Reflex Physiology and Reaction Times

Depolarization Phase

sodium driving the charge difference across the plasma membrane from threshold

Repolarization Phase

the return to the resting membrane potential as potassium leaves the cell

Saltatory conduction

impulse jumps from node to node

Type A fibers

most myelin, largest diameter, and conduct impulses at 15-130 m/sec

Type B fibers

have some myelin, medium diameter, and conduct impulses 3-15 m/sec

Type C fibers

lack myelin, smallest diameter, and conduct impulses at less than 3 m/sec

Monosynaptic reflex

no association neurons are involved

Continuous conduction

voltage gated ion channels are located along the entire length of the axon

Muscle spindle apparatus

stretch reflex arc in a special muscle fiber apparatus

Intrafusal fibers

thin non-contractile muscle cells that are enclosed in connective tissue

patellar reflex

most common observed stretch reflex

latent period

short period of time when there is no apparent response at all

Electromyography

measures the electrical activity in the muscle that stimulate contraction

Electromyogram

recording of the electrical activity

Facilitation

enhancing a reflex

Reaction time

time it takes for an individual to voluntarily respond to a stimulus

hypoactive reflexes

reflexes that are much weaker than normal or that are absent

peripheral neuropathy

most common cause of absent reflexes