Chapter 5.1: Evolution of the Nervous System

Question 1

the nervous system coordinates rapid responses involving multiple organs, and translates ____ info into APs that can be integrated and lead to an ____ activation.

Answer 1

the nervous system coordinates rapid responses involving multiple organs, and translates SENSORY info into APs that can be integrated and lead to an EFFECTOR activation.

Question 2

simplest reflex arc.

Answer 2

has a sensory neuron that CONTROLS an effector cell directly. LOOK AT NOTE FOR DRAWING.

Question 3

multiple synapse reflex arc

Answer 3

sensory neuron synapses with an integrator neuron, it no longer controls the effector neuron directly. LOOK AT NOTE FOR DRAWING

Question 4

an ____ neuron is the simplest form of a CNS. Why?

Answer 4

integrator neuron is the simplest form of a CNS. integrator neuron can alsoo have multiple inputs from higher integrators (ex/ brain or EFFECTOR NEURONS)

Question 5

What can higher regulatory centers do to a reflex pathway?

Answer 5

can alter the reflex pathway. can alter its sensitivity, can activate the pathway in advance prior to the stimulus, can modify the reflex based on past memory, and allows for sophisticated behaviors.

Question 6

Draw how a spine can act as a higher integrator

Answer 6

refer to notes

stimulus –> sensor neuron –> spine interneuron –> effector neuron —> muscle

Question 7

3 main nervous system evolution trends

Answer 7

1) integrating neurons in the CNS
2) longitudinal centralization in a nerve cord
3) cephalization: neurons became concentrated in the head.

Question 8

building blocks of a nervous system

Answer 8

1) neurons: ability to transmit info, regulate ion flow and electrical excitation.
2) circuitry: pathways for electrical conduction

Question 9

how is it proved that voltage gated ion channels are an evolutionary advantage?

Answer 9

since its been held onto for so many years, they are present in bacteria and in humans.

Question 10

Sponges are the only eukaryotes that do not have nerves. What do they use instead to respond to electrical signals?

Answer 10

they have action potentials that last a super long time, and are spread through a function syncyticum/ TRABECULAR RETICULUM: a group of joined cells acting as one unit that connects all parts of the sponge.

Question 11

In terms of genetics, what do sponges and higher mammals have in common?

Answer 11

1) sponge larvae express genes that develop into full-fledged NEURONS in higher aniamls.
2) sponges also have genes that form proteins located on post synaptic membranes. In higher animals, these genes code for post-synaptic RECEPTORS/

Question 12

Cnidarians have ___ ____ which are the most simple nervous systems.

Answer 12

nerve nets

Question 13

T/F: cnidarians nerve nets are centralized

Answer 13

false. there is no centralization of cephalization. the nerve net extends through the entire body and monitors the environment.

Question 14

T/F: cnidarians have higher integrations

Answer 14

false. sensory and motor neurons synapse together directly, muscles are activated with no integration at all.

Question 15

T/F: cnidarians have neurons

Answer 15

true. all neurons are in the nerve net. they can generate action potentials and release Neurotransmitters like any other neuron.

Question 16

Are nerve nets still seen in higher vertebrates?

Answer 16

yes. they still have an evolutionary advance because we still see them in our gut system. We have a NERVE PLEXUS.

Question 17

after the cnidarians and their nerve net, what was the next step towards CNS development?

Answer 17

Ganglia and nerve rings seen in jelly fish and hydromedusa

Question 18

what is a nerve ring

Answer 18

a single GIAN AXON condensed into a simple ganglia

Question 19

what is a ganglia

Answer 19

a group of nerve cell bodies with related function

Question 20

ganglia can be found in ____ in jelly fish. what is a ____?

Answer 20

ganglia can be found in RHOMPHALUM in jelly fish.

a rhomphalum are primitive sensory organs that also functions as a pacemaker to generate swimming rhythym.

Question 21

a hydromedusa uses 2 nerve rings for what function

Answer 21

1) outer ring: single giant axon that forms an annulus and used for escape swimming and bell pulsation
2) inner ring: used for slow swimming and generates action potentials which originate from a pacemaker system.

Question 22

a true CNS first evolved in animals with ____

Answer 22

bilateral symmetry

Question 23

T/F: Radially symmetric animals had a CNS

Answer 23

false. they only had nerve rings, ganglia, o r a nerve net

Question 24

flatworms had 2 ____ ____ that are connected by 2 ___ ___.

Answer 24

flatworms had 2 anterior ganglia that are connected by 2 nerve cords.

Although the ganglia are considered to be too reudimentary to be a brain, it is showing initial encephalization localization!! (anterior)

Question 25

earthworms contain a chain of ganglion going down the organism longitudinally, signifying:

Answer 25

a rudimentary nerve cord.

Question 26

arthropods show more developed sensory organs and specialized ganglia. Some of the ganglia was organized into a ____, which served the purpose of:

Answer 26

some cell bodies of ganglia were organized into a neutrophil, which reduced the transmission delays seen in cnidarian nerve nets.

Question 27

when the true brain was developed, it developed at the ____ end because animals moved forward.

Answer 27

anterior end.

Question 28

with the evolution of bilateral symmetry, came the development of (2 important aspects)

Answer 28

1) longitudinal nerve cord that coordinated activity with a PNS (initially seen in earthworm)
2) communication network that extends between CNS and all parts of the animal body.

Question 29

which two classes of organisms have the most “developed brains”

Answer 29

cephalopods and vertebrates: there are now lobes dedicated to specific function and are proportionate to their importance. there is also more neural folder and generation of wave paterns.

Question 30

Key developments in the evolution of the nervous system?

Answer 30

1) trabecular reticulum (functional synctium) in sponges
2) nerve net in cnidarians
3) ganglia and nerve ring in jelly fish (RADIAL SYMETTRY )
4) nerve cords in animals with BILATERAL SYMMETRY
5) brain “superganglia”