Ultra-Structure of Skeletal Muscle

Question 1

Muscles can pull but cannot push. As a result of this limitation muscles generally operate in pairs.

Describe Antagonistic muscle action.

Answer 1

A muscle pulls in one direction at a joint and the other muscle pulls in the opposite direction

Question 1

Muscles can pull but cannot push. What connects muscle to bones ?

Answer 1

Tendons

Question 2

Give an example of Antagonistic muscle action

Answer 2

To raise the lower arm
The bicep contracts and the tricep relaxes

Question 3

What are the specialised cells in skeletal muscle called ?

Answer 3

Muscle fibres

Question 4

What organelle do muscle fibres have a lot of ?

Answer 4

Nuclei

Question 5

What is the membrane surrounding each fibre called ?

Answer 5

Sarcolemma

Question 6

What is the cytoplasm of muscle fibre called ?

Answer 6

Sarcoplasm

Question 7

The sarcolemma has many deep tube-like projections that fold in from its outer surface:

What is the name of these projections and what do they run close to ?

Answer 7

T-tubules
These run close to the SR

Question 8

What are the myofibrils made up of ?

Answer 8

Myofilaments

Question 9

What does the sarcoplasm contain ?

Answer 9

Mitochondria
Myofibrils

Question 10

What is each unit of a myofibril called ?

Answer 10

A sarcomere

Question 11

Why is it an advantage that muscle fibres contain lots of mitochondria

Answer 11

The mitochondria carry out aerobic respiration to generate the ATP required for muscle contraction

Question 12

What are the two different types of protein filaments that Myofibrils contain ?

Answer 12

Actin Filaments (thin)
Myosin Filaments (thick)

Question 13

What is the A band composed of ? HINT : A band is made up of DARK BANDS

Answer 13

Thick myosin filaments and actin filaments

Question 14

What is the I Band composed of ? HINT: I band is light

Answer 14

Thin actin filaments

Question 15

What is the Z line and where is it found ?

Answer 15

Attachment site for actin

The centre of the I band

Question 16

The distance from one z line to another z line is known as what ?

Answer 16

a sarcomere

Question 17

What is the M line and where is it found ?

Answer 17

attachment site for myosin
found in the centre of the A band.

Question 18

Where it the H zone found ?

Answer 18

the centre of the A band

Question 19

Describe the Ultrastructure of Skeletal muscle

Answer 19

Muscle fibres are made up of numerous parallel myofibrils

These are subdivided into myofilaments

The myofilaments are made up of actin (thin filaments) and myosin (thick filaments)

Question 20

Describe what a tendon is and its function

Answer 20

Lengths of connective tissue
That join skeletal muscle to bone

Question 21

Describe what happens to the length of the i bands and the length of the A bands during muscle contraction.

Answer 21

The A band would stay the same size / will not change
Because it is the region containing both myosin and actin filaments and the filaments themselves do not change length during contraction
AND

The I band would decrease / become smaller
Because it is the region containing only actin filaments between which myosin filaments slide