Sponge: Set up Cornell Notes on pg. 45

Topic: 12.2 Touch: Pain

Essential Question:1.How do viscera (internal organs) respond differently to pain than surface tissues do?2.What is referred pain?

2.1 Atoms, Ions, and Molecules

12.2 Touch: Pain

Please turn in Lab 30 to printer

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Sense of Pain• PAIN or NOCICEPTORS are widely distributed

throughout skin and internal tissues• almost every surface and organ has them….

• EXCEPT the nervous tissue of the brain lacks pain receptors

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• Provides protection as they are stimulated by tissue damage

•pain is supposed to be unpleasant so you remove source of stimulation•caused by chemical or mechanical forces, and extremes in temperature

Why do we need to experience pain? What is its major function?

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• Injury is a major cause, but pain may also arise from an illness

• It may accompany a psychological condition, such as depression

What types of events can be the cause of pain?

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Visceral Pain (Internal Organs)• pain receptors are the only receptors in viscera (internal

organs) whose stimulation produces sensations • not well localized- not easy to identify

• Ex: damage to intestinal tissue during surgery may not elicit any pain, even in someone conscious

• when subjected to widespread stimulation, a strong pain sensation follows• Ex: when intestinal walls undergo spasms, a strong

pain sensation may follow (due to mechanoreceptors)

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Referred Pain• Referred pain may feel as if coming from some other

part of the body•Ex: Before a heart attack the person may feel strong pain in their left arm/shoulder region

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• Pain threshold- The point at which an individual perceives a stimulus as painful

• Not a lot of difference between people

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• Pain tolerance- The LENGTH of time an individual can endure pain before responding noticeably

• A LOT of variation between people

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Acute vs. Chronic Pain

Acute pain

• associated with sharp pain• pain stops when pain producing stimulus stops OR when injury heals• can pinpoint where pain occurs

•EX: A pinch•sunburn•broken bone•pulled muscle

Chronic pain

• associated with dull, aching pain•persists after injury heals• difficult to pinpoint- stimulus may be unknown

EX: Arthritis, cancer, depression

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Pain receptors adapt VERY LITTLE

Once a pain receptor is activated, even by a single stimulus, it may continue to send impulse into the CNS for some time

What is adaptation?

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Regulation of Pain Impulses

Thalamus : allows person to be aware of pain

Cerebral Cortex:• judges intensity of pain • locates source of pain• produces emotional and motor responses to pain

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Regulation of Pain Impulses

Pain Inhibiting Substances

• Serotonin•Stimulates the release of enkephalins-suppresses pain, relieving strong pain sensations (like morphine)

• Endorphins•Released in response to extreme pain•provide natural pain control much like morphine

Suppressing Pain: The Brain’s Emergency Response (8m)

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Inability to Feel Pain

Hereditary Sensory and Autonomic Neuropathies (HSANs)

The inability to feel sensation, and therefore pain•5 different types•People with HSANs rarely survive beyond their 20s

• Ex: Babies loose teeth from chewing toys• Cuts and scrapes won’t heal• Break a bone and keep moving it- playing- etc

Hidden Curse: The Inability to Feel Pain (2m)

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12-Year Old Girl Cannot Feel Pain Video

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Summary of Receptors of the General Senses