7.1.2 - Muscle Fibres

Question 1

Describe The Skeletal Muscle
(2 Points)

Answer 1

~ Makes up muscles in the body, that are attached to the skeleton.

~ Is made up of muscle fibres.

Question 2

Describe The Muscle Fibre
(5 Points)

Answer 2

~ Is multi-nucleated.

~ Cell surface membrane, known as the sarcolemma.

~ Bits of the sarcolemma fold inwards, known as T-tubules.

~ Cytoplasm, known as the sarcoplasm.

~ Endoplasmic reticulum, known as the sarcoplasmic reticulum.

Question 3

Describe The Sarcoplasm, Of The Muscle Fibre
(2 Points)

Answer 3

~ Contains mitochondria and myofibrils.

~ Mitochondria -> Carry out aerobic respiration to generate the ATP, required for muscle contraction.

Question 4

What Are Myofibrils

Answer 4

Bundles of actin and myosin filaments, which slide past each other during muscle contraction.

Question 5

Describe The T-Tubules, Of The Muscle Fibre

Answer 5

They run close to the sarcoplasmic reticulum, and help spread electrical impulses throughout the muscle fibre.

Question 6

Describe The Sarcoplasmic Reticulum, Of The Muscle Fibre
(2 Points)

Answer 6

~ Stores and releases calcium ions, needed for muscle contraction.

~ Membrane of the SR, contain protein pumps that transport calcium ions into the lumen of the SR.

Question 7

Describe Myofibrils
(4 Points)

Answer 7

~ Located in the sarcoplasm.

~ Each myofibril is made up of myosin and actin protein filament.

~ Thick filaments, made of myosin.

~ Thin filaments, made of actin.

Question 8

Describe Myofibrils, Under A Microscope
(6 Points)

Answer 8

~ Sarcomere -> Section of myofibril, between the Z lines.

~ Z Line -> Attachment for actin filaments, and end of each sarcomere.

~ M Line -> Attachment for myosin filaments.

~ H Band -> Only thick myosin filaments present.

~ I Band -> Only thin actin filaments present.

~ A Band -> Areas where myosin filaments are present, and where myosin and actin filaments overlap.

Question 9

What Are The 2 Types Of Muscle Fibres, That Skeletal Muscles Are Made Up From?

Answer 9

~ Slow twitch muscle fibres.

~ Fast twitch muscle fibres.

Question 10

What Is Myoglobin?
(2 Points)

Answer 10

~ Acts as a store of oxygen in muscles.

~ Increases the rate of oxygen absorption from the capillaries.

Question 11

Describe Slow Twitch Muscle Fibres
(5 Points)

Answer 11

~ Highly endurance focused, don’t fatigue quickly.

~ Perform repetitive, low-force movements for long periods of time.

~ Appear darker red, due to higher capillary and myoglobin density.

~ Main metabolic pathway is aerobic.

~ Has a high mitochondrial density.

Question 12

Describe Fast Twitch Muscle Fibres
(5 Points)

Answer 12

~ Power focused, so fatigue quickly.

~ Produces short, intense burst of force.

~ Appear lighter, due to lower capillary and myoglobin density.

~ Main metabolic pathway is anaerobic.

~ Low mitochondrial density.