Chapter 10 (Muscular Tissue IX) Flashcards
Muscle Fatigue
Inability of muscle to maintain force of contraction after prolonged activity
Factors that contribute to muscle fatigue
Inadequate release of calcium ions from the SR
Depletion of creatine phosphate
Insufficient oxygen
Depletion of glycogen and other nutrients
Buildup of lactic acid and ADP
Failure of the motor neuron to release enough acetylcholine
Oxygen Consumption After Exercise
After exercise, heavy breathing continues and oxygen consumption remains above the resting level
Oxygen debt
The added oxygen that is taken into the body after exercise
Added oxygen is used to restore muscle cells to the resting level in three ways
1) to convert lactic acid into glycogen
2) to synthesize creatine phosphate and ATP
3) to replace the oxygen removed from myoglobin
Control of Muscle Tension
The tension or force of muscle cell contraction varies
Maximum Tension (force) is dependent on
The rate at which nerve impulses arrive
The amount of stretch before contraction
The nutrient and oxygen availability
The size of the motor unit
Motor Units
Consists of a motor neuron and the muscle fibers it stimulates
The axon of a motor neuron branches out forming neuromuscular junctions with different muscle fibers
Control of precise movements consist of many small motor units
The total strength of a contraction depends on the size of the motor units and the number that are activated
Control of precise movements consist of many small motor units
Muscles that control voice production have 2 - 3 muscle fibers per motor unit
Muscles controlling eye movements have 10 - 20 muscle fibers per motor unit
Muscles in the arm and the leg have 2000 - 3000 muscle fibers per motor unit (Large motor units)
All-or-none principle of muscle contraction
When an individual muscle fiber is stimulated to contract, it will contract to its full force; it cannot partially contract
When a single motor unit is recruited to contract, all the muscle fibers in that motor unit will contract at the same time
