Nervous Systems

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Slide 1

Command and Control Center

The circuits in the brain are more complex than the most powerful computers.

Functional magnetic resonance imaging (MRI) can be used to construct a 3-D map of brain activity.

The vertebrate brain is organized into regions with different functions.

Slide 2

Scientists map activity within the human brain

Slide 3

Nervous systems consist of circuits of neurons and supporting cells

The simplest animals with nervous systems, the cnidarians, have neurons arranged in nerve nets.

A nerve net is a series of interconnected nerve cells. There is no central pathway / or directional organization.

More complex animals have nerves.

Slide 4

Nerves are bundles that consist of the axons of multiple nerve cells.

Sea stars have a nerve net in each arm connected by radial nerves to a central nerve ring.

Slide 5

Nervous system organization

(e) Insect (arthropod)

Segmental

ganglia

Ventral

nerve cord

Brain

(a) Hydra (cnidarian)

Nerve net

Nerve

ring

Radial

nerve

(b) Sea star (echinoderm)

Anterior

nerve ring

Longitudinal

nerve cords

(f) Chiton (mollusc)

(g) Squid (mollusc)

Ganglia

Brain

Ganglia

(c) Planarian (flatworm)

Nerve

cords

Transverse

nerve

Brain

Eyespot

Brain

(d) Leech (annelid)

Segmental

ganglia

Ventral

nerve

cord

Brain

Spinal

cord

(dorsal

nerve

cord)

Sensory

ganglia

(h) Salamander (vertebrate)

Slide 6

Hydra (cnidarian)

Nerve net

Nerve

ring

Radial

nerve

Sea star (echinoderm)

Slide 7

Bilaterally symmetrical animals exhibit cephalization.

Cephalization is the clustering of sensory organs at the front end of the body.

Relatively simple cephalized animals, such as flatworms, have a central nervous system (CNS).

The CNS consists of a brain and longitudinal nerve cords.

Slide 8

Planarian (flatworm)

Nerve

cords

Transverse

nerve

Brain

Eyespot

Brain

Leech (annelid)

Segmental

ganglia

Ventral

nerve

cord

Slide 9