Chapter 14: Brain and Cranial Nerves
Objectives
· Name the major brain regions, vesicles, and ventricles, and describe the locations and functions of each.
· Explain how the brain is protected and supported, and discuss the formation, circulation, and function of cerebrospinal fluid.
· Describe the anatomical differences between the medulla oblongata and the spinal cord, and identify the medulla oblongata’s main components and functions.
· List the main components of the pons, and specify the functions of each.
· List the main components of the cerebellum, and specify the functions of each.
· List the main components of the mesencephalon, and specify the functions of each.
· List the main components of the diencephalon, and specify the functions of each.
· Identify the main components of the limbic system, and specify the locations and functions of each.
· Identify the major anatomical subdivisions and functions of the cerebrum, and discuss the origin and significance of the major types of brain waves seen in an encephalogram.
An Introduction to the Brain and Cranial Nerves
· The Adult Human Brain
o Ranges from 750 cc to 2100 cc
o Contains almost 97% of the body’s neural tissue
o Average weight about 1.4 kg ( ______lb)
The Brain
· Six Regions of the Brain
o Cerebellum
o Diencephalon
o Mesencephalon
o Pons
o ______
o Medulla oblongata
The Brain
· Cerebrum
o ______part of brain
o Controls higher mental functions
o Cerebral hemispheres
o Gray matter (neural cortex)
The Brain
· Cerebrum
o Neural ______
§ Also called cerebral cortex
§ Folded surface increases surface area
§ Elevated ridges (______)
§ Shallow depressions (sulci)
§ Deep grooves (fissures)
The Brain
· Cerebellum
o Second largest part of brain
o Coordinates ______body movements
o Two hemispheres
o Covered with cerebellar cortex
The Brain
· Diencephalon
o Located under cerebrum and cerebellum
o ______cerebrum with brain stem
o Three divisions
§ Left thalamus
§ Right thalamus
§ Hypothalamus
The Brain
· Diencephalon
o T______
§ Relays and processes sensory information
o Hypothalamus
§ Hormone production
§ Emotion
§ Autonomic function
o Pituitary gland
The Brain
· The Brain Stem
o Processes information between
o Spinal cord and cerebrum or cerebellum
§ Includes
· M______
· Pons
· Medulla oblongata
The Brain
· The Brain Stem
o Mesencephalon
§ Also called ______
§ Processes sight, sound
§ Maintains consciousness
o Pons
§ Connects cerebellum to brain stem
The Brain
· The Brain Stem
o Medulla oblongata
§ Connects brain to spinal cord
§ Relays information
§ Regulates autonomic functions:
· ______rate, blood pressure, and digestion
The Brain
· Embryological Development
o Neural tube
§ Origin of brain
§ Enlarges into three ______brain vesicles
· prosencephalon
· mesencephalon
· rhombencephalon
The Brain
· Five ______Brain Vesicles
o Telencephalon
o Diencephalon
o M______
o Metencephalon
o Myelencephalon
The Brain
· Telencephalon:
o Becomes cerebrum
· Metencephalon
o Forms cerebellum and pons
· Myelencephalon
o Becomes medulla oblongata
Brain Protection and Support
· Physical protection
o Bones of the cranium
o Cranial ______
o Cerebrospinal fluid
· Biochemical isolation
o ______barrier
Brain Protection and Support
· The Cranial Meninges
o Have three layers:
§ Dura mater
§ ______mater
§ Pia mater
o Are continuous with spinal meninges
o Protect the brain from cranial trauma
Brain Protection and Support
· ______Fluid (CSF)
o Surrounds all exposed surfaces of CNS
o Interchanges with interstitial fluid of brain
o Functions of CSF
§ Cushions delicate neural structures
§ Supports brain
§ Transports nutrients, chemical messengers, and waste products
Brain Protection and Support
· Cerebrospinal Fluid (CSF)
o Choroid ______
o Specialized ependymal cells and capillaries:
§ secrete CSF into ventricles
§ remove waste products from CSF
§ adjust composition of CSF
o Produces about 500 mL of CSF/day
Brain Protection and Support
· Cerebrospinal Fluid (CSF)
o CSF circulates
§ From choroid plexus
§ Through ventricles
§ To central canal of spinal cord
§ Into ______space around the brain, spinal cord, and cauda equina
Brain Protection and Support
· Cerebrospinal Fluid (CSF)
o CSF in subarachnoid space
§ Arachnoid ______:
· absorb CSF into venous circulation
Brain Protection and Support
· Blood Supply to the Brain
o Supplies nutrients and oxygen to brain
o Delivered by internal carotid arteries and vertebral arteries
o Removed from dural sinuses by internal jugular veins
Brain Protection and Support
· Cerebrovascular Disease
o Disorders interfere with blood circulation to brain
o ______or cerebrovascular accident (CVA) or Brain Attack
§ Shuts off blood to portion of brain
§ Neurons die
Brain Protection and Support
· Blood–Brain Barrier
· Isolates CNS neural tissue from general circulation
· Formed by network of tight junctions between endothelial cells of CNS capillaries
· Astrocytes control blood–brain barrier
· Lipid-soluble compounds (O2, CO2), steroids, and prostaglandins diffuse into interstitial fluid of brain and spinal cord
Brain Protection and Support
· Blood–CSF Barrier
o Formed by special ______cells
o Surround capillaries of choroid plexus
o Allows chemical composition of blood and CSF to differ
Brain Protection and Support
· Four Breaks in the BBB
o Portions of hypothalamus
§ Secrete hypothalamic hormones
o Posterior lobe of pituitary gland
§ Secretes hormones ADH and oxytocin
o Pineal glands
§ Pineal secretions
o Choroid plexus
§ Where special ependymal cells maintain blood–CSF barrier
Brain Protection and Support
· Review
o Meninges stabilize brain in cranial cavity
o Cerebrospinal fluid protects against sudden movement
o CSF provides nutrients and removes wastes
o Blood–brain barrier and blood–CSF barrier
§ Selectively isolate brain from chemicals in blood that might disrupt neural function
The Medulla Oblongata
· The Medulla Oblongata
o Allows brain and spinal cord to communicate
o Coordinates complex autonomic reflexes
§ ______
§ ______
o Controls visceral functions
The Pons
· The Pons
o Links ______with mesencephalon, diencephalon, cerebrum, and spinal cord
o Sensory and motor nuclei of many cranial nerves
The Cerebellum
· Functions of the Cerebellum
o Adjusts postural muscles
o Fine-tunes conscious and subconscious ______
The Mesencephalon
· Structures of the Mesencephalon
o Tectum
§ Two pairs of sensory nuclei (corpora ______):
· superior colliculus (visual)
· inferior colliculus (auditory)
o Tegmentum
§ Red nucleus (many blood vessels)
§ Substantia nigra (pigmented gray matter)
The Diencephalon
· Integrates sensory information and motor commands
· Thalamus, epithalamus, and hypothalamus
o The pineal gland
§ Found in posterior epithalamus
§ Secretes hormone ______
The Diencephalon
· The Thalamus
o Filters ascending sensory information for primary sensory cortex
o Relays information between basal nuclei and cerebral cortex
o The third ventricle
§ Separates ______
The Diencephalon
· Functions of the Hypothalamus
o Provides subconscious control of skeletal muscle
o Controls autonomic function
o Coordinates activities of nervous and endocrine systems
§ Secretes hormones
· ______(ADH)
· Oxytocin (OT; OXT)
o Produces emotions and behavioral drives
§ The feeding center (hunger)
§ The thirst center (thirst)
o Coordinates voluntary and autonomic functions
o Regulates body temperature
o Controls circadian rhythms (day–night cycles)
The Limbic System
· The Limbic System
o Is a ______grouping that
§ Establishes emotional states
§ Links conscious functions of cerebral cortex with autonomic functions of brain stem
§ Facilitates memory storage and retrieval
The Cerebrum
· The Cerebrum
o Is the largest part of the brain
o Controls all conscious thoughts and intellectual functions
o Processes somatic sensory and motor information
The Cerebrum
· ______matter
o In cerebral cortex and basal nuclei
· ______matter
o Deep to basal cortex
o Around basal nuclei
The Cerebrum
· Three Functional Principles of the Cerebrum
o Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of the body
o The two hemispheres have different functions, although their structures are alike
o Correspondence between a specific function and a specific region of cerebral cortex is not precise
The Cerebrum
· White Matter of the Cerebrum
o Association fibers
§ Connections within one hemisphere
o ______fibers
§ Bands of fibers connecting two hemispheres:
§ ______callosum
o Projection fibers
§ Pass through diencephalon
§ Link cerebral cortex with:
· diencephalon, brain stem, cerebellum, and spinal cord
The Cerebrum
· The Basal Nuclei
o Also called cerebral nuclei
o Are masses of gray matter
o Are embedded in white matter of cerebrum
o Direct subconscious activities
The Cerebrum
· Motor and Sensory Areas of the Cortex
o Central sulcus separates motor and sensory areas
§ Motor areas
· ______gyrus of frontal lobe:
o directs voluntary movements
· Primary motor cortex:
o is the surface of precentral gyrus
§ Sensory areas
· ______gyrus of parietal lobe:
o receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature)
· Primary sensory cortex:
o surface of postcentral gyrus
The Cerebrum
· Special Sensory Cortexes
o Visual cortex
§ Information from sight receptors
o Auditory cortex
§ Information from sound receptors
o ______cortex
§ Information from odor receptors
o Gustatory cortex
§ Information from taste receptors
The Cerebrum
· ______Centers
o Are located in lobes and cortical areas of both cerebral hemispheres
o Receive information from association areas
o Direct complex motor or analytical activities
The Cerebrum
· General ______Area
o Also called Wernicke area
o Present in only one hemisphere
o Receives information from all sensory association areas
o Coordinates access to complex visual and auditory memories
The Cerebrum
· Other Integrative Areas
o ______center
§ Is associated with general interpretive area
§ Coordinates all vocalization functions
o Prefrontal cortex of frontal lobe
§ Integrates information from sensory association areas
§ Performs abstract intellectual activities (e.g., predicting consequences of actions)
The Cerebrum
· Interpretive Areas of Cortex
o Brodmann areas
§ Patterns of cellular organization in cerebral cortex
The Cerebrum
· Hemispheric Lateralization
o Functional differences between left and right hemispheres
o Each cerebral hemisphere performs certain functions that are not ordinarily performed by the opposite hemisphere
The Cerebrum
· The Left Hemisphere
o In most people, left brain (dominant hemisphere) controls
§ Reading, writing, and math
§ Decision making
§ Speech and language
· The Right Hemisphere
o Right cerebral hemisphere relates to
§ Senses (touch, smell, sight, taste, feel)
§ Recognition (faces, voice inflections)
The Cerebrum
· Monitoring Brain Activity
o Brain activity is assessed by an ______(EEG)
§ Electrodes are placed on the skull
§ Patterns of electrical activity (brain waves) are printed out
The Cerebrum
· Four Categories of Brain Waves
o Alpha waves
§ Found in healthy, awake adults at rest with eyes closed
o Beta waves
§ Higher frequency
§ Found in adults concentrating or mentally stressed
o Theta waves
§ Found in children
§ Found in intensely frustrated adults
§ May indicate brain disorder in adults
o Delta waves
§ During sleep
§ Found in awake adults with brain damage
Cranial Nerves
· Olfactory Nerves (I)
o Primary function
§ Special sensory (______)
o Origin
§ Receptors of olfactory epithelium
o Pathway
§ Olfactory foramina in cribriform plate of ethmoid
o Destination
§ Olfactory bulbs
Cranial Nerves
· Optic Nerves (II)
o Primary function
§ Special sensory (______)
o Origin
§ Retina of eye
o Pathway
§ Optic canals of sphenoid
o Destination
§ Diencephalon via optic chiasm
Cranial Nerves
· Oculomotor Nerves (III)
o Primary function
§ Motor (______)
o Origin
§ Mesencephalon
o Pathway
§ Superior orbital fissures of sphenoid
o Destination
§ Somatic motor:
· superior, inferior, and medial rectus muscles
· inferior oblique muscle
· levator palpebrae superioris muscle
§ Visceral motor:
· intrinsic eye muscles
Cranial Nerves
· The Trochlear Nerves (IV)
o Primary function
§ Motor (______)
o Origin
§ Mesencephalon
o Pathway
§ Superior orbital fissure of sphenoid
o Destination
§ Superior oblique muscle
Cranial Nerves
· The Abducens Nerves (VI)
o Primary function
§ Motor (______)
o Origin
§ Pons
o Pathway
§ Superior orbital fissures of sphenoid
o Destination
§ Lateral rectus muscle
Cranial Nerves
· The Trigeminal Nerves (V)
o Primary function
§ ______(sensory and motor) to face
o Origin
§ Ophthalmic branch (sensory):
· orbital structures
· nasal cavity
· skin of forehead, upper eyelid, and eyebrow
· part of nose
§ Maxillary branch (sensory):
· lower eyelid
· upper lip, gums, and teeth
· cheek and nose
· palate and part of pharynx
§ Mandibular Branch
· Mandibular branch (sensory):
o lower gums, teeth, and lips
o palate and part of tongue
· Mandibular branch (motor):
o motor nuclei of pons
o Pathway
§ Ophthalmic branch:
· superior orbital fissure
§ Maxillary branch:
· foramen rotundum
§ Mandibular branch:
· foramen ovale
Cranial Nerves
· The Facial Nerves (VII)
o Primary function
§ ______(sensory and motor) to face
o Origin
§ Sensory:
· taste receptors on anterior 2/3 of tongue
§ Motor:
· motor nuclei of pons
o Pathway
§ Internal acoustic meatus to facial canals (stylomastoid foramina)
o Destination
§ Sensory:
· sensory nuclei of pons
§ Somatic motor:
· muscles of facial expression
§ Visceral motor:
· tear and nasal mucous glands
· submandibular and sublingual salivary glands
Cranial Nerves
§ Facial Nerve Structures
o Facial nerve branches
o Temporal
o Zygomatic
o Buccal
o Mandibular
o Cervical branches
Cranial Nerves
§ The Vestibulocochlear Nerves (VIII)
o Primary function: special sensory
§ Vestibular branch:
· ______and ______
§ Cochlear branch:
· ______
o Origin
§ Receptors of inner ear
o Pathway
§ Internal acoustic meatus of temporal bones
o Destination
§ Vestibular and cochlear nuclei of pons and medulla oblongata
Cranial Nerves
§ Vestibulocochlear Nerve Structures
o Vestibular branch
§ Originates at receptors of vestibule (balance)
§ Connects to vestibular nuclei of pons and medulla oblongata
o Cochlear branch
§ Originates at sensors of cochlea (hearing)
§ Connects with cochlear nuclei of pons and medulla oblongata