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Divisions of the Vertebrate Nervous System
Neuroanatomy Central Nervous System-the brain and the spinal cord
Peripheral Nervous System-the nerves outside the brain and spinal
cord
By Two Division of the PNS
Somatic Nervous System-the nerves that convey messages
Shahzad Bashir from the sense organs to the CNS and from the CNS to the
muscles and glands
RN, BScN Autonomic Nervous System-a set of neurons that control the
NMC (ION) heart, the intestines, and other organs
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Figure 4.1 The human nervous system
Both the central nervous system and the peripheral nervous system have
major subdivisions. The closeup of the brain shows the right hemisphere
as seen from the midline. 3 4
The Nervous System
The Spinal Cord-part of the CNS found within the spinal column
The spinal cord communicates with the sense organs and
muscles below the level of the head
Bell-Magendie Law-the entering dorsal roots carry sensory
information and the exiting ventral roots carry motor
information to the muscles and glands
Dorsal Root Ganglia-clusters of neurons outside the spinal
cord
Figure 4.3 Diagram of a cross section through the spinal cord
The dorsal root on each side conveys sensory information to the spinal cord; the
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ventral root conveys motor commands to the muscles. 6
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Autonomic Nervous System
The Brain
Sympathetic-prepares the Parasympathetic-facilitates vegetative,
body for arousal nonemergency responses by the The Hindbrain/rhombencephalon
Ex: increased body’s organs Posterior part of brain
breathing, increased Ex: increase digestive activity, Medulla-controls vital reflexes like breathing, heart beat, etc
heart rate, decreased activities opposing
sympathetic system Pons-Area where many axons cross from one side of the brain to the
digestive activity other
Form chain of ganglia Consists of cranial nerves and
nerves from sacral spinal cord Reticular formation-control motor areas of the spinal cord and sends
just outside spinal output to cerebral cortex increasing arousal and attention
cord Long preganglionic axons
extend from the spinal cord to Raphe system-sends axons to much of the forebrain, increasing or
Short preganglionic decreasing the brain’s readiness to respond to stimuli
axons release parasympathetic ganglia
norepinephrine close to each internal organ; Cerebellum-control movement, shifts of attention, balance and
release norepinephrine coordination
Long postganglionic
axons release Shorter postganglionic fibers
norepinephrine then extend from the
parasympathetic ganglia in
the organs; release
acetylcholine 7 8
The Brain
The Midbrain-middle of the brain
Tegmentum-”roof or covering”
Nuclei for third and fourth cranial nerves
Parts of Reticular formation
Extensions of the pathways between the forebrain and the
spinal cord or hindbrain
Tectum-”roof”
Superior Colliculus & Inferior Colliculus-important in routes
of sensory information
Figure 4.8 The human brain stem
This composite structure extends from the top of the spinal cord into the
center of the forebrain. The pons, pineal gland, and colliculi
9 are ordinarily surrounded by the cerebral cortex. 10
The Brain
The Forebrain-most anterior and most prominent part of the
mammalian brain
Thalamus
Part of the Diencephalon
Center of forebrain
Relay Station for Sensory Information
Hypothalamus
Part of Diencephalon
Regulates homeostasis, sexual behavior, fighting, feeding
Pituitary Gland
Endocrine gland attached to the base of the hypothalamus
Figure 4.10 The limbic system is a set of subcortical structures that form a
border (or limbus) around the brain stem
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The Brain
Forebrain Cont’d
Basal Ganglia
Responsible for motor behavior, some memory and
emotional expression
Basal Forebrain
Located on the dorsal surface of the forebrain
Received input from the hypothalamus and basal ganglia
Send axons to cerebral cortex
Important in arousal, wakefulness, and attention
Hippocampus
Located between thalamus and cerebral cortex
Critical for the formation of new memory
Figure 4.12 A sagittal section through the human brain
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The Brain
The Ventricles-Assists in cushioning the brain
Central Canal-fluid-filled channel in the center of the spinal
cord
Ventricles-four fluid-filled cavities within the brain
CSF-clear fluid similar to blood plasma
Formed in choroid plexus
Flows from lateral to third to fourth ventricle to central canal
or between meninges
Meninges-membranes that surround the brain and spinal cord
Figure 4.14 The basal ganglia
The thalamus is in the center, the basal ganglia are lateral to it, and the cerebral
cortex is on the outside.
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The Cerebral Cortex
Organization of the Cerebral Cortex
Contains six distinct layers of cells
Organized into columns-cells with similar properties; arranged
perpendicular to the laminae
Cells within a given column have similar or related
properties
Figure 4.16 The cerebral ventricles
Diagram showing positions of the four ventricles.
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The Parts of the Brain
Left Hemisphere
Cortex (Cerebrum) The Left hemisphere controls the right side of the body. It
The cortex, or cerebrum, is made up of controls speech, comprehension, arithmetic, and writing.
two hemispheres (or sides) connected by
a band of tissue called the corpus Right Hemisphere
callosum. These hemispheres control The right hemisphere controls the left side of the body. It is
speech, intelligence, and memory. There responsible for more abstract skills, such as creativity, spatial
are specific centres for specific functions; ability, and artistic and musical skills.
for example, the speech centre governs
the ability to form sounds into meaningful Each cerebral hemisphere is divided into lobes. (In this
words, phrases, etc. illustration, the Frontal Lobe, the Temporal Lobe, the Parietal
Lobe, Occipital Lobe, Motor Strip and Sensory Strip are all
19 the different parts that make up the Cortex). 20
Temporal Lobe
The temporal lobe is located alongside the frontal
and parietal lobes, just above the ear. It is the
centre for the senses of hearing, taste, and Cerebellum The cerebellum is
smell. It is also involved in receiving auditory located beneath the cerebral cortex in
information and in memory. the back of the skull. It is smaller than
Occipital Lobe
The occipital lobe rests in back of the cortex
the cortex. Its job is to transmit and
behind the parietal and temporal lobes. Damage coordinate the signals from the
to this area may affect sight, such as perceiving cortex. It also controls the movement
or understanding visual information. of voluntary muscles, balance, posture,
21 and in coordinating movements. 22
Brain Stem The brain stem is
in front of the cerebellum and
beneath the cerebral cortex. It
connects the spinal cord to the
cortex. Its role includes passing
messages back and forth
between various parts of the
body and the cerebral cortex.
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Brain Function
How Do the Pieces Work Together?
Does the Brain Operate as a Whole or a Collection of Parts?
Each brain area has a function but it can’t do much by itself
The Binding Problem
The question of how the visual, auditory, and other areas of
your brain influence on another to produce a combined
perception of the single object
Synchronized neural activity?
Figure 4.20 Some major subdivisions of the human cerebral cortex
The four lobes: occipital, parietal, temporal, and frontal.
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