3.6 Skeletal muscles are stimulated to contract by nerves Flashcards
What is an antagonistic pair ?
One muscle contacts and the other relaxes
What is an antagonist ?
The muscle that is relaxing
What is an agonist ?
The muscle that is contracting
Name the 5 main structures of a muscle
- Sarcolemma
- Sacrcoplasmic reticulum
- Mitochondria and nuclei
- Myofibrils
- Tubules
What is the structure/ function of the sarcolemma ?
It is the membrane of muscle fibres and folds inwards to the sarcoplasm (Membrane). These inward folds are called tubules and are important at initiating muscle contraction
What is the sarcoplasmic reticulum a store for and why is this important ?
Ca2+ ions that are important for contraction
Why do muscle fibres have lots of mitochondria ?
In order to provide lots of ATP for muscle contraction
What are myofibrils and why are they important ?
They are cylindrical organelles that run along the length of muscle fibres and are the site of muscle contraction
What is the A band ?
The total width of myosin (thick band)
What is the H zone ?
Just the parts where it is myosin only (In the centre). It overlaps the A band
What is the I band ?
Labels just where the actin is by itself. There is no overlap with myosin
What is the M line ?
The middle point of myosin
What do the Z lines indicate ?
The parameters of one sarcomere
On a micrograph does actin or myosin show up darker ?
Myosin will show up darker as it is a much thicker protein, Actin will show up a lot paler
What happens to the I band when the muscle contracts ?
It decreases in width