13. C. elegans II Flashcards
(17 cards)
What is the C. elegans pharynx?
A muscular tube-like organ that serves as the worm’s feeding apparatus
It consists of several key anatomical components including the corpus, isthmus, and terminal bulb.
What are the key anatomical components of the C. elegans pharynx?
- Corpus (procorpus and metacorpus)
- Isthmus
- Terminal bulb
Each component plays a specific role in the feeding process.
What are the two main actions performed by the pharynx?
- Pumping
- Peristalsis
Pumping draws bacteria in, while peristalsis transports food through the pharynx.
Describe the food processing sequence in the C. elegans pharynx.
- Bacteria are sucked in during muscle contraction
- Concentrated in the metacorpus
- Transported through isthmus via peristalsis
- Crushed by grinder in terminal bulb before entering intestine
This sequence ensures effective food processing.
How many neurons are in the pharyngeal nervous system?
20 neurons
These neurons coordinate feeding activity and include motor and interneurons.
What is the role of motor neurons in the pharyngeal nervous system?
They innervate muscles
Motor neurons are essential for the movement and function of the pharynx.
What is the function of interneurons in the pharyngeal nervous system?
They process signals
Interneurons play a critical role in coordinating the activity of the motor neurons.
What happens when the M4 neuron is ablated?
The pharynx becomes stuffed with bacteria
M4 is essential for isthmus peristalsis.
What is the function of the MC neuron?
Regulates pumping rate
It releases acetylcholine to control the activity of pharyngeal muscles.
What does the M3 neuron do?
Inhibits pumping
M3 is a glutamatergic neuron that reduces the pumping rate.
How is the pharyngeal nervous system connected to the main nervous system?
By a single neuron
This allows for some degree of independent function.
What occurs when food is present in relation to the feeding pathway?
Food → ADF sensory neuron → Serotonin (5-HT) release → MC neuron → Acetylcholine release → Pharyngeal muscles
This pathway results in a high pumping rate for rapid feeding.
What is the result of the feeding pathway when food is absent?
Low pumping rate (energy conservation)
This occurs through the M3 motor neuron and glutamate release.
What evidence supports the role of serotonin in feeding?
Tryptophan hydroxylase mutants show reduced pumping rate when food is present
These mutants cannot synthesize serotonin.
What happens in EAT-4 mutants when food is absent?
They fail to reduce pumping rate
EAT-4 mutants lack a vesicular glutamate transporter.
What experimental approaches are used to study pharyngeal pumping?
- Laser ablation
- Genetic mutants
- Reporter genes
- Quantitative measurement
These methods help determine neuron function and neurotransmitter roles.
Fill in the blank: The terminal bulb of the pharynx contains the _______.
[grinder]
