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Neural Integration
--Pools of neurons communicate
Types of Circuits:
a. Divergent--amplifying
b. Convergent--concentrating
c. Oscillating
Reflex Arc
Rapid, automatic responses to stimuli
Components of reflex arc:
Stimulus
Receptor--translates stimulus into A.P.
Sensory neuron--carries A.P. to CNS
Integration center--CNS
Motor neuron--carries A.P. to effector (muscle)
Effector--executes appropriate response
2 Types of Reflexes:
1. Somatic--skeletal muscles
Includes spinal reflexes--stretch, deep
tendon, flexor, crossed extensor, superficial
2. Visceral--glands
Somatic Reflex
1. Stretch reflex
Muscle spindle: embedded in skeletal muscle
Spindle (this picture
shows the spindle
enlarged, but they are
tiny and each skeletal
muscle contains many of
them)
When large skeletal muscle is stretched, spindle is
also stretched. Stretch irritates sensory nerve
fibers. Fire A.P.
spinal cord.
A.P. to spinal
cord
At spinal cord, synapse with !-motor neuron,
supplying skeletal muscle and antagonist muscle.
Stimulated skeletal muscle
contracts, the antagonist
muscle relaxes.
2. Deep Tendon Reflex-Golgi Tendon Organ--collagen fibers in tendon with
sensory nerve endings attached. Synapse in
spinal cord.
In response to stretch of tendon, GTO is stimulated
and A.P. fires off along sensory nerve. Nerve
synapses with !-motor neurons of both stretched
muscle and antagonistic muscle.
Causes relaxation of
stretched muscle and
contraction of
antagonist muscle
Prevents tearing
3. Flexor--withdrawal due to painful stimulus
4. Crossed Extensor--ipsilateral (same side)
withdrawal and contralateral (opposite side)
extension
Superficial Reflexes
i) Plantar--L4-S2 integrity. Normal = downward
flexion of toes. Abn = Babinski sign
ii) Abdominal--T8-T12. Normal = umbilicus moves
to stimulated side due to abd. muscle contraction
Tickle here
Scrape bottom of foot in this
direction, toes plantar flex