Sarcomeres Flashcards
Seven components of a sarcomere
-myosin, myosin cross-bridges, H zone, A band, I band, Z line, actin
Myosin outline
Thick filament
Myosin cross bridges outline
Used to grab the actin
Actin outline
Thin filaments that slide in and out when the muscle contracts and relaxes
A band
Length of the myosin
H zone outline
Distance between actin on one side of the sarcomere and actin on the other side
Z line outline
Side wall of the sarcomere. Separates one sarcomere from the next one
I band outline
Distance between myosin in one sarcomere and the myosin in the next one
How can you vary the amount of force in an effort
By varying the number of motor units recruited
Recruitment
-involves increasing number of motor units activated
-motor units are activated in order of size
- when muscle is first activated, earliest motor units to fire are small in size and then larger units are recruited as strength of muscular contraction is increased
- MORE MOTOR UNITS ARE ACTIVATED IN ORDER TO PRODUCE MORE FORCE
What does a motor unit consist of
-motor neuron
-muscle fibre it stimulates
What do you have to do if you want to contract a muscle
-electrical impulses are sent from brain to motor unit which cause bundles of nerve fibres to contract
What happens to a band when contracting
Stays the same
What happens to a band when relaxing
Stays the same
What happens to the h zone when contracting
It shortens and then disappears
What happens to the h zone when relaxing
Lengthens and then reappears
What happens to the i band when contracting
Shortens and then decreases
What happens to the i band when relaxing
Lengthens
What happens to the i band when contracting
-move closer together
- unchanged in height
What happens to the z line when relaxing
-move further away
-unchanged in height
