Scientific Basis of Strength and power: Neuromusclar system Slides

Neuron

Smallest unit of nervous system

Neuron - Cell Body

Soma

Neuron - Dendrite

Conduct impulses toward the cell body

Neuron - Axon

conducts impulses away from the cell body

Sensory/Afferent Neuron

carries signal toward CNS

Motor/Efferent Neuron

Carries signal away from CNS to muscles

An action potential is created when?

Depolarization of cell membrane increases the permeability for sodium/potassium and theres a propagation go charges

When does an action potential stop?

when the sodium potassium pump re-establishes resting membrane potential

Nerve fibers that conduct impulses faster than others are typically…

myelinated and larger in diameter

Fast twitch fibers are innervated by…

Myelinated larger diameter nerve fibers

Slow twitch fibers are innervated by…

Unmyelinated smaller diameter nerve fibers

Motor Unit

Smallest functional unit of the neuromuscular system

What does a motor unit consist of

a single motor neuron and all the muscle fibers it innervates

The fewer # of muscle fibers in a motor unit will result in what?

Finer motor coordination

Neuromuscular Junction/Motor End Plate

synapse between motor neuron and skeletal muscle fibers

Neuromuscular Junction/Motor End Plate Consist of: Terminal End Plate

contains vesicles filled with a neurotransmitter called acetylcholine (Ach)

Muscle force production can be modified by:

Recruitment, Firing Frequency, Synchronization

Recruitment

increase in # of motor units and muscle fibers stimulated in order to produce a stronger contraction

Firing Frequency

increasing the frequency of stimulation(summation) until a frequency is beyond which force no longer increases (tetanus)

Synchronization

Simultaneous firing of different motor units to generate force

Bilateral Force Deficit

combined force of both limbs is less than the sum of the force of the left and right limb acting alone

Force Production decrement due to Fatigue: CNS

cannot maintain neural impulses due to increase metabolites, decreased glucose

Force Production decrement due to Fatigue: Neuromuscular junction

depletion of acetylcholine

Force Production decrement due to Fatigue: Muscle fiber

depletion of ATP

Neuromuscular Junction/Motor End Plate Consist of: the other part

region of muscle membrane directly under the terminal (end) portion of the motor neuron axon

Treppe Effect

gradual increase in the strength of a muscles contractions when stimulated by the same strength

Evidence of Nervous system effect on Force production

the ability to recruit higher threshold motor units with training, ability to lower threshold of high threshold motor units with training, requires less neural recruitment/effort for the same force of contraction with training, increased rate of stimulation to increase rate of force development and power production and ability to maintain it with training, increase in force production due to an ability to increase synchronization of motor units without an increase in muscle size with training, specificity of training, Bilateral deficit

Myelinated nerve fibers conduct impulses via

saltatory conduction

Tetanization

an increase in the frequency of stimulation until a frequency is reached beyond which the force no longer increases