Chapter 5.1: Evolution of the Nervous System Flashcards
the nervous system coordinates rapid responses involving multiple organs, and translates ____ info into APs that can be integrated and lead to an ____ activation.
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.
simplest reflex arc.
has a sensory neuron that CONTROLS an effector cell directly. LOOK AT NOTE FOR DRAWING.
multiple synapse reflex arc
sensory neuron synapses with an integrator neuron, it no longer controls the effector neuron directly. LOOK AT NOTE FOR DRAWING
an ____ neuron is the simplest form of a CNS. Why?
integrator neuron is the simplest form of a CNS. integrator neuron can alsoo have multiple inputs from higher integrators (ex/ brain or EFFECTOR NEURONS)
What can higher regulatory centers do to a reflex pathway?
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.
Draw how a spine can act as a higher integrator
refer to notes
stimulus –> sensor neuron –> spine interneuron –> effector neuron —> muscle
3 main nervous system evolution trends
1) integrating neurons in the CNS
2) longitudinal centralization in a nerve cord
3) cephalization: neurons became concentrated in the head.
building blocks of a nervous system
1) neurons: ability to transmit info, regulate ion flow and electrical excitation.
2) circuitry: pathways for electrical conduction
how is it proved that voltage gated ion channels are an evolutionary advantage?
since its been held onto for so many years, they are present in bacteria and in humans.
Sponges are the only eukaryotes that do not have nerves. What do they use instead to respond to electrical signals?
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.
In terms of genetics, what do sponges and higher mammals have in common?
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/
Cnidarians have ___ ____ which are the most simple nervous systems.
nerve nets
T/F: cnidarians nerve nets are centralized
false. there is no centralization of cephalization. the nerve net extends through the entire body and monitors the environment.
T/F: cnidarians have higher integrations
false. sensory and motor neurons synapse together directly, muscles are activated with no integration at all.
T/F: cnidarians have neurons
true. all neurons are in the nerve net. they can generate action potentials and release Neurotransmitters like any other neuron.
Are nerve nets still seen in higher vertebrates?
yes. they still have an evolutionary advance because we still see them in our gut system. We have a NERVE PLEXUS.
after the cnidarians and their nerve net, what was the next step towards CNS development?
Ganglia and nerve rings seen in jelly fish and hydromedusa
what is a nerve ring
a single GIAN AXON condensed into a simple ganglia
what is a ganglia
a group of nerve cell bodies with related function
ganglia can be found in ____ in jelly fish. what is a ____?
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.
a hydromedusa uses 2 nerve rings for what function
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.
a true CNS first evolved in animals with ____
bilateral symmetry
T/F: Radially symmetric animals had a CNS
false. they only had nerve rings, ganglia, o r a nerve net
flatworms had 2 ____ ____ that are connected by 2 ___ ___.
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)
earthworms contain a chain of ganglion going down the organism longitudinally, signifying:
a rudimentary nerve cord.
arthropods show more developed sensory organs and specialized ganglia. Some of the ganglia was organized into a ____, which served the purpose of:
some cell bodies of ganglia were organized into a neutrophil, which reduced the transmission delays seen in cnidarian nerve nets.
when the true brain was developed, it developed at the ____ end because animals moved forward.
anterior end.
with the evolution of bilateral symmetry, came the development of (2 important aspects)
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.
which two classes of organisms have the most “developed brains”
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.
Key developments in the evolution of the nervous system?
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”
