Sensory Receptor Organs Detect Energy or Substances

1
Sensory Receptor Organs Detect Energy or
Substances

• Sensory receptor organs are organs specialized to
  detect a certain stimulus.
• Receptor cells within the organ convert the
  stimulus into an electrical signal a
  transduction process.
• Receptor organs are very diverse because they
  specialize in detecting different types of
  stimuli in the environment.
• An adequate stimulus is the type of stimulus to
  which a sensory organ is particularly adapted.
• photic (light) energy for the eye
• mechanical energy for touch

2
Classification based on type of information
detected by specialized sensory receptors each of
which has an adequate stimulus type.
3
Do You Hear What I Hear?Evolutionary influence
on auditory perception.
4
Receptors in Skin are TransducersThey can
change mechanical energy into action potentinals.
5
The Structure and Function of the Pacinian
Corpuscle as an example of transduction of
mechanical to action potentials
6
Different types of sensory information comes in
on different pathways the so called Labeled
Lines concept.
7
Intensity Coding correlated to amount intensity
of stimulus detected by the receptors measured by
frequency of action potentials.
8
Sensory Adaptation occurs even with constant
stimulation so frequency of action potentials
decreases after an initial high frequency at the
onset of the stimulus.
9
Sensory information is processed through several
levels of Sensory Circuits
Vision Hearing Taste Odor
Touch Proprioception
10
Representation of the Body Surface in
Somatosensory Cortex
11
Somatosensory Receptive Field is the area on the
skin with receptors that send touch information
to particular neurons in the somatosensory cortex.
12
The Chemical Senses Taste and Smell

• The Human Tongue Discriminates at least Five
  Basic Tastes
• salty, sour, sweet, bitter, umami
• Taste receptor cells are located within taste
  buds on papillae on the tongue.
• Taste cells extend cilia into the taste pore to
  contact tastants.
• Chemicals in the Air Elicit Odor Sensations
• Flavor is the perception of taste and smell
  together.

13
Figure 9.22 A Taste Bud and Taste Receptor Cells
14
A Cross Section of the Tongue
15
Salty and Sour Transduction


And Maybe TRPV1
May require PKD2L1 ion channel
16
Sweet and Bitter Transduction


T2R 30 different types
gusducin
T1R2 T1R3
17
Its All a Matter of Taste BudsNumber of taste
buds and type of T2R receptors determine
sensitivity to bitter taste.
18
Is Oleogustus the sixth taste ?

• Criteria for primary tastes, including that the
  sensation
• 1) has ecological consequence
• 2) is elicited by a distinctive class of
  chemicals
• 3) stems from activation of specialized receptors
• 4) is detected through gustatory nerves and is
  processed in taste centers
• 5) has a quality nonoverlapping with other
  primary qualities
• 6) evokes a behavioral and/or physiological
  response
• Oleogustus fat taste is triggered by
  nonesterified fatty acids (NEFA)
• medium and long-chain NEFA
• oleic acid, linoleic acid or 9-decenoic acid
• have a taste sensation that is distinct from
  other basic tastes
• Oleogustus The Unique Taste of Fat. Cordelia A.
  Running, Bruce A. Craig, and Richard D. Mattes.
  Chemical Senses, 2015, 110.

19
Anatomy and Main Pathways of the Human Gustatory
System
20
Chemicals in the Air Elicit Odor Sensations

• The sense of smell starts with receptor neurons
  in the nose-within the olfactory epithelium.
• Three types of cells in the epithelium
• Receptor neurons
• supporting cells
• basal cells
• From the receptor cell an apical dendrite extends
  to the mucosal surface.
• Cilia emerge from the dendritic knob.
• An axon extends from the other end of the
  receptor cell to the olfactory bulb.

21
Anatomy and Main Pathways of the Human Olfactory
System
22
Chemicals in the Air Elicit Odor Sensations

• A large number of different odor receptors
• Mice have about 1000 different types of receptor
  proteins
• divided into four different subfamilies of about
  250 receptors each
• Each subfamily of receptors is synthesized in a
  separate band of the epithelium. See figure 9.27
• humans have approximately 400 different receptor
  proteins
• Each type of olfactory receptor can bind a range
  of odor molecules
• a single odorant molecule may bind to a number of
  olfactory receptors

23
Steps in Olfactory Sensory Transduction
many different types
Golf
24
Anatomy and Main Pathways of the Human Olfactory
System