Ultimately, the purpose of the brain is to control behaviours, and behaviours are ____.
All animal movement depends on muscle ____.
Vertebrate muscles fall into three categories: ____ muscles, which control the digestive system and other organs; ____ or striated muscles, which controls the movement of the body in relation to the environment; and ____ muscles (heart muscles), which have properties intermediate between those of smooth and skeletal muscles.
smooth : skeletal : cardiac
Each muscle is composed of many ____.
Although each muscle fibre receives information from only one ____, a given axon may innervate more than one muscle fibre.
For example, the eye muscles have a ratio of one axon per three muscle fibres, and the bicep muscles of the arm have a ratio of one axon to more than 100 fibres. This difference allows the eye to move more ____ than the biceps.
A ____ ____ is a synapse between a motor neuron axon and a muscle fibre.
In skeletal muscles, every axon releases acetylcholine at the neuromuscular junction, and acetylcholine always excites the muscle to ____.
A deficit of acetylcholine or its receptors ____ movement.
Each muscle makes just one movement, contraction. There is no message causing ____; the muscle simply relaxes when it receives no message to contract.
Moving a leg or arm back-and-forth requires opposing sets of muscles, called ____ ____.
At your elbow, for example, your ____ muscle brings your hand toward your shoulder and your ____ muscle straightens the arm.
flexor : extensor
Muscle contractions, being chemical processes, ____ ____ in the cold.
A fish has three kinds of muscles: red, pink, and white. Red muscles produce the slowest movements, but they do not ____. White muscles produce the fastest movements, but they ____ rapidly. Pink muscles are intermediate in speed and rate of ____.
Human and other mammalian muscles have various kinds of muscle fibres ____ ____, not in separate bundles as an fish.
Our muscle types range from ____ fibres with fast contractions and rapid fatigue too ____ fibres with less vigourous contractions and no fatigue.
fast-twitch : slow-twitch
We rely on our slow-twitch and intermediate fibres for ____ activities.
Slow-twitch fibres do not fatigue because they are ____ – they use oxygen during their movements.
Prolonged use of fast-twitch fibres results in fatigue because the process is ____ – using actions that do not require oxygen at the time but need oxygen for recovery. Using them builds up an ____ ____.
anaerobic : oxygen debt
Your muscles use ____, and after a while your glucose supplies begin to dwindle. Low glucose activates the gene that inhibits the muscles from using glucose, thereby saving glucose for the brains use.
People vary in their percentages of fast-twitch and slow-twitch fibres, for reasons based on both ____ and ____.
genetics and training