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. © 2012 Pearson Education, Inc. 1

28.12 Vertebrate nervous systems are highly centralized 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). © 2012 Pearson Education, Inc. 2

Central nervous system (CNS) Brain Cranial nerves Spinal cord Figure 28.12A Central nervous system (CNS) Brain Cranial nerves Spinal cord Peripheral nervous system (PNS) Ganglia outside CNS Spinal nerves Figure 28.11A A vertebrate nervous system (back view) 3

The PNS can be divided into two functional components: 28.12 The peripheral nervous system of vertebrates can be divided into functional components The PNS can be divided into two functional components: the motor system, mostly voluntary, and the autonomic nervous system, mostly involuntary. © 2012 Pearson Education, Inc. 4

The motor nervous system 28.12 The peripheral nervous system of vertebrates can be divided into functional components 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. © 2012 Pearson Education, Inc. 5

(Control of skeletal muscle) Figure 28.13 CNS Sensory neurons Motor neurons Autonomic nervous system Motor system Sensory receptors (Control of skeletal muscle) Figure 28.13 Functional divisions of the vertebrate PNS Parasympathetic division Sympathetic division Stimuli (“Rest and digest”) (“Fight or flight”) Enteric division (Control of digestive system) 6

The autonomic nervous system is composed of three divisions. 28.13 The peripheral nervous system of vertebrates can be divided into functional components The autonomic nervous system is composed of three divisions. The parasympathetic division primes the body for activities that gain and conserve energy for the body (rest and digest). The sympathetic division prepares the body for intense, energy-consuming activities (flight and fight). The enteric division consists of networks of neurons in the digestive tract, pancreas, and gallbladder that control secretion and peristalsis. © 2012 Pearson Education, Inc. 7

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. © 2012 Pearson Education, Inc. 8

Embryonic Brain Regions Brain Structures Present in Adult Figure 28.14 Embryonic Brain Regions Brain Structures Present in Adult Cerebrum (cerebral hemispheres; includes cerebral cortex, white matter, basal ganglia) Forebrain Diencephalon (thalamus, hypothalamus, posterior pituitary, pineal gland) Midbrain Midbrain (part of brainstem) Pons (part of brainstem), cerebellum Hindbrain Medulla oblongata (part of brainstem) Diencephalon Cerebrum Midbrain Midbrain Figure 28.14 Embryonic development of the human brain Hindbrain Pons Cerebellum Medulla oblongata Spinal cord Forebrain Embryo (1 month old) Fetus (3 months old) 9

28.14 The vertebrate brain develops from three anterior bulges of the neural tube In birds and mammals the cerebrum is much larger and correlates with their sophisticated behavior. © 2012 Pearson Education, Inc. 10

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: Brain stem (medulla oblongata) Cerebellum Thalmus Hypothalmus Cerebrum © 2012 Pearson Education, Inc. 11

Table 28.15 Table 28.14 Major Structures of the Human Brain 12

Cerebral cortex (outer region of cerebrum) Figure 28.15A Cerebral cortex (outer region of cerebrum) Cerebrum Forebrain Thalamus Hypothalamus Pituitary gland Figure 28.15A The main parts of the human brain Midbrain Pons Spinal cord Medulla oblongata Hindbrain Cerebellum 13