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32 Cards in this Set

  • Front
  • Back

Describe pain

- protective mechanism meant to bring a conscious awareness of tissue being damaged is or is about to damage

What helps us avoid potentially harmful events in the future?

Storage of painful experiences

Sensation of pain is accompanied by:

1. motivated behavioural response: withdrawal of defense

2. emotional reaction: crying or fear

3. past or present experience: heightened pain

What are the types of pain?

1. acute

2. chronic pain/neuropathic pain

Acute pain(3)

- temporary and lasts less than 6 months

- person experiences higher than normal level of anxiety

- distress arises from pain but subsidizes as condition improves

Chronic pain/neuropathic pain (3)

- characterized by repeated and intense episodes separated by periods without pain

- presence of discomfort all the time but not related to disease

- discomfort and pain becomes intense as condition worsen and warn about actual damage to body

Abnormal chronic pain can result from

1. Damaged pathways in peripheral nerves or CNS

2. Abnormal signalling within the pain pathways in absence of peripheral injury or painful stimuli

Example of abnormal chronic pain

neuropathic pain during stroke damage afferent pathways, leading to abnormal and persistent pain

3 categories of pain receptors

1. mechanical nociceptors: respond to mechanical damage (cutting, pinching, crushing)

2. thermal nociceptors respond to temperature extremes

3. polymodal nociceptors respond to all kinds of damaging stimuli (irritating chemicals released from injured tissues)

Nociceptors do not have...

specialized structure, posses naked nerve ending

Pain impulse travel:

1. pain umpulses -> 2. nociceptors -> 3. A-deltra fibres OR C-fibres -> 4. CNS

Fast pain pathways are called

A-delta fibres

Pain impulses sent via A-delta fibres

1. passes signals arising from mechanical and thermal nociceptors

2. these fibres are small and myelinated

3. transmit pain impulses are rate up to 6-30 met/sec

Ex of pain impulse sent via A-delta fibres

pain from cut or burned fingers -> pain can be felt as twinge at first, followed by more diffuse, disagreeable, sharp and prickling sensatio

Slow pain pathways are called


Pain impulses sent via C-fibres

- carry impulses from polymodal nociceptors to CNA

- are small, NON-mylinated fibres and carry impulses at a rate of 1-2 met/sec

- feeling of pain is dull, unpleasant, aching, poorly localized and persists for longer time

Bradykinin ( this happens in C-fibre path)...

- is activated by enzymes from injured tissue

- stimulate polymodal receptor causing the long-lasting, aching pain that continues after removal of the mechanical or thermal stimulus

How do hot peppers activat the peripheral receptors of C-fibres?

Capsaicin (from peppers) activates the peripheral receptors of C-fibres

- this substance binds to both pain and thermal receptors causing burning sensation when eating hot peppers

Characteristics of fast pain (4)

- occurs on stimulation of mechnical and thermal nociceptors

- carried by small myelinated A-delta fibres

- produces sharp, prickling sensation

- easily localized

- occurs FIRST

Characteristics of slow pain (5)

- occurs on stimulation of polymodal nociceptors

- carried by small, unmyelinated C-fibres

- produces dull, aching, burning sensation

- poorly localized

- occurs SECOND - persists for longer time, more unpleasant

A-delta fibres:

1. general characteristics

2. speed

3. diameter

4. stimuli

5. description

6. receptor classification

1. small and myelinated

2. 6-3m/sec

3. 1-5 um

4. fast pain,cold, warmth, mechanical

5. sharp, stabbing or acute

6. free nerve ending


1. general characteristics

2. speed

3. diameter

4. stimuli

5. description

6. receptor classification

1. small and UNmyelinated

2. <1-2m/sec

3. 0.5-2 um

4. slow pain, heat, cold, mechanical

5. burning, aching, throbbing

6. free nerve ending

List two pain neurotransmitters and briefly describe each

1. Substance P: activates ascending pathways that transmit nociceptive signals to higher levels for further processing

2. Glutamate: major excitatory neurotransmitter

The brain has a built in analgesic system that: (2)
1. supresses transmission in pain pathways as they enter spinal cord

2. depends on presence of opiate receptors (endogenous opiates: endorphins, enkephalins, dynorphin)

Will a person with am amputated limb continue to receive pain from that limb?

WILL continue to receive a pain from amputated limb as pain sensation evoked in the brain is projected to the amputation

Pathway of pain from amputated limb

amputated limb -> irritation of severed nerve endings -> action potential -> afferent pathways -> somatosensory cortex -> interpreted as pain from missing limb

What are dematomes?

areas of the body that are served by a particular spinal nerve and its branches

Patient suffering from a myocardial infraction (MI)

- may thin kthe pain is originating from his left arm when the sensory input is coming from the heart

Shared pathways of dematomes and internal organs are evident in

referred pain

where does the perception of pain occur


glutamate binds with what 2 receptors on plasma membrane of dorsal horn?

1. AMPA receptors (transmit pain msg to higher brain centers)

2. NMDA receptors ( do not involve pain transmission, bu Ca2+ initiates 2nd msngr sys. and contributes to exaggerated sensitivity of area to pain)

What are the 2 built-in pain suppressing systems?

1. periaqueductal gray matter (electrical stimulation)

2. reticular formation (blocks release of sub. P)

- they both release endogenous opiates