2014A12 Describe the alterations to the physiology of the nervous system in the older patient
 and outline the consequent effects on pain perception.

List:

· Intro: definitions and significance

· Central nervous system

· Peripheral nervous system

· Autonomic nervous system

Intro:

Pain	· Unpleasant sensory and emotional experience associated with actual or potential tissue damage or is described in such terms
Ageing	· Gradual time-dependent loss of cellular function and physiological reserve, resulting in death
Summary	· ↓Nociceptive response to noxious stimuli · ↑Susceptible to analgesic toxicity · ↓Ability to communicate · Frequently undertreated

Central nervous system:

Changes	· ↓Grey matter: o ↓10,000 neurons per day from age 20 o Total 10% loss by age 80 · ↓White matter (less affected) · ↓Neurotransmitters: o ↓Serotonin and noradrenaline (+/-depression) o ↓Dopamine in substantia nigra (+/-Parkinson’s disease) o ↓Acetylcholine in hypothalamus (+/-senile dementia)
Effect on pain	· ↓Cognition · ↓Communication of pain · ↓Reflex speed -> slower withdrawal from insult · ↓Activity of endogenous analgesic pathways
Disease	· Dementia and delirium common · Inability to communicate · Pain perception preserved

Peripheral nervous system:

Changes	· Generally less affected · ↓Neurons · ↓Axons (myelinated and not) · ↓Synapses · ↓Neurotransmitters (substance P, CGRP)
Effect on pain	· ↓Nociceptive afferents · ↓Sensitisation · ↓Speed of conduction
Disease	· ↑Risk diabetes, +/- peripheral neuropathy -> ↓ pain e.g. toe amputation

Autonomic nervous system:

Changes	· ↓Cardiac β1 adrenoceptors · ↓post-adrenoceptor signalling · (↑Circulating noradrenaline partly offsets above)
Effect on pain	· ↓Autonomic response to pain · Risk of undertreatment intra-op
Drugs	· β-blockers commonly prescribed -> attenuates HR response -> risk of undertreatment