Nervous Systems and Body Plan

Question 1

What groups don’t have a nervous system?

Answer 1

sponges
placozoa

Question 2

When did nervous system arise?

Answer 2

Early Cambrian

Question 3

How are all nervous systems similar?

Answer 3

same sets of proteins and signaling molecules

Question 4

What is the dorsal ventral axis inversion hypothesis?

Answer 4

ventral nerve cord of invertebrates and dorsal nerve cord of vertebrates are homologous

Question 5

What is the most primitive nervous system, and what is it seen in?

Answer 5

most primitive is seen in xecacoelomorpha and some flatworms

longitudinal cords form a ladderlike connectives

Question 6

When did nervous systems become centralized, and examples?

Answer 6

those with active lifestyles

errant polychaetes, arthropods, cephalopods

Question 7

How did nerve systems become centralized?

Answer 7

centralized by reducing number of longitudinal nerve chords

Question 8

What organisms has decentralized their systems?

Answer 8

ectoprocts, tunicates, echinoderms

Question 9

What is the structure of the nervous system related to?

Answer 9

body plan and mode of life

Question 10

What is a radial nervous system, and examples?

Answer 10

receptor organs are non-centralized meshwork (nerve net)

jellyfish and sea anemone

Question 11

What do nerve nets allowed? (2)

Answer 11

able to respond to stimuli in all environment

impulses can travel in all directions from point of stimulation

Question 12

How can nerve net synapses differ?

Answer 12

can be polarizied (uni-directional) or non-polarized (multi-directional) synapses

Question 13

What is a bilateral nervous system, and structure?

Answer 13

centralized and concentrated nervous system

anteriorly located ganglion (cerebral ganglion) where 1 or more longitudinal nerve cords bear additional ganglia

Question 14

What is a supraenteric ganglion?

Answer 14

cerebral ganglion doral to the anterior gut

Question 15

What is cephalization, and what does it allow?

Answer 15

formation of a head organ

allows to hunt, track, and locate food

Question 16

Why is the term brain no longer used?

Answer 16

it is mulitfaceted

Question 17

What are the groups based on structures and position of nervous system?

Answer 17

Protostomia (formerly Zygoneura)

Chordata (formerly Chordonia)

Ambulacraria

Question 18

What are the principle elements of the CNS? (3)

Answer 18

apical organs

a pair of cerebral ganglia that develops in the larval stage and persists

paired longitudinal nerve cord

Question 19

What is an apical organ?

Answer 19

present in almost all ciliate larvae but degenerates before/ during metamorphosis

Question 20

What does the apical organ develop from, and what is it used for?

Answer 20

develops from apical embryonic blastomeres

sensory, and may be used for metamorphosis

Question 21

What is the position of the paired longitudinal nerve cord?

Answer 21

ventral in protostomes, dorsal in deuterostomes

Question 22

How did paired longitudinal nerve cords develop in protostomes and deuterostomes?

Answer 22

homologous

Question 23

What do paired longitudinal nerve cords do? (3)

Answer 23

receives info through peripheral sensory nerves from sense organs

carries impulse from cerebral ganglion to peripheral motor nerves to effector sites

serves for reflexes and coordinated activities

Question 24

What groups are ciliated larvae/ primary larvae found and not found in?

Answer 24

Porifera, Cnidaria, Spiralia, Ambulacraria (none in Ecdysozoa and Chordata)

Question 25

How did ciliated larvae develop?

Answer 25

homologous

Question 26

How do protostome larvae differ?

Answer 26

protostomes have ganglia/ nerve chord that is retained as an adult

Question 27

What does the protostome ganglia/ nerve cord develop into as an adult (2)?

Answer 27

cerebral ganglia pair (adult brain) circumblastoporal nerve cord

Question 28

What do adult NS develop as in the larval stage?

Answer 28

ciliary structures

Question 29

How did deuterostome CNS develop?

Answer 29

homologous in echinoderms and other bilaterians

Question 30

How do echinoderm CNS differ?

Answer 30

cerebral ganglion does not exist

Question 31

What do radial nerves develop from in echinoderms, and what are they homologous to?

Answer 31

ectoderm chordate nerual tube

Question 32

What is the chordate neural tube, and what is it found in?

Answer 32

where the chordate central nevous system develops (Cephalochordates, Urochordates, Vertebrates)

Question 33

What are two strategies for achieving increased neuronal conduction speed?

Answer 33

increased axon diameter improves conduction speed, body speed, and reaction time myelinated sheaths around axons of neurons

Question 34

What group increases axon diameters?

Answer 34

cephalopod molluscs

Question 35

How does mylinated sheaths increase conduction speed?

Answer 35

increases rate of nerve transmission, body movemement, and response

Question 36

What groups have myelinated sheaths?

Answer 36

rare in invertebrates, only in chordates, annelids, and crustaceans

Question 37

How did myelinated sheaths arise?

Answer 37

format differs and arisen differently in each group

Question 38

How does the sheaths form?

Answer 38

myelin forms a glial plasma membrane and sheaths with multiple layers

Question 39

How do cnidaria and xenacoelomorpha differ in sheaths?

Answer 39

naked axons

Question 40

How do Nephrozoans differ in sheaths?

Answer 40

glial plasma membrane cover