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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
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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
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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)
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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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Figure 28.15A
Cerebral cortex(outer regionof cerebrum)
Cerebrum
Thalamus
Hypothalamus
Pituitary gland
Midbrain
Forebrain
Hindbrain
Pons
MedullaoblongataCerebellum
Spinalcord