STRUCTURE + MUSCLE CONTRACTION Flashcards
What are the three different types of sheath of connective tissue?
- Epimysium
- Perimysium
- Endomysium
What is found in the muscle (organ)?
Epimysium
What is found in the muscle fascicle?
Perimysium
What is found in the muscle fiber?
Endomysium
What is the myofibril made up of?
Many sacromeres
What is the sacroplasmic reticulum?
Stores Ca2+ for muscle contraction
What is a sacromere?
The basic contractile unit of muscle
What are the boundaries of sacromeres called?
A pair of Z-lines
What is the centre of a sacromere called?
An M-line
What is the structure of a sacromere?
Interdigitation of thick (myosin) and thin (actin) filaments
Is myosin thick or thin?
Thick
Is actin thick or thin?
Thin
What kind of filaments does the H-band contain?
Contains thick filaments only
What kind of filaments does the I-band contain?
Contains thin filaments only
What kind of filaments does the A-band contain?
Contains both thin and thick filaments (zone of overlap)
What three things occur to the bands during muscle contraction?
- Width of the I-band decreases (thin actin filaments)
- Width of the H-band decreases (thick myosin filaments)
- Width of the A-band remains constant (thin actin and thick myosin)
What three things happen during muscle contraction?
- Intake of calcium increases
- Cross-bridging between thick and thin filaments
- Pivoting of myosin heads toward the M-line
Which direction are the myosin heads facing when the sacromeres are at rest?
Towards Z-line
Which direction are the myosin heads facing when the sacromeres are contracting and filament sliding?
Towards M-line
What are the three steps of nerve stimulation and muscle contraction?
- Each muscle cell (fibre) is innervated by a motor neuron (nerve cell)
- When the neuron fires, it signals the muscle cell to contract
- Contraction is an ALL OR NONE phenomenon: the muscle cell either contracts fully, or it does not contract at all
When is the lag phase?
Between action potential and contraction
What does the motor neuron do?
Innervates multiple muscle cells
How are all muscle cells controlled by?
A single motor neuron constitute a motor unit
What is a motor unit?
Nerve from spinal cord that innervates a muscle fibre
What is important to note about motor units?
The number of muscle fibers can be big or small
What is the amount of muscle tension produced dependent on?
The number of motor units that are stimulated
What happens when you have more nerves?
You have more motor units therefore you generate more force
What happens when you have less nerves?
You have** less **motor units therefore you have fine control of muscle
