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Chapter 2
Exploring the Nervous System
Anatomical Views
Horizontal section Shows structures
viewed from above
 Sagittal section Divides structures
into right and left
parts
 Coronal section Shows views from
the front
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Anatomical Directions
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Anatomical directions are used for locating
structures with the body:
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Anterior - toward the front
Posterior - toward the rear
Ventral - toward the belly
Dorsal - toward the back
Rostral - toward the head
Caudal - toward the tail
Medial - toward the midline
Lateral - away from the midline
Superior - above a structure
Inferior - below a structure
The Importance of the Nervous System
1) Detect stimuli in the environment
2) Determine the significance of the
environmental stimuli
3) Make a decision based on the stimuli
4) Execute a response
Organization of the Nervous System:
Two Major Divisions
Peripheral Nervous System (PNS)
 Detects environmental information inside and
outside the body, which is transmitted to the
CNS
 Executes responses to stimuli
 Central Nervous System (CNS)
 Recognizes and analyzes information from the
PNS
 Makes and transmits decisions to glands,
organs, and muscles for execution

Cells of the Nervous System:
Nerve cells – neurons perform the information
processing and communication functions of the
nervous system
Glial cells - supportive cells in the nervous system. The
glial cells surround neurons and provide support
for and insulation between them.
Cells of the Nervous System:
Neurons
Perform information processing
and communications functions
of the nervous system
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Consist of three major parts:
1. Soma - contains nucleus, mitochondria, and
ribosomes
2. Dendrites - portions of the neuron that transmit
information toward the cell body
3. Axon - a structure on the neuron which transmits
information away from the cell body
Cells of the Nervous System:
Terminology
Groups of neurons form four functional groups:
 A collection of axons
 Nerve – in the Peripheral Nervous System (PNS)
 Tract – in the Central Nervous System (CNS)

A collection of cell bodies
 Ganglion – within the PNS
 Nucleus - within the CNS
Cells of the Nervous System:
Functional Types of Neurons
Sensory neurons - carry information to
the CNS
 Interneurons - connect sensory and
motor neurons or communicate with
other interneurons
 Motor neurons - carry information from
the CNS to muscles, organs, and glands to
control their functioning.

Physical
Types of
Neurons
Cells of the Nervous System:
Types of Synapses
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Axodendritic - the axon synapses with dendrites of
another neuron
Axosomatic - the axon synapses with the cell body
of another neuron
Dendrodendritic synapse - occurs when the
dendrites of one neuron synapses with the
dendrites of another neuron
Axoaxonic synapse - the axon of one neuron
synapses with the axon of another neuron
Neuromuscular junction - the axon synapses with a
muscle
Cells of the Nervous System:
Glial Cells

Glial cells
• One-tenth the size of neurons
• Ten times as numerous as neurons

Types of Glial cells
• Astrocytes - provide physical support to neurons,
nourishment and other functions.
• Microglial cells - remove debris
• Oligodendrocytes - produce myelin which covers
the axons of neurons in CNS
• Schwann cells - produce myelin which covers the
axons of neurons in PNS
Myelination
Organization of the Nervous System:
The Peripheral Nervous System
Detects internal and external environmental
information; relays information to CNS
 Executes CNS’ decisions in muscles, glands and
organs
 Spinal nerves and Cranial nerves
 Peripheral Nervous System includes:

 Somatic Nervous System - Includes both sensory and
motor systems
 Autonomic Nervous System - Regulates the internal
environment
The Peripheral Nervous System:
Somatic Nervous System

Enables us to interact with the physical
environment
• Afferent neurons – transmit messages from sensory
receptors to the CNS
• Efferent neurons – transmit messages from the CNS
to skeletal muscle
• Spinal nerves – 31 pairs of nerves that send messages
to/from the brain thru the spinal cord
• Cranial nerves – 12 pairs of nerves that link sensory
receptors in the head directly to the brain and the
brain to certain muscles
Cranial Nerves
The Peripheral Nervous System:
Autonomic Nervous System
Primarily efferent neurons
 Controls internal environment - glands
and internal organs
 Consist of two parts that are typically
antagonistic:

• Sympathetic
• Parasympathetic
The
Autonomic
Nervous
System
Organization of the Nervous System:
The Central Nervous System
 Recognizes and analyzes information received
from the PNS
 Makes and transmits decisions to glands, organs,
and muscles for execution

Central Nervous System includes:
 Spinal cord - responsible for limited analysis and
decision making, transmits information to and
from the brain.
 Brain - responsible for analyzing sensory
information and making appropriate responses to
it.
The Protective Features of the
Central Nervous System
Protecting the spinal cord
• Vertebral Column - outer bony covering
that encases the spinal cord
Protecting the brain
• Skull - outer bony covering that encases the
brain
• Ventricular system
Meninges protects both
• Dura matter
• Arachnoid matter
• Pia mater
The Central Nervous System: Spinal
Cord
• Serves as a conduit to and from
the brain
• Controls spinal reflexes
The Central Nervous System:
The Brain

Three main functions:
• Recognizing stimuli detected by the PNS
• Analyzing the information
• Initiating the appropriate response
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Three main areas:
• Hindbrain
• Midbrain
• Forebrain
The Brain: The Hindbrain
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Myelencephalon
 Medulla oblongata, which controls basic life functions
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Metencephalon
 Pons - a “bridge” for fibers passing from one side of
the brain to the other. Sensory fibers, fibers from the
cortex to cerebellum, and fibers that relay
information on sleep, arousal and dreaming pass
through it.
 Cerebellum - involved in the development and
coordination of movement
• Reticular formation
 Involved in arousal, begins in the medulla and extends
to other areas of the brain
The Hindbrain
The Brain: The Midbrain
Mesencephalon
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Tectum - relays visual and auditory information and
controls simple reflexes, eye and ear orientation
movements
Tegmentum • substantia nigra - integration of voluntary
movements
• red nucleus - controls basic body movements
• reticular formation - controls arousal and
consciousness
Brain stem = midbrain + hindbrain not including the
cerebellum
The Brain: Forebrain
Diencephalon
• Epithalamus - contains habenula (olfactory
functions) and pineal gland
• Thalamus - major relay station for sensory
information
• Hypothalamus - detects need states, controls
the autonomic nervous system, and controls
pituitary hormone production and release
• Pituitary - regulates other glandular activity of
the body; often called the “master gland”
The Diencephalon
The Brain: Forebrain
Telencephalon
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Limbic System
 The limbic system is a group of structures
surrounding the brain stem.
 The limbic system structures include the
amygdala, cingulate gyrus, and hippocampus.
 Governs emotions such as anger, fear, and
happiness, and is involved in the storage and
retrieval of memories.
The Limbic System
The Brain: Forebrain
Telencephalon
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Basal Ganglia - have widespread connections to the
cortex and forebrain and are involved in the initiation
of voluntary movements, maintaining muscle tone and
posture
The Brain: Forebrain
Telencephalon
Cerebral Cortex - the convoluted outer layer of
the forebrain that processes sensory
information, controls thinking, decision making,
stores and retrieves memory, and initiates
motor responses
 The cortex is divided into two hemispheres
connected by the corpus callosum and each
hemisphere has four lobes
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The Cerebral
Cortex
The Brain:
Lobes of the Cerebral Cortex
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Occipital lobe - primary function is the analysis
of visual information
Parietal lobe - The anterior portion analyses
sensory information such as pain, pressure and
body position. The posterior portion is involved
in spatial perception.
Temporal lobe - includes the primary auditory
cortex, a visual area and language centers
The Brain:
Lobes of the Cerebral Cortex
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Frontal lobe  Broca’s area - area for programming and sequencing
of motor movements for speech production
 Prefrontal cortex - controls complex intellectual
functioning such as planning and sequencing of
behavior.
 Motor cortex - area of the frontal lobe anterior to
the central sulcus.
Representation of body parts in the
somatosensory cortex and motor
cortex