The Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS)
Copyright © 2009 Pearson Education, Inc. The Nervous System The nervous system is divided into the...
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Transcript of Copyright © 2009 Pearson Education, Inc. The Nervous System The nervous system is divided into the...
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
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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
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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)
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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
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The Central Nervous System
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)
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The Central Nervous System
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
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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
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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
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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
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The Brain
The thalamus Serves as the relay station of the brain for all
sensory information except smell Also directs motor activity and memory
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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
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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
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Brain Stem
The brain stem consists of Medulla oblongata Pons Midbrain
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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
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The Midbrain
Processes information about sights and sounds and controls simple reflex responses to these stimuli
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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
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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
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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
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The Spinal Cord Transmits Messages
The spinal cord Conducts messages between the brain and
the body Serves as a reflex center
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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
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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
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The Peripheral Nervous System
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.
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The Peripheral Nervous System
The peripheral nervous system includes The sensory receptors The peripheral nerves Specialized motor endings that stimulate the
effectors
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The Peripheral Nervous System
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
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The Peripheral Nervous System
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
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The Peripheral Nervous System
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
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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
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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
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Disorders of the Nervous System
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
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Disorders of the Nervous System
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