Muscle Lecture 1

Question 1

Features of Skeletal muscle

Answer 1

single long cylindrical cells

Striated

Multiple peripheral nuclei

Voluntary control

Question 2

Features of Cardiac muscle

Answer 2

branched

1-3 peripheral nuclei

involuntary

located in the heart

connected via intercalated discs

Question 3

Features of Smooth muscle

Answer 3

uninucleic

located within gut and blood vessels

non voluntary

spindle shaped

Question 4

how are muscles attached to bone

Answer 4

via tendon

Question 5

how are skeletal muscle organized

Answer 5

highly organized contractile units

Question 6

Function and location of M line

Answer 6

in the center of the sarcomere connects adjacent thick filaments

Question 7

Location of the A band

Answer 7

runs the entire length of the thick filaments

Question 8

location of the Z discs and function

Answer 8

connects to adjacent sarcomere. anchors thin filament

sheeted proteins

Question 9

H region location

Answer 9

in the middle of the sarcomere (m line) where their is no filament overlapping

Question 10

What are the elastic components within the sarcomere

Answer 10

titin

Question 11

I band

Answer 11

between each z disc with the adjacent sarcomere only contains thin filaments

Question 12

T tubulues structure location and function

Answer 12

Structure: continuation of the sarcolemma

deep invagination which circle each sarcomere

Located: between A and I band junction

function: allows action potential to be carried deep within the muscle cell

Question 13

Sarcoplasmic reticulum
location,
function

Answer 13

location: above the M line

Function: stores/ releases calcium

Question 14

Describe the Thick Myosin filament

structure
function

Answer 14

structure: 2 tails that are entwined to form a helix

2 globular heads that face away from the M line

heads: enzymatic which hydrolyses ATP

Question 15

what are the regulatory proteins of the actin

Answer 15

Troponin- calcium binds to

tropomyosin- exposes the actin binding site

Question 16

Which muscle is troponin and tropomyosin within

Answer 16

cardiac and skeletal muscle

Question 17

describe the sliding filament theory during a contraction

Answer 17

z line gets pulled towards the m line

h area narrows

actin and myosin region overlap

Question 18

what is needed in order for the cross bridge formation to occur

Answer 18

calcium must be bound to troponin therefore, tromyosin exposes binding sites of actin

Question 19

what are the 4 cycles of the cross bridge cycle

Answer 19

1. Cross bridge formation
2. Powerstroke
3. Detachment
4. energization of the myosin head

Question 20

describe cross bridge formation

Answer 20

occurs first

only occurs if tropinin has calcium and tromyosin has moved away from actin binding sit

ATP binds to myosin head causing to to attach to the exposed actin binding site

Question 21

Powerstroke description

Answer 21

2nd process

ATp is hydrolysed to ADP and P and detaches from the myosin head

causing the myosin head to retract into its low energy position (45 degree angle)

causing the sarcomere to shorten

Question 22

Detachment description

Answer 22

3rd process

Atp binds to the head of the myosin causing the myosin to lose attraction with the actin

therefore detachment occurs

Question 23

Energization of the myosin head

Answer 23

ATP hydroylses into ADP and P causing the myosin head to retract into its high energy position (90 degrees)

Question 24

Calcium importance

Answer 24

Allows the cross bridge cycle to occur

calcium levels must remain above critical threshold for CB cycle to occur

Question 25

Describe the release of calcium

Answer 25

calcium is released from the SR into the cytoplasm

Question 26

Describe the inactivation of the release of calcium

Answer 26

the active transport pump (ATPase) are constantly move the CA from the cytosol to the SR

Question 27

Isometric contraction

Answer 27

tension variable
no shortening
length constant

Question 28

isotonic contraction

Answer 28

tension constant
shortening
length variable