Afferent Nervous System

1
Afferent Nervous System
2
Sensory Receptor Types
p. 329
Figure 10-1 Sensory receptors
List and describe the 5 types of sensory
receptors.
An appropriate stimulus will result in a _______
potential at a receptor, regardless of its
strength.
These unipolar neurons are now known as
__________________.
Speculate as to the types of ion channels
involved in creating a generator or receptor
potential at each receptor type.
3
Exteroceptors Special Senses
p. 333
What class of receptor is involved for each of
these Special Senses?
Differentiate between exteroceptors and
interoceptors.
Somatic senses ?
Figure 10-4 Sensory pathways
4
Ascending Pathway for Somatosensory Information
p. 331
Add the components of a spinal reflex arc to this
diagram.
The general classification (according to
function) of this neuron is _______.
5
Somatosensory Pathways
p. 337
located where?
Distinguish between sensation perception.
If the cortex is asleep, can there still be the
perception of pain if nociceptors are stimulated?
Figure 10-9 Sensory pathways cross the bodys
midline
6
Integration of Sensory Information

• Sensory Acuity
• Receptive field size
• Lateral inhibition
• SA at sensory cortex
• Stimulus Intensity
• Frequency code
• Population code
• Duration
• Action Potential series
• Sensory adaptation
• Tonic receptors
• Phasic receptors

7
Sensory Acuity Receptive Field Size
p. 332
Figure 10-3 Two-point discrimination
8
Sensory Acuity and Lateral Inhibition
p. 335
Figure 10-6 Lateral inhibition
9
Sensory Acuity Somatosensory Cortex
p. 338
10
Stimulus Intensity Duration
p. 336
Are the APs different in height?
How is the frequency code different?
Is this a graded response?
Figure 10-8 Sensory coding for stimulus
intensity and duration
11
Stimulus Intensity and Population Code
For practice
How many primary neurons are stimulated in each
figure? How many secondary neurons are stimulated
in each figure?
Has the population code changed? Predict the
change in frequency code.
12
Tonic and Phasic Receptors
p. 336
What is the advantage of having phasic receptors
for some types of stimuli? Explain with an
example.
Provide an example each for tonic and phasic
receptors.
13
Hair Cell Transduction
p. 352
Are these hair cells tonic receptors or phasic
receptors?
Figure 10-21 Signal transduction in hair cells
14
Taste and Smell Transduction
p. 346
In what ways are the functions of taste and
smell receptors similar? How are these receptors
different? (See pp. 343-345)
15
Primary Sensory Pathways
p. 112 in packet
(except olfaction)
What secondary pathways in the cerebrum might
be stimulated by pain?
List the key nociceptor transmitter(s)
_______________.
This describes the Fast Pain pathway
In this figure, identify and describe the two
different pathways that nociceptors may activate
a the level of the spinal cord.
16
Slow Pain Pathway
Somatosensory cortex
Limbic system
only _at_ 25
Thalamus
Hypothalamus
RAS
(Secondary pathways)
_at_ 75
C-fiber
Dorsal horn (Substance P)
Why is it difficult to localize this kind of pain?
17
Characteristics of Conduction Pathways for Pain
18
Fast and Slow Pain Pathways compared
and a first look at natural pain control
Does this form of natural pain control affect
fast or slow pain pathways?
Descending analgesia is a form of natural pain
control
Fast pain is new
NA Nor-Adrenaline, a.k.a. Nor-Epinephrine also
Serotonin (5-HT) GABA
Slow pain is old
From http//www.clinic-clinic.com/prblm/smptm/Pai
n.htm
19
Anatomy of the Gate in natural pain control

The enkephalin-releasing Gate Interneuron
provides pre-synaptic inhibition
Explain why there is no axon collateral to a
motor neuron to stimulate a withdrawl reflex
p. 341 is incorrect
20
Opening the Gate
21
Closing the Gate
Describe the GPSP on the Gate Interneuron that
results if both the C fiber and A? fiber fire
simultaneously.
22
Gate Theory in Natural Pain Control
23
Sensory Projection and Referred Pain
p. 342
Figure 10-13 Referred pain