Difference between revisions of "Amphid Neurons"

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'''Amphid neurons''' are one type of chemosensory neurons that are found in the anterior head region of nematode Caenorhabditis elegans (C. elegans).
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'''Amphid neurons''' are chemosensory neurons located in the anterior head region of the nematode ''Caenorhabditis elegans''.
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[[Image:Amphid neurons.jpg|thumb|400px|right|This image in A. shows all of the amphid neurons in the head region of C. elegans.
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Ortis, Christopher  Etchberger, John F. (2006)]]
 
== Basic information ==
 
== Basic information ==
 
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'''Amphid Neurons:''' are sensory neurons. There are 12 amphid sensory neurons, 11 of which are chemosensory neurons (ADF, ADL, ASE, ASG, ASH, ASI, ASJ, ASK, AWA, AWB, AWC) which C.elegans use to sense chemicals.  The twelfth, AFD, is a thermosensory amphid neuron. As a result of what these tiny animals sense, they can either decide to move toward the chemical (as with chemical attractants), away from the chemical (as with chemical repellants), or not at all.
'''Amphid Neurons:''' are sensory neurons or sensilla; specifically 12 sensory 11 of which are chemosensory neurons (ADF, ADL, AFD, ASE, ASG, ASH, ASI, ASJ, ASK, AWA, AWB, AWC) which C.elegans use to sense chemicals. As a result of what these tiny animals sense, they can either decide to move toward the chemical (as with chemical attractants), away from the chemical (as with chemical repellants), or not at all. Phasmid neurons are another type of chemosensory neurons that share many of the functions expressed by amphid neurons; however,  only the amphid neurons (ASH 5) are required for chemotaxis. 
 
  
 
== Anatomy ==
 
== Anatomy ==
''[[Image:Amphid neuron anatomy|thumb|Description]]
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C. elegans have 11 pairs of bilaterally symmetric amphid chemosensory neurons.  Amphid neurons have ciliated dendrites that extend to the tip of the animal's nose.  The cell bodies are located outside of the nerve ring.  The nerve ring, or nerve bundle, is where the axons of amphid neurons reside and make synaptic connections with neighboring cells.
''[[Image:AMpocket.jpg|thumb|Description]]
 
 
 
''C. elegans have 12 pairs of bilaterally symmetric amphid chemosensory neurons (ADF, ADL, AFD, ASE, ASG, ASH, ASI, ASJ, ASK, AWA, AWB, AWC)The cell bodies of amhpid neurons, with cillliated dendrites that extend to the tip of the animals nose, are located outside of the nerve ring.  The nerve ring, or nerve bundle, is where the axons of amphid neurons reside and make synaptic connections with neighboring cells.
 
  
 
== Molecular profile ==
 
== Molecular profile ==
* '''Neurotransmitter:''' In response to stimuli, C. elegan neurons propagate an action potential and release biogenic amines such as dopamine, tyramine, and octopamine as neurotransmitter. C. elegan amphid neurons (ASE, ASG, ASH, and ASI) express tyramine as their neurotransmitter.  One of the functions of tyramine is to inhibit head oscillations in absence of food.  
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* '''Neurotransmitter:'''  Amphid neurons (ASE, ASG, ASH, and ASI) express tyramine as their neurotransmitter.  One of the functions of tyramine is to inhibit head oscillations in absence of food.  
 
== Behavior ==
 
== Behavior ==
In response to stimuli, the C. elegans can use more than one type of sensory neuron at a time.  For example, when a "drop test" was used to drop chemical repellant on the tail of C. elegans, the animal sensed the touch with the dendrites of its mechanosensory phasmid neurons, located in the posterior region of the animal, and moved forward. However, when the chemical repellant reached the anterior head region of the animal, the dendrites of the amphid neurons sensed the chemical causing the animal to move backward.
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In response to stimuli, the C. elegans can use more than one type of sensory neuron at a time.  For example, when a "drop test" was used to drop chemical repellent on the tail of ''C. elegans'', the animal sensed the touch with the dendrites of its mechanosensory phasmid neurons, located in the posterior region of the animal, and moved forward. However, when the chemical repellent reached the anterior head region of the animal, the dendrites of the amphid neurons sensed the chemical causing the animal to move backward.
 
When food is available, the amphid chemosensory neurons act on the phasmid motor neurons and cause the C. elegans move their heads toward the food source.  When there is a mutation in the gene responsible for normal amphid neuron function and there is no food available, head oscillations still occur. When food is unavailable the amphid neurons release tyramine that inhibit the actions of phasmid motor neurons which, thereby, prevents head oscillation.
 
When food is available, the amphid chemosensory neurons act on the phasmid motor neurons and cause the C. elegans move their heads toward the food source.  When there is a mutation in the gene responsible for normal amphid neuron function and there is no food available, head oscillations still occur. When food is unavailable the amphid neurons release tyramine that inhibit the actions of phasmid motor neurons which, thereby, prevents head oscillation.
 
== References ==
 
== References ==
 
1. Bargmann CI. (2006) Chemosensation in C. elegans, WormBook, pages: 1-29. PMID: 18050433 [PubMed-indexed for MEDLINE}
 
1. Bargmann CI. (2006) Chemosensation in C. elegans, WormBook, pages: 1-29. PMID: 18050433 [PubMed-indexed for MEDLINE}
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2. Hilliard, C.  Bargmann, P. (2002) C. elegans Responds to Chemical Repellents by Integrating Sensory Inputs from Head to Tail, Current Biology, vol: 12 pages 730-734 M
 
2. Hilliard, C.  Bargmann, P. (2002) C. elegans Responds to Chemical Repellents by Integrating Sensory Inputs from Head to Tail, Current Biology, vol: 12 pages 730-734 M
3. Gray, Jesse M.  Hill, Joseph J. (2004) A Circuit for Navigation in Caenorhabditis elegans, PNAS
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3. Gray, Jesse M.  Hill, Joseph J. (2004) A Circuit for Navigation in Caenorhabditis elegans, PNAS, vol. 102 no.9 pages 3184-3191
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4. Ortis, Christopher  Etchberger, John F. (2006) Searching for Neuronal Left/Right Asymmetry: Genomewide Analysis of Nematode Receptor-Type Guanylyl Cyclases Genetics, Vol. 173, 131-149
  
 
== Additional information ==
 
== Additional information ==
[www.wormbook.org/chapters/www_monoamines/monoamines.html| Biogenic amine neurotransmitters in C. elegans
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* [http://www.wormbook.org/chapters/www_monoamines/monoamines.html| Biogenic amine neurotransmitters in C. elegans]
http://www.wormatlas.org/ward_buildv0.1/discussion.html The Nerve Ring of the Nematode Caenorhabditis elegans: Sensory Input and Motor Output
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* [http://www.wormatlas.org/ward_buildv0.1/discussion.html| The Nerve Ring of the Nematode Caenorhabditis elegans: Sensory Input and Motor Output]
http://www.genetics.org/cgi/content/full/173/1/131/FIG1  Searching for Neural Left/Right Asymmetry: Genomewide Analysis of Nematode Receptor
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* [http://www.genetics.org/cgi/content/full/173/1/131/FIG1  Searching for Neural Left/Right Asymmetry: Genomewide Analysis of Nematode Receptor]
http://www.wormatlas.org/handbook/hypodermis/Amphidimagegallery.htm]
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*[http://www.wormatlas.org/handbook/hypodermis/Amphidimagegallery.htm Worm Atlas ampid neuron gallery]
  
 
[[Category: User contributed neurons]]
 
[[Category: User contributed neurons]]
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[[Category: Biol6102 student pages]]
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[[Category: C. elegans]]

Latest revision as of 00:52, 14 September 2009

Amphid neurons are chemosensory neurons located in the anterior head region of the nematode Caenorhabditis elegans.

This image in A. shows all of the amphid neurons in the head region of C. elegans. Ortis, Christopher Etchberger, John F. (2006)

Basic information

Amphid Neurons: are sensory neurons. There are 12 amphid sensory neurons, 11 of which are chemosensory neurons (ADF, ADL, ASE, ASG, ASH, ASI, ASJ, ASK, AWA, AWB, AWC) which C.elegans use to sense chemicals. The twelfth, AFD, is a thermosensory amphid neuron. As a result of what these tiny animals sense, they can either decide to move toward the chemical (as with chemical attractants), away from the chemical (as with chemical repellants), or not at all.

Anatomy

C. elegans have 11 pairs of bilaterally symmetric amphid chemosensory neurons. Amphid neurons have ciliated dendrites that extend to the tip of the animal's nose. The cell bodies are located outside of the nerve ring. The nerve ring, or nerve bundle, is where the axons of amphid neurons reside and make synaptic connections with neighboring cells.

Molecular profile

  • Neurotransmitter: Amphid neurons (ASE, ASG, ASH, and ASI) express tyramine as their neurotransmitter. One of the functions of tyramine is to inhibit head oscillations in absence of food.

Behavior

In response to stimuli, the C. elegans can use more than one type of sensory neuron at a time. For example, when a "drop test" was used to drop chemical repellent on the tail of C. elegans, the animal sensed the touch with the dendrites of its mechanosensory phasmid neurons, located in the posterior region of the animal, and moved forward. However, when the chemical repellent reached the anterior head region of the animal, the dendrites of the amphid neurons sensed the chemical causing the animal to move backward. When food is available, the amphid chemosensory neurons act on the phasmid motor neurons and cause the C. elegans move their heads toward the food source. When there is a mutation in the gene responsible for normal amphid neuron function and there is no food available, head oscillations still occur. When food is unavailable the amphid neurons release tyramine that inhibit the actions of phasmid motor neurons which, thereby, prevents head oscillation.

References

1. Bargmann CI. (2006) Chemosensation in C. elegans, WormBook, pages: 1-29. PMID: 18050433 [PubMed-indexed for MEDLINE}

2. Hilliard, C. Bargmann, P. (2002) C. elegans Responds to Chemical Repellents by Integrating Sensory Inputs from Head to Tail, Current Biology, vol: 12 pages 730-734 M

3. Gray, Jesse M. Hill, Joseph J. (2004) A Circuit for Navigation in Caenorhabditis elegans, PNAS, vol. 102 no.9 pages 3184-3191

4. Ortis, Christopher Etchberger, John F. (2006) Searching for Neuronal Left/Right Asymmetry: Genomewide Analysis of Nematode Receptor-Type Guanylyl Cyclases Genetics, Vol. 173, 131-149

Additional information