1. The Reflex Arc
Reflex—rapid, predictable, and involuntary response to a stimulus
Occurs over pathways called reflex arcs
Occur without the use of the brain
Brain is usually “advised” that the reflex has occurred (Sometimes resulting in a secondary response- OUCH, which occurs after the reflex)

2. Simple Reflex Arc Figure 7.11c, step 1
Sensory receptors (pain receptors in the skin)
Spinal cord
(c)
Figure 7.11c, step 1

3. Simple Reflex Arc Figure 7.11c, step 2
Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
(c)
Figure 7.11c, step 2

4. Simple Reflex Arc Figure 7.11c, step 3
Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Inter- neuron
(c)
Figure 7.11c, step 3

5. Simple Reflex Arc Figure 7.11c, step 4a
Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Inter- neuron
Motor (efferent) neuron
(c)
Figure 7.11c, step 4a

6. Simple Reflex Arc Figure 7.11c, step 4b
Sensory receptors (pain receptors in the skin)
Spinal cord
Sensory (afferent) neuron
Inter- neuron
Motor (efferent) neuron
Effector (biceps brachii muscle)
(c)
Figure 7.11c, step 4b

7. 2 Types of Reflexes and Regulation
1. Somatic reflexes
Activation of skeletal muscles
Examples:
Gag Reflex This reflex helps to prevent choking.
Withdrawal Reflex Sharp, sudden pain causes the affected arm or leg to be withdrawn.
Scratch Reflex An irritant to the skin causes scratching movement to relieve the itch.

8. 2. Autonomic reflexes
Smooth muscle regulation
Heart and blood pressure regulation
Regulation of glands
Digestive system regulation
Saliva
Sweating
Pupil dilation
For more examples see next slide