Copyright © 2009 Pearson Education, Inc. The Nervous System The nervous system is divided into the central nervous system and the peripheral nervous

Copyright © 2009 Pearson Education, Inc.

The Nervous System

The nervous system is divided into the central nervous system and the peripheral nervous system

The central nervous system is the brain and spinal cord

It is concerned with integrating incoming information and coordinating all voluntary and involuntary responses


The Nervous System

The peripheral nervous system consists of the nerves branching from the central nervous system and the ganglia It can be further subdivided on the basis of

function


The Nervous System

The somatic nervous system Receives sensory information and directs

voluntary movements (e.g., bend my arm)

The autonomic nervous system Regulates involuntary reactions (e.g.,

heartbeat)


The Central Nervous System

The brain and spinal cord are protected by The bones of the vertebral column and skull Three connective tissue membranes that

form the meninges Cerebrospinal fluid



Inflammation of the meninges is called meningitis

It is caused by many forms of bacteria and viruses, rarely fungal

It can lead to encephalitis (inflammation of the brain)



The blood-brain barrier also protects the central nervous system by permitting certain substances to enter the brain, while inhibiting others from entering

It inhibits many potentially life-saving, infection-fighting, or tumor-suppressing drugs that are not lipid soluble from reaching brain tissue

You are responsible for Figure 8.3


The Brain Is the Central Command Center

The cerebrum is the thinking, conscious part of the brain

The cerebrum consists of two hemispheres, which receive sensory information from, and direct the movements of, the opposite side of the body


The Brain

The cerebrum consists of The outer layer of gray matter

Called the cerebral cortex Not myelinated

The underlying white matter Made of myelinated nerve tracts Allows for communication between

various areas of the brain


The Brain

The sensory, motor, and association areas are in the cerebral cortex

The most complex of these areas is the prefrontal cortex which enables us to reason and think in the abstract


The Brain

The thalamus Serves as the relay station of the brain for all

sensory information except smell Also directs motor activity and memory


The Brain

The hypothalamus Maintains homeostasis by regulating blood

pressure, heart rate, breathing rate, digestion and body temperature

The hypothalamus coordinates the nervous and endocrine systems through its connection to the pituitary gland

It is a center for emotions and serves as the master biological clock


The Brain

The cerebellum Integrates information from the motor cortex

and sensory pathways to produce smooth, well-timed voluntary movements

Controls equilibrium and posture Stores memories of learned motor skills


Brain Stem

The brain stem consists of Medulla oblongata Pons Midbrain


The Brain

The medulla oblongata Contains reflex centers to regulate the

rhythm of breathing, force and rate of the heartbeat, and blood pressure

Serves as the pathway for all sensory messages to the higher brain centers and motor messages leaving the brain


The Midbrain

Processes information about sights and sounds and controls simple reflex responses to these stimuli


The Pons

Means “bridge” Connects the spinal cord and cerebellum

with the cerebrum, thalamus, and hypothalamus

Has a region that assists the medulla in regulating respiration


The Brain

The limbic system, which includes several brain structures, is largely responsible for emotions

It includes parts of several brain regions and the neural pathways that connect them


Memory

The limbic system plays a role in forming memory. The storage and retrieval of information takes place in two stages: Short-term memory, which holds a small

amount of information for a few seconds or minutes

Long-term memory, which stores limitless amounts of information for hours, days or years


The Spinal Cord Transmits Messages

The spinal cord Conducts messages between the brain and

the body Serves as a reflex center


The Spinal Cord

A reflex action is an automatic response to a stimulus in a pre-wired circuit called a reflex arc

Spinal reflexes are essentially decisions made by the spinal cord that are beneficial when a speedy reaction is important to a person’s safety (i.e., the brain is NOT involved)

E.g., step on broken glass


The Peripheral Nervous System

The peripheral nervous system consists of spinal nerves and cranial nerves

The body has 31 pairs of spinal nerves, each of which originates in the spinal cord and services a specific region of the body

All spinal nerves carry both sensory and motor fibers



The body has 12 pairs of cranial nerves, which arise from the brain and service the structures of the head and certain body parts, including the heart and diaphragm

Some cranial nerves carry only sensory fibers, others carry only motor fibers, and others carry both types of fibers.



The peripheral nervous system includes The sensory receptors The peripheral nerves Specialized motor endings that stimulate the

effectors



The peripheral nervous system is divided The somatic nervous system governs

conscious sensations and voluntary movements

The autonomic nervous system is concerned with our unconscious, involuntary internal activities



The autonomic nervous system can be divided into the sympathetic and parasympathetic nervous systems, two branches with antagonistic actions (they work opposite each other- e.g., one increases heart rate while the other decreases heart rate)

Work to maintain homeostasis



The sympathetic nervous system Gears up the body for stressful or

emergency situations (“fight or flight”)

The parasympathetic nervous system Adjusts body functioning so that energy is

conserved during nonstressful times


Disorders of the Nervous System Vary in Health Significance

Headaches are usually caused by tension in the neck or by dilation (widening) of the blood vessels of the head

Migraine headaches are caused by an imbalance in the brain’s chemistry


Disorders of the Nervous System

A stroke results when the brain is deprived of blood and nerve cells die

The extent and location of the damage caused by a stroke depends on the affected region of the brain



A coma is caused by trauma to neurons in regions of the brain responsible for stimulating the cerebrum

A comatose person is totally unresponsive to all sensory input and cannot be awakened



A spinal cord injury results in loss of function below the site of injury (nerves are one-way streets)

Depending on which nerve tracts are damaged, injury may result in paralysis, loss of sensation, or both

If the cord is completely severed there is complete loss of sensation and voluntary movement below the level of the cut

Documents

Copyright © 2009 Pearson Education, Inc. The Nervous System The nervous system is divided into the central nervous system and the peripheral nervous