Neuromuscular Junction to Myocyte

Question 1

Neurotransmitter is always ___________ in skeletal muscle contraction

Answer 1

Neurotransmitter is always ACETYLCHOLINE in skeletal muscle contraction

Question 2

Acetylcholine after triggering an A.P on Ach receptor on myocyte is eliminated by ______________

Answer 2

Acetylcholine after triggering an A.P on Ach receptor on myocyte is eliminated by Acetylcholinesterase

Question 3

What is a sarcolemma

Answer 3

The plasma membrane on a muscle fibre

Question 4

Labelling the sacromere

Answer 4

Z line at the beginning and end of each sarcomere
H(alf myosin) band
A(ll myosin) band
I(nbetween the sarcomere) band

Question 5

During a contraction. Which of the bands shortens

A band, H band, I band

Answer 5

H band and I band

Question 6

What is Myosin

Answer 6

Myosin is the ‘‘motor protein’’

Pulls actin

Question 7

1 Myosin has access to ____ Actin

Answer 7

1 Myosin has access to 6 Actin

Question 8

1 Actin has access to ___ Myosin

Answer 8

1 Actin has access to 3 Myosin

Question 9

During a contraction, Z line of each sarcomere come closer together. True or False

Answer 9

True

Question 10

The centre of each Myosin (thick filament) is called the ______

Answer 10

Bare zone (only myosin tail, no myosin head)

Question 11

The M line of the Myosin is made up of ________ . The function of the M line is to ____________________________

Answer 11

The M line of the Myosin is made up of MINOR PROTEINS . The function of the M line is to KEEP PARALLEL MYOSIN ALIGNED.

Question 12

List 3 components of Actin Filaments

Answer 12

1. Actin
2. Tropomyosin- block actin-myosin activity
3. Troponin- controls tropomyosin

Question 13

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

Answer 13

True

Question 14

Troponin attaches to both the actin filament and tropomyosin. True or False

Answer 14

True

Question 15

What is Excitation?

Answer 15

When a neuron stimulates a muscle cell

Question 16

What is Excitation-Contraction Coupling?

Answer 16

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

Question 17

What is the second messenger in muscle contraction?

Answer 17

Free Calcium

Question 18

Where are Ca2+ ions stored in the myocyte

Answer 18

Sarcoplasmic Reticulum

Question 19

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

Answer 19

True

Question 20

Tetany lasts for a long period of time. True or False

Answer 20

False

Question 21

Twitch is fast, tetany is slow. True or False

Answer 21

False. Tetany is fast, Twitch is slow.

Tetany is continuous muscle contraction.

Question 22

What is cross bridge cycling

Answer 22

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

Question 23

At rest, ________ blocks the actin-myosin interaction

Answer 23

At rest, TROPOMYOSIN blocks actin-myosin interaction

Question 24

Troponin is made up of 3 sub-units. List them and explain their function

Answer 24

1. Troponin I = Inhibitory/binds to actin
2. Troponin T = Tropo-myosin binding
3. Troponin C = Calcium ion binding

Question 25

How many Ca2+ binding sites are present on a single Troponin C sub-unit

Answer 25

4

Question 26

Beside Ca2+ ion, what other ion is necessary in muscle contraction

Answer 26

Magnesium ion , for the production of ATP

Question 27

myosin head cleaves ATP into ADP and P which activates myosin head into high energy state. True or False

Answer 27

True

Question 28

Myosin head + ADP binds actin if Ca2+ is absent. True or False

Answer 28

False. Only if ca2+ is present

Question 29

Myosin head swivels from 45 degrees to 90 degrees angle. True or False

Answer 29

False. | It swivels head from 90 degrees to 45 degrees.

Question 30

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

Answer 30

True

Question 31

List a drug for the following Nicotinic Agonist Nicotinic Antagonist Acetylcholinesterase inhibitor

Answer 31

``` Nicotinic Agonist : Carbachol - treats glaucoma Nicotinic Antagonist: Curare poison AChE inhibitor Donepezil for Alzheimer's ```

Question 32

What is rigor mortis and how does it occur

Answer 32

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.