14 The Brain and Cranial Nerves C h a p t e r PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Major regions and landmarks Six regions in the adult brain Cerebrum Diencephalon Mesencephalon Pons Cerebellum Medulla oblongata Brain contains extensive areas of neural cortex Layer of gray matter on the surface of the cerebellum and cerebrum

Figure 14.1 The Adult Brain Figure 14.1a, c

Figure 14.1 The Adult Brain Figure 14.1b

Figure 14.1 The Adult Brain Figure 14.1d

Figure 14.2 An Introduction to Brain Functions

Embryology of the brain Brain forms from three swellings at the tip of the developing neural tube Prosencephalon Forms the telencephalon and eventually the cerebrum and diencephalon Mesencephalon Rhombencephalon Forms the metencephalon (cerebellum and pons) and myelencephalon (medulla oblongata)

Ventricles of the brain Central passageway of the brain enlarges to form ventricles Contain cerebrospinal fluid (CSF)

Figure 14.3 Ventricles of the Brain Figure 14.3a, b

The cranial meninges Continuous with the three layers of the spinal cord Folds of dura mater help stabilize the position of the brain Falx cerebri Tentorium cerebelli Falx cerebelli

Figure 14.4 The Relationship among the Brain, Cranium, and Meninges Figure 14.4a, b

Cerebrospinal fluid (CSF) CSF cushions delicate neural structures Supports the brain Transports nutrients, chemical messengers, and waste products Pathway of CSF Produced at the Choroid plexus, Travels through the lateral and medial apertures to the subarachnoid space, Diffuses across the arachnoid granulations into the superior sagittal sinus

Figure 14.5 The Circulation of Cerebrospinal Fluid Figure 14.5a, b

Blood supply to the brain Blood brain barrier isolates neural tissue from general circulation Incomplete barrier in areas Parts of the hypothalamus Pituitary gland Pineal gland Choroid plexus

Medulla oblongata Connects the brain with the spinal cord Contains relay stations and reflex centers Olivary nuclei Cardiovascular and respiratory rhythmicity centers Reticular formation begins in the medulla oblongata and extends into more superior portions of the brainstem

Figure 14.7 The Diencephalon and Brain Stem Figure 14.7a, b

Figure 14.7 The Diencephalon and Brain Stem Figure 14.7c

Figure 14.8 The Medulla Oblongata and Pons Figure 14.8a, b

Figure 14.8 The Medulla Oblongata and Pons Figure 14.8c

The pons contains Sensory and motor nuclei for four cranial nerves Nuclei that help control respiration Nuclei and tracts linking the cerebellum with the brain stem, cerebrum and spinal cord Ascending, descending and transverse tracts

Figure 14.8 The Medulla Oblongata and Pons Figure 14.8a, b

Figure 14.8 The Medulla Oblongata and Pons Figure 14.8c

The cerebellum Adjusts postural muscles and tunes on-going movements Cerebellar hemispheres Anterior and posterior lobes Vermis Flocculonodular lobe Superior, middle and inferior cerebellar peduncles link cerebellum with brain stem, diencephalon, cerebrum, and spinal cord Interconnects the two cerebellar hemispheres

Figure 14.9 The Cerebellum Figure 14.9a

Figure 14.9 The Cerebellum Figure 14.9b

The mesencephalon The tectum (roof) contains the corpora quadrigemina Superior and inferior colliculi The mesencephalon contains many nuclei Red nucleus Substantia nigra Cerebral peduncles RAS headquarters

Figure 14.10 The Mesencephalon Figure 14`10a, b

The diencephalon is composed of Epithalamus Hypothalamus Thalamus

The thalamus Final relay point for ascending sensory information Coordinates the activities of the cerebral cortex and basal nuclei

Figure 14.11 The Thalamus Figure 14.11

The hypothalamus Controls somatic motor activities at the subconscious level Controls autonomic function Coordinates activities of the endocrine and nervous systems Secretes hormones Produces emotions and behavioral drives Coordinates voluntary and autonomic functions Regulates body temperature Coordinates circadian cycles of activity

Figure 14.12 The Hypothalamus in Sagittal Section Figure 14.12a

Figure 14.12 The Hypothalamus in Sagittal Section Figure 14.12b

The limbic system or motivational system includes Amygdaloid body Cingulated gyrus Parahippocampal gyrus Hippocampus Fornix Functions of the limbic system involved emotions and behavioral drives

Figure 14.13 The Limbic System

Figure 14.14 The Brain in Section

The cerebral cortex Surface contains gyri and sulci or fissures Longitudinal fissure separates two cerebral hemispheres Central sulcus separates frontal and parietal lobes Temporal and occipital lobes also bounded by sulci

White matter of the cerebrum Contains association fibers Commissural fibers Projection fibers

Figure 14.15 The White Matter of the Cerebrum

The basal nuclei Caudate nucleus Globus pallidus Putamen Control muscle tone and coordinate learned movement patterns

Motor and sensory areas of the cortex Primary motor cortex of the precentral gyrus directs voluntary movements Primary sensory cortex of the postcentral gyrus receives somatic sensory information Touch Pressure Pain Taste Temperature

Figure 14.17 The Cerebral Hemispheres PLAY Figure 14.17

Association areas Control our ability to understand sensory information and coordinate a response Somatic sensory association area Visual association area Somatic motor association area

General interpretive and speech areas General interpretive area Receives information from all sensory areas Present only in left hemisphere Speech center Regulates patterns of breathing and vocalization

Cortex functions and hemispheric differences Prefrontal cortex Coordinates information from secondary and special association areas Performs abstract intellectual functions Hemispheric differences Left hemisphere typically contains general interpretive and speech centers and is responsible for language based skills Right hemisphere is typically responsible for spatial relationships and analyses

Figure 14.18 Hemispheric Lateralization PLAY Figure 14.18

Electroencephalogram (EEG) Measures brain activity Alpha waves = healthy resting adult Beta waves = concentrating adult Theta waves = normal children Delta waves = normal during sleep

Figure 14.19 Brain Waves PLAY Figure 14.19a-d

Focus: Cranial Nerves 12 pairs of cranial nerves Each attaches to the ventrolateral surface of the brainstem near the associated sensory or motor nuclei

Figure 14.20 Origins of the Cranial Nerves PLAY Figure 14.20a

Figure 13420 Origins of the Cranial Nerves PLAY Figure 14.20b

Figure 14.20 Origins of the Cranial Nerves PLAY Figure 14.20c

Olfactory nerves (I) Carry sensory information responsible for the sense of smell Synapse within the olfactory bulb

Figure 14.21 The Olfactory Nerve PLAY Figure 14.21

Cranial nerves II, III, IV Optic nerves (II) Carry visual information from special sensory receptors in the eyes Occulomotor nerves (III) Primary source of innervation for 4 of the extraocular muscles Trochlear nerves (IV) Innervate the superior oblique muscles

Figure 14.23 Cranial Nerves Controlling the Extra-ocular Muscles PLAY Figure 14.23

Cranial nerves V, VI, VII Trigeminal nerves (V) Missed nerves with ophthalmic, maxillary and mandibular branches Abducens nerve (VI) Innervates the lateral rectus muscles Facial nerves (VII) Mixed nerves that control muscles of the face and scalp Provide pressure sensations over the face Receive taste information from the tongue

Figure 14.24 The Trigeminal Nerve PLAY Figure 14.24

Figure 14.25 The Facial Nerve PLAY Figure 14.25a, b

Cranial nerves VIII, IX Vestibulocochlear nerves (VIII) Vestibular branch monitors balance, position and movement Cochlear branch monitors hearing Glossopharyngeal nerves (IX) Mixed nerves that innervate the tongue and pharynx Control the action of swallowing

Cranial nerves X Vagus nerves (X) Mixed nerves Vital to the autonomic control of visceral function

Figure 14.26 The Vestibulocochlear Nerve PLAY Figure 14.26

Figure 14.27 The Glossopharyngeal Nerve PLAY Figure 14.27

Figure 14.28 The Vagus Nerve PLAY Figure 13428

Cranial nerves XI, XII Accessory nerves (XI) Internal branches Innervate voluntary swallowing muscles of the soft palate and pharynx External branches Control muscles associates with the pectoral girdle Hypoglossal nerves (XII) Provide voluntary motor control over tongue movement

Figure 14.29 The Accessory and Hypoglossal Nerve PLAY Figure 14.29

Cranial reflexes Involve sensory and motor fibers of cranial nerves

You should now be familiar with: The major regions of the brain and their functions. The formation, circulation and functions of the CSF. The main components of the medulla oblongata, the pons, the cerebellum, the mesencephalon, the diencephalon, and the limbic system and their functions. The major anatomical subdivisions of the cerebrum. The motor, sensory and association areas of the cerebral cortex. Representative examples of cranial reflexes.