Skeletal Muscle 1

Question 1

Sarcotubukar system made up of

Answer 1

Sarcoplasmic reticulum and transverse tubules

Question 2

Thin filaments are found in the muscle in the form of

Answer 2

G actin which are polymerased to form a strand called f actin, which are interwoven over one another to form helix

Question 3

What are regulatory proteins of muscles

Answer 3

Tropomyosin and Troponin

Question 4

Tropomyosin?

Answer 4

Rod like protein which covers the site for myosin attachment on the F actin molecule. Forms part of thin filamentd

Question 5

Troponin

Answer 5

It’s a globular protein complex. Forms part of thin filaments. Troponin C, binds to Ca2+. Troponin I is inhibitory in function. Troponin T is Attached to tropomyosin

Question 6

What is Titin?

Answer 6

Protein that holds myosin filament to center of I band

Question 7

What does thick filament consist of

Answer 7

S symmetrical halves that are mirror imagined of each other.
Had 6 peptide chains. 2 identical heavy chains
4 light chains

Question 8

What are the 2 binding sites of myosin molecule

Answer 8

Binding site for Actin

ATP ase site

Question 9

Nebulum?

Answer 9

Runs in the middle of thin filament

Question 10

What are the anchoring proteins?

Answer 10

Alpha actin
Titin
Nebulin
Dystrophin

Question 11

When there is contraction, what essentially happens in the contractile proteind

Answer 11

Calcium enters sarcolemma, binds with troponin. Interacts with tropomyosin and displace it from active site of actin for myosin binding. Calcium therefore very important for activation of thin filament

Question 12

When is thick filament activated

Answer 12

When ATP binds to it and is hydrolyzed to ADP. Myosin head in high energy state will bind to actin.

Question 13

What is the rate determining step of muscle contractions

Answer 13

Availability of calcium in sarcoplasm

Question 14

What is the motor end plate

Answer 14

Part of sarcolemma which interacts with the motor neurone

Question 15

Which enzyme breaks down Ach

Answer 15

Acetylcholine esterase

Question 16

Neuromuscular junction is made up of

Answer 16

Motor end plate, motor neurone and synaptic cleft

Question 17

Which receptor in t tubule is activated by action potential

Answer 17

Dihydropyridine receptors

Question 18

Which gates are opened as a result of activation of dhp receptors

Answer 18

Voltage gated foot proteins/ ryanodine channel/ Ca release channel. Channels present in cisterns of the sarcoplasmic reticulum

Question 19

Muscle relaxation is initiated by

Answer 19

Ach broken down by AchE. After which sarcoplasmic reticulum recaptures Ca2+

Question 20

Drugs that block the release of Ach?

Answer 20

Botulinum toxin, lack of Ca, excess of Mg

B prevents release of ach by blocking fusion of ach containing vesicles with pre synaptic membrane and prevents exocytosis. Has therapeutic use to relieve pain and pathological contraction

Lack of calcium also leads to blocking of exocytosis of the secretory vesicles

Question 21

Drugs that block transmission at neuromuscular junction?

Answer 21

Curaruform drugs, eg, D tubocurarine
Prevent passage of impulses from nerve ending into muscle
Done by competing with Ach for the receptor sites on post synaptic membrane
Drug prevents ach from activating receptors decreasing permeability of membrane and inability to initiate action potential
Used to control convulsions or during surgery when complete muscle relaxation is required

Question 22

Drugs that stimulate muscle fibre by Ach like action

Answer 22

Methacholine, carbachol, nicotine

Question 23

Drugs that stimulate neuromuscular junction by inactivation achE

Answer 23

Neostigmine, physostigmine, diisopropyl fluorophosphate

Fluorophosphate used as powerful military nerve gas poison

Question 24

Myasthenia gravis ?

Answer 24

Antibodies in bodies destroy receptors and ach cannot act upon them to cause an action potential

Question 25

Alpha actinic function :

Answer 25

Cross link actin filaments at area of z line

Question 26

Titin function

Answer 26

Largest known protein in the body. Connects the z line to the m line in the sarcomere and forms the sec of the muscle

Question 27

Nebulin function

Answer 27

Nebulin is an actin-bindingproteinwhich can bind upto 200 actin molecules. Nebulin length is proportional to the length of the thinfilament. It may function as a regulator of thinfilamentlength during sarcomere assembly.

Question 28

Function of dystrophin

Answer 28

Dystrophin is aproteinfound in muscle cells. It is one of a group ofproteinsthat work together to strengthen muscle fibers and protect them from injury asmusclescontract and relax.

Question 29

Motor end plate potential?

Answer 29

Membrane potential formed in the form of graded potential after ach binds to receptors

Question 30

Ach is broken down into

Answer 30

Acetyl coA and choline