BIO 102 Chapter 6
Motor unit size, the number of motor units active at any one time, and the frequency of stimulation of individual motor units
Three factors that determine how much muscle tension is generated by muscle
Isotonic contractions
When a muscle shortens while maintaining a constant force
Isometric contractions
When a muscle tension increases, and the muscle may even shorten a little as tendons are stretched slightly, but ones and objects do not move
Insertion
One end of skeletal muscle that attaches to another bone across a joint
Summation
Increasing muscle cell force by increasing the rate of stimulation of motor units
Recruitment
Increasing tone (or force) by activating more motor units
Relaxation
Muscle cell returns to its original length
Antagonistic muscles
Muscle groups that oppose each other
Synergistic muscles
Muscle groups that work together to create the same movement
Voluntary muscle
Muscle movement over which we have conscious control
Involuntary musle
Muscle movement which is generally beyond our conscious control
Origin
One end of the skeletal muscle that joins to a bone that remains relatively stationary
Cardiac muscle
Rhythmic contractions of this type of muscle found in the heart pumps blood throughout the body
Contract
Shorten
Intercalated disks
Structures which join cardiac muscle cells
Excitable
The characteristic of all muscle cells which means they contract in response to chemical and/or electrical signals from other organ systems
Muscle tension
The mechanical force that muscles generate when they contract
Motor unit
The muscle neuron and all the muscle cells it controls; the smallest functional unit of muscle contraction
Action potential
The stimuli for muscle contraction
Latent period
The time between stimulation and the start of muscle contraction
Contraction
The time during which the muscle cell actually shortens
Skeletal muscle
The type of muscle that interacts with the skeleton and causes bones to move (or prevents them from moving) relative to each other
Slow-twitch fibers
This type of skeletal muscle fiber breaks down ATP slowly, and so it contracts slowly; they tend to make ATP as they need it by aerobic metabolism (called "red" muscle).
Fast-twitch fibers
This type of skeletal muscle fiber contracts quickly because it breaks down ATP quickly. They have fewer mitochondria, fewer blood vessels, and little or no myoglobin (called "white" muscle).
Twitch
A complete cycle of contraction and relaxation
Muscle fatigue
A decline in muscle performance during exercise
Single muscle
A group of individual muscle cells, all with the same origin and insertion and all with the same function
Motor neuron
A single nerve cell which controls each group of muscle cells
All-or-none principle
According to this, muscle cells are completely under the control of their motor neuron; muscle cells never contract on their own.
Pacemaker cells
Cardiac cells with the fastest rhythm of contraction and relaxation; the rest of the cells follow their faster pace.