Page 62 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

A. Continuous (1a, 1b) and saltatory propagation (2) of action potentials
AP AP Myelin sheath
Na + Na +
Action potential
(AP) Na +

Continuous charge balance Depolarization potential Na + Propagation of Action Potentials in Nerve Fiber
Action
Rest
1a

Refractory charge balance (balancing current) Internode

Na + Na + AP Saltatory
Depo-
Depolarization larization Node
Plate 2.4
1b 2
B. Pulse propagation (action currents) in myelinated and unmyelinated nerve fibers

AP

2 mm AP 2 mm

1nA 1nA
AP

1 2 ms 2 0.1ms 0.1ms
C. Classification of nerve fibers (in humans)
Fiber type Function according to fiber type Diameter Conduction
(Lloyd and Hunt types I–IV) (µm) rate (m/s)
Aα Skeletal muscle efferent, afferents in muscle 11–16 60 – 80
spindles (Ib) and tendon organs (Ib)
Aβ Mechanoafferents of skin (II) 6 –11 30 – 60
Aγ Muscle spindle efferents
Aδ Skin afferents (temperature 1– 6 2 – 30
and „fast“ pain) (III)
B Sympathetic preganglionic; 3 3 –15
visceral afferents
C Skin afferents (“slow” pain); 0.5–1.5
sympathetic postganglionic afferents (IV) (unmyelinated) 0.25 – 1.5 49
(After Erlanger and Gasser)
Despopoulos, Color Atlas of Physiology © 2003 Thieme
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