15.7 Structure Of Skeletal Muscle

Question 1

What are the 3 types of muscle in the body?

Answer 1

• cardiac muscle
• smooth muscle
• skeletal muscle

Question 2

What are the tiny muscle fibres called?

Answer 2

Myofibrils

Question 3

What is the cytoplasm found in the muscle fibres called?

Answer 3

Sarcoplasm

Question 4

What do muscle fibres share?

Answer 4

Nuclei and sarcoplasm

Question 5

Which organelles are in high concentration in the sarcoplasm?

Answer 5

• Mitochondria

- Endoplasmic reticulum

Question 6

What 2 types of protein filament is myofibrils made up of?

Answer 6

• actin

- myosin

Question 7

What is actin?

Answer 7

Thinner protein filament and consists of 2 strands twisted around one another

Question 8

What is myosin?

Answer 8

Thicker protein filament and consists of long rod- shaped tails with bulbous heads that project to the side

Question 9

What are I bands short for?

Answer 9

Isotropic bands

Question 10

What are A bands short for?

Answer 10

Anisotropic bands

Question 11

What is the A band made up of?

Answer 11

Actin and myosin

Question 12

What is the I band made up of?

Answer 12

Actin

Question 13

What is the H zone?

Answer 13

Where only myosin is present

Question 14

What is the z line?

Answer 14

Line in the centre of each I band

Question 15

Sarcomere definition

Answer 15

Distance between adjacent z-lines

Question 16

What is tropomyosin?

Answer 16

Fibrous protein strand around the actin filament

Question 17

Slow- twitch fibre adaptations

Answer 17

• large store of myoglobin
• lots of blood vessels
• numerous mitochondria

Question 18

Fast- twitch adaptations

Answer 18

• lots of thicker myosin filaments
• lots of glycogen
• lots of enzymes for anaerobic respiration
• store of phosphocreatine

Question 19

What are the 2 types of muscle fibres?

Answer 19

• slow twitch

- fast twitch

Question 20

Speed of contraction in slow- twitch fibres

Answer 20

Slowly

Question 21

Strength of contraction in slow- twitch fibres

Answer 21

Not powerful

Question 22

How long does the contraction last in slow- twitch fibres?

Answer 22

Longer period

Question 23

What are slow- twitch fibres adapted for?

Answer 23

Endurance work e.g marathon

Question 24

Where are slow- twitch fibres found?

Answer 24

Calf muscle

Question 25

What sort of respiration are slow- twitch fibres adapted for?

Answer 25

Aerobic respiration in order to avoid a build- up of lactic acid

Question 26

How fast does fast- twitch fibres contract?

Answer 26

Rapidly

Question 27

Strength of fast- twitch fibre contractions?

Answer 27

Powerful

Question 28

How long does the muscle contraction last in the fast- twitch fibres?

Answer 28

Short period

Question 29

What are fast- twitch fibres adapted for?

Answer 29

Intense exercise e.g weight- lifting

Question 30

Where are fast- twitch fibres found?

Answer 30

Biceps

Question 31

Neuromuscular junction definition

Answer 31

Point where a motor neurone meets a skeletal muscle fibre

Question 32

Why are there many neuromuscular junctions?

Answer 32

All fibres would contract simultaneously so movement would be fast

Question 33

What is a motor unit?

Answer 33

Muscle fibres supplied by a single motor neurone that act as a single functional unit

Question 34

What happens if only a small force is needed?

Answer 34

Only a few units are stimulated

Question 35

What happens if a greater force is required?

Answer 35

Larger number of units are stimulated

Question 36

Similarities between cholinergic synapses and neuromuscular junctions

Answer 36

- have neurotransmitters that are transported by diffusion - have receptors, that bind with neurotransmitter, cause an influx of Na+ - use a sodium- potassium pump to repolarise the axon - use enzymes to breakdown the neurotransmitter

Question 37

Types of synapses between neuromuscular junctions and cholinergic synapses

Answer 37

- Neuromuscular junction -> excitatory | - cholinergic synapse -> excitatory or inhibitory

Question 38

Where are neuromuscular junctions and cholinergic synapses

Answer 38

- neuromuscular junction -> links neurones to muscles | - cholinergic synapse -> neurones to neurones OR neurones to effector

Question 39

What sort of neurones are involved in neuromuscular junction and cholinergic synapses?

Answer 39

- neuromuscular junction -> motor neurones | - cholinergic synapses -> motor, sensory and intermediate neurones

Question 40

What happens to the action potential in neuromuscular junctions and cholinergic synapses?

Answer 40

- neuromuscular junction -> action potential ends | - cholinergic synapse -> action potential may be produced along another neurone

Question 41

Where does the acetylcholine bind to in neuromuscular junctions and cholinergic synapses?

Answer 41

- neuromuscular junction -> bonds to receptors on the membrane of muscle fibres - cholinergic synapse -> binds to receptors on membrane of post- synaptic neurone