Topic 108 - Receptors, taste, olfaction

Question 1

Words to include in receptors

Answer 1

• Stimuli
• Membranes of the afferent nerve endings
• Membranes
• Stimuli
• Local membrane potential
  
  • Hyperpolarization
  • Depolarization
  • Local response
• Threshold
• Action potential
  
  • Conducted along axon
• Amplitude
• Frequency
• Neuron
  
  • Primary
    
    • Conformational change
    • Cation channel
    • Receptor potential
    • Action potential
  • Secondary
    
    • Second cell of sensation
    • Cation channels
    • Receptor potential
    • Primary sensory neuron
    • Electron potential
    • Action potential
    • Sound reception
      
      • Hair cell
      • Auditory nerve
  • Tertiary
    
    • Third cell
    • Transduction
    • Stimulus
    • Cell 1
      
      • Rodes
      • Cones
      • Sensing stimuli
      • Olfaction
        
        • Primary chemical reception
    • Cell 2
      
      • Bipolar cells
        
        • Transduction
        • Transformation
    • Cell 3
      
      • Ganglion cell
        
        • Afferent nerve
• Interoceptors
• Exteroceptors
  
  • Free nerve endings
• Free nerve endings
  
  • Interoceptors
  • Exteroceptors
• Pacinian corpscle
  
  • Exteroceptors
  • Golgi-mazzoni
• Golgi tendon organ
  
  • Interoceptor
• Surface receptor
  
  • Potential change
• Transduces
• Receptor potential
• Myelin sheets
• Generator potential
• Decrement (possible info loss)
• Mechanical reception
  
  • Vibration sensation
    
    • Pacini corpuscles
  • Encoding pressure
    
    • Ruffini coruscles
  • Touch realization
  • Hair follicle sensation
    
    • Hair follicle sensation
    • Orientation
• Thermal reception
  
  • Dual receptor system
  • Warm receptor
    
    • AP between 30-45 degrees
    • A delta
    • C fibers
  • Cold receptor
    
    • 15-42 degrees
    • Paradox cold sensation

Question 2

Words to include in olfaction

Answer 2

• Chemical receptors
  
  • Chemical signals of the gaseous phase
  • Liquid phase
• Adapts
• High differenet threshold
• Location of the source (difficult)
• Dorsocaudal portion of the nasal cavity
• Vomeronasal organ
  
  • Organ of Jacobsen
• Olfactory musosa
  
  • Receptor cells
    
    • ​Bipolar neurons
    • Microvilli
    • Unmyelinated axons
    • Glomeruli of the olfactory organ (terminates here)
  • Supporting cells
    
    • ​Microvilli
  • Basal cells​
• Olfactory tract
  
  • Myelinated axons
    
    • Thinnest nerve fibers
  • Olfactory bulb
  • Criboform plate
  • Synapses
  • Dendrite
  • Mitral and tufted cells
  • Glomerulus
    
    • Periglomerular cells
    • Granule cells
• Primary olfactory cortex
  
  • Amygdala
  • Prepyriform area
  • Olfactory tubercle

Question 3

Words to include in taste

Answer 3

• Gustation
• Liquid phase
• Mechano-receptor system
  
  • Texture
  • Odor
  • Taste
• Gustation receptors
  
  • Gustatory papillae
    
    • Filiform papillae
      
      • Mechanoreceptors
    • Fungiform papillae
    • Circumvallate papillae
    • Foliate papillae
  • Serous glands of Ebner
• Sweet
• Salty
• Sour
• Bitter

Taste pathway

• N. chorda tympani
• N. glossopharyngeus
• N. vagus
• N. trigemini
• N. facialis
  
  • Geniculate ggl
• N. vagus / n. glossopharyngeus
  
  • Ggl. craniale
  • Ggl. caudale
• Solitary nucleus of the myencephalon
• Nerve impulses
  
  • Pons
  • Thalamus
• Efferents of gustatory area of the pons
  
  • Thalamus
  • Amygdala
    
    • Hypothalamic area
• Gustatory area in the thalamus
  
  • Ventral posteromedial nucleus
  • Thermal stimuli
• Gustatory area in the cortex
  
  • Ipsilateral area (stimuli from)
  • Contralateral area (stimuli from)

Question 4

Receptors

1. Role of receptors
2. How does receptors function in general?

Answer 4

• Role: Sensing the stimuli from the outer or inner environment
• Sensing stimuli is accomplished by the membranes of the afferent nerve endings
• The membranes of these nerve terminals is able to generate local membrane potential change in response to a given stimuli
  
  • Either hyperpolarization or depolarization
  • Also called local response
• At a given stimulus the evoked potential change will reach threshold and generate AP, which will be conducted along the axon
  
  • Increasing amplitude of the stimulus will increase the frequency of the APs of the afferent nerve
  • The extent of the stimulus is coded by the amplitude first, and then by the frequency

Question 5

Receptors

Classification of receptors

Answer 5

Question 6

Reseptor

Classification of receptor: According to the receptor

Answer 6

• Primary
  
  • ​Stimulus elicit a conformational change on the cation channel or protein coupled to the channel of the sensory neuron
  • Receptor potential and action potential are generated directly on that cell
  • E.g. Olfaction (primary chemical reception)
• Secondary
  
  • ​stimuli is sensed by the second cell of sensation
  • Cation channels open → generation of receptor potential
  • E.g. Sound reception:
    
    1. ​​Hair cells
    2. Auditory nerve
• Tertiary
  
  • ​Afferent nerve fibersbelongs only to thethird cell involved in the transduction of stimulus
  • Cell 1: Rods and cones (sensing the stimuli)
  • Cell 2: Bipolar cells (transduction and tranformation)
  • Cell 3: Ganglion cells (afferent nerve)

Question 7

Reseptor

Classification of receptor: Localization of stimulus

Answer 7

1. ​Interoceptors
   
   • ​​Receptor sensing stimuli from inner environment
2. Exteroceptors
   
   • ​​Free nerve endings sensing stimuli from the external environment

• Free nerve ending
  
  • ​Exteroceptor and interoceptor
• Pacinian corpuscle
  
  • ​Exteroceptor
• Golgi tendon organ
  
  • ​Interoceptor

Question 8

Reseptor

Classification of receptor: Forms of energy of the stimulus

Answer 8

1. Mechanical reception
   
   • ​​Vibration sensation
   • Encoding pressure
   • Touch realization
   • Hair follicle sensation
     
     • ​Animals: orientation through mechanical sensation
2. Thermal reception
   
   • ​​​​Receptors feel changes in temperature
   • If the change is dangerous, pain will be felt
   • Dual receptor system
   • Warm receptors
     
     • ​Generate AP between 30-45 ºC
   • Cold receptors
     
     • ​Activated between 15-42 ºC
   • Paradox cold sensation
     
     • ​Cold can be felt with pain
   • Twice as many cold receptors as warm receptors
3. Photo
4. Chemical

Question 9

Olfaction

General

Answer 9

• Two chemical receptors (taste & smell) co-operate:
  
  • Smell receives chemical signals of the gaseous phase
  • Taste receives those of the liquid phase
• Their co-operation is important for the sense of flavor

Question 10

Olfaction

In contrast with other sensory organs

Answer 10

• It adapts to stimuli quickly
• High differential threshold
• Location of source is difficult due to the diffusion

Question 11

Olfaction

Location of the receptors of the olfaction organs

Answer 11

• In the dorsocaudal portion of the nasal cavity
• In the vomeronasal organ (organ of Jacobsen)

Question 12

Olfaction

Which cell are the olfactory mucosa composed of?

Answer 12

• The olfactory mucosa consists of 3 types of cells:
  
  1. Receptor cells
  2. Supporting cells
  3. Basal cells

Question 13

Olfaction

Olfactory tract

Answer 13

• Myelinated axons that leave the olfactory mucosa terminates in the glomeruli of the olfactory bulb after passing through the fenestration of the cribiform plate
• Here they form synapses with the dendrites of the mitral and tufted cells
• There are two types of cells inside the glomerulus, whose fibers do not leave the bulb:
  
  • ​Periglomerular cells
  • Granule cells

Question 14

Taste

General

Answer 14

• Gustation indentifies substances dissolved in a liquid phase
• Taste is accompanied by a mechano-receptor system: odor, texture and taste of the subustance taken up by the animal provide information to the animal
  
  • E.g. animals prefer “real” forage to powder forage, even if they have the same nutritive value

Question 15

Taste

Gustation receptors

Answer 15

• Four types of gustation papillae:
  
  1. ​​Filiform papillae
     
     • ​​Mechanoreceptors
  2. Fungiform papillae
     
     • ​​All over the tongue
  3. Circumvallate papillae
  4. ​Foliate papillae
• On the bottom of foliate and circumvallate papillae there are serous glands of Ebner
  
  • Role: washes out chemical substances

Question 16

Taste

Elements of taste

Answer 16

1. Sweet
   
   • ​​Apex of tongue
2. Salty
   
   • ​​Sides of tongue
3. Sour
   
   • ​​Posterior edges of tongue
4. Bitter
   
   • ​​Radix of tongue

Question 17

Taste

Taste pathway

Answer 17

• N. chordae tympani (belonging to n. facialis)
  
  • Anterior 2/3 of tongue
  • Afferent
• N. glossopharyngeus
  
  • ​Posterior 3^rd of the tongue
  • Pharyngeal arch
• N. vagus
  
  • ​Radix of tongue
  • Epiglottis
• N. trigemini
  
  • ​Tactic and temperature receptors in oral cavity
• Soma of these nerves are located in:
  
  • Ggl. geniculate of n. facialis
  • Ggl. craniale and ggl. caudale of n. glossopharyngeus and n. vagus
• Terminates in the solitary nucleus of myencephalon
• Nerve impulses are forwarded towards the pons and thalamus
• Efferents of the gustatory area of the pons terminates partly in the thalamus and hypothalamic area of the amygdala
• Gustatory area in the thalamus is in the ventral posteromedial nucleus
• Gustatory areas in the cortex receives info from both ipsilateral and contralateral areas