d. pyridostigmine
c
Pralidoxime removes the sarin moiety from the serine in the active site of AChE. Atropine is also used as an antidote, but it works by counteracting the hyperstimulation of muscarinic receptors that sarin causes. Pyridostigmine can be used to protect the active site against sarin (by occupying it) but cannot remove sarin once it has bound.
