Chapter 28 Nervous Systems

The central nervous system (CNS) consists of the

– brain and spinal cord (vertebrates).

The peripheral nervous system (PNS)

– is located outside the CNS and

– consists of

– nerves (bundles of neurons wrapped in connective tissue)

Neurons are

– cells specialized for carrying electrical signals.

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In the vertebrates, the central nervous system (CNS)– consists of the brain and spinal cord and

The vertebrate peripheral nervous system (PNS) consists of– cranial nerves,

– spinal nerves, and

– Ganglia (clusters of neurons).

28.12 Vertebrate nervous systems are highly centralized

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Figure 28.12A

Centralnervoussystem(CNS)

Peripheralnervoussystem(PNS)

Spinalcord

Cranialnerves

GangliaoutsideCNS

Spinalnerves

Brain

28.12 The peripheral nervous system of vertebrates can be divided into functional components

The PNS can be divided into two functional components:

1. the motor system, mostly voluntary, and

2. the autonomic nervous system, mostly involuntary.

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The motor nervous system

– carries signals to and from skeletal muscles and

– mainly responds to external stimuli.

The autonomic nervous system

– regulates the internal environment and

– controls smooth and cardiac muscle and organs and glands of the digestive, cardiovascular, excretory, and endocrine systems.

28.12 The peripheral nervous system of vertebrates can be divided into functional components

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Figure 28.13

CNS

Sensoryneurons

Sensoryreceptors

Stimuli

Motorneurons

Motorsystem

Autonomicnervous system

(Control of skeletal muscle)

Parasympatheticdivision

Sympatheticdivision

(“Rest and digest”) (“Fight or flight”)

(Control of digestive system)

Entericdivision

28.13 The peripheral nervous system of vertebrates can be divided into functional components

The autonomic nervous system is composed of three divisions.

1. The parasympathetic division primes the body for activities that gain and conserve energy for the body (rest and digest).

2. The sympathetic division prepares the body for intense, energy-consuming activities (flight and fight).

3. The enteric division consists of networks of neurons in the digestive tract, pancreas, and gallbladder that control secretion and peristalsis.

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28.14 The vertebrate brain develops from three anterior bulges of the neural tube

The vertebrate brain evolved by the enlargement and subdivision of the

– forebrain,

– midbrain, and

– hindbrain.

In the course of vertebrate evolution, the forebrain and hindbrain gradually became subdivided

– structurally and

– functionally.

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Figure 28.14Embryonic

Brain RegionsBrain StructuresPresent in Adult

Forebrain

Midbrain

Hindbrain

HindbrainMidbrain

Forebrain

Embryo (1 month old) Fetus (3 months old)

Cerebrum (cerebral hemispheres; includescerebral cortex, white matter, basal ganglia)

Diencephalon (thalamus, hypothalamus,posterior pituitary, pineal gland)

Pons (part of brainstem), cerebellum

Medulla oblongata (part of brainstem)

Cerebrum Diencephalon

Midbrain

Pons

Cerebellum

Medullaoblongata

Spinal cord

Midbrain (part of brainstem)

In birds and mammals the cerebrum

– is much larger and

– correlates with their sophisticated behavior.

28.14 The vertebrate brain develops from three anterior bulges of the neural tube

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28.15 The structure of a living supercomputer: The human brain

The human brain is

– more powerful than the most sophisticated computer and

– composed of five major structures:

1) Brain stem (medulla oblongata)

2) Cerebellum

3) Thalmus

4) Hypothalmus

5) Cerebrum

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Table 28.15

Figure 28.15A

Cerebral cortex(outer regionof cerebrum)

Cerebrum

Thalamus

Hypothalamus

Pituitary gland

Midbrain

Forebrain

Hindbrain

Pons

MedullaoblongataCerebellum

Spinalcord