Transcript Document

UNIT B: Human Body Systems
Chapter 8: Human Organization
Chapter 9: Digestive System
Chapter 10: Circulatory System and
Lymphatic System
Chapter 11: Respiratory System
Chapter 12: Nervous System:
Section 12.3
Chapter 13: Urinary System
Chapter 14: Reproductive System
UNIT B Chapter 12: Nervous System
Chapter 12: Nervous System
In this chapter, you will learn about the
structure and function of the nervous
system.
How might a researcher study the
effects of frequent head trauma?
Sport-Related Head Trauma and Brain
Function. Neurosurgeon Dr. Robert Cantu has
studied the brains of many deceased athletes,
including hockey and football players. He has
found that these players often suffered from
chronic traumatic encephalopathy (CTE), a
degenerative brain disease caused by repeated
blunt impact to the head.
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How might one determine which part
of the brain has been affected by
repeated blunt impacts?
Given the available information about
CTE, what steps do you feel should be
taken to prevent its occurrence (if any)?
UNIT B Chapter 12: Nervous System
Section 12.3
12.3 The Central Nervous System
The central nervous system is composed of the spinal cord
and the brain.
• Brain: controls breathing, heart rate, body temperature,
blood pressure, emotions, reasoning, memory, and
creativity
• Spinal cord: a means of communication between the
brain and the peripheral nerves that leave the cord
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UNIT B Chapter 12: Nervous System
Section 12.3
• The brain and spinal cord are wrapped in protective
membranes called meninges
• The spaces between meninges are filled with
cerebrospinal fluid, which cushions and protects the
CNS
o This fluid is produced and stored in the brain’s
ventricles (hollow cavities) and the spinal cord’s
central canal
o If the fluid accumulates in the brain and does not
properly drain, the brain can push against the skull,
causing brain damage
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UNIT B Chapter 12: Nervous System
Figure 12.7 Organization of the
nervous system. The CNS is
composed of the spinal cord and
brain. The PNS is composed of
the motor and sensory pathways.
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Section 12.3
UNIT B Chapter 12: Nervous System
Section 12.3
The Spinal Cord
Structure of the Spinal Cord
• Individual vertebra protect
the spinal cord
• Spinal nerves project from
the cord between the
vertebrae in the vertebral
column
• Fluid-filled intervertebral
disks cushion and separate
the vertebrae
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Figure 12.8 Spinal cord. a. The spinal
cord passes through the vertebral canal
formed by the vertebrae.
UNIT B Chapter 12: Nervous System
• Central canal: contains the
cerebrospinal fluid
• Grey matter: centrally located,
shaped like the letter H
o Contains parts of sensory
neurons, motor neurons,
and interneurons
• Dorsal root: contains sensory
fibres entering grey matter
• Ventral root: contains motor
fibres exiting grey matter
• Spinal nerves: part of PNS
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Section 12.3
Figure 12.8 Spinal cord. b. The spinal cord has
a central canal filled with cerebrospinal fluid,
grey matter in an H-shaped configuration, and
white matter. The white matter contains tracts
that take nerve impulses to and from the brain.
UNIT B Chapter 12: Nervous System
• White matter: surrounds grey
matter
o Contains ascending tracts
taking information to the
brain and descending tracts
taking information from the
brain
o Tracts cross each other after
entering and exiting CNS
− Left side of brain: controls
right side of body
− Right side of brain:
controls left side of body
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Section 12.3
Figure 12.8 Spinal cord.
c. Photomicrograph of a cross
section of the spinal cord.
UNIT B Chapter 12: Nervous System
Section 12.3
Functions of the Spinal Cord
The spinal cord sends sensory information to the brain, receives
motor input from the brain, and carries out reflex actions.
• Example: Sensation
o When someone touches your hand, sensory receptors
generate nerve impulses that pass through sensory fibres
to the spinal cord and up ascending tracts to the brain
• Example: Voluntary movement
o When we move our limbs, motor impulses in the brain
pass down descending tracts to the spinal cord and out to
our muscles through motor fibres
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UNIT B Chapter 12: Nervous System
The Brain
The brain has four
major parts:
• Cerebrum (two
lateral ventricles)
• Diencephalon
(third ventricle)
• Cerebellum
(fourth ventricle)
• Brain stem (fourth
ventricle)
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Section 12.3
UNIT B Chapter 12: Nervous System
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Section 12.3
Figure 12.9 The human brain. a. The cerebrum, seen here in longitudinal section, is
the largest part of the brain in humans. The right cerebral hemisphere is shown here.
UNIT B Chapter 12: Nervous System
Section 12.3
The Cerebrum
The cerebrum is the largest part of the brain in humans
• Communicates with and coordinates activities of other parts of
the brain
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UNIT B Chapter 12: Nervous System
Section 12.3
Structure and Function of
the Cerebrum
The cerebrum has two halves
(cerebral hemispheres) that
communicate via the corpus callosum,
a bridge of nerve tracts.
• The cerebral cortex is a thin outer
layer of grey matter that covers the
cerebral hemispheres
• Grooves called sulci divide the
hemisphere into four lobes: frontal,
parietal, occipital, temporal
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Figure 12.9 The human brain. The
cerebrum has left and right cerebral
hemispheres, which are connected by
the corpus callosum.
UNIT B Chapter 12: Nervous System
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Section 12.3
Figure 12.10 The lobes of a cerebral hemisphere. Each cerebral hemisphere is
divided into four lobes: frontal, parietal, temporal, and occipital. The frontal lobe
contains centres for reasoning and movement, the parietal lobe for somatic
sensing and taste, the temporal lobe for hearing, and the occipital lobe for vision.
UNIT B Chapter 12: Nervous System
Section 12.3
Frontal Lobe
• Primary motor area: involved in voluntary movement
• Premotor area: involved in organizing motor functions
• Prefrontal area: processing centre involved in reasoning and
planning
• Broca’s area: involved in speech musculature (lips, tongue, larynx)
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UNIT B Chapter 12: Nervous System
Section 12.3
Parietal Lobe
• Primary somatosensory area: involved in somatic sensing
• Primary taste area: involved in taste
• Somatosensory association area: processes and analyzes sensory
information from skin and muscles
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UNIT B Chapter 12: Nervous System
Section 12.3
Temporal Lobe
• Primary auditory area: involved in hearing
• Auditory association area: associates new audio information with
previous audio information
• Wernicke’s area: helps us understand written and spoken words
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UNIT B Chapter 12: Nervous System
Section 12.3
Occipital Lobe
• Primary visual area: involved in vision
• Visual association area: associates new visual information with
previous visual information (e.g., facial recognition)
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UNIT B Chapter 12: Nervous System
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Section 12.3
12.11 The primary motor and somatosensory areas. In these drawings, the size
of the body part reflects the amount of cerebral cortex devoted to that body part.
For example, the amount of primary motor cortex (a) and somatosensory cortex (b)
devoted to the thumb, fingers, and hand is greater than that for the foot and toes.
UNIT B Chapter 12: Nervous System
Central White Matter
• Most of the cerebrum beneath the cerebral cortex is
composed of white matter
• Tracts within the cerebrum take information between
different sensory, motor, and association areas
Basal Nuclei
• Basal nuclei are masses of grey matter located deep
within the white matter of the cerebrum
• Integrate motor commands to ensure proper muscle
groups are activated or inhibited
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Section 12.3
UNIT B Chapter 12: Nervous System
Section 12.3
The Diencephalon
The diencephalon is a region that encircles the third ventricle.
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UNIT B Chapter 12: Nervous System
Structure and Function
of the Diencephalon
Hypothalamus
• Integrating centre that helps
maintain homeostasis
• Regulates hunger, sleep,
thirst, body temperature, and
water balance
• Controls the pituitary gland
and serves as a link between
the nervous and endocrine
systems
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Section 12.3
UNIT B Chapter 12: Nervous System
Section 12.3
Thalamus
• Consists of grey matter that receives all sensory input
except smell
• Integrates visual, auditory, taste, and somatosensory
information and sends it to the appropriate area in the
cerebrum
• Involved in higher mental functions (memory, emotions)
Pineal gland
• Secretes the hormone melatonin, which is involved in
maintaining a normal sleep-wake cycle
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UNIT B Chapter 12: Nervous System
The Cerebellum
The cerebellum is located under the occipital lobe of the
cerebrum.
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Section 12.3
UNIT B Chapter 12: Nervous System
Section 12.3
Structure and Function of the Cerebellum
• Has two portions that are primarily composed of white
matter (a thin layer of grey matter overlays the white matter)
• Involved in maintaining posture and balance
o Receives sensory input from the joints, muscles, and
other sensory pathways about the position of body parts
o Receives motor output from the cerebral cortex about
where body parts should be located
• Involved in producing smooth, coordinated voluntary
movements (e.g., playing piano, hitting a baseball)
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UNIT B Chapter 12: Nervous System
The Brain Stem
The brain stem contains the midbrain, the pons, and the
medulla oblongata.
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Section 12.3
UNIT B Chapter 12: Nervous System
Section 12.3
Structure and Function of the Brain Stem
Midbrain
• A relay station for tracts passing between the cerebrum and
spinal cord or cerebellum
• Has reflex centres for visual, auditory, and tactile responses
Pons
• Contains bundles of axons travelling between the
cerebellum and the rest of the CNS
• Functions with medulla oblongata to regulate breathing rate
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UNIT B Chapter 12: Nervous System
Section 12.3
Medulla oblongata
• Regulates heartbeat, breathing, and blood pressure
• Contains reflex centres for vomiting, coughing, sneezing,
hiccupping, and swallowing
Reticular activating system (RAS)
• Relay centre that is involved in alertness
• Also involved in filtering out unnecessary sensory stimuli
(e.g., studying while the TV is on)
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UNIT B Chapter 12: Nervous System
Section 12.3
Check Your Progress
1. Summarize the functions of the spinal cord.
2. Identify the four major parts of the brain and describe
the general functions of each.
3. Describe the types of symptoms you would expect to
see in a person who has sustained damage to the
cerebellum, medulla oblongata, or RAS.
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UNIT B Chapter 12: Nervous System
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Section 12.3
UNIT B Chapter 12: Nervous System
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Section 12.3