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Chapter 11
The Nervous System
The Brain, Cranial Nerves,
Autonomic Nervous System,
and the Special Senses
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Introduction
• Brain is divided into four main parts
– Brainstem: controls breathing, heartbeat rates
and reactions to auditory and visual stimuli
– Diencephalon: controls homeostasis
– Cerebrum: controls intellectual processes and
emotions
– Cerebellum: maintains body posture and
balance
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The Principal Parts of the
Brain
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The Principal Parts of the Brain
(cont’d.)
• Main parts: brainstem, diencephalon,
cerebrum, and cerebellum
• Protection
– Cranial bones
– Meninges
– Cerebrospinal fluid
• Ventricles
– Interventricular foramen
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The Principal Parts of the Brain
(cont’d.)
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The Anatomy and Functions of
the Brainstem
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The Anatomy and Functions of the
Brainstem (cont’d.)
• Medulla oblongata
– Ascending and descending tracts
– Connect spinal cord with the brain
– Some tracts cross over in medulla
– Reticular formation: controls consciousness
– Reflex centers
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The Anatomy and Functions of the
Brainstem (cont’d.)
• Pons varolii
– Connects spinal cord with brain
– Connects parts of brain with each other
– Helps control breathing
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The Anatomy and Functions of the
Brainstem (cont’d.)
• Midbrain
– Ventral cerebral peduncles: convey impulses
from cortex to pons and spinal cord
– Dorsal tectum: reflex center
– Controls movement of head and eyeball
(visual stimuli)
– Controls movement of head and trunk
(auditory stimuli)
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The Anatomy and Functions of
the Diencephalon
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The Anatomy and Functions of the
Diencephalon (cont’d.)
• Optic tracts
• Mamillary bodies: memory and emotional
responses
• Thalamus
– Relay station for sensory impulses
– Interpretation center for pain, temperature,
and touch
• Epithalamus: contains pineal gland
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The Anatomy and Functions of the
Diencephalon (cont’d.)
• Hypothalamus: homeostasis
– Controls and integrates autonomic nervous
system
– Receives sensory impulses from internal
organs
– Controls pituitary gland and links endocrine
and nervous systems
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The Cerebrum: Structure and
Function
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The Cerebrum: Structure and
Function (cont’d.)
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The Cerebrum: Structure and
Function (cont’d.)
• Cerebral cortex: gray matter surface
• Longitudinal fissure separates two
hemispheres
• Gyri: folds
• Sulci: grooves
• Corpus callosum: bridge connecting two
hemispheres
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The Cerebrum: Structure and
Function (cont’d.)
• Surface of the cortex
– Motor areas control muscular movements
– Sensory areas interpret sensory impulses
– Association areas process emotions and
intellect
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The Cerebrum: Structure and
Function (cont’d.)
• Cerebral hemispheres
– Frontal lobe: muscle movement, moods,
aggression, smell, motivation
– Parietal lobe: touch, pain, balance, taste,
temperature
– Temporal lobe: hearing, smell, memory,
abstract thought, judgment
– Occipital lobe: vision
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The Cerebrum: Structure and
Function (cont’d.)
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The Cerebellum: Structure
and Function
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The Cerebellum: Structure and
Function (cont’d.)
• Butterfly-shaped
• Two partially separated hemispheres
connected by vermis
• Functions
– Coordinating muscular movements
– Maintaining posture
– Maintaining balance
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The Autonomic Nervous
System
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The Autonomic Nervous System
(cont’d.)
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•
•
•
•
Subdivision of efferent PNS
Functions without conscious effort
Regulates functions of internal organs
Assists in maintaining homeostasis
Helps deal with emergency situations
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The Autonomic Nervous System
(cont’d.)
• Sympathetic
– Energy and stressful situations
– Increases heartbeat and breathing rates
– Neurotransmitters: acetylcholine and
norepinephrine
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The Autonomic Nervous System
(cont’d.)
• Parasympathetic
– Restores body to nonstressful state
– Neurotransmitter: acetylcholine
– Stimulates digestion, urination, and defecation
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The 12 Cranial Nerves and
Their Functions
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The 12 Cranial Nerves and Their
Functions (cont’d.)
• (I) Olfactory: smell
• (II) Optic: sight
• (III) Oculomotor: movement of eyeball,
constriction of pupil
• (IV) Trochlear: movement of eyeball
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The 12 Cranial Nerves and Their
Functions (cont’d.)
• (V) Trigeminal: chewing, sensations in
teeth
• (VI) Abducens: movement of eyeball
• (VII) Facial: facial expression, taste, tear
and salivary glands
• (VIII) Vestibulocochlear: equilibrium,
hearing
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The 12 Cranial Nerves and Their
Functions (cont’d.)
• (IX) Glossopharyngeal: swallowing, taste,
salivary glands
• (X) Vagus: certain muscle movements,
sensory impulses
• (XI) Accessory: swallowing, head
movement
• (XII) Hypoglossal: swallowing, speech
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The Special Senses
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The Sense of Smell
• Molecules in air dissolve in nasal mucus
• Bipolar sensory neurons transfer chemical
impulse
• Olfactory bulbs receive impulse
• Impulse sent to olfactory cortex
• Odor variety dependent on brain
interpretation
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The Sense of Smell
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The Sense of Taste
• Taste buds on tongue, palate, and pharynx
• Taste bud cell types
– Exterior capsule: epithelial cells
– Interior: taste cells
• Taste depends on chemicals dissolved in
saliva
• Taste influenced by olfactory sensations
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The Sense of Taste
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The Sense of Sight
• Eyes protected by eyelids and eyelashes
• Tears
– Lubricate the eyes
– Contain bacteriolytic lysozyme enzyme
– Contain salt and gamma globulin
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The Sense of Sight (cont’d.)
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The Sense of Sight (cont’d.)
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The Sense of Hearing and
Equilibrium
• Outer ear
– Auricle: external, visible, flexible part
– External auditory meatus
• Lined with hair and ceruminous glands
– Tympanic membrane: vibrates in response to
sound
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The Sense of Hearing and
Equilibrium
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The Sense of Hearing and
Equilibrium
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The Sense of Hearing and
Equilibrium (cont’d.)
• Middle ear
– Auditory ossicles: malleus, incus, and stapes
– Openings: oval and round windows
– Eustachian tube: equalizes pressure
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The Sense of Hearing and
Equilibrium (cont’d.)
• Inner ear
– Cochlea: hearing
– Equilibrium
• Static: vestibule
• Kinetic: semicircular canals
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Summary
• Named the principal parts of the brain
• Discussed the functions of the major parts
of the brain
• Named the 12 cranial nerves
• Discussed the role of the autonomic
nervous system and its divisions
• Described the special senses and the
organs involved
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