Muscle

Question 1

where is the sarcoplasmic reticulum located and what does it store

Answer 1

surrounds myofibrils

stores calcium ions

Question 2

z lines

Answer 2

represents the boundary between 1 sarcomere and the next

Question 3

m line

Answer 3

middle of a band

Question 4

actin

Answer 4

thin

Question 5

myosin

Answer 5

thick

Question 6

A band

Answer 6

Dark- overlap both actin and myosin

Question 7

I band

Answer 7

Light- Only actin

Question 8

H Zone

Answer 8

Dark Area in middle only myosin

Question 9

What happens to Z lines, A,I band and H zones during muscle contraction

Answer 9

A band unchanged
I,H bands shorten
Z lines become closer together

Question 10

Sarcomere

Answer 10

Distance between 2 Z lines

Question 11

role of tropomyosin in muscle contraction

Answer 11

1. Moves out of the way when calcium ions bind;

2. Allowing myosin to bind (to actin)/crossbridge formation;

Question 12

role myosin in muscle contraction

Answer 12

1. Head (of myosin) binds to actin and moves/pulls/slides actin past;
2. (Myosin) detaches from actin and re-sets/moves further along (actin)
3. This uses ATP;

Question 13

Why do fast muscle fibres have a high glycogen content

Answer 13

1. (Glycogen broken down) gives (lots of) glucose for glycolysis/anaerobic respiration;
2. Glycolysis/anaerobic respiration not very efficient/only yields 2 ATP per glucose;

Question 14

Why do slow muscle fibres have many capliaries

Answer 14

1. (Many capillaries) give high concentration/lots of oxygen/ shorter diffusion pathway for oxygen/large surface area for oxygen exchange/diffusion;
2. Good glucose supply with little glycogen present;
3. Allows high rate of/more aerobic respiration OR prevents build-up of lactic acid/(muscle) fatigue;

Question 15

process that occurs after depolarisation that allows myosin head to bind

Answer 15

Relaxed muscle – 
tropomyosin 
Covering myosin binding sitesCa ions flood into muscle 
from the S-R after 
depolarisation Ca ions bind TROPONIN – 
this alters the 
shape of the 
T-T-A complexTROPOMYOSIN gets 
displaced and exposes 
(unblocks) MYOSIN 
BINDING SITES

Question 16

What is a motor unit and what are its advantages

Answer 16

when all muscle fibres supplied by single motor neurone and they act as a single functional unit
arrangement gives control over the force muscle exerts-If only slight force is needed, only a few units are stimulated. If a greater force is required, a larger number of units are stimulated.