AP-Ch13

Chapter

13 The Brain and Cranial Nerves PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris

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An Introduction to the Brain and Cranial Nerves  The Adult Human Brain  Ranges from 750 cc to 2100 cc  Contains almost 97% of the body s neural tissue  Average weight about 1.4 kg (3 lb)

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The Brain  Six Regions of the Brain  Cerebrum  Cerebellum  Diencephalon  Mesencephalon  Pons  Medulla oblongata 3D Peel-Away of the Brain Copyright © 2010 Pearson Education, Inc.

The Brain  Cerebrum  Largest part of brain  Controls higher mental functions  Divided into left and right cerebral hemispheres  Surface layer of gray matter (neural cortex)

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The Brain  Cerebrum  Neural cortex  Also called cerebral cortex  Folded surface increases surface area  Elevated ridges (gyri)  Shallow depressions (sulci)  Deep grooves (fissures)

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The Brain  Cerebellum  Second largest part of brain  Coordinates repetitive body movements  Two hemispheres  Covered with cerebellar cortex

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The Brain  Diencephalon  Located under cerebrum and cerebellum  Links cerebrum with brain stem  Three divisions  Left thalamus  Right thalamus  Hypothalamus

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The Brain  Diencephalon  Thalamus  Relays and processes sensory information

 Hypothalamus  Hormone production  Emotion  Autonomic function

 Pituitary gland    

Major endocrine gland Connected to hypothalamus Via infundibulum (stalk) Interfaces nervous and endocrine systems

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The Brain  The Brain Stem  Processes information between  Spinal cord and cerebrum or cerebellum

 Includes  Mesencephalon  Pons  Medulla oblongata

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The Brain  The Brain Stem  Mesencephalon  Also called midbrain  Processes sight, sound, and associated reflexes  Maintains consciousness

 Pons  Connects cerebellum to brain stem  Is involved in somatic and visceral motor control Copyright © 2010 Pearson Education, Inc.

The Brain  The Brain Stem  Medulla oblongata  Connects brain to spinal cord  Relays information  Regulates autonomic functions: – heart rate, blood pressure, and digestion

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The Brain

Figure 13–1 An Introduction to Brain Structures and Functions.

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The Brain  Embryological Development  Determines organization of brain structures  Neural tube  Origin of brain  Enlarges into three primary brain vesicles – prosencephalon – mesencephalon – rhombencephalon Copyright © 2010 Pearson Education, Inc.

The Brain  Five Secondary Brain Vesicles  Telencephalon  Diencephalon  Mesencephalon  Metencephalon  Myelencephalon

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The Brain  Origins of Brain Structures  Diencephalon and mesencephalon persist  Telencephalon:  Becomes cerebrum

 Metencephalon  Forms cerebellum and pons

 Myelencephalon  Becomes medulla oblongata Copyright © 2010 Pearson Education, Inc.

The Brain

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The Brain  Ventricles of the Brain  Origins of ventricles  Neural tube encloses neurocoel  Neurocoel expands to form chambers (ventricles) lined with ependymal cells

 Each cerebral hemisphere contains one large lateral ventricle  Separated by a thin medial partition (septum pellucidum)

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The Brain  Ventricles of the Brain  Third ventricle  Ventricle of the diencephalon  Lateral ventricles communicate with third ventricle: – via interventricular foramen (foramen of Monro)

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The Brain  Ventricles of the Brain  Fourth ventricle  Extends into medulla oblongata  Becomes continuous with central canal of the spinal cord  Connects with third ventricle: – via narrow canal in mesencephalon – aqueduct of midbrain Copyright © 2010 Pearson Education, Inc.

The Brain

Figure 13–2 Ventricles of the Brain.

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The Brain  The brain is a large, delicate mass of neural tissue containing internal passageways and chambers filled with cerebrospinal fluid  Each of the six major brain regions has specific functions  Ascending from the medulla oblongata to the cerebrum, brain functions become more complex and variable  Conscious thought and intelligence are produced in the neural cortex of the cerebral hemispheres Copyright © 2010 Pearson Education, Inc.

Brain Protection and Support  Physical protection  Bones of the cranium  Cranial meninges  Cerebrospinal fluid

 Biochemical isolation  Blood–brain barrier

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Brain Protection and Support  The Cranial Meninges  Have three layers:  Dura mater  Arachnoid mater  Pia mater

 Are continuous with spinal meninges  Protect the brain from cranial trauma

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Brain Protection and Support  The Cranial Meninges  Dura mater  Inner fibrous layer (meningeal layer)  Outer fibrous layer (endosteal layer) fused to periosteum  Venous sinuses between two layers

 Arachnoid mater  Covers brain  Contacts epithelial layer of dura mater  Subarachnoid space: between arachnoid mater and pia mater

 Pia mater  Attached to brain surface by astrocytes Copyright © 2010 Pearson Education, Inc.

Brain Protection and Support  Dural Folds  Folded inner layer of dura mater  Extend into cranial cavity  Stabilize and support brain  Contain collecting veins (dural sinuses)  Falx cerebri, tentorium cerebelli, and falx cerebelli

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Brain Protection and Support  Dural Folds  Falx cerebri  Projects between the cerebral hemispheres  Contains superior sagittal sinus and inferior sagittal sinus

 Tentorium cerebelli  Separates cerebellum and cerebrum  Contains transverse sinus

 Falx cerebelli  Divides cerebellar hemispheres below the tentorium cerebelli Copyright © 2010 Pearson Education, Inc.

Brain Protection and Support

Figure 13–3a The Relationship among the Brain, Cranium, and Meninges.

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Brain Protection and Support

Figure 13–3b The Relationship among the Brain, Cranium, and Meninges.

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Brain Protection and Support  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 Copyright © 2010 Pearson Education, Inc.

Brain Protection and Support  Cerebrospinal Fluid (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

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Brain Protection and Support  Cerebrospinal Fluid (CSF)  CSF circulates  From choroid plexus  Through ventricles  To central canal of spinal cord  Into subarachnoid space around the brain, spinal cord, and cauda equina

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Brain Protection and Support  Cerebrospinal Fluid (CSF)  CSF in subarachnoid space  Arachnoid villi: – extensions of subarachnoid space – extend through dura mater to superior sagittal sinus

 Arachnoid granulations: – large clusters of villi – absorb CSF into venous circulation

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Brain Protection and Support

Figure 13–4 The Formation and Circulation of Cerebrospinal Fluid.

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Brain Protection and Support

Figure 13–4a The Formation and Circulation of Cerebrospinal Fluid.

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Brain Protection and Support

Figure 13–4b The Formation and Circulation of Cerebrospinal Fluid.

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Brain Protection and Support  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

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Brain Protection and Support

Figure 19–22 Arteries of the Neck and Head.

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Brain Protection and Support

Figure 19–23 Arteries of the Brain.

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Brain Protection and Support

Figure 19–28 Major Veins of the Head, Neck, and Brain.

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Brain Protection and Support

Figure 19–28 Major Veins of the Head, Neck, and Brain.

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Brain Protection and Support  Cerebrovascular Disease  Disorders interfere with blood circulation to brain  Stroke or cerebrovascular accident (CVA)  Shuts off blood to portion of brain  Neurons die

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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  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 Copyright © 2010 Pearson Education, Inc.

Brain Protection and Support  Blood–CSF Barrier  Formed by special ependymal cells  Surround capillaries of choroid plexus  Limits movement of compounds transferred  Allows chemical composition of blood and CSF to differ

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Brain Protection and Support  Four Breaks in the BBB  Portions of hypothalamus  Secrete hypothalamic hormones

 Posterior lobe of pituitary gland  Secretes hormones ADH and oxytocin

 Pineal glands  Pineal secretions

 Choroid plexus  Where special ependymal cells maintain blood– CSF barrier Copyright © 2010 Pearson Education, Inc.

Brain Protection and Support  Meninges stabilize brain in cranial cavity  Cerebrospinal fluid protects against sudden movement  CSF provides nutrients and removes wastes  Blood–brain barrier and blood–CSF barrier  Selectively isolate brain from chemicals in blood that might disrupt neural function

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The Medulla Oblongata  The Medulla Oblongata  Allows brain and spinal cord to communicate  Coordinates complex autonomic reflexes  Controls visceral functions  Nuclei in the Medulla  Autonomic nuclei: control visceral activities  Sensory and motor nuclei: of cranial nerves  Relay stations: along sensory and motor pathways Copyright © 2010 Pearson Education, Inc.

The Medulla Oblongata

Figure 13–5a The Diencephalon and Brain Stem.

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The Medulla Oblongata

Figure 13–5b The Diencephalon and Brain Stem.

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The Medulla Oblongata

Figure 13–5c The Diencephalon and Brain Stem.

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The Medulla Oblongata  The Medulla Oblongata  Includes three groups of nuclei  Autonomic nuclei  Sensory and motor nuclei of cranial nerves  Relay stations along sensory and motor pathways

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The Medulla Oblongata  Autonomic Nuclei of the Medulla Oblongata  Reticular formation  Gray matter with embedded nuclei  Regulates autonomic functions

 Reflex centers  Control peripheral systems: – cardiovascular centers: » cardiac center » control blood flow through peripheral tissues – respiratory rhythmicity centers sets pace for respiratory movements Copyright © 2010 Pearson Education, Inc.

The Medulla Oblongata  Sensory and Motor Nuclei of the Medulla Oblongata  Associated with 5 of 12 cranial nerves (VIII, IX, X, XI, XII)

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The Medulla Oblongata  Relay Stations of the Medulla Oblongata  Nucleus gracilis and nucleus cuneatus  Pass somatic sensory information to thalamus

 Solitary nucleus  Receives visceral sensory information

 Olivary nuclei (olives)  Relay information about somatic motor commands

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The Medulla Oblongata

Figure 13–6a The Medulla Oblongata and Pons.

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The Medulla Oblongata

Figure 13–6b The Medulla Oblongata and Pons.

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The Pons  The Pons  Links cerebellum with mesencephalon, diencephalon, cerebrum, and spinal cord  Sensory and motor nuclei of cranial nerves V, VI, VII, VIII

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The Pons  The Pons  Nuclei involved with respiration  Apneustic center and pneumotaxic center: – modify respiratory rhythmicity center activity

 Nuclei and tracts  Process and relay information to and from cerebellum  Ascending, descending, and transverse tracts: – transverse fibers (axons): » link nuclei of pons with opposite cerebellar hemisphere Copyright © 2010 Pearson Education, Inc.

The Pons

Figure 13–6a The Medulla Oblongata and Pons.

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The Pons

Figure 13–6b The Medulla Oblongata and Pons.

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The Pons

Figure 13–6c The Medulla Oblongata and Pons.

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The Pons

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The Pons

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The Cerebellum  Functions of the Cerebellum  Adjusts postural muscles  Fine-tunes conscious and subconscious movements

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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

 Vermis  Narrow band of cortex

 Flocculonodular lobe  Below fourth ventricle Copyright © 2010 Pearson Education, Inc.

The Cerebellum  Structures of the Cerebellum  Purkinje cells  Large, branched cells  Found in cerebellar cortex  Receive input from up to 200,000 synapses

 Arbor vitae  Highly branched, internal white matter of cerebellum  Cerebellar nuclei: embedded in arbor vitae: – relay information to Purkinje cells Copyright © 2010 Pearson Education, Inc.

The Cerebellum  Structures of the Cerebellum  The peduncles  Tracts link cerebellum with brain stem, cerebrum, and spinal cord: – superior cerebellar peduncles – middle cerebellar peduncles – inferior cerebellar peduncles

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The Cerebellum  Disorders of the Cerebellum  Ataxia  Damage from trauma or stroke  Intoxication (temporary impairment)  Disturbs muscle coordination

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The Cerebellum

Figure 13–7a The Cerebellum.

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The Cerebellum

Figure 13–7b The Cerebellum.

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The Cerebellum

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The Mesencephalon  Structures of the Mesencephalon  Tectum  Two pairs of sensory nuclei (corpora quadrigemina): – superior colliculus (visual) – inferior colliculus (auditory)

 Tegmentum  Red nucleus (many blood vessels)  Substantia nigra (pigmented gray matter)

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The Mesencephalon  Structures of the Mesencephalon  Cerebral peduncles  Nerve fiber bundles on ventrolateral surfaces  Contain: – descending fibers to cerebellum – motor command fibers

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The Mesencephalon

Figure 13–8a The Mesencephalon.

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The Mesencephalon

Figure 13–8b The Mesencephalon.

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The Mesencephalon

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The Diencephalon  Integrates sensory information and motor commands  Thalamus, epithalamus, and hypothalamus  The pineal gland  Found in posterior epithalamus  Secretes hormone melatonin

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The Diencephalon  The Thalamus  Filters ascending sensory information for primary sensory cortex  Relays information between basal nuclei and cerebral cortex  The third ventricle  Separates left thalamus and right thalamus  Interthalamic adhesion (or intermediate mass): – projection of gray matter – extends into ventricle from each side Copyright © 2010 Pearson Education, Inc.

The Diencephalon  The Thalamus  Thalamic nuclei  Are rounded masses that form thalamus  Relay sensory information to basal nuclei and cerebral cortex

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The Diencephalon  Five Groups of Thalamic Nuclei  Anterior group  Anterior nuclei  Part of limbic system (emotions)

 Medial group  Provides awareness of emotional states

 Ventral group  Relays sensory information Copyright © 2010 Pearson Education, Inc.

The Diencephalon  Five Groups of Thalamic Nuclei  Posterior group  Pulvinar nucleus (sensory)  Lateral geniculate nucleus (visual)  Medial geniculate nucleus (auditory)

 Lateral group  Affects emotional states  Integrates sensory information Copyright © 2010 Pearson Education, Inc.

The Diencephalon

Figure 13–9 The Thalamus.

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The Diencephalon

Figure 13–9a The Thalamus.

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The Diencephalon

Figure 13–9b The Thalamus.

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The Diencephalon

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The Diencephalon  The Hypothalamus  Mamillary bodies  Process olfactory and other sensory information  Control reflex eating movements

 Infundibulum  A narrow stalk  Connects hypothalamus to pituitary gland

 Tuberal area  Located between the infundibulum and mamillary bodies  Helps control pituitary gland function

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The Diencephalon

Figure 13–10a The Hypothalamus in Sagittal Section.

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The Diencephalon

Figure 13–10b The Hypothalamus in Sagittal Section.

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The Diencephalon  Eight 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) by supraoptic nucleus  Oxytocin (OT; OXT) by paraventricular nucleus

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The Diencephalon  Eight Functions of the Hypothalamus  Produces emotions and behavioral drives  The feeding center (hunger)  The thirst center (thirst)

 Coordinates voluntary and autonomic functions  Regulates body temperature  Preoptic area of hypothalamus

 Controls circadian rhythms (day–night cycles)  Suprachiasmatic nucleus Copyright © 2010 Pearson Education, Inc.

The Diencephalon

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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

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The Limbic System  Components of the Limbic System  Amygdaloid body  Acts as interface between the limbic system, the cerebrum, and various sensory systems

 Limbic lobe of cerebral hemisphere  Cingulate gyrus  Dentate gyrus  Parahippocampal gyrus  Hippocampus Copyright © 2010 Pearson Education, Inc.

The Limbic System  Components of the Limbic System  Fornix  Tract of white matter  Connects hippocampus with hypothalamus

 Anterior nucleus of the thalamus  Relays information from mamillary body to cingulate gyrus

 Reticular formation  Stimulation or inhibition affects emotions (rage, fear, pain, sexual arousal, pleasure) Copyright © 2010 Pearson Education, Inc.

The Limbic System

Figure 13–11a The Limbic System.

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The Limbic System

Figure 13–11b The Limbic System.

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The Limbic System

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The Cerebrum  The Cerebrum  Is the largest part of the brain  Controls all conscious thoughts and intellectual functions  Processes somatic sensory and motor information

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The Cerebrum  Gray matter  In cerebral cortex and basal nuclei

 White matter  Deep to basal cortex  Around basal nuclei

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The Cerebrum  Structures of the Cerebrum  Gyri of neural cortex  Increase surface area (number of cortical neurons)

 Insula (island) of cortex  Lies medial to lateral sulcus

 Longitudinal fissure  Separates cerebral hemispheres

 Lobes  Divisions of hemispheres Copyright © 2010 Pearson Education, Inc.

The Cerebrum  Structures of the Cerebrum  Central sulcus divides  Anterior frontal lobe from posterior parietal lobe

 Lateral sulcus divides  Frontal lobe from temporal lobe

 Parieto-occipital sulcus divides  Parietal lobe from occipital lobe

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The Cerebrum

Figure 13–12a The Brain in Lateral View.

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The Cerebrum

Figure 13–12b The Brain in Lateral View.

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The Cerebrum

Figure 13–12c The Brain in Lateral View.

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The Cerebrum  Three Functional Principles of the Cerebrum  Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of the body  The two hemispheres have different functions, although their structures are alike  Correspondence between a specific function and a specific region of cerebral cortex is not precise Copyright © 2010 Pearson Education, Inc.

The Cerebrum  White Matter of the Cerebrum  Association fibers  Commissural fibers  Projection fibers

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The Cerebrum  White Matter of the Cerebrum  Association fibers  Connections within one hemisphere: – arcuate fibers: » are short fibers » connect one gyrus to another

– longitudinal fasciculi: » are longer bundles » connect frontal lobe to other lobes in same hemisphere

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The Cerebrum  White Matter of the Cerebrum  Commissural fibers  Bands of fibers connecting two hemispheres: – corpus callosum – anterior commissure

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The Cerebrum  White Matter of the Cerebrum  Projection fibers  Pass through diencephalon  Link cerebral cortex with: – diencephalon, brain stem, cerebellum, and spinal cord

 Internal capsule: – all ascending and descending projection fibers

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The Cerebrum

Figure 13–13a Fibers of the White Matter of the Cerebrum.

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The Cerebrum

Figure 13–13b Fibers of the White Matter of the Cerebrum.

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The Cerebrum  The Basal Nuclei  Also called cerebral nuclei  Are masses of gray matter  Are embedded in white matter of cerebrum  Direct subconscious activities

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The Cerebrum  Structures of Basal Nuclei  Caudate nucleus  Curving, slender tail

 Lentiform nucleus  Globus pallidus  Putamen

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The Cerebrum

Figure 13–14a The Basal Nuclei.

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The Cerebrum

Figure 13–14b The Basal Nuclei.

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The Cerebrum

Figure 13–14c The Basal Nuclei.

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The Cerebrum  Functions of Basal Nuclei  Involved with  The subconscious control of skeletal muscle tone  The coordination of learned movement patterns (walking, lifting)

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The Cerebrum  Motor and Sensory Areas of the Cortex  Central sulcus separates motor and sensory areas  Motor areas  Precentral gyrus of frontal lobe: – directs voluntary movements

 Primary motor cortex: – is the surface of precentral gyrus

 Pyramidal cells: – are neurons of primary motor cortex Copyright © 2010 Pearson Education, Inc.

The Cerebrum  Motor and Sensory Areas of the Cortex  Sensory areas  Postcentral gyrus of parietal lobe: – receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature)

 Primary sensory cortex: – surface of postcentral gyrus

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The Cerebrum  Special Sensory Cortexes  Visual cortex  Information from sight receptors

 Auditory cortex  Information from sound receptors

 Olfactory cortex  Information from odor receptors

 Gustatory cortex  Information from taste receptors Copyright © 2010 Pearson Education, Inc.

The Cerebrum

Figure 13–15a Motor and Sensory Regions of the Cerebral Cortex.

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The Cerebrum  Association Areas  Sensory association areas  Monitor and interpret arriving information at sensory areas of cortex

 Somatic motor association area (premotor cortex)  Coordinates motor responses (learned movements)

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The Cerebrum  Sensory Association Areas  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

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The Cerebrum  Integrative Centers  Are located in lobes and cortical areas of both cerebral hemispheres  Receive information from association areas  Direct complex motor or analytical activities

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The Cerebrum  General Interpretive Area  Also called Wernicke area  Present in only one hemisphere  Receives information from all sensory association areas  Coordinates access to complex visual and auditory memories

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The Cerebrum  Other Integrative Areas  Speech center  Is associated with general interpretive area  Coordinates all vocalization functions

 Prefrontal cortex of frontal lobe  Integrates information from sensory association areas  Performs abstract intellectual activities (e.g., predicting consequences of actions) Copyright © 2010 Pearson Education, Inc.

The Cerebrum

Figure 13–15b Motor and Sensory Regions of the Cerebral Cortex.

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The Cerebrum  Interpretive Areas of Cortex  Brodmann areas  Patterns of cellular organization in cerebral cortex

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The Cerebrum

Figure 13–15c Motor and Sensory Regions of the Cerebral Cortex.

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The Cerebrum

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The Cerebrum  Hemispheric Lateralization  Functional differences between left and right hemispheres  Each cerebral hemisphere performs certain functions that are not ordinarily performed by the opposite hemisphere

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The Cerebrum  The Left Hemisphere  In most people, left brain (dominant hemisphere) controls  Reading, writing, and math  Decision making  Speech and language

 The Right Hemisphere  Right cerebral hemisphere relates to  Senses (touch, smell, sight, taste, feel)  Recognition (faces, voice inflections) Copyright © 2010 Pearson Education, Inc.

The Cerebrum

Figure 13–16 Hemispheric Lateralization.

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The Cerebrum  Monitoring Brain Activity  Brain activity is assessed by an electroencephalogram (EEG)  Electrodes are placed on the skull  Patterns of electrical activity (brain waves) are printed out

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The Cerebrum  Four 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 Copyright © 2010 Pearson Education, Inc.

The Cerebrum

Figure 13–17a-d Brain Waves.

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The Cerebrum  Synchronization  A pacemaker mechanism  Synchronizes electrical activity between hemispheres

 Brain damage can cause desynchronization

 Seizure  Is a temporary cerebral disorder  Changes the electroencephalogram  Symptoms depend on regions affected Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  12 pairs connected to brain  Four Classifications of Cranial Nerves  Sensory nerves: carry somatic sensory information, including touch, pressure, vibration, temperature, and pain  Special sensory nerves: carry sensations such as smell, sight, hearing, balance  Motor nerves: axons of somatic motor neurons  Mixed nerves: mixture of motor and sensory fibers Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  Cranial nerves are classified by primary functions  May also have important secondary functions  Distributing autonomic fibers to peripheral ganglia

 The 12 cranial nerve groups are identified by  Primary function  Origin  Pathway  Destination Copyright © 2010 Pearson Education, Inc.

Cranial Nerves

Figure 13–18 Origins of the Cranial Nerves.

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Cranial Nerves  Olfactory Nerves (I)  Primary function  Special sensory (smell)

 Origin  Receptors of olfactory epithelium

 Pathway  Olfactory foramina in cribriform plate of ethmoid

 Destination  Olfactory bulbs

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Cranial Nerves  Olfactory Nerve Structures  Olfactory bulbs  Located on either side of crista galli

 Olfactory tracts  Axons of postsynaptic neurons  Leading to cerebrum

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Cranial Nerves

Figure 13–19 The Olfactory Nerve.

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Cranial Nerves  Optic Nerves (II)  Primary function  Special sensory (vision)

 Origin  Retina of eye

 Pathway  Optic canals of sphenoid

 Destination  Diencephalon via optic chiasm

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Cranial Nerves  Optic Nerve Structures  Optic chiasm  Where sensory fibers converge  And cross to opposite side of brain

 Optic tracts  Reorganized axons  Leading to lateral geniculate nuclei

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Cranial Nerves

Figure 13–20 The Optic Nerve.

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Cranial Nerves  Oculomotor Nerves (III)  Primary function  Motor (eye movements)

 Origin  Mesencephalon

 Pathway  Superior orbital fissures of sphenoid

 Destination  Somatic motor: – superior, inferior, and medial rectus muscles – inferior oblique muscle – levator palpebrae superioris muscle

 Visceral motor: – intrinsic eye muscles Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  Oculomotor Nerve Structures  Oculomotor nerve  Controls four of six eye-movement muscles  Delivers autonomic fibers to ciliary ganglion: – ciliary ganglion: controls intrinsic muscles of iris and lens

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Cranial Nerves  The Trochlear Nerves (IV)  Primary function  Motor (eye movements)

 Origin  Mesencephalon

 Pathway  Superior orbital fissure of sphenoid

 Destination  Superior oblique muscle

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Cranial Nerves  The Abducens Nerves (VI)  Primary function  Motor (eye movements)

 Origin  Pons

 Pathway  Superior orbital fissures of sphenoid

 Destination  Lateral rectus muscle Copyright © 2010 Pearson Education, Inc.

Cranial Nerves

Figure 13–21 Cranial Nerves Controlling the Extra-Ocular Muscles.

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Cranial Nerves  The Trigeminal Nerves (V)  Primary function  Mixed (sensory and motor) to face

 Origin  Ophthalmic branch (sensory): – orbital structures – nasal cavity – skin of forehead, upper eyelid, and eyebrow – part of nose

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Cranial Nerves  The Trigeminal Nerves (V)  Origin  Maxillary branch (sensory): – lower eyelid – upper lip, gums, and teeth – cheek and nose – palate and part of pharynx

 Mandibular branch (sensory): – lower gums, teeth, and lips – palate and part of tongue

 Mandibular branch (motor): – motor nuclei of pons Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  The Trigeminal Nerves (V)  Pathway  Ophthalmic branch: – superior orbital fissure

 Maxillary branch: – foramen rotundum

 Mandibular branch: – foramen ovale

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Cranial Nerves  The Trigeminal Nerves (V)  Destination  Sensory nerves: – sensory nuclei in pons

 Motor nerves of mandibular branch: – muscles of mastication

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Cranial Nerves  Trigeminal Nerve Structures  Trigeminal nerves  Largest cranial nerves  With three major branches

 Semilunar ganglion  Contains cell bodies of sensory neurons

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Cranial Nerves

Figure 13–22 The Trigeminal Nerve.

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Cranial Nerves  The Facial Nerves (VII)  Primary function  Mixed (sensory and motor) to face

 Origin  Sensory: – taste receptors on anterior 2/3 of tongue

 Motor: – motor nuclei of pons

 Pathway  Internal acoustic meatus to facial canals (stylomastoid foramina) Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  The Facial Nerves (VII)  Destination  Sensory: – sensory nuclei of pons

 Somatic motor: – muscles of facial expression

 Visceral motor: – tear and nasal mucous glands – submandibular and sublingual salivary glands Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  Facial Nerve Structures  Facial nerve branches  Temporal  Zygomatic  Buccal  Mandibular  Cervical branches

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Cranial Nerves  Facial Nerve Structures  Geniculate ganglia  Hold cell bodies of sensory neurons

 Pterygopalatine ganglia  Postganglionic fibers innervate glands (lacrimal, nasal cavity, and pharynx)

 Submandibular ganglia  Innervate salivary glands

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Cranial Nerves

Figure 13–23a The Facial Nerve.

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Cranial Nerves

Figure 13–23b The Facial Nerve.

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Cranial Nerves  The Vestibulocochlear Nerves (VIII)  Primary function: special sensory  Vestibular branch: – balance and equilibrium

 Cochlear branch: – hearing

 Origin  Receptors of inner ear

 Pathway  Internal acoustic meatus of temporal bones

 Destination  Vestibular and cochlear nuclei of pons and medulla oblongata Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  Vestibulocochlear Nerve Structures  Vestibular branch  Originates at receptors of vestibule (balance)  Connects to vestibular nuclei of pons and medulla oblongata

 Cochlear branch  Originates at sensors of cochlea (hearing)  Connects with cochlear nuclei of pons and medulla oblongata

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Cranial Nerves

Figure 13–24 The Vestibulocochlear Nerve.

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Cranial Nerves  The Glossopharyngeal Nerves (IX)  Primary function  Mixed (sensory and motor) to head and neck

 Origins  Sensory: – posterior 1/3 of tongue – part of pharynx and palate – carotid arteries

 Motor: – motor nuclei of medulla oblongata Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  The Glossopharyngeal Nerves (IX)  Pathway  Jugular foramina between occipital and temporal bones

 Destination  Sensory: – sensory nuclei of medulla oblongata

 Somatic motor: – nerves involved in swallowing

 Visceral motor: – parotid salivary gland Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  Glossopharyngeal Nerve Structures  Superior and inferior ganglion  Sensory neurons of tongue and pharynx

 Otic ganglion  Synapse visceral motor fibers

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Cranial Nerves

Figure 13–25 The Glossopharyngeal Nerve.

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Cranial Nerves  The Vagus Nerves (X)  Primary function  Mixed (sensory and motor)  Widely distributed in thorax and abdomen

 Origins  Sensory: – part of pharynx – auricle and external acoustic meatus – diaphragm – visceral organs of thoracic and abdominopelvic cavities

 Motor: – motor nuclei in medulla oblongata Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  The Vagus Nerves (X)  Pathway  Jugular foramina  Between occipital and temporal bones

 Destination  Sensory: – sensory nuclei and autonomic centers of medulla oblongata

 Visceral motor: – muscles of the palate and pharynx – muscles of the digestive, respiratory, and cardiovascular systems in thoracic and abdominal cavities Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  Vagus Nerve Structures  Vagus nerves  Branch and radiate extensively

 Superior (jugular) ganglion and inferior (nodose) ganglion  Hold sensory neurons

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Cranial Nerves

Figure 13–26 The Vagus Nerve.

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Cranial Nerves

Figure 13–26 The Vagus Nerve.

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Cranial Nerves  The Accessory Nerves (XI)  Primary function  Motor to muscles of neck and upper back

 Origin  Motor nuclei of spinal cord and medulla oblongata

 Pathway  Jugular foramina between occipital and temporal bones

 Destination  Internal branch: – voluntary muscles of palate, pharynx, and larynx

 External branch: – sternocleidomastoid and trapezius muscles Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  Accessory Nerve Structures  Spinal root  Motor fibers that originate in anterior gray horns of first five cervical segments of spinal cord

 Cranial root  Motor fibers that originate in medulla oblongata

 Internal branch  Joins the vagus nerve

 External branch  Controls muscles of neck and back Copyright © 2010 Pearson Education, Inc.

Cranial Nerves  The Hypoglossal Nerves (XII)  Primary function  Motor (tongue movements)

 Origin  Motor nuclei of medulla oblongata

 Pathway  Hypoglossal canals of occipital bone

 Destination  Muscles of tongue Copyright © 2010 Pearson Education, Inc.

Cranial Nerves

Figure 13–27 The Accessory and Hypoglossal Nerves.

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Cranial Nerves

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Cranial Nerves

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Cranial Reflexes  Cranial Reflexes  Monosynaptic and polysynaptic reflex arcs  Involve sensory and motor fibers of cranial nerves  Clinically useful to check cranial nerve or brain damage

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Cranial Reflexes

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