Anatomy

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The Brain and Cranial Nerves Objectives • Name the major regions of the brain and describe their functions. • Discuss the formation, circulation, and functions of the CSF. • List the main components of the medulla oblongata, the pons, the cerebellum, the

mesencephalon, the diencephalon, and the limbic system and specify their functions • Identify the major anatomical subdivisions of the cerebrum. • Locate the motor, sensory, and association areas of the cerebral cortex. • Describe representative examples of cranial reflexes.

Major regions and landmarks • Six regions in the adult brain

• Cerebrum • Diencephalon • Mesencephalon or Midbrain • Pons • Cerebellum • Medulla oblongata

• Brain contains extensive areas of neural cortex • Layer of gray matter on the surface of the cerebellum and cerebrum

Ventricles of the brain • Central passageway of the brain enlarges to form ventricles

• Contain cerebrospinal fluid (CSF) • Lateral ventricles (2) in cerebral hemispheres • Third ventricle – in diencephalons

• Communicates with lateral ventricles via interventricular foramen • Fourth ventricle – between pons and cerebellum

• Communicates with third ventricle via cerebral aquaduct

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

Cerebrospinal fluid (CSF) • CSF cushions delicate neural structures • Supports the brain • Transports nutrients, chemical messengers, and waste products • Pathway of CSF

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• Produced at the Choroid plexus with the ventricles • Travels through the lateral and medial apertures to the subarachnoid space • Diffuses across the arachnoid granulations into the superior sagittal sinus

Blood supply to the brain • Blood brain barrier isolates neural tissue from general circulation

Medulla oblongata • Connects the brain with the spinal cord • Contains relay stations and reflex centers

Pons • 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

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

Mesencephalon or midbrain • The tectum (roof) contains the corpora quadrigemina

• Superior and inferior colliculi • The mesencephalon controls:

• Reflexes to visual stimuli • Auditory processing • Some muscle tone • Alertness and awareness via reticular activating system

Diencephalon • Epithalamus • Hypothalamus • Thalamus Epithalamus • Contains portions of choroids plexus • Contains the pineal gland which secretes melatonin that regulates circadian rhythm

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

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

The Limbic System A collection of nuclei and tracts along border between cerebrum and diencephalon. Functions involve emotions, behavioral drives, memory storage and retrival The limbic system or motivational system includes • Amygdaloid body • Cingulated gyrus • Parahippocampal gyrus • Hippocampus • Fornix

Cerebrum Largest region of brain Conscious thoughts and intellectual function

Gray materof the Cerebrum: The cerebral cortex • collection of mostly neuronal cell bodies • 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

White matter of the cerebrum contains also contains the basal nuclei • Caudate nucleus, Globus pallidus, Putamen

• Control muscle tone and coordinate learned movement patterns

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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

The Cerebral Hemispheres

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

Electroencephalogram (EEG) • Measures brain activity

• Alpha waves = resting adult • Beta waves = concentrating adult • Theta waves = normal children • Delta waves = normal during sleep

Cranial nerves • Twelve pairs of cranial nerves

• Each attaches to the ventrolateral surface of the brainstem near the associated sensory or motor nuclei

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Olfactory nerves (I) • Carry sensory information for the sense of smell, synapses with the olfactory bulb

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 four of the extraocular muscles • Trochlear nerves (IV)

• Innervate the superior oblique muscles

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 and taste information from the tongue

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, controls swallowing

Cranial nerves X • Vagus nerves (X)

• Mixed nerves • Vital to the autonomic control of visceral function

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

Cranial reflexes • Involve sensory and motor fibers of cranial nerves

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Identify the Below Landmarks in Superficial Lateral Brain View

Frontal lobe Parietal lobe Temporal lobe Occipital lobe Lateral sulcus Central sulcus

Precentral gyrus Postcentral gyrus Medulla oblongata Pons Cerebellum

Identify the Below Landmarks in Superficial Superior Brain View

Longitudinal fissure Left and right cerebral hemispheres Corpus callosum

Identify the Below Landmarks in Midsagittal Brain Section

Central sulcus Precentral gyrus Postcentral gyrus Fornix Thalamus Hypothalamus Pineal gland Hypothalmus Corpora quadrigemina

Superior colliculus Inferior colliculus

Mesencephalic (cerebral) aquaduct Cerebellum

Arbor vitae

Ventricles Lateral, Third, Interventricular foramen, Mesencephalic (cerebral) aqueduct, Fourth

Brain stem Medulla oblongata, Pons, Mesencephalon (midbrain)

Optic chiasim Septum pellucidum Corpus callosum Fornix Infundibulum Pituitary

Identify the Below Landmarks in Inferior Brain View

Brain stem Medulla oblongata, Pons, Mesencephalon (midbrain)

Cerebellum Spinal cord Olfactory Nerve (I)

Olfactory Tract Olfactory bulb Optic Nerve (II) Optic chiasm

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List of Cranial Nerves and Function

Region View Nerve Function Brain Inferior Olfactory (I) Olfaction – sensory

Optic (II) Sight – sensory Oculomotor (III) Extrinsic/intrinsic eye movement – motor Trochlear (IV) Extrinsic eye movement – motor Trigeminal (V) Facial sensation – sensory

Ophthalmic Mastication – motor Maxillary Mandibular

Abducens (VI) Extrinsic eye movement – motor Facial (VII) Taste – sensory

Facial expression, lacrimation Salivation submand/subling– motor

Vestibulocochlear (VIII) Vestibular Balance & equilibrium – sensory Cochlear Hearing – sensory

Glossopharyngeal (IX)Taste/tongue – sensory Swallowing – motor

Vagus (X) Sensory & motor functions in pharynx & visceral organs in thoracic & abdominopelvic cavities

Accessory (XI) Pharyngeal & sternocleidomastoid muscles – motor

Hypoglossal (XII) Tongue musculature – motor

Identify the Below Landmarks in Spinal Cord Cross Section View

Anterior gray horn Lateral gray horn Posterior gray horn Gray commissure Central canal Anterior white column Lateral white column Posterior white column Anterior median fissure Posterior median sulcus Spinal nerve

Ventral root Dorsal root

Dorsal root ganglion

Meninges Dura mater Arachnoid Pia mater

Epidural space (with adipose tissue) Subdural space Subarachnoid space (with CSF) Automonic (sympathetic) ganglia