STRUCTURE + MUSCLE CONTRACTION

Question 1

What are the three different types of sheath of connective tissue?

Answer 1

1. Epimysium
2. Perimysium
3. Endomysium

Question 2

What is found in the muscle (organ)?

Answer 2

Epimysium

Question 3

What is found in the muscle fascicle?

Answer 3

Perimysium

Question 4

What is found in the muscle fiber?

Answer 4

Endomysium

Question 5

What is the myofibril made up of?

Answer 5

Many sacromeres

Question 6

What is the sacroplasmic reticulum?

Answer 6

Stores Ca2+ for muscle contraction

Question 7

What is a sacromere?

Answer 7

The basic contractile unit of muscle

Question 8

What are the boundaries of sacromeres called?

Answer 8

A pair of Z-lines

Question 9

What is the centre of a sacromere called?

Answer 9

An M-line

Question 10

What is the structure of a sacromere?

Answer 10

Interdigitation of thick (myosin) and thin (actin) filaments

Question 11

Is myosin thick or thin?

Answer 11

Thick

Question 12

Is actin thick or thin?

Answer 12

Thin

Question 13

What kind of filaments does the H-band contain?

Answer 13

Contains thick filaments only

Question 14

What kind of filaments does the I-band contain?

Answer 14

Contains thin filaments only

Question 15

What kind of filaments does the A-band contain?

Answer 15

Contains both thin and thick filaments (zone of overlap)

Question 16

What three things occur to the bands during muscle contraction?

Answer 16

1. Width of the I-band decreases (thin actin filaments)
2. Width of the H-band decreases (thick myosin filaments)
3. Width of the A-band remains constant (thin actin and thick myosin)

Question 17

What three things happen during muscle contraction?

Answer 17

1. Intake of calcium increases
2. Cross-bridging between thick and thin filaments
3. Pivoting of myosin heads toward the M-line

Question 18

Which direction are the myosin heads facing when the sacromeres are at rest?

Answer 18

Towards Z-line

Question 19

Which direction are the myosin heads facing when the sacromeres are contracting and filament sliding?

Answer 19

Towards M-line

Question 20

What are the three steps of nerve stimulation and muscle contraction?

Answer 20

1. Each muscle cell (fibre) is innervated by a motor neuron (nerve cell)
2. When the neuron fires, it signals the muscle cell to contract
3. Contraction is an ALL OR NONE phenomenon: the muscle cell either contracts fully, or it does not contract at all

Question 21

When is the lag phase?

Answer 21

Between action potential and contraction

Question 22

What does the motor neuron do?

Answer 22

Innervates multiple muscle cells

Question 23

How are all muscle cells controlled by?

Answer 23

A single motor neuron constitute a motor unit

Question 24

What is a motor unit?

Answer 24

Nerve from spinal cord that innervates a muscle fibre

Question 25

What is important to note about motor units?

Answer 25

The number of muscle fibers can be big or small

Question 26

What is the amount of muscle tension produced dependent on?

Answer 26

The number of motor units that are stimulated

Question 27

What happens when you have **more nerves**?

Answer 27

You have **more** motor units therefore you generate more force

Question 28

What happens when you have **less nerves**?

Answer 28

You have** less **motor units therefore you have fine control of muscle