Ganong's Review of Medical Physiology, 23rd Edition

154
SECTION II
Physiology of Nerve & Muscle Cells

FIGURE 8–3
Relationship between stimulus and impulse frequency in an afferent fiber.
Action potentials in an afferent fiber from a
mechanoreceptor of a single sensory unit increase in frequency as branches of the afferent neuron are stimulated by pressure of increasing mag-
nitude.
(From Widmaier EP, Raff H, Strang KT:
Vander’s Human Physiology.
McGraw-Hill, 2008.)

FIGURE 8–4
Relation between magnitude of touch stimulus (S) and frequency of action potentials in sensory nerve fibers (R).
Dots
are individual values from cats and are plotted on linear coordinates
(left)
and log–log coordinates
(right).
The equation shows the calculated
power function relationship between R and S.
(Reproduced, with permission, from Werner G, Mountcastle VB: Neural activity in mechanoreceptive cutaneous
afferents. Stimulus–response relations, Weber functions, and information transmission. J Neurophysiol 1965;28:359.)

Action

potentials

Skin

Time

Pressure(mmHg)

180

120

60

Glass probe

Afferent neuron

100

90

80

70

60

50

40

30

20

10

S (% maximum stimulus)

R = 9.4 S0.52

R (% response to maximum stimulus)

10 20 30 40 50 60 70 80 90 100

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

.2 .3 .4.5.6.7 .8.91.01.11.21.31.41.51.61.71.81.92.02.1

Log S

Log R