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Special Senses and Pain

I). Sense Pathway

STIMULUS ê Peripheral nervous system Sensory receptors ê Receptor Proteins ê Ion Channels Open ê Nerve Impulse ê Sensory Nerve Fiber (afferent) ê Central Nervous System Spinal Cord
ê Reflex Arc (efferent nerve fiber) ê Motor unit ê Muscle ê response	ê Brain Stem ê Thalamus ê Sensory Area In the cerebral cortex ê Sensory association area ê Sensation ê Perception

II. Sensory Receptors

A). Receptors are specialized to receive a certain type of stimuli which will result in sensation in the cerebral cortex

B). Types of senses

1). Somatic

2). Special Senses

C. Types of receptors

1.Chemoreceptors

2.Pain Receptors

3.Mechanoreceptors

4.Thermoreceptors

5.Photoreceptors

III) Pain

Free Nerve Endings

A). Stimulated when tissues are damaged signals that action must be taken.

B). Pain receptors are responsive to different stimuli:

Temperature

Mechanical damage

Chemicals .

Ischemia:

Hypoxia:

Mechanical Sensitive

C). Pain receptors do not adapt

D). Pain receptor become more sensitive to pain producing chemicals thus lowering the pain threshold.

E). Pain Pathways

1). Acute Pain Fibers

2). Chronic Pain Nerve Fibers

Pain can become debilitating even if the stimuli is no longer present

F. Pain Travels

Free nerve ending ↓ Spinal nerve (some cranial nerves) peripheral nervous
↓ Reflex Arc (efferent nerve fiber) ↓ Motor unit ↓ Muscle ↓ response	↓ Terminate in the reticular formation ↓ Hypothalamus ↓ Thalamus Awareness of pain ↓ Cerebral cortex Mechanical and emotional response

IV. Temperature

A). Receptors:

Thermoreceptors

Free nerve endings

B). Warm receptors:

C). Cold receptors:

V. Touch & Pressure

Mechanical Receptors

Sense mechanical forces that deform or displace tissues

A). Free Nerve Endings

B). Meissner’s Corpuscles

C). Pacinian Corpuscles