Announcements
Lecture Outline
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Organization of the nervous system
Central Nervous system
Major areas of the brain
Peripheral Nervous system
Nervous system disorders
The Nervous System
• The nervous system consists of the central and
peripheral nervous systems
• Bones, membranes, and cerebrospinal fluid
protect the central nervous system
• The brain is the central command center
• The spinal cord transmits messages to and
from the brain, and is a reflex center
The Nervous System
• The nervous system is divided into the central
nervous system and the peripheral nervous
system
Arrangement of the Nervous System
Figure 8.1 (2 of 2)
The 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
• Large clusters of nerve cells, called ganglia, are
located outside the central nervous system
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
• The autonomic nervous system
– Regulates involuntary reactions
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
• Dura mater
• Arachnoid mater
• Pia mater
– Cerebrospinal fluid
The bones of the skull and
vertebral column are hard
cases that protect the brain
and spinal cord.
The meninges are three
membranes that protect
the brain and spinal cord.
Ventricles
of the brain
Cerebrospinal fluid cushions
the brain and spinal cord.
Figure 8.2
Cerebrospinal Fluid
• The cerebrospinal fluid has several important
functions
– Shock absorption
– Support
– Nourishment and waste removal
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
The Brain Is the Central Command
Center
• The cerebrum is the thinking, conscious part
of the brain
• It is the largest and most prominent part of
the brain
• It accounts for 83 % of the total brain weight
Brainstem
The Brain Is the Central Command Center
Midbrain
• Relays information between
the cerebellum or spinal cord
and the cerebrum
• Integrates sensory input
Pons
• A bridge between higher and
lower brain centers
Medulla oblongata
• Contains autonomic centers for
heart rate and digestive activities
• Relays sensory information to
thalamus
Cerebellum
• Coordinates sensory–motor
voluntary movement
• Stores memory of learned
motor patterns
Figure 8.3 (1 of 2)
The Brain Is the Central Command
Center
Thalamus
• Processes all sensory
information
(except olfaction)
• Relays information to
appropriate higher
brain centers
Hypothalamus
• Controls heart rate,
blood pressure,
breathing rate, body
temperature, food intake
• Is a center for emotions
• Serves as “master
biological clock”
Cerebrum
• Contains sensory areas
for skin senses, vision,
hearing, olfaction
• Motor areas for voluntary
control of movement
• Association areas for
interpreting sensations,
language, thinking,
decision making,
self-awareness,
creativity, and storage
of memories
Corpus callosum
• Allows left and right
cerebral hemispheres
to communicate with
one another
Figure 8.3 (2 of 2)
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 many ridges and grooves make it appear
wrinkled
• The longitudinal fissure separates the
cerebrum into two hemispheres
The human brain has 3 major regions
Higher thought is compartmentalized
to the cerebrum
Regions of the cerebral cortex are
themselves compartmentalized
The Brain
Figure 8.4
The Brain
• The cerebrum consists of
– The outer layer of gray matter
• Called the cerebral cortex
– The underlying white matter
• Made of myelinated nerve tracts
• Allows for communication between various areas of the
brain
The Brain
• The corpus callosum connects the two
cerebral hemispheres
• Grooves on the surface of the brain mark the
boundaries of four lobes on each hemisphere:
the frontal, parietal, temporal and occipital
lobes
The Brain
The corpus callosum is a
band of white matter that allows
communication between the
cerebral hemisperes.
Gray matter consists of
interneurons, cell bodies,
and unmyelinated axons
that integrate information.
White matter
consists of myelinated
axons that allow
communication over
long distances.
Figure 8.5
The Brain
• The sensory, motor, and association areas are
in the cerebral cortex
• The primary somatosensory area receives
sensory information from the body while the
primary motor area controls the skeletal
muscles
• Just in front of the motor cortex is the
premotor cortex which coordinates learned
motor skills
The Brain
Figure 8.7
A homonculus shows the area of the
brain devoted to regions of the body
The Nervous System
• The nervous system consists of the central and
peripheral nervous systems
• Bones, membranes, and cerebrospinal fluid
protect the central nervous system
• The brain is the central command center
• The spinal cord transmits messages to and
from the brain, and is a reflex center
The Brain
Wrist
Hip Knee
Neck Trunk
Arm
Elbow
Fingers
Thumb
Brow
Eye
Face
Leg
Foot
Toes
Lips
Jaw
Tongue
Swallowing
Primary
motor area
Parietal lobe
Frontal lobe
Figure 8.7 (1 of 2)
Knee
Leg
The Brain
Hip
Trunk
Neck
Arm
Elbow
Forearm
Fingers
Foot
Toes
Genitals
Thumb
Eye
Nose
Primary
somatosensory
area
Lips
Teeth and
gums
Tongue
Pharynx
Figure 8.7 (2 of 2)
The Brain
Figure 8.6a
Different Brain regions are activated by different
processes
Figure 8.6b
The Brain
• The thalamus
– Serves as the relay station of the brain for all
sensory information except smell
– Also directs motor activity, cortical arousal, and
memory
The Brain
• The hypothalamus
– Maintains homeostasis by regulating blood
pressure, heart rate, breathing rate, digestion and
body temperature
The Brain
• 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
Brainstem
The Brain
Midbrain
• Relays information between
the cerebellum or spinal cord
and the cerebrum
• Integrates sensory input
Pons
• A bridge between higher and
lower brain centers
Medulla oblongata
• Contains autonomic centers for
heart rate and digestive activities
• Relays sensory information to
thalamus
Cerebellum
• Coordinates sensory–motor
voluntary movement
• Stores memory of learned
motor patterns
Figure 8.3 (1 of 2)
The Brain
• The limbic system, which includes several
brain structures, is largely responsible for
emotions
• It is defined on the basis of function rather
than anatomy
• 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
Memory
Cerebrum
Thalamus
Hypothalamus
Hippocampus
Amygdala
Olfactory bulb
Figure 8.8
The Brain
• The reticular activating system (RAS)
– An extensive network of neurons that runs
through the medulla and projects to the cerebral
cortex
– Filters sensory input and keeps the cerebral cortex
in an alert state
The Spinal Cord Transmits Messages
• The spinal cord
– Conducts messages between the brain and the
body
– Serves as a reflex center
The Spinal Cord
• Spinal nerves arise from the cord and exit
through the openings between the stacked
vertebrae of the vertebral column
The Spinal Cord
Figure 8.9ab
The Spinal Cord
Figure 8.9c
The Spinal Cord
Connective tissue surrounding one nerve
Blood supply
Axons within a connective
tissue sheath
One axon
(d) The anatomy of a nerve
Figure 8.9d
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
The reflex
arc
Step 1: A stimulus initiates a pain
sensation.
Step 2: Sensory messages are carried
to the spinal cord by a sensory neuron.
Step 3: Interneurons in the spinal
cord integrate information from
sensory neurons and stimulate
the appropriate motor neurons.
Step 4: Motor neurons
stimulate the appropriate
muscles.
Step 5: Leg muscles
contract, causing them to
lift the foot off the glass.
Figure 8.10
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 Peripheral Nervous System
White matter
Gray matter
Dorsal root
Dorsal-root
ganglion
Ventral root
(a) View from front of body
Pair of
spinal nerves
Figure 8.11a
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.
The Peripheral Nervous System
I From olfactory receptors
II From retina of eyes
III To eye muscles
IV To eye muscles
V From mouth and to jaw
muscles
VI To eye muscles
VII From taste buds and to
facial muscles and glands
VIII From inner ear
IX From pharynx and to
pharyngeal muscles
X From and to internal
organs
XII To tongue muscles
XI To neck and back
muscles
(b) View of underside of brain
Figure 8.11b
The Peripheral Nervous System
• The peripheral nervous system includes
– The sensory receptors
– The peripheral nerves and ganglia
– Specialized motor endings that stimulate the
effectors
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
The Peripheral
Nervous System
Consists of
sympathetic and
parasymtathetic
networks
Parasympathetic Nervous System
(Cranial and sacral
regions of spinal cord)
Constricts
pupil
Increases
salivation
Decreases
breathing rate
Slows
heart rate
Widens
blood
vessels
Increases
digestive activity
Increases
digestive activity
Synapse
between
neurons
Contracts
bladder
muscles
Stimulates
defecation
Sympathetic Nervous System
(Thoracic and lumbar
regions of spinal cord)
The sympathetic
Nervous System
activates and
speeds up; the
parasympathetic
nervous system
calms
Dilates
pupil
Decreases
salivation
Increases
breathing rate
Increases
heart rate
Narrows
blood vessels
Slows
digestive activity
Slows
digestive activity
Ganglion
Stimulates secretion
of epinephrine and
norepinephrine
Causes salt and
water retention
Relaxes
bladder muscles
Inhibits
defecation
The Peripheral Nervous System
• The autonomic nervous system can be divided
into the sympathetic and parasympathetic
nervous systems, two branches with
antagonistic actions
The Peripheral Nervous System
• The sympathetic nervous system
– Gears up the body for stressful or emergency
situations
• 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 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
Disorders of the Nervous System
• A spinal cord injury results in loss of function
below the site of injury
• 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