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Chapter 11The 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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• Pons varolii– Connects spinal cord with brain– Connects parts of brain with each other– Helps control breathing

The Anatomy and Functions of the Brainstem (cont’d.)

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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.)

• 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