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Chapter 14: The Brain and Cranial Nerves. 6 Regions of the Brain. Cerebrum Cerebellum Diencephalon Mesencephalon Pons Medulla oblongata. Cerebrum. Largest part of brain Controls higher mental functions Divided into left and right cerebral hemispheres

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6 regions of the brain
6 Regions of the Brain
  • Cerebrum
  • Cerebellum
  • Diencephalon
  • Mesencephalon
  • Pons
  • Medulla oblongata
  • Largest part of brain
  • Controls higher mental functions
  • Divided into left and right cerebral hemispheres
  • Surface layer of gray matter (neural cortex)
    • Also called cerebral cortex
  • Folded surface increases surface area
    • Elevated ridges (gyri)
    • Shallow depressions (sulci)
    • Deep grooves (fissures)
  • Second largest part of brain
  • Coordinates repetitive body movements
  • 2 hemispheres
  • Covered with cerebellar cortex
  • Located under cerebrum and cerebellum
  • Links cerebrum with brain stem
  • 3 divisions:
    • Thalamus - relays and processes sensory information
    • Hypothalamus - hormone production, emotion, & autonomic function
    • Epithalamus (Pineal gland)
pituitary gland
Pituitary Gland
  • Major endocrine gland
  • Connected to hypothalamus
  • Via infundibulum (stalk)
  • Interfaces nervous and endocrine systems
the brain stem
The Brain Stem
  • Processes information between:
    • spinal cord and cerebrum or cerebellum
  • Includes:
    • Mesencephalon (midbrain)
      • Processes sight, sound, and associated reflexes, & maintains consciousness
    • Pons
      • Connects cerebellum to brain stem & is involved in somatic and visceral motor control
    • Medulla oblongata
      • Regulates autonomic functions: HR, BP, and digestion
primary brain vesicles
Primary Brain Vesicles
  • The anterior end of the neural tube expands and constricts to form the three primary brain vesicles
    • Prosencephalon – the forebrain
    • Mesencephalon – the midbrain
    • Rhombencephalon – hindbrain
secondary brain vesicles
Secondary Brain Vesicles
  • In week 6 of embryonic development, secondary brain vesicles form
    • Telencephalon and diencephalon arise from the forebrain
    • Mesencephalon remains undivided
    • Metencephalon and myelencephalon arise from the hindbrain
adult brain structures
Adult Brain Structures
  • Fates of the secondary brain vesicles:
    • Telencephalon – cerebrum: cortex, white matter, and basal nuclei
    • Diencephalon – thalamus, hypothalamus, and epithalamus
    • Mesencephalon – brain stem: midbrain
    • Metencephalon – brain stem: pons
    • Myelencephalon – brain stem: medulla oblongata
  • Lateral ventricles
    • Deep w/in cerebrum
  • Third ventricle
    • Connected by interventricular foramen (Monro)
  • Fourth ventricle
    • Connected by cerebral aqueduct (Sylvius)
    • Connects to subarachnoid space to return to bloodstream
brain protection and support
Brain Protection and Support
  • Physical protection:
    • bones of the cranium
    • cranial meninges
    • cerebrospinal fluid
  • Biochemical isolation:
    • blood–brain barrier
the cranial meninges
The Cranial Meninges
  • Has 3 layers:
    • dura mater
    • arachnoid mater
    • pia mater
  • Is continuous with spinal meninges
  • Protects the brain from cranial trauma
characteristics of cranial meninges
Characteristics of Cranial Meninges
  • Dura mater:
    • inner fibrous layer (meningeal layer)
    • outer fibrous layer (endosteal layer) fused to periosteum
    • venous sinuses between 2 layers
  • Arachnoid mater:
    • contacts epithelial layer of dura mater
      • Subarachnoid space b/t arachnoid and pia mater
  • Pia mater:
    • attached to brain surface by astrocytes
dural folds
Dural Folds
  • Folded inner layer of dura mater
  • Extend into cranial cavity to stabilize and support brain
  • Contain collecting veins (dural sinuses)
  • Falx cerebri, tentorium cerebelli, and falx cerebelli
cerebrospinal fluid csf
Cerebrospinal Fluid (CSF)
  • Surrounds all exposed surfaces of CNS
  • Interchanges with interstitial fluid of brain
  • Functions of CSF
    • Cushions delicate neural structures
    • Supports brain
    • Transports nutrients, chemical messengers, and waste products
forming csf
Forming CSF
  • Choroid plexus:
    • Specialized ependymal cells and capillaries:
      • secrete CSF into ventricles
      • remove waste products from CSF
      • adjust composition of CSF
  • Produces about 500 ml of CSF/day
    • Room for ~ 150 ml
circulating csf
Circulating CSF
  • CSF produced from choroid plexus (in all ventricles)
    • Lateral Ventricle (thru interventricular foramen of Monro)
    • Third Ventricle (thru cerebral aquaduct of Sylvius)
    • Fourth Ventricle (thru median & lateral apertures)
    • To central canal of spinal cord & subarachnoid space around the brain, spinal cord, and caudaequina
    • Thru arachnoidvilli/granulations (into dural venous sinuses)
    • DVS’s merge into Internal Jugular Vein
blood supply to the brain
Blood Supply to the Brain
  • Supplies nutrients and oxygen to brain
  • Delivered by internal carotid arteries and vertebral arteries
  • Removed from dural sinuses by internal jugular veins
cerebrovascular disease
Cerebrovascular Disease
  • Disorders interfere with blood circulation to brain
  • Stroke or cerebrovascular accident (CVA):
    • shuts off blood to portion of brain
    • neurons die
  • Transient ischemic attack (TIA):
    • temporary reduction in blood flow
blood brain barrier bbb
Blood–Brain Barrier (BBB)
  • Isolates CNS neural tissue from general circulation
  • Formed by network of tight junctions between endothelial cells of CNS capillaries
  • Lipid–soluble compounds (O2, CO2), steroids, and prostaglandins diffuse into interstitial fluid of brain and spinal cord
  • Astrocytes control blood–brain barrier by releasing chemicals that control permeability of endothelium
4 breaks in the bbb
4 Breaks in the BBB
  • Portions of hypothalamus:
    • secrete hypothalamic hormones
  • Posterior lobe of pituitary gland:
    • secrete hormones ADH and oxytocin
  • Pineal glands:
    • pineal secretions
  • Choroid plexus:
    • where special ependymal cells maintain blood–CSF barrier
the medulla oblongata
The Medulla Oblongata
  • Allows brain and spinal cord to communicate
  • Coordinates complex autonomic reflexes
  • Controls visceral functions
medulla oblongata
Medulla Oblongata
  • Vital reflex centers (life sustaining decisions)
    • Cardiac center – rate/force of contractions
    • Vasomotor center – smooth mm in b.v.’s (BP control)
    • Respiratory center – rate/depth of breathing (up into pons)
  • Non-vital reflex centers
    • Vomiting, hiccough, swallowing, coughing, sneezing
  • CN VIII through XII nuclei
  • Vestibular nuclei complex – subconsciously maintain balance (equilibrium)
  • Solitary nucleus - receives visceral sensory information
  • Olivary nuclei (olives)…lateral to pyramids
    • Receive sensory info from proprioceptors (position) in skeletal muscles & joints & act as a relay point to the cerebellum
the pons
The Pons
  • Links cerebellum with mesencephalon, diencephalon, cerebrum, and spinal cord
  • Nuclei of cranial nerves V, VI, VII, VIII
  • Nuclei involved with respiration:
    • apneustic center and pneumotaxic center
    • modify respiratory rhythmicity center activity
  • Cerebellar peduncles – connect cerebellum to brainstem (6 in all)
      • Superior cerebellar peduncles – to midbrain
      • Middle cerebellar peduncles – to pons (largest)
      • Inferior cerebellar peduncles – to medulla
functions of the cerebellum
Functions of the Cerebellum
  • Adjusts postural muscles
  • Fine-tunes conscious and subconscious movements
  • Ataxia:
    • damage from trauma or stroke
    • intoxication (temporary disturbance)
    • disturbs muscle coordination
structures of the cerebellum
Structures of the Cerebellum
  • Folia:
    • surface of cerebellum
    • highly folded neural cortex
  • Anterior and posterior lobes:
    • separated by primary fissure
  • Cerebellar hemispheres:
    • separated at midline by vermis
  • Flocculonodular lobe:
    • below fourth ventricle
  • Arbor vitae: Highly branched, internal white matter of cerebellum
structures of the mesencephalon
Structures of the Mesencephalon
  • Tectum: (corpora quadrigemina):
    • superior colliculus (visual)
    • inferior colliculus (auditory)
  • Tegmentum:
    • red nucleus (many blood vessels)
    • substantia nigra (pigmented gray matter)
  • Cerebral peduncles:
    • Contain descending fibers to cerebellum
      • motor command fibers
the diencephalon
The Diencephalon
  • Integrates sensory information and motor commands
  • Thalamus
  • Epithalamus
    • Secretes hormone melatonin
  • Hypothalamus

Figure 14–5a

the thalamus
The Thalamus
  • Filters ascending sensory information for primary sensory cortex
  • Relays center to funnel information between basal nuclei and cerebral cortex
5 groups of thalamic nuclei
5 Groups of Thalamic Nuclei
    • Anterior group: part of limbic system (emotions)
  • Medial group: provides awareness of emotional states
  • Ventral group: relays sensory information
  • Posterior group:
    • pulvinar nucleus (sensory)
    • lateral geniculate nucleus (visual)
    • medial geniculate nucleus (auditory)
  • Lateral group: affects emotional states
    • integrates sensory info
structures of the hypothalamus
Structures of the Hypothalamus
  • Mamillary bodies:
    • process olfactory and other sensory information
    • control reflex eating movements
  • Infundibulum:
    • a narrow stalk
    • connects hypothalamus to pituitary gland
8 functions of the hypothalamus
8 Functions of the Hypothalamus
  • Provides subconscious control of skeletal muscle
  • Controls autonomic function
  • Coordinates activities of nervous and endocrine systems
  • Secretes hormones:
    • antidiuretic hormone (ADH) & oxytocin (OT)
  • Produces emotions and behavioral drives:
    • the feeding center (hunger) & the thirst center
  • Coordinates voluntary and autonomic functions
  • Regulates body temperature:
  • Controls circadian rhythms (day–night cycles)
the limbic system
The Limbic System
  • Is a functional grouping that:
    • establishes emotional states
    • links conscious functions of cerebral cortex with autonomic functions of brain stem
    • facilitates memory storage and retrieval
components of the limbic system
Components of the Limbic System
  • Amygdala: deals with anger, danger, and fear responses
    • interfaces limbic system, cerebrum, and sensory systems
  • Limbic lobe of cerebral hemisphere:
    • cingulategyrus - plays a role in expressing emotions via gestures, and resolves mental conflict
    • hippocampus - converts short-term memory to long-term memory…memories charged w/ emotion are often retained
  • Fornix: tract of white matter
    • connects hippocampus with hypothalamus
  • Anterior nucleus of the thalamus:
    • relays information from mamillary body to cingulategyrus
  • Reticular formation:
    • stimulation or inhibition affects emotions (rage, fear, pain, sexual arousal, pleasure)
the cerebrum
The Cerebrum
  • Is the largest part of the brain
  • Controls all conscious thoughts and intellectual functions
  • Processes somatic sensory and motor information
  • Gray matter:
    • in cerebral cortex and basal nuclei
  • White matter:
    • deep to cortex
    • around basal nuclei
structures of the cerebrum
Structures of the Cerebrum
  • Gyri of neural cortex: increase surface area (number of cortical neurons)
  • Longitudinal fissure: separates cerebral hemispheres
  • Lobes: divisions of hemispheres
  • Central sulcusdivides: anterior frontal lobe from posterior parietal lobe
  • Lateral sulcusdivides: frontal lobe from temporal lobe
  • Parieto-occipital sulcusdivides: parietal lobe from occipital lobe
3 functional principles of the cerebrum
3 Functional Principles of the Cerebrum
  • Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of body
  • The 2 hemispheres have different functions although their structures are alike
  • Correspondence between a specific function and a specific region of cerebral cortex is not precise
3 types of axons in the cerebrum
3 Types of Axons in the Cerebrum
  • Association fibers
    • Connections within 1 hemisphere
  • Commissural fibers
    • Bands of fibers connecting 2 hemispheres
  • Projection fibers
    • Link cerebral cortex with diencephalon, brain stem, cerebellum, and spinal cord
basal nuclei
Basal Nuclei
  • Are masses of gray matter embedded in white matter of cerebrum
  • Direct subconscious activities
  • Are involved with:
    • the subconscious control of skeletal muscle tone
    • the coordination of learned movement patterns (walking, lifting)
  • Caudate nucleus:
  • Lentiform nucleus:
    • globuspallidus
    • putamen
motor and sensory areas of the cortex
Motor and Sensory Areas of the Cortex
  • Central sulcusseparates motor and sensory areas
  • Precentralgyrus(Primary motor cortex) of frontal lobe:
    • directs voluntary movements
  • Postcentralgyrus(Primary sensory cortex) of parietal lobe:
    • receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature)
special sensory cortexes
Special Sensory Cortexes
  • Visual cortex: occipital lobe
    • information from sight receptors
  • Auditory cortex: temporal lobe
    • information from sound receptors
  • Olfactory cortex: frontal & medial temporal lobe
    • information from odor receptors
  • Gustatory cortex: insula (deep to temporal lobe)
    • information from taste receptors
association areas
Association Areas
  • Premotor cortex:
    • coordinates somatic motor responses (learned movements)
  • Somatic sensory association area:
    • interprets input to primary sensory cortex (e.g., recognizes and responds to touch)
  • Visual association area:
    • interprets activity in visual cortex
  • Auditory association area:
    • monitors auditory cortex
integrative areas
Integrative Areas
    • Wernicke’s area (General Interpretive Area )
    • Present in only 1 hemisphere
    • Receives information from all sensory association areas
    • Coordinates access to complex visual and auditory memories
    • Speech center: coordinates all vocalization functions
    • is associated with general interpretive area
  • Prefrontal cortex of frontal lobe:
    • integrates information from sensory association areas
    • performs abstract intellectual activities (e.g., predicting consequences of actions)
brodmann s areas
Brodmann’s Areas
  • Patterns of cellular organization in cerebral cortex

Figure 14–15c

hemispheric lateralization
Hemispheric Lateralization
  • Functional differences between left and right hemispheres
  • In most people (90%), left brain (dominant hemisphere) controls:
    • reading, writing, and math
    • decision-making
    • speech and language
  • Right cerebral hemisphere relates to:
    • senses (touch, smell, sight, taste, feel)
    • recognition (faces, voice inflections)
  • Unclear dominance may lead to dyslexia
monitoring brain activity
Monitoring Brain Activity
  • Brain activity is assessed by an electroencephalogram (EEG):
    • electrodes are placed on the skull
    • patterns of electrical activity are printed out (brain waves)
4 categories of brain waves
4 Categories of Brain Waves
  • Alpha waves:
    • found in healthy, awake adults at rest with eyes closed
  • Beta waves:
    • higher frequency
    • found in adults concentrating or mentally stressed
  • Theta waves:
    • found in children
    • found in intensely frustrated adults
    • may indicate brain disorder in adults
  • Delta waves:
    • during sleep
    • found in awake adults with brain damage
cranial nerves
Cranial Nerves
  • 12 pairs connected to brain
  • Name
  • Number
  • Function
olfactory cn i
Olfactory – CN I
  • Sensory
  • Terminates in olfactory bulbs
  • Discrimination of smell
optic cn ii
Optic – CN II
  • Sensory
  • Vision
  • Terminates at optic chiasm
occulomotor cn iii
Occulomotor – CN III
  • Motor
  • Inferior oblique, sup/inf/medial rectus
  • Test planes of gaze
  • PSNS Function:
  • Test constrictor mm of iris (ciliary mm)
    • Pupillary reflex
trochlear cn iv
Trochlear – CN IV
  • Motor
  • Superior oblique (down & out)
  • Test planes of gaze
trigeminal cn v
Trigeminal – CN V
  • Mixed
  • 3 divisions: ophthalmic, maxillary, mandibular
    • Test:
    • Motor- mandibular division to mm of mastication
    • Corneal reflex to elicit blinking
abducens cn vi
Abducens – CN VI
  • Motor
  • Lateral rectus
  • Test planes of gaze
facial cn vii
Facial – CN VII
  • Mixed
  • Taste on anterior 2/3 of tongue
  • Motor to mm of facial expression (not chewing)
    • 5 motor branches
      • Temporal, zygomatic, buccal, mandibular, cervical
  • PSNS to lacrimal gland
  • Test making faces
vestibulocochlear cn viii
Vestibulocochlear – CN VIII
  • Sensory
  • Equilibrium & hearing
  • Test hearing
glossopharyngeal cn ix
Glossopharyngeal – CN IX
  • Mixed
  • Motor fibers to pharynx
  • PSNS to parotid salivary gland
  • Sensory conduct taste from posterior 1/3 of tongue; carotid sinus pressure & chemoreceptors (Oxygen), general sensation of pharynx
  • Test swallowing (gag reflex w/ CN X)
vagus cn x
Vagus – CN X
  • Mixed
  • Only nerve to descend beyond neck (into thorax & abdomen)
  • PSNS serving heart, lung, abd viscera to regulate heart rate, breathing, & digestive activity
  • Test gag reflex (w/ CN IX)
spinal accessory cn xi
Spinal accessory – CN XI
  • Motor
  • Trapezius & SCM
  • Test shrugging shoulders
hypoglossal cn xii
Hypoglossal CN XII
  • Motor
  • Extrinsic & intrinsic muscles of the tongue
  • Test by sticking out tongue