BSC2085L LESSON 11: Reflex Physiology and General Sensation

Reflex Arc

Mediated by neural paths (connections of neurons) to yield rapid involuntary muscle response to stimuli.

Autonomic Reflexes

Mediated through the autonomic nervous system (ANS) involving smooth muscles in digestion and glands in sweating.

Somatic Reflexes

Involve sensory stimulation that causes skeletal muscles to react, such as the withdrawal reflex from pain.

Receptor

Site of stimulus.

Sensory Neuron

Transmits afferent impulse to CNS

Integration Center

One or more synapses in the CNS.

Motor Neuron

Conducts efferent impulse to effector.

Effector

Muscle or glands that respond to impulses.

Monosynaptic Reflex Arc

Utilizes a 2 neuron (sensory and motor neurons) reflex arc with no interneuron, such as the knee-jerk reflex.

Polysynaptic Reflex Arc

Utilizes sensory and motor neurons connected by interneurons.

Stretch Reflex

Maintains posture/balance and locomotion; tendon stretch causes agonist muscle contraction and antagonistic relaxation.

Patellar Reflex

Example of a stretch reflex, also known as the knee jerk reflex.

Crossed Extensor Reflex

Flexion of one limb followed by extension of the opposite limb.

Superficial Cord Reflex

Result from pain and temperature changes.

Plantar Reflex

Babinski's sign; abnormal response is flared toes, which may indicate ALS or other damage/disorder of CNS.

Corneal Reflex

A function of cranial nerve V (trigeminal); touching of the cornea causes blinking to occur.

Gag Reflex

A function of cranial nerves IX (glossopharyngeal) & X (vagus); touching of the uvula causes gag reflex.

Pupillary Reflexes

Reflex caused by light stimulation of cranial nerve II (optic) causing iris constriction by cranial nerve III (oculomotor).

Pupillary Light Reflex

Pupil constricts due to light stimulus.

Consensual Reflex

Light stimulation of one eye causes pupil constriction in the contralateral (opposite side) eye.

Ciliospinal Reflex

Stimulation (almost painful) of the back of the neck causes ipsilateral (same side) pupil dilation.

Salivary Reflex

Food odor detection causes salivation.

General Senses

General sensory receptors respond to touch, pressure, pain, heat, cold, stretch, vibration, & body position.

Special senses

Localized in groups; receptors for sight, hearing, equilibrium, smell, & taste.

Exteroceptors

React to external stimuli.

Interoceptor/visceroceptor

React to internal stimuli.

Proprioceptor

Detects body/limb position.

Free/naked nerve endings

Detects light touch, pain, and temperature.

Hair follicle receptor

Detects light touch.

Tactile (Meissner's) corpuscle

Detects light touch and light pressure.

Bulbous (Ruffini's) corpuscle

Detects deep pressure/stretching.

Lamellar (Pacinian) corpuscle

Detects deep pressure/high frequency vibrations.

Qualities of cutaneous sensations

Touch, heat, cold, & pain.

Two-point threshold

Smallest distance 2 points of contact can be perceived; closer on face than on back.

Tactile localization

Determining which point on skin has been stimulated.

Adaptation

Sensory receptor discharge from stimulus slows, causing the perception of stimulus to decrease.

Referred pain

Perception of pain from one area of body when another area is actually receiving the noxious stimulus.