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Chapter Four Anatomy of the Nervous System. Divisions of the Vertebrate Nervous System. Central Nervous System-the brain and the spinal cord Peripheral Nervous System-the nerves outside the brain and spinal cord Two Division of the PNS

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Chapter Four Anatomy of the Nervous System

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Chapter four anatomy of the nervous system l.jpg

Chapter FourAnatomy of the Nervous System

Divisions of the vertebrate nervous system l.jpg

Divisions of the Vertebrate Nervous System

Central Nervous System-the brain and the spinal cord

Peripheral Nervous System-the nerves outside the brain and spinal cord

Two Division of the PNS

Somatic Nervous System-the nerves that convey messages from the sense organs to the CNS and from the CNS to the muscles and glands

Autonomic Nervous System-a set of neurons that control the heart, the intestines, and other organs

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Figure 4.1  The human nervous systemBoth the central nervous system and the peripheral nervous system havemajor subdivisions. The closeup of the brain shows the right hemisphereas seen from the midline.

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The Nervous System

The Spinal Cord-part of the CNS found within the spinal column

The spinal cord communicates with the sense organs and muscles below the level of the head

Bell-Magendie Law-the entering dorsal roots carry sensory information and the exiting ventral roots carry motor information to the muscles and glands

Dorsal Root Ganglia-clusters of neurons outside the spinal cord

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Figure 4.3  Diagram of a cross section through the spinal cordThe dorsal root on each side conveys sensory information to the spinal cord; the ventral root conveys motor commands to the muscles.

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Sympathetic-prepares the

body for arousal

Ex: increased breathing, increased heart rate, decreased digestive activity

Form chain of ganglia just outside spinal cord

Short preganglionic axons release norepinephrine

Long postganglionic axons release norepinephrine

Parasympathetic-facilitates vegetative, nonemergency responses by the body’s organs

Ex: increase digestive activity, activities opposing sympathetic system

Consists of cranial nerves and nerves from sacral spinal cord

Long preganglionic axons extend from the spinal cord to parasympathetic ganglia close to each internal organ; release norepinephrine

Shorter postganglionic fibers then extend from the parasympathetic ganglia in the organs; release acetylcholine

Autonomic Nervous System

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The Brain

The Hindbrain/rhombencephalon

Posterior part of brain

Medulla-controls vital reflexes like breathing, heart beat, etc

Pons-Area where many axons cross from one side of the brain to the other

Reticular formation-control motor areas of the spinal cord and sends output to cerebral cortex increasing arousal and attention

Raphe system-sends axons to much of the forebrain, increasing or decreasing the brain’s readiness to respond to stimuli

Cerebellum-control movement, shifts of attention, balance and coordination

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The Brain

The Midbrain-middle of the brain

Tegmentum-”roof or covering”

Nuclei for third and fourth cranial nerves

Parts of Reticular formation

Extensions of the pathways between the forebrain and the spinal cord or hindbrain


Superior Colliculus & Inferior Colliculus-important in routes of sensory information

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Figure 4.8  The human brain stemThis composite structure extends from the top of the spinal cord into the center of the forebrain. The pons, pineal gland, and colliculi are ordinarily surrounded by the cerebral cortex.

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The Brain

The Forebrain-most anterior and most prominent part of the mammalian brain


Part of the Diencephalon

Center of forebrain

Relay Station for Sensory Information


Part of Diencephalon

Regulates homeostasis, sexual behavior, fighting, feeding

Pituitary Gland

Endocrine gland attached to the base of the hypothalamus

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Figure 4.10  The limbic system is a set of subcortical structures that form a border (or limbus) around the brain stem

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Figure 4.12  A sagittal section through the human brain

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The Brain

Forebrain Cont’d

Basal Ganglia

Responsible for motor behavior, some memory and emotional expression

Basal Forebrain

Located on the dorsal surface of the forebrain

Received input from the hypothalamus and basal ganglia

Send axons to cerebral cortex

Important in arousal, wakefulness, and attention


Located between thalamus and cerebral cortex

Critical for the formation of new memory

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Figure 4.14  The basal gangliaThe thalamus is in the center, the basal ganglia are lateral to it, and the cerebral cortex is on the outside.

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The Brain

The Ventricles-Assists in cushioning the brain

Central Canal-fluid-filled channel in the center of the spinal cord

Ventricles-four fluid-filled cavities within the brain

CSF-clear fluid similar to blood plasma

Formed in choroid plexus

Flows from lateral to third to fourth ventricle to central canal or between meninges

Meninges-membranes that surround the brain and spinal cord

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Figure 4.16  The cerebral ventriclesDiagram showing positions of the four ventricles.

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The Cerebral Cortex

Organization of the Cerebral Cortex

Contains six distinct layers of cells

Organized into columns-cells with similar properties; arranged perpendicular to the laminae

Cells within a given column have similar or related properties

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The Lobes

The Occipital Lobe-posterior end of cortex

Contains primary visual cortex

The Parietal Lobe-between occipital love the central sulcus

Contains the primary somatosensory cortex-receiving touch sensation, muscle-stretch information and joint position information

The Temporal Lobe-lateral portion of each hemisphere, near the temples

Contains targets for audition, essential for understanding spoken language, complex visual processes, emotional and motivational behaviors

The Frontal Lobe-extends from the central sulcus to the anterior limit of the brain

Contains Primary Motor Cortex-fine movements

Contributes to shifting attention, planning of action, delayed response tasks as examples

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Figure 4.20  Some major subdivisions of the human cerebral cortexThe four lobes: occipital, parietal, temporal, and frontal.

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Brain Function

How Do the Pieces Work Together?

Does the Brain Operate as a Whole or a Collection of Parts?

Each brain area has a function but it can’t do much by itself

The Binding Problem

The question of how the visual, auditory, and other areas of your brain influence on another to produce a combined perception of the single object

Synchronized neural activity?

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