5.5.14 Mammalian Muscle Structure (needs redoing)

Question 1

What are the types of muscle?

Answer 1

• Skeletal (striated or voluntary)
• Smooth (involuntary)
• Cardiac

Question 2

What is a striated muscle?

Answer 2

• Muscle made of muscle fibres

Question 3

What are skeletal muscles?

Answer 3

• Responsible for moving skeleton of mammals
• Muscles are attached to the skeleton

Question 4

What is a muscle fibre?

Answer 4

• Contains contractile proteins in cytoplasm
• Muscle fibres surrounded by cell surface membrane
• Each muscle fibre contains many nuclei, so fibres are not usually referred to as cells

Question 5

What are the names of muscle fibres

Answer 5

Cell surface membrane - Sarcolemma
Cytoplasm - Sarcoplasm
Endoplasmic reticulum - sarcoplasmic reticulum

Question 6

What is the sarcolemma?

Answer 6

• Has many tube-like projections folding in from its outer surface (T-tubules)
• Run close to the sarcoplasmic reticulum

Question 7

What is the sarcoplasm?

Answer 7

• Contains mitochondria and myofibrils
• Myofibrils are bundles of actin and myosin filaments, sliding past each other during muscle contraction

Question 8

What happens in the sarcoplasmic reticulum?

Answer 8

Membranes contain protein pumps transporting calcium ions into lumen of sarcoplasmic reticulum, and contain calcium reabsorbing proteins

Question 9

What do myofibrils do?

Answer 9

• Located in sarcoplasm
• Made of 2 protein filament types
• Thich filaments of myosin
• Thin filaments of actin

Question 10

What is the H zone

Answer 10

• Only thick myosin filaments present
• Compresses

Question 11

What is the I band?

Answer 11

Only thin actin filaments present

Question 12

What is the A band?

Answer 12

Contains myosin and actin filament overlap

Question 13

What is the M line?

Answer 13

Attachment for myosin filaments in the middle of the H zone, anchors the whole thing

Question 14

What is the Z line?

Answer 14

Attachment site for actin filaments between each sracomere

Question 15

What is the sarcomere?

Answer 15

Section of myofibril between 2 Z lines

Question 16

Myofibril Structure Table

Answer 16

Question 17

Sarcomere Structure Diagram

Answer 17

Question 18

Difference Between Smooth Muscle and Skeletal Muscle

Answer 18

• Smooth muscle is for unconscious control
• Contains Actin and Myosin but NO BANDING or STRIATION
• Walls of gut, blood vessels, arteries, etc

Question 19

What is special about cardiac muscle?

Answer 19

• Only in heart
• Myogenic (does not require an electrical stimulus to contract)
• Does not tire of fatigue (can continuously beat)
• Lots of mitochondria

Question 20

Skeletal Muscle under the microscope

Answer 20

Question 21

Limitations of observing muscle fibres under microscopes

Answer 21

• Size of cells are inconsistent between different specimens
• Treatment of specimens could alter structure of cells