Neurotransmitter is always ___________ in skeletal muscle contraction
Neurotransmitter is always ACETYLCHOLINE in skeletal muscle contraction
Acetylcholine after triggering an A.P on Ach receptor on myocyte is eliminated by ______________
Acetylcholine after triggering an A.P on Ach receptor on myocyte is eliminated by Acetylcholinesterase
What is a sarcolemma
The plasma membrane on a muscle fibre
Labelling the sacromere
Z line at the beginning and end of each sarcomere
H(alf myosin) band
A(ll myosin) band
I(nbetween the sarcomere) band
During a contraction. Which of the bands shortens
A band, H band, I band
H band and I band
What is Myosin
Myosin is the ‘‘motor protein’’
Pulls actin
1 Myosin has access to ____ Actin
1 Myosin has access to 6 Actin
1 Actin has access to ___ Myosin
1 Actin has access to 3 Myosin
During a contraction, Z line of each sarcomere come closer together. True or False
True
The centre of each Myosin (thick filament) is called the ______
Bare zone (only myosin tail, no myosin head)
The M line of the Myosin is made up of ________ . The function of the M line is to ____________________________
The M line of the Myosin is made up of MINOR PROTEINS . The function of the M line is to KEEP PARALLEL MYOSIN ALIGNED.
List 3 components of Actin Filaments
- Actin
- Tropomyosin- block actin-myosin activity
- Troponin- controls tropomyosin
Actin is made up of G actin monomers that polymerises into double helix strand to form F- actin helix.
F- actin helix has groove on each side that is occupied by tropomyosin. True or False
True
Troponin attaches to both the actin filament and tropomyosin. True or False
True
What is Excitation?
When a neuron stimulates a muscle cell
What is Excitation-Contraction Coupling?
the link between depolarisation of the myocytes through a little influx of ca2+ and the consequent huge increase in cytosolic ca2+ that leads to a contraction
What is the second messenger in muscle contraction?
Free Calcium
Where are Ca2+ ions stored in the myocyte
Sarcoplasmic Reticulum
During Twitch, ca2+ is pumped back into SR,
During Tetany, relaxation is not long enough to pump ca2+ back into SR despite Vm repolarisation. True or False
True
Tetany lasts for a long period of time. True or False
False
Twitch is fast, tetany is slow. True or False
False. Tetany is fast, Twitch is slow.
Tetany is continuous muscle contraction.
What is cross bridge cycling
The process of the myosin head pulling the actin, consuming ATP and resetting.
It is controlled by ca2+ ions binding to troponin, which moves tropomyosin away from F- actin groove on actin double helix
At rest, ________ blocks the actin-myosin interaction
At rest, TROPOMYOSIN blocks actin-myosin interaction
Troponin is made up of 3 sub-units. List them and explain their function
- Troponin I = Inhibitory/binds to actin
- Troponin T = Tropo-myosin binding
- Troponin C = Calcium ion binding
How many Ca2+ binding sites are present on a single Troponin C sub-unit
4
Beside Ca2+ ion, what other ion is necessary in muscle contraction
Magnesium ion , for the production of ATP
myosin head cleaves ATP into ADP and P which activates myosin head into high energy state. True or False
True
Myosin head + ADP binds actin if Ca2+ is absent. True or False
False. Only if ca2+ is present
Myosin head swivels from 45 degrees to 90 degrees angle. True or False
False.
It swivels head from 90 degrees to 45 degrees.
Nicotinic receptors and Muscarinic receptors both require agonists. Nicotinic 2nd messenger is an ion channel (Na+/K+) while Muscarinic 2nd messenger is G-protein (which can then act on an ion channel). True or False
True
List a drug for the following
Nicotinic Agonist
Nicotinic Antagonist
Acetylcholinesterase inhibitor
Nicotinic Agonist : Carbachol - treats glaucoma Nicotinic Antagonist: Curare poison AChE inhibitor Donepezil for Alzheimer's
What is rigor mortis and how does it occur
Rigor Mortis is the rigidity of the dead.
It occurs as a result of depleted ATP as respiration stops. Ca2+ is not recycled back into S.R. High cytosolic ca2+ allows cross-bridge cycle contraction. Without ATP, myosin head remain attached to F-actin groove and just stops after power stroke.