Transcript central nervous system

Mammalian Nervous System
Chapter 46
How Is the Mammalian Nervous System
Organized?
Vertebrate nervous systems consist of a brain, a spinal cord,
and peripheral nerves that extend throughout the body.
The central nervous system or CNS contains the brain and
spinal cord.
The peripheral nervous system or PNS consists of the cranial
and spinal nerves that connect the CNS to all tissues.
Figure 46.1 Organization of the Nervous System
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Figure 46.2 Development of the Human Nervous System (Part 1)
Figure 46.2 Development of the Human Nervous System (Part 2)
Add Figure 46.2 middle panel only (40 days)
Figure 46.2 Development of the Human Nervous System (Part 3)
Add Figure 46.2 bottom panel only (100 days)
The three parts of the embryonic brain develop into structures in the
adult brain.
The hindbrain becomes the medulla, the pons, and the cerebellum.
Physiological functions, such as breathing and swallowing are
controlled by the medulla and pons.
Muscle control is coordinated in the cerebellum.
The embryonic midbrain becomes structures that
process visual and auditory information.
Together the hindbrain and midbrain are known
as the brain stem.
The embryonic forebrain develops the central diencephalon and the
surrounding telencephalon.
The diencephalon consists of the:
 Thalamus, which is the final relay station for sensory information
 Hypothalamus, which regulates physiological functions such as
hunger and thirst
The telencephalon consists of two cerebral hemispheres and is also
called the cerebrum.
An evolutionary trend in which the telencephalon increases in size and
complexity in vertebrates is telencephalization.
In humans, the telencephalon is the largest brain region and is
involved in sensory perception, learning, memory, and behavior.
The spinal cord:
 Conducts information between brain and organs.
 Integrates information coming from PNS.
 Responds by issuing motor commands.
Anatomy of the spinal cord:
 Gray matter is in the center, and contains cell bodies of spinal
neurons.
 White matter surrounds gray matter and contains axons that
conduct information up and down the spinal cord.
 Spinal nerves extend from the spinal cord.
Spinal reflex: afferent information converts to efferent activity without the
brain.
The knee-jerk reflex is monosynaptic:
 Stretch receptors send axon potentials through dorsal horn to ventral
horn, via sensory axons.
 At synapses with motor neurons in the ventral horn, action potentials are
sent to leg muscles, causing contraction.
Figure 46.3 The Spinal Cord Coordinates the Knee-Jerk Reflex
Structures in primitive regions of the telencephalon
form the limbic system.
 Amygdala: involved in fear and fear memory
 Hippocampus: transfers short-term memory to
long-term memory
Figure 46.4 The Limbic System
Cerebral hemispheres are dominant in mammals.
Cerebral cortex – a sheet of gray matter covering
each hemisphere that is convoluted to fit into the skull
 Gyri: (sing. gyrus) ridges of the cortex
 Sulci: (sing. sulcus) valleys of the cortex
Figure 46.5 The Human Cerebrum (Part 1)
Figure 46.5 The Human Cerebrum (Part 2)
Regions of the cerebral cortex have specific functions.
Association cortex is made up of areas that integrate
or associate sensory information or memories.
Four cortical lobes:
 Temporal
 Frontal
 Parietal
 Occipital
Temporal lobe:
 Receives and processes auditory information
 Association areas of the temporal lobe involve:
• Identification
• Object naming
• Recognition
Agnosia: a disorder of the temporal lobe
Frontal Lobe:
 Central sulcus: divides the frontal and parietal lobes
 Primary motor cortex is located in front of the central sulcus and controls
muscles in specific body areas.
 Association areas involve:
• Planning
• Personality
Parietal Lobe:
 Primary somatosensory motor cortex is located behind the
central sulcus; it receives touch and pressure information.
 Association areas involve attending to complex stimuli.
Contralateral neglect syndrome: an inability to recognize stimuli
on one side of the body when the opposite parietal lobe is
damaged
Occipital Lobe:
 Receives and processes visual information
 Association areas involve:
• Making sense of the visual world
• Translating visual experience into language
Autonomic Nervous System (ANS): the output of the
CNS that controls involuntary functions
ANS has two divisions that work in opposition: one will
increase a function and the other will decrease it.
Sympathetic and parasympathetic divisions are
distinguished by anatomy, neurotransmitters, and their
actions.
Sympathetic and parasympathetic divisions have
different anatomy.
The sacral region contains preganglionic neurons of
the parasympathetic region.
The thoracic and lumbar regions contain sympathetic
preganglionic neurons.
Figure 46.10 The Autonomic Nervous System
Electroencephalogram (EEG):
 Measures activity of groups of neurons
 Records changes in electrical potential between
electrodes, over time
Electromyogram (EMG) records skeletal muscle activity.
Electrooculogram (EOG) measures eye movement.
Figure 46.14 Patterns of Electrical Activity in the Cerebral Cortex Characterize Stages of Sleep (1)
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Figure 46.14 Patterns of Electrical Activity in the Cerebral Cortex Characterize Stages of Sleep (2)
Language areas:
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Broca’s area located in the frontal lobe: damage results in slow
or lost speech but a person can read and understand language.
Wernicke’s area is in the temporal lobe: damage results in an
inability to speak sensibly, as written or spoken language is not
understood. A person may still be able to produce speech.
Angular gyrus: adjacent area essential for integrating spoken
and written language
Figure 46.15 Language Areas of the Cortex (Part 1)
Figure 46.15 Language Areas of the Cortex (Part 2)
Figure 46.16 Imaging Techniques Reveal Active Parts of the Brain