Building the Nervous System L2 Flashcards
What is the name for the earliest multicellular organisms?
Metazoans
What is the name of a single celled organism?
Protazoa. Although they’re single celled, they can be surprisingly differentiated and show complex behaviors in the complete absence of a nervous system.
What is ethology?
The scientific analysis of animal behavior
What 3 fundamental classes of behavior are displayed by protazoa and metazoans for survival?
Ingestive, digestive and reproductive behaviors. (ingestive refers to the internal regulation of water and nutrients.)
Name 4 mechanisms for ingestive behavior displayed by the protazoan Paramecia.
Gullet/Oral groove used to take in food
A system of vacuoles that shuttle food around and digest it within cells.
Anal pore/Cytophyge used for waste expulsion.
Cilia/flagella to move towards sources of food or away from an environmental threat.
What is a taxis?
The movement of an organism in response to a stimulus
What organelle is responsible for energy production in Protazoans?
Chloroplasts.
What is the simplest multicellular organism?
Sponge
How long did it take for a sponge to evolve from a protazoa?
1 billion years
Name two considerable advantages of the sponge over unicellular organisms.
Larger size provides a greater resistance to environmental stress.
Having different cell types allows a division of labor in that different cell types can have different jobs, increasing the efficiency of specific tasks, such as nutrition and defense.
Describe the passage of water into and out of a sea sponge.
Environmental water flows into the sponge through pores into the inner cavity called the spongocoel. The water then travels out through the osculum.
What is responsible for the circulation of water though the pores of the sponge?
The circulation of water through the pores to the spongocoel and back out through the osculum is determined by the beating of flagellated cells which line the inside of the spongocoel.
What regulates the feeding behaviour (and ultimately water flow) in sponges?
Myocytes.
What is the most important property of a myocyte in sponges and why?
Contractility. As they’re able to shorten, they’re able to ‘do work’. They’re arranged concentrically (similar to that of a dart board) around channels in the sponge body wall allowing them to cat as Sphincters so that when they contract, they are able to control the rate of nutrient saturated water flowing through the animal.
Why are myocytes described as independent effectors?
As they’re cells that produce a motor response when directly stimulated, without the interference of a neurone.
Why is the response in myocytes slower than that of neurones?
As myocytes are independent effectors, they’re not under the interference of a neurone. As a result, myocytes are less sensitive which means they require a large stimulus to initiate a response. These responses are typically much slower but last much longer, compared to that of neurones.
Give two reasons why HYDRA (cnidaria) provide are a favorite example of how the nervous system originally evolved.
They have a simple body plan (A mouth at one end and a foot at the other.
They have intriguing patterns of feeding and locomotion behaviors, in that they bring food into their mouths using their tentacles which they also use to move around the environment.
What does the prototypical sensory neurone derive from in HYDRA?
The ectodermal layer
Where does gangliation occur in flatworms?
The Cephalic region (anterior/rostral end - head)
How many neurones does c.elegans have?
302
How many glia does c.elegans have?
56
What is the function of a glial cell?
A glial cell is a NON- neuronal cell, responsible for maintaining homeostasis, forming myelin and providing structural protection for neurones in the peripheral and central NS.
What is the name for the initial ganglia in the worm what are it’s advantages?
Super-pharyngeal. It is located around the mouth, allowing the worm to process what they’re eating, providing a more efficient way of food digestion, capturing and releasing, allowing better survival.
What is delamination?
The process of cells pinching off from the outside surface of the embryo and migrating towards the center. This is an important featire in developing a complex NS. These cells are still ectodermal cells (not mesenchymal).
What cell type does delamination form?
neuroblasts
What is the function of neuroblasts?
Neuroblasts form ganglion mother cells which ultimately form neurones and glia.