part one Flashcards
do single celled organisms have a nervous system?
no, they’re single celled
what are single celled organisms receptive and responsive to?
external stimuli
why do single celled organisms have spontaneous activity?
it’s in response to their internal environment
what properties to single celled organisms share with a nervous system?
receptive, responsive and also spontaneous activity.
when does a nervous system appear?
in multicellular organisms
what comes with multicellularity?
specialisation
in marine sponges what does water flow through? flow out of? and what causes this flow?
flows through the cell wall, flows out of the osculum and flagella cause this flow
what is water flow in marine sponges regulated by?
it is regulated by myocytes.
what are myocytes? where are they found?
they are primitive muscle like cells, found in the channels
what does it mean when something is an independant effector?
that they can act without the nervous system
what does autoregulative refer to?
refers to independant effectors
what do myocytes respond to?
they respond to stretch when water moves through or to signals such as chemical signals.
what kind of cells are the first neurons? where do these span from?
probably sensorimotor cells. span from the exterior to effector cells
why are neurons important in hydra?
they help the hydras tenticles trap particles
where do motor neurons receive input from?
from true sensory neurons
where do motor neurons have output to? (2)
effector cells and other motorneurons
what are amacrine processes?
they conduct action potentials both ways
what is a nerve net?
the nerves are scattered eveny around organs
what are interneurons and why do they allow more complex interactions?
they are between sensory and motor neurons. because they allow inhibition or excitation
what does spontaneity in all classes refer to?
it means all neurons are capable pf spontaneity
in higher organisms what may spontaneous activity regulate?
the development of connectivity
what may the modulation of spontaneous activity do?
it may underly learning
if something can move what does this mean?
it has a front and a back
what do flatworms have a clustering of?
neurons
what do clustered neurons in flatworms show? (5)
gangliation cephalization bilateral symmetry fasciculation commisures
what is cephalization
it’s the development of a head
what is fasiculation
axonal bundles
what are commissures
clustering of processes running from one side to another
in annelids what fuses?
the longitudinal nerve cords
how many neurons and glia does the c. elegans have?
302 neurons and 56 glia
what nerve cords does the c.elegans have?
ventral, dorsal and lateral
what lineage does the c. elegans NS have? what are most neurons derived from?
ectodermal, most neurons derived from AB cells
where are the precursor neuronal cells found first, then what happens?
found on the surface of the embryo and then migrate in
what’s different about the drosphilla embryo development
it forms a syncytial blastoderm due to nuclear division occuring interiorily without any cytokinesis
in drosophilla embryo development what happens once the nucleii are generated? what does this form
nuclear migration and cellularization occurs, forms a cellular blastoderm
what is cellularization?
the cell wall forms
what two processes occur after the cellular blastoderm is formed?
gastrulation and then neurogenesis
what does delamination lead to?
the formation of neuroblasts
what is delamination?
when cells pull away from the surface and migrate
what do neuroblasts form?
ganglion mother cells
what do ganglion mother cells form?
neurons and glia
what does the vertebrate nervous system form from?
ectoderm
what is different about the nervous system in vertebrates to that of insects?
it is dorsal unlike in insects where it’s ventral
what’s the common feature of the NS across organisms?
we all have a phase where surface cells involute under other surface cells
what does a variety in neurons give?
flexibility and co-ordination
what happens when organisms become polarised?
neurons and axons become aggregated
