G

D

H

A

C

E

B

F

The lens becomes more spherical through the action of the ciliary muscles

The lens is pulled taut by the ciliary muscles

The lens is pulled taut by the intraocular pressure

The lens becomes more spherical through the action of the intraocular pressure changes

The lens becomes more cuboid through the action of pupillary constriction

Lock-and-key theory

Z-lines theory

Sliding filament model

Sarcomere and Ca++ hypothesis

Mendellian laws

At its shortest length

At its natural length

At any length, maximum force is only dependent on the number of motor units recruited

At its longest length

Completely independent of its length

 never reaches its potential maximum because of the attachment of the muscles to the bones of the skeleton.

 is determined mainly by the myosin ATPase activity of the muscle.

 is normally graded by both recruitment of motor units and variations in action potential frequency.

 is graded mainly by varying the amount of Ca²⁺ released per action potential.

 Ca²⁺; tropomyosin; attachment

Ca²⁺; actin; rotation

 ATP; myosin; rotation

ATP; myosin; detachment