5.5.14 Mammalian Muscle Structure (needs redoing) Flashcards
What are the types of muscle?
- Skeletal (striated or voluntary)
- Smooth (involuntary)
- Cardiac
What is a striated muscle?
- Muscle made of muscle fibres
What are skeletal muscles?
- Responsible for moving skeleton of mammals
- Muscles are attached to the skeleton
What is a muscle fibre?
- 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
What are the names of muscle fibres
Cell surface membrane - Sarcolemma
Cytoplasm - Sarcoplasm
Endoplasmic reticulum - sarcoplasmic reticulum
What is the sarcolemma?
- Has many tube-like projections folding in from its outer surface (T-tubules)
- Run close to the sarcoplasmic reticulum
What is the sarcoplasm?
- Contains mitochondria and myofibrils
- Myofibrils are bundles of actin and myosin filaments, sliding past each other during muscle contraction
What happens in the sarcoplasmic reticulum?
Membranes contain protein pumps transporting calcium ions into lumen of sarcoplasmic reticulum, and contain calcium reabsorbing proteins
What do myofibrils do?
- Located in sarcoplasm
- Made of 2 protein filament types
- Thich filaments of myosin
- Thin filaments of actin
What is the H zone
- Only thick myosin filaments present
- Compresses
What is the I band?
Only thin actin filaments present
What is the A band?
Contains myosin and actin filament overlap
What is the M line?
Attachment for myosin filaments in the middle of the H zone, anchors the whole thing
What is the Z line?
Attachment site for actin filaments between each sracomere
What is the sarcomere?
Section of myofibril between 2 Z lines
Myofibril Structure Table
Sarcomere Structure Diagram
Difference Between Smooth Muscle and Skeletal Muscle
- Smooth muscle is for unconscious control
- Contains Actin and Myosin but NO BANDING or STRIATION
- Walls of gut, blood vessels, arteries, etc
What is special about cardiac muscle?
- Only in heart
- Myogenic (does not require an electrical stimulus to contract)
- Does not tire of fatigue (can continuously beat)
- Lots of mitochondria
Skeletal Muscle under the microscope
Limitations of observing muscle fibres under microscopes
- Size of cells are inconsistent between different specimens
- Treatment of specimens could alter structure of cells
