15.1.10
Skeletal Muscle
Muscle Fibres
Muscle Fibres
The structure of skeletal muscles is specialised for contraction. Skeletal muscle is a type of striated muscle.


Muscle fibres
Muscle fibres
- Skeletal muscle consists of many bundles of muscle fibres.
- Muscle fibres are long, specialised cells.


Sarcolemma
Sarcolemma
- The membrane of muscle fibres is called the sarcolemma.
- The sarcolemma folds inwards to the sarcoplasm (muscle fibre cytoplasm) at certain points.
- The inwards folds are called transverse (T) tubules. The tubules are very important in initiating muscle contraction.


Sarcoplasmic reticulum
Sarcoplasmic reticulum
- The sarcoplasmic reticulum (SR) is an organelle in the sarcoplasm.
- The SR is a store for calcium (Ca2+) ions. This is important in muscle contraction.


Mitochondria and nuclei
Mitochondria and nuclei
- Muscle fibres also have many mitochondria and nuclei.
- The mitochondria provide lots of ATP to power muscle contraction.


Myofibrils
Myofibrils
- Myofibrils are cylindrical organelles that run along the length of muscle fibres.
- Myofibrils are the site of muscle contraction.
Myofibrils
Myofibrils
Myofibrils are cylindrical organelles in muscle fibres. Myofibril structure is highly specialised for muscle contraction.


Sarcomere
Sarcomere
- Myofibrils are made of multiple units that run end-to-end along the myofibril. These units are called sarcomeres.
- The end of a sarcomere is called the Z-line.


Myofilaments
Myofilaments
- Sarcomeres are made from two types of myofilaments.
- The two myofilaments slide past each other. This movement is what makes muscles contract.
- The two types of myofilaments are:
- Thick myofilaments - made of myosin protein.
- Thin myofilaments - made of actin protein.


Myosin filaments
Myosin filaments
- Myosin and actin filaments are arranged in an alternating pattern in sarcomeres.
- Thick myosin filaments overlap with the thin actin filaments at each end.
- The overlapping region is called the A-band.
- The region with only myosin filament is called the H-zone.


Actin filaments
Actin filaments
- Thin actin filaments only overlap with myosin filaments in the middle of the sarcomere. The middle is called the M-line.
- The region with only actin filament is called the I-band.
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
Jump to other topics
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
Unlock your full potential with Seneca Premium
Unlimited access to 10,000+ open-ended exam questions
Mini-mock exams based on your study history
Unlock 800+ premium courses & e-books