Skeletal System
This is the total number of bones in the adult human skeleton.
206 bones
This type of muscle is found only in the heart and is involuntary.
Cardiac muscle
This muscle fibre type is slow-twitch, fatigue-resistant, and best suited to aerobic endurance activities.
Type 1 (slow-twitch oxidative) fibres
This chemical neurotransmitter helps a nerve impulse cross the neuromuscular junction.
Acetylcholine
This type of contraction occurs when a muscle shortens while producing force, such as lifting a dumbbell during a biceps curl.
A concentric contraction
This is the term for a rigid structure that rotates around a fixed point.
A lever
This type of bone tissue is found in the shaft (diaphysis) of long bones and gives the body its rigid framework.
Compact bone
This type of muscle is under voluntary control and attaches to bones to create movement.
Skeletal muscle
This muscle fibre arrangement, seen in the deltoid, generates the greatest force of all fibre arrangements.
Multipennate
This term describes one motor neuron plus all the muscle fibres it stimulates.
A motor unit
This type of contraction occurs when a muscle lengthens while producing force, such as lowering into a squat.
An eccentric contraction
In the human body, this component of a lever is represented by the joint.
The axis
This joint type is freely moveable and includes the knee and shoulder.
A synovial joint
This muscle is responsible for elbow flexion, such as during a pull-up.
Biceps brachii
This thin protein myofilament attaches to the Z-line within a sarcomere.
Actin
This principle states that a muscle fibre will only contract once a nerve impulse reaches a certain threshold, and will then contract maximally.
The all-or-nothing principle
This type of contraction produces the most force of all three types but involves no change in muscle length, such as in a rugby scrum.
An isometric contraction
This class of lever is the most common in the human body, with the force located between the axis and the resistance.
A third-class lever
This anatomical movement describes a decrease in the angle of a joint, such as bending the elbow.
Flexion
This large posterior muscle is responsible for hip extension, used when running or sprinting.
Gluteus maximus
This theory explains how actin and myosin slide across one another to shorten the sarcomere during a contraction.
The sliding filament theory
This principle states that motor unit recruitment begins with small units and progresses to large units as force demands increase.
The size principle
This is the muscle that causes the major action during a movement, also known as the prime mover.
The agonist
This is the term for the trade-off where a third-class lever increases speed and range of motion but reduces force.
Mechanical disadvantage
This type of synovial joint allows movement in only one direction (flexion/extension), such as at the elbow or knee.
This muscle is responsible for plantar flexion during a ballet toe point.
Soleus
This fast-twitch fibre type is white in colour, fatigues quickly, and is suited to short, explosive activities like sprinting.
Type 2B (fast-twitch glycolytic) fibres
This is the name of the gap between a nerve ending and a muscle fibre, across which a nerve impulse must travel.
The neuromuscular junction
This term describes the process where the agonist contracts while the antagonist relaxes to produce smooth, coordinated movement.
Reciprocal inhibition
During a kick, the quadriceps act as the force and the knee as the axis — this body part acts as the resistance.
The foot (and lower leg)