ULO 6- Physiology and perception of pain & pain control

Question 1

What factors are involved in Pain Perception

Answer 1

• Physiological source

- Psychological reaction

Question 2

Explain: Pain Reception

Answer 2

The principle of pain reception is that several million bare sensory nerve endings weave their way through all the tissues and organs of the body (except the brain) and respond to noxious stimuli

Question 3

Which chemical appears to provide the stimulus for pain

Answer 3

Bradykinn

- its released from damaged tissues and triggers the release of inflammatory chemicals (prostaglandin and histamine)

Question 4

What are the 2 types of pain

Answer 4

Somatic- skin, muscles and joints

Visceral- body organs

Question 5

What nerve fibres are involved in pain recpetion

Answer 5

C fibres- small nerve fibres that sense burning and longer aching pain

A δ (DELTA) fibres– medium nerve fibres that sense hot and cold and touch

A β (Beta) fibres– large nerve fibres that sense hot and cold

Question 6

Explain: Pain Modulation

Answer 6

is the means by which our body releases substances to interrupt or reduce the amount of pain being felt

Question 7

List pain modulation sources during labour

Answer 7

• Endorphins- release an amnesic and drowsy affect, thought to provide protection from the intensity of labour pain.
• Endogenous opiates: inhibit prostaglandin production which is thought to be a key element in pain perception
• Encephalin

Question 8

Labour Pain Pathways

Explain: Visceral and Somatic pain in labour

Answer 8

Visceral pain- is caused by the uterine contractions, the dilatation of the cervix and, later, by the stretching of the vagina and pelvic floor.

Somatic pain- is caused by the pressure of the fetus as it distends the birth canal, vulva and perineum.

Question 9

Pain Pathways in Labour

Explain: Visceral and Somatic pain pathways in labour

Answer 9

Visceral- Nerve pulses from the uterus and cervix stimulate spinal cord neurons of the abdominal wall

Somatic- Sensations from the pelvic floor are relayed from the pudendal nerve to the sacral plexus

• Woman may experience pain in the thighs, buttocks, iliac crests, lumbar and sacral areas of the back and lower abdomen.

Question 10

List some of the effects of pain in labour

Answer 10

• increased cardiac output
• decreased uterine contractions
• rise in blood pressure
• decreased uterine blood flow

Question 11

Pain Perception

List factors that can alter and influence levels of pain

Answer 11

• knowledge
• previous experience
• culture
• age
• quality of caregiver/woman relationship
• self-confidence in birthing ability
• immobility
• medical interventions

Question 12

Physiological pain V pathological pain

Explain: Physiological Pain

Answer 12

• consistent with labour rhythms in active phases
• endorphins release to offset contraction pain
• allows for rest phases

Question 13

Physiological pain V pathological pain

Explain: Pathological

Answer 13

• Abnormal labour rhythm in active phase
• anxiety/stress hormone release counteract endorphins effect
• minimal progress

Question 14

List Non-Pharmacological methods of pain relief

Answer 14

• water
• heat
• positioning
• massage/acupressure
• sterile water injections
• movement

Question 15

List Pharmacological methods of pain relief

Answer 15

• TENS
• Nitrous oxide and oxygen
• Epidural
• Morphine

Question 16

Explain: Gate Control Theory of Pain

Answer 16

• The large Aβ (beta) fibres (rapid movement of message) get priority over the smaller C and Aδ (delta) pain fibres
• This effectively shuts the gate on C an Aδ fibres and inhibits their entry into the brain
• If pain intensifies C and Aδ fibres can reopen the gate

The essence of the gate control theory

• Gating of the spinothalamic tract response to C fibre activity can be achieved by stimulating large myelinated mechanoreceptor afferents by rub or tickle.
• These impulses inhibit the ascending pain impulse.
• Inputs from the large myelinated fibres conveying touch and smaller A δ (Delta) and C fibres conveying pain interact at the level of the spinal cord. T
• The large-diameter sensory nerve impulses come into the spinal cord more rapidly.
• This normally inhibits the slower smaller fibre pain impulses presynaptically.
• This inhibition constitutes the gate that is normally closed against small-diameter fibre impulses unless the stimulation is so great that it over-comes the gate

Question 17

Who developed the Gate Control Theory of Pain

Answer 17

Melzack and Wall in 1965