Reflexes

What is a reflex?

• A reflex is an involuntary reaction to a stimulus.

Reflexes may:

• be intrinsic or acquired.
• involve ONLY the peripheral nerves and spinal cord.
• involve higher brain centers.

The Parts of a Reflex Arc are:

1. Receptor (located at the site of the stimulus)
2. Sensory Neuron (afferent)-carries the signal from the stimulus to the spinal cord.
3. Integration Center (CNS)-processes and sends a response back.
4. Motor Neuron (efferent)-carries the integration center's response back to the effector.
5. Effector-carries out the effects of the original stimulus.

Let's see how it all goes together: http://www.brainviews.com/abFiles/AniPatellar.htm

Sensory Reception

In order for reflexes to occur, a stimulus must be detected by sensory receptors. These receptors may be classified by the type of stimulus they detect or by their location.

Receptor Classification by Stimulus Type:

• Mechanoreceptors-respond to touch, pressure, vibration, stretch, and itch.
• Thermoreceptors-detect changes in temperature.
• Photoreceptors-are sensitive to light (photosensitivity).
• Chemoreceptors-respond to chemicals (smell, taste, blood chemistry).
• Nociceptors-are sensitive to pain.

Receptor Classification by Location:

• Exteroceptors-are susceptible to external stimuli (i.e. skin, eyes, ears, nose, and mouth).
• Interoceptors-detect internal stimuli (i.e. a "full" stomach after you eat).
• Proprioceptors-detect information about skeletal muscles, ligaments, tendons, and joints.