Nerve Fiber Classification😊

Nerve Fiber Classification

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Nerve Fibre Classification

Fiber Type Erlanger and Gasser Fibre glass	Numerical Lloyd & Hunt Hunt Number	Conduction Velocity (m/sec)	Diameter (μm)
A → Myelinated	ㅤ	ㅤ	ㅤ
A Alpha	Ia	70 – 120	12 – 20 (70/6)
ㅤ	Ib	ㅤ	ㅤ
A Beta	II	30 – 70	ㅤ
A Gamma	ㅤ	15 – 30	ㅤ
A Delta	III	12 – 30	2 – 5 (30/6)
B → Myelinated	ㅤ	3 – 12	ㅤ
C → Unmyelinated	IV	0.5 – 2	ㅤ

Fibres	Function	Mnemonic
A Alpha	• Proprioception → Golgi tendon; • Somatic motor neurons	ㅤ
A Beta	• Touch, pressure Clinical Relevance: • When compressed or irritated ↳ Cause tingling or numbness.	Dont touch () my beta () with too (II) much pressure
A Gamma	• Efferent to Muscle Spindles	Gamma → gaME → Muscle Efferent
A Delta	• Fast Pain, cold temperature	Deal 3 times Deal with fast time and cold temp in UK in 3 months
B ↳ Myelinated	• Preganglionic autonomic	ㅤ
C ↳ Unmyelinated	• Slow pain, Warm temperature • Burning, freezing • Postganglionic sympathetic	See 4 times See (C) Hot (Warm) and Slow () Touching () Gangbang Posted (Post ganglionic) in …

Important summary

Fiber Type	Myelination	Pain Type	Pathway	Neurotransmitter
Aδ fibers	Myelinated	1st pain / fast pain / epicritic pain	Neospinothalamic	Glutamate
C fibers	Unmyelinated	2nd pain / slow pain / protopathic pain	Paleospinothalamic	Substance P

Fibres	Functions
B	Preganglionic autonomic
C	Postganglionic sympathetic

Susceptibility to Agents (Most Sensitive First):

ㅤ	ㅤ
Regional anaesthesia	Autonomic (B) > Sensory (C fibers = A delta) > A gamma > Motor (A beta > A alpha) ↳ B → C=δ → γ → β → α Busy (B, C) day (delta to alpha) for Anaesthesia
Experimental model LA	A gamma > A delta > A alpha/A beta > B > C ↳ A > B > C LA is a Good (Gamma) Deal (Delta) → Always (Alpha) Block (B) Completely (C)
Pressure	A alpha > B > C (or A > B > C) Always (Alpha) Block (B) Completely (C)
Hypoxia	B > A > C BronchoAlveolarConstriction (BAC)
Spike Duration	C (2 ms) > B (1.2 ms) > A (0.5 ms) ↳ ↓↓ conduction → ↑↑ action potential CBI will put u on Spike

Reflex	Hering Breuer inflation reflex	Hering Breuer deflation reflex	Head's Paradoxical reflex	J Reflex
Significance	Prevents lung injury due to overstretching	Prevents lung collapse	To replace fluid with air in fetal lung	Detects pulmonary edema
Mechanism	Prolonged inspiration	Prolonged expiration	Prolonged inspiration	Pulmonary edema → Activates J (Juxtapulmonary) receptors
Effect	Further inspiration stops → Next expiration begins	Further expiration stops → Next inspiration begins	Further inspiration	Apnea, breathlessness, hypotension, bradycardia
Feedback Neural signal	Myelinated vagal fibres (Slow adapting)	Myelinated vagal fibres (Slow adapting)	-	Unmyelinated vagal fibres (Slow C fibres)

Chronaxie and Rheobase

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Chronicles of Rio (Rheobase)

ㅤ	Definition
Rheobase	Minimum voltage/strength to produce an action potential irrespective of duration Rio → Rio is strong → Voltage
Chronaxie	Minimum duration required for a stimulus of double the rheobase strength to produce an action potential. Chronicle → Time → For double rio strength

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