practice q's - SMS Flashcards
What is the neurotransmitter released at the neuromuscular junction?
acetylcholine
What type of receptor does acetylcholine bind to at the motor end plate?
nicotinic receptor
What type of receptor does acetylcholine bind to at the motor end plate?
calcium (Ca2+)
what is the role of T-tubules?
transmits action potentials deep into the muscle fiber
What is the direct function of the dihydropyridine receptor (DHPR)?
voltage sensor to activate RyR
what is the primary role of troponin C in muscle contraction?
binds calcium
what is the cause of myasthenia gravis?
autoantibodies block nicotinic receptors
What ion is responsible for muscle fiber depolarization?
sodium (Na+)
what does the tropomyosin protein do? the myosin-binding sites on actin at rest?
covers the myosin-binding sites on actin at rest
what is the role of SERCA (Ca2+ ATPase)?
reuptakes calcium into the sarcoplasmic reticulum
which best describes the cross-bridge cycle?
ATP binds to myosin, allowing detachment
what is the role of RyR and what is it activated by?
activated by DHPR to release calcium
which drug blocks acetylcholine release at NMJ? which drug causes explosive release of ACh at NMJ?
blocks: botulinum toxin (BOTOX- fights wrinkles)
explosive release: black spider venom (so much contraction that muscle paralyzes)
Which of the following best describes malignant hyperthermia?
uncontrolled calcium release from sarcoplasmic reticulum
malignant hyperthermia: rapid rise in body temp & severe muscle contractions
A researcher applies a drug to a neuromuscular junction that prevents opening of voltage-gated calcium channels in the presynaptic terminal.
What will be the primary effect on synaptic transmission?
Decreased acetylcholine release
skeletal muscle contraction is tightly regulated by what?
conc. of Ca2+ in the sarcoplasm
name 2 differences b/w smooth and skeletal muscle contraction
- Smooth muscle contraction uses less energy and lasts longer compared to skeletal muscle - resistant to fatigue
- Smooth muscle contraction does not require an action potential
smooth muscle maximal force of contraction
higher maximal force of contraction b/c of slower cross-bridge cycle
which of the following best describes an attribute of visceral smooth muscle not shared by skeletal muscle?
contracts in response to stretch
what does the H zone contain?
myosin but no actin
H zone: region in center of sarcomere composed of light bands on either of and including the M line
- there are no overlapping actin filaments here
Resting membrane potential of nerve fiber is near to the equilibrium potential of which of the following ion?
potassium (K+)
Resting membrane potential of a typical nerve cell is primarily maintained by
The sodium-potassium pump (Na+/K+ ATPase)
Which enzyme is responsible for the dephosphorylation of myosin light chain in smooth muscle relaxation?
Myosin light-chain phosphatase (MLCP)
responsible for smooth muscle relaxation
Hydrolysis of ATP by myosin is directly responsible for what?
Generating the power stroke during muscle contraction
During a laboratory experiment, a researcher applies a drug that blocks voltage-gated sodium channels in a nerve fiber. What will happen to the action potential?
No action potential will be generated
Voltage-gated Na+ channels are essential for the depolarization phase of an action potential
A 60-year-old man with a neuromuscular disorder has impaired calcium release from the sarcoplasmic reticulum. How does this affect the sliding filament model?
Tropomyosin remains covering the myosin-binding sites
which structure is mainly responsible for conductivity in cardiac muscle?
gap junctions
