Structure of skeletal muscle

Question 1

What are the three types of muscle?

Answer 1

• smooth muscles = found in the walls of blood vessels and in the gut
• cardiac muscles = found in the heart
• skeletal muscles

Question 2

How do muscles act?

Answer 2

• muscles act in antagonistic pairs
• they pull in opposite directions
• when one relaxes, the other contracts

Question 3

What is the structure of skeletal muscle?

Answer 3

• skeletal muscle is made up of large bundles of long cells called muscle fibres
• the cell membrane of muscle fibre cells is called the sarcolemma
• bits of the sarcolemma fold inward across the muscle fibre and stick into the sarcoplasm, these are called transverse t tubules
• t tubules help spread electrical impulses throughout the sarcoplasm so they reach all parts of muscle fibre
• within the muscle fibre, there are are many myofibirls which are made up of proteins and are specialised for contraction

Question 4

Which types of protein filaments are myofibrils made of?

Answer 4

• actin = thinner and consists of two strands twisted around eachother
• myosin = this is thicker and consists of long rod shaped tails with bulbous heads that project to the side

Question 5

What are the components of myofibrils?

Answer 5

• I bands
• A bands
• Z - line
• sarcomeres
• M line

Question 6

What colour are myofibrils?

Answer 6

• myofibrils appear striped due to their alternating light coloured and dark coloured bands

Question 7

What are I bands?

Answer 7

• these are light bands
• they appear lighter as actin and mysosin do not overlap in this reigon, therefore the I band only contains actin

Question 8

What are A bands?

Answer 8

• A bands appear darker as they are the reigon that contains the overlap of actin and myosin
• at the centre of A bands is a darker coloured reigon which is called the H zone (only contains myosin)

Question 9

What is the H zone?

Answer 9

• the middle of the A band which only contains myosin

Question 10

What is a Z line?

Answer 10

• The centre of each I band
• The distance between each Z line is called a sarcomere

Question 11

What is an M line?

Answer 11

• The middle of the myosin filament?

Question 12

What is each myofibril made of?

Answer 12

• many sarcomeres

Question 13

What is tropomysoin?

Answer 13

• A protein found in muscle that forms a fibrous strand around actin filaments