Muscle Contraction

Question 1

Structure of skeletal

Answer 1

Striated, long, contain many nuclei and mitochondria

Question 2

Structure of cardiac

Answer 2

striated, only one nucleus

Question 3

Structure of smooth muscle

Answer 3

single nucleus, no t tubule system, irregular arrangement

Question 4

t tubule system is

Answer 4

structural system of membrane folds characteristic of skeletal and cardiac muscle

Question 5

ryanodine receptors are

Answer 5

calcium release channels in the sarcoplasmic reticulum

Question 6

troponin is

Answer 6

calcium sensor in skeletal and cardiac muscle

Question 7

tropomyosin is

Answer 7

protein associated with actin that prevents myosin binding

Question 8

calmodulin

Answer 8

calcium sensor in smooth muscle cells

Question 9

myosin light chain kinase (MLCK)

Answer 9

activated by calcium-calmodulin that converts smooth muscle myosin to more active form

Question 10

organisation of skeletal muscle

Answer 10

-organised as group of bundles (fasciles).
-each fascile has many muscle cells (known as muscle fibre)
-within the muscle fibre (single cell), contains contractile units

Question 11

neuromuscular junction (NMJ)

Answer 11

a synaptic connection between the terminal end of a motor nerve and a muscle

Question 12

ACh is released and binds to receptor on muscle membrane. what happens when it reaches receptors?

Answer 12

-membrane channels open and contraction of relaxed muscle fibres begin

Question 13

opening of what ion channels causes depolarisation?

Answer 13

sodium ion

Question 14

ACh containing vesicles fuses with membrane. what is released and where does it bind?

Answer 14

acetylcholine is released and diffuses a short distance binding to nAChR

Question 15

When do muscle fibres relax?

Answer 15

when nervous system signal is no longer present

Question 16

one sarcomere runs from

Answer 16

one z disc to the next

Question 17

thick filaments contain

Answer 17

mysoin

Question 18

thin filaments contain

Answer 18

actin

Question 19

sarcoplasmic reticulum is

Answer 19

big energy store for calcium
surrounds each myofibril

Question 20

mechanism behind muscle contraction

Question 21

role of myosin ATPase

Answer 21

allows myosin to consume ATP and convert it into ADP and pi

Question 22

sliding filament model

Answer 22

• Both in skeletal and cardiac muscle rise in calcium will bind to troponin and remove tropomyosin from the myosin binding site on actin leaving them exposed
• Allows myosin head (on myosin filament), with hydrolysed ATP to then bind leading to power stroke when ADP released
  -More ATP binding will cause detachment of myosin head and the subsequent hydrolysis will cause shape of myosin to change and move along another actin binding site
• Causes muscle cell to shorten and contract

Question 23

summarise muscle contraction

Answer 23

• Neuron AP leads to ca2+ influx
  -ACh released
  -Activate nAChR
• Depolarisation open voltage gated Na+ ion channel
  -T-tubule dihydropyridine activated
  -Calcium released
  -Calcium binds to troponin
  -Sliding filament model

Question 24

V SNAREs found in

Answer 24

vesicles

Question 25

T SNAREs found in

Answer 25

cell membrane

Question 26

Two main types of T SNAREs

Answer 26

syntax-1 and SNAP 25

Question 27

How is a SNARE PIN created?

Answer 27

-Rise in calcium, Ca2+ binds to synaptotagamin - The SNAP has higher afinity for phospholipids and stops interacting with VSNARE -brings vesicle a little closer, allowing VSNARE (synaptobrevin) to interact with the TSNARE

Question 28

what effect does botox have on SNAREs

Answer 28

degrades VSNARE/ TSNARE so vesicle for ACh cannot fuse

Question 29

what is synaptotagamin?

Answer 29

calcium sensor

Question 30

role of sarcoplasmic reticulum

Answer 30

big calcium store

Question 31

function of ryanodine receptor, RyR

Answer 31

Calcium release channel, suppresses the opening and stops leak of calcium

Question 32

mechanism for calcium release out of RyR

Answer 32

- activated of nAChR -opening of voltage sodium channels -passes excitation down the t tubules -activated DHPR - molecular change thats caused, removes physical interaction

Question 33

CICR

Answer 33

calcium induced calcium release

Question 34

function of CICR

Answer 34

calcium influx induces RyR to release calcium

Question 34

function of CICR

Answer 34

calcium influx induces RyR to release calcium

Question 35

Summarise muscle contraction

Answer 35

- Neuronal A.P leads to calcium influx -ACh release activates nAChr -depolarisation open voltage-gated Na+ channel - t-tubule DHP activated - Calcium release -Calcium ions bind to troponin, leading to removal of inhibitory tropomyosin -ATP hydrolysis by myosin -This primed myosin binds to actin -As ADP released , it moves the actin towards the middle of the cell leading to cell shortening

Question 36

difference between skeletal and cardiac for excitation through t tubules

Answer 36

skeletal- voltage sensitive DHP protein leads to calcium release from SarcR Cardiac- voltage- sensitive calcium channel leads to CICR from SR

Question 37

What happens in the contractile cycle?

Answer 37

-Cross bridge formation releases pi troponin bind to myosin head -power stroke, ADP is released and myosin undergoes a conformational change pulled towards centre of sarcomere -ATP binds to myosin, causing detachment of myosin from actin, cross-bridge dissociates -ATP hydrolysis occurs, cocking myosin head

Question 38

T-tubule define:

Answer 38

structural system of membrane folds characteristic of skeletal and cardiac muscle

Question 39

Ryanodine receptors define :

Answer 39

calcium release channels in the sarcoplasmic reticulum

Question 40

Troponin define:

Answer 40

calcium sensor in skeletal and cardiac muscle

Question 41

tropomyosin define:

Answer 41

A protein associated with actin that prevents myosin binding

Question 42

calmodulin define:

Answer 42

calcium sensor in smooth muscle cells

Question 43

Myosin Light Chain Kinase (MLCK) define:

Answer 43

Activated by calcium-calmodulin that converts smooth muscle myosin to a more active form