Chapter 11 The Nervous System The Brain, Cranial Nerves, Autonomic Nervous System, and the Special Senses

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

The Principal Parts of the Brain

The Principal Parts of the Brain (cont’d.) Main parts: brainstem, diencephalon, cerebrum, and cerebellum Protection Cranial bones Meninges Cerebrospinal fluid Ventricles Interventricular foramen

The Principal Parts of the Brain (cont’d.)

The Anatomy and Functions of the Brainstem

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

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

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)

The Anatomy and Functions of the Diencephalon

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

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

The Cerebrum: Structure and Function

The Cerebrum: Structure and Function (cont’d.) Needs Fig 11-4

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

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

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

The Cerebrum: Structure and Function (cont’d.)

The Cerebellum: Structure and Function

The Cerebellum: Structure and Function (cont’d.) Butterfly-shaped Two partially separated hemispheres connected by vermis Functions Coordinating muscular movements Maintaining posture Maintaining balance

The Autonomic Nervous System

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

The Autonomic Nervous System (cont’d.) Sympathetic Energy and stressful situations Increases heartbeat and breathing rates Neurotransmitters: acetylcholine and norepinephrine

The Autonomic Nervous System (cont’d.) Parasympathetic Restores body to nonstressful state Neurotransmitter: acetylcholine Stimulates digestion, urination, and defecation

The 12 Cranial Nerves and Their Functions

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

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

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

The Special Senses

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

The Sense of Smell

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

The Sense of Taste

The Sense of Sight Eyes protected by eyelids and eyelashes Tears Lubricate the eyes Contain bacteriolytic lysozyme enzyme Contain salt and gamma globulin

The Sense of Sight (cont’d.) Needs Fig 11-10

The Sense of Sight (cont’d.) Needs Fig 11-10

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

The Sense of Hearing and Equilibrium

The Sense of Hearing and Equilibrium

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

The Sense of Hearing and Equilibrium (cont’d.) Inner ear Cochlea: hearing Equilibrium Static: vestibule Kinetic: semicircular canals

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