Invertebrate-Vertebrate NS Organization

Question 1

How do paramecium use calcium channels?

Answer 1

1) stretch receptors release calcium when they bump into an obstacle
2) calcium allows cilia to beat backwards
3) once the calcium is used the paramecium moves forward again

Question 2

Describe the nervous system of a cnidarian.

Answer 2

they have a nerve net and neural “plexi”

they have little or no ganglia or anterior “brain”

Question 3

What are ganglia?

Answer 3

collections of neurons

Question 4

What are neural “plexi”?

Answer 4

loose collections of neurons similar to enteric ns in vertebrates

Question 5

Describe the nervous system of a non-segmented flatworm.

Answer 5

with bilateral symmetry came cephalization (brain and nerve cord present)

Question 6

What is cephalization?

Answer 6

concentration of neurons into ganglia at the anterior end

Question 7

Describe the nervous system of a leech.

Answer 7

• with segmentation came segmental “ganglia”
• brain/head ganglia present
• processes of packet glia surrounding neural somata

Question 8

What is segmental ganglia?

Answer 8

in each segment there is the same cells (number, position, type) connected by intersegmental connectives and with nerves to the periphery

Question 9

Describe the nervous system of an arthropod.

Answer 9

• the fusion and specialization of segments accompanied the fusion and specialization of ganglia
• elaborate sensory functions = larger brains
• specialization of thoracic ganglia for locomotion
• “interior” neuropil

Question 10

What is “interior” neuropil?

Answer 10

where input and output synapses intermix

Question 11

Describe the nervous system of a gastropod (mollusk).

Answer 11

• large neuronal somata that can fire action potentials (up to 1 mm)
• supra and subesophogeal ganglia and pleural ganglia
• buccal ganglia

Question 12

Are all of the gastropods neurons large?

Answer 12

no (ex. limax maximus has small neurons to process olfactory/olfacto-spatial information)

Question 13

Describe the nervous system of a cephalopod.

Answer 13

• largest amount of cells and density in invertebrates
• largely visual processing
• retina - optic nerves - optic lobes
• cell bodieson outside with neuralpil inward

Question 14

What is a central pattern generator?

Answer 14

network of cells oscillate (ex. nudibranch swimming, human walking, dog swimming)

Question 15

How is a central pattern generator constructed?

Answer 15

1) the half-centre oscillator

2) neurogenic leech heart (rhythm generator)

Question 16

If all are inhibitory synapses - where does the excitatory drive come from?

Answer 16

neurons within pattern generator are intrinsically active themselves so disinhibition leads to firing

Question 17

What is important about the re-setting of the phase?

Answer 17

capacity to “reset” rhythm is a property of neurons that are controlling elements (hyperpolarize an HN)

Question 18

What serves as evidence of autonomy of central pattern generators?

Answer 18

lobster stomatogastric ganglion - ~30 neurons in ganglion - controls many muscles and motor patterns

Question 19

What is a polymorphic network?

Answer 19

concept that circuits can dynamically re-wire to generate alternative outputs

Question 20

Where is the mammalian cycle of locomotion organized?

Answer 20

by central pattern generators in the spinal cord (cats on treadmill)

Question 21

What modifications did the vertebrate brain undergo early on?

Answer 21

hindbrain became divided into ventral portion (medulla oblongata) and dorsal portion (cerebellum and anterior pons)

Question 22

What is the medulla specialized for?

Answer 22

connecting tract between spinal cord and anterior brain that is the control center for autonomic pathways concerned with vital functions (heart rate, respiration, blood pressure)

Question 23

Which part of the brain has changed much through vertebrate evolution and how?

Answer 23

in mammals and birds the cerebellum enlarged and became concerned with balance, equilibrium and muscular coordination/learning

Question 24

In what ways did the midbrain become specialized?

Answer 24

optic lobes, visual centers associated with the optic nerves

Question 25

In what ways did the forebrain change?

Answer 25

divided into anterior portion (cerebrum with prominent olfactory bulbs) and posterior portion (thalmus and hypothalamus)

Question 26

Was the expansion of the forebrain equally distributed?

Answer 26

no, expansion mainly in “association” areas (not primary sensory or motor)

Question 27

What determines the proportions of brain tissue?

Answer 27

amount of brain tissue devoted to processing information depends on amount of information that is needed to be processed

Question 28

What are some examples of brain tissue proportions dependent on information processing?

Answer 28

1) star nose mole

2) weakly electric fish (larger cerebellum devoted to generating and interpreting electric field signals)

Question 29

What change was seen in the cellular organization of the cerebrum with mammals?

Answer 29

multi-layered cerebrum (neocortex) and further extensive expansion and elaboration

Question 30

What is the neocortex?

Answer 30

has 6 layers of cell bodies that appeared early in mammalian evolution (triassic jurassic)

Question 31

Generally, what are the layers of the neocortex?

Answer 31

I/II: “principal” or projection neurons
III/IV: thalamic (sensory) input
VI: action potential output

Question 32

What characteristics do interneurons possess?

Answer 32

they have short axons (mostly local connections/not projecting) and are mostly inhibitory)

Question 33

How much does folding increase the area of the brain?

Answer 33

5 to 6 fold increase in area

Question 34

What does a cubic mm of neocortex ontain?

Answer 34

• 90, 000 neurons
• 400 meters of dendrites
• 4 km of axons
• 7 x 10^8 synapses

Question 35

What is the most cell dense part of the brain?

Answer 35

granule layer of the cerebellum