Skeletal muscle structures & function: Flashcards
What are the Skeletal muscle tissue functions:
- Produce body movement
- Is to develop tension or force (only in one direction).
- Maintain body position and posture.
- Support soft tissue
- Guard body entrances and exits
- Store nutrients.
What are the major cell types in skeletal muscle:
Skeletal muscle fibres are huge multinucleate (have more than one nucleus) cells containing large amounts of protein.
Connective tissue covers the muscle fibres, and connect fibres to the bone.
The muscle is richly supplied with blood vessels and nerve fibres.
Whole muscle structures:
Muscle fibres are gathered into bundles called fascicles. Fascicles are gathered into bundles called muscles.
A muscle fibre is comprised of bundles of myofibrils. The myofibrils are made of repeating units known as sarcomas. Sarcomere are made of contractile proteins of myofilaments.
What are the two types of myofilaments:
Actin (thin)
Myosin (thick)
The organisation of these myofilaments give muscles its striated (striped) appearance.
What is the structure and function of Transverse tubules
Transverse tubules (T tubules): are narrow tubes that are tubular extensions of the surface membrane. ( their job is to conduct electrical signals (action potentials deep into the cpre of the fibre.
Structure and function of Sarcomers:
Transverse tubule (yellow) Sarcoplasmic reticulum (blue).
What is the structure and function of the sarcoplasmic reticulum (SR):
Is an extensive membranous tubular network associated precisely with the T tubules at regular intervals.
The job of the SR is to take up stored calcium, then to release Ca2+ into the cytoplasm on receipt of an action potential conducted along the associated T-tubules.
What is the function and structure of the terminal chambers:
Of each SR structure associated with the T-tubules to form a membrane triplet called a traid.
How is the sarcomeric structure of the myosilaments arise?
Due to the arrangements of the contractile proteins.
What is the molecular structure of Actin?
Is a globular protein (G-actin). The globules assemble to form filamentous protein strands (F-actin).
Each thin filament is a twisted strand of 2 rows of F-actin terminating at one end at the z-line.
What is the molecular structure of Myosin?
The myosin molecule has a long thin tail and a globular head.
The thick filament is formed from arrays of pairs of myosin molecules arranged with eh tails point towards the M\line and forming a complex double headed structure.
The myosin heads are able to flex.
What is the sliding filament theory?
These contractile proteins develop force by triggered molecular interaction that allows association of the myosin head with the nearby thin actin filament followed nu the flexing of the myosin head to allow it to ‘walk’ along the thin filament.
This creates the interlaced thick and thin filaments to be able to slide pass one another.
This means the end of the sarcomere are drawn closer together by the flexing of my myosin heads ( the sarcomere Z- lines are drawn closer to the central M-line).
Electrical events in the brain initiate what?
Muscle contractions are triggered by electrical events.
Action potentials arise in brain, are conducted down spinal cord to motor neurons in spinal cord.
Action potentials in spinal cord motor neurons are conducted out of CNS along motor axons to muscle fibres.
What is the neuromuscular junction?
The myelinated axon of a motor neuron terminates at a single point on the muscle fibre.
This specialised synapse is the neuromuscular junction (NMJ).
Each muscle fibre receives contact from one motor neuron at one site. A motor neuron and all the muscle fibres it controls is called a motor unit.
