The Neruromuscular System Flashcards
Type 1 muscle fibres are also known as?
Type 1 muscle fibres are also known as slow oxidative muscle fibres.
Characteristics of slow oxidative (type 1) muscle fibres
• Small motor neuron size
• Large myoglobin content
• High oxidative capacity
• Slow contraction time
• Suited for aerobic exercise
• High resistance to fatigue
• Low force production
• Low glycolytic capacity
• High capillary density
What are slow oxidative (type 1) muscle fibres useful for?
Endurance events such as marathon running.
Type 2a muscle fibres are also known as?
Type 2a muscle fibres are also know as fast oxidative glycolytic muscle fibres
Characteristics of fast oxidative glycolytic (type 2a) muscle fibres
• Large motor neuron size
• Intermediate myoglobin content
• High oxidative capacity
• Fast contraction time
• Suited for lengthy anaerobic exercise
• Medium resistance to fatigue
• High force production
• High glycolytic capacity
• Medium capillary density
Type 2b muscle fibres are also know as?
Type 2b muscle fibres are also known as fast glycolytic muscle fibres.
Characteristics of fast glycolytic (type 2b) muscle fibres
• Large motor neuron size
• Small myoglobin content
• Low oxidative capacity
• Fastest contraction time
• Suited for short anaerobic exercise
• Low resistance to fatigue
• Highest force production
• High glycolytic capacity
• Low capillary density
What sports are suitable for type 2a muscle fibres?
Swimming
What sports are suitable for type 2b muscle fibres?
100m sprint
Muscle fibres and their motor neuron size
Type 1 - Small motor neuron size
Type 2a - Large motor neuron size
Type 2b - Large motor neuron size
Muscle fibres and their myoglobin content
Type 1 - Large myoglobin content
Type 2a - Intermediate myoglobin content
Type 2b - Small myoglobin content
Muscle fibres and their oxidative capacity
Type 1 - High oxidative capacity
Type 2a - High oxidative capacity
Type 2b - Low oxidative capacity
Muscle fibres and their contraction times
Type 1 - Slow contraction time
Type 2a - Fast contraction time
Type 2b - Fastest contraction time
Muscle fibres and what exercise types they are suited to
Type 1 - aerobic exercise
Type 2a - lengthy anaerobic exercise
Type 2b - short anaerobic exercise
Muscle fibres and their resistance to fatigue
Type 1 - High resistance to fatigue
Type 2a - Medium resistance to fatigue
Type 2b - Low resistance to fatigue
Muscle fibres and their force production
Type 1 - Low force production
Type 2a - High force production
Type 2b - Highest force production
Muscle fibres and their glycolytic capacity
Type 1 - Low glycolytic capacity
Type 2a - High glycolytic capacity
Type 2b - High glycolytic capacity
Muscle fibres and their capillary density
Type 1 - High capillary density
Type 2a - Medium capillary density
Type 2b - Low capillary density
Muscle fibre recruitment explained
Muscle fibre recruitment is dependent on the intensity of the exercise, higher intensity requires more force, lower intensity requiring less force.
What is the size principle (Henneman)
Smaller motor units are recruited first as they have a smaller firing threshold than larger motor units.
What is the autonomic nervous system responsible for?
The autonomic nervous system is responsible for subconsciously controlling muscular contractions.
What two systems make up the autonomic nervous system?
• Parasympathetic nervous system
• Sympathetic nervous system
Both nervous systems innervate the muscle tissues by sending a nervous impulse to them.
What is the parasympathetic nervous system responsible for?
The parasympathetic nervous system is responsible for actions that occur when resting
What is the sympathetic nervous system responsible for?
The sympathetic nervous system is responsible for actions when active
What is the proprioceptive neuromuscular facilitation?
A form of stretching which aims to overcome the stretch reflex, an isometric contraction is performed when the muscle is stretched to its limit.
What is the role of muscle spindles?
• Sensory receptors
• Found in the centre of the muscle
• Provide information regarding the length of the muscle to the brain
• This information is used to initiate the stretch reflex when the muscle is stretched to its limit.
What is the role of the Golgi tendon organ?
• Sensory receptor
• Found at the connection of the muscle with the bone
• Detects changes in tension of the muscle
• Initiates the Golgi-tendon reflex which reduces muscle tension when it is high.
What is the ‘All or None’ law?
Each muscle fibre controlled by a motor unit is either fully contracted or not contracted at all
They can contract in different ways depending on how they are innervated
Therefore, a muscle fibre cannot partially contract
What are the three types of motor neuron recruitment?
Spatial summation
Wave summation
Tetanic summation
What is spatial summation?
Many motor units firing
What is wave summation?
One motor unit firing continuously
What is tetanic summation?
A continuous muscle contraction
Key structures of motor units?
• Myelin sheath
• Axons
• Myofibrils
• Sacrolemma
• Snyaptic vesicle
• Synaptic cleft
• Motor end plate
What is the myelin sheath?
Acts as an electrical insulator around the axons
What are axons?
Axons are extensions of a nerve cell that carry an impulse
What are myofibrils?
Myofibrils are contractile structures of the muscle consisting of actin and myosin.
What is the sacrolemma?
Sacrolemma is the cell membrane
What is the synaptic vesicle?
The synaptic vesicles is where acetylcholine is stored
What is the synaptic cleft?
The synaptic cleft is the gap between neurons
What is the motor end plate?
The motor end plate is where the action potential from an action travels to stimulate a muscle.
A motor unit consists of…?
A motor unit consists of a motor neuron and the muscle fibres that it stimulates.
Nervous stimulation of a motor unit stages
A motor unit needs to be stimulated to enable a muscular contraction
1) A neuron becomes depolarised, firing an action potential.
2) The action potential reaches the neuromuscular junction.
3) This causes the neurotransmitter acetylcholine to move to the motor end plate.
4) The motor end plate becomes depolarised, resulting in muscular contraction.
What is an action potential?
An action potential is an electrical impulse that acts as a signal.
Motor units key facts
• Motor units vary in the number of muscle fibres that they stimulate
• The fibres are made up of only one type.
• The brain recruits smaller motor units before larger motor units.
• Smaller motor units consist of slow-twitch muscle fibres
• Larger motor units consist of fast-twitch muscle fibres.
