A&P Lab - Reflexes

Somatic Reflexes

Involuntary motor response of skeletal muscle
Travels through reflex arc
Reciprocal innervation
Simultaneous contraction in agonistic muscles with inhibition of antagonist muscles

Agonistic Muscles

Muscle that contracts

Antagonistic Muscles

Muscle that stretches

5 Components of Reflex Arc

1. Sensory Receptor

2. Sensory Neuron

3. Integrating Center

4. Motor Neuron

5. Effector

Sensory Receptor

Stimulus on sensory receptor (proprioceptor -muscle spindle) creates action potential (A.P.) in sensory neuron

Sensory Neuron

Propagates A.P; synapses with neurons in spinal cord/brain stem

Integrating Center

Located in gray matter in CNS
Transfers info from sensory neuron to motor neuron

Motor Neuron

Carries A.P. from integrating center to Effector

Effector

Muscle/gland
A reflex is the response of effector to stimulation by the motor neuron

Reflex Responses

0
+1
+2
+3
+4

0 Response

No response

+1 Response

Little response

+2 Response

Normal response

+3 Response

Above normal response

+4 Response

Exaggerate reflex

Reflex Tests Purpose

Help diagnose nervous system disorders
Specific tests isolate specific nerves (reflex arcs)

What Nerve is Tested by the Achilles Reflex?

Tibial Nerve

What Nerve is Tested by the Biceps Reflex?

Musculocutaneous Nerve

What Nerve is Tested by the Patellar Reflex?

Femoral Nerve

What Nerve is Tested by the Plantar Flexion Reflex?

Upper Motor Neuron/Corticospinal Tract

What Nerve is Tested by the Triceps Reflex?

Radial Nerve

Babinski's Sign/Response in Infant

Stimulate sole of foot, big toe goes up

Babinski's Sign/Response in Adult

Not normal in adults
Signals potential CNS problem

Autonomic Reflexes

Involuntary response of cardiac/smooth muscle or gland

ex. Pupillary Light Reflex or Lie Detector