Anatomy of the Brain and Cranial Nerves

The Nervous System can be divided in: Central Nervous System (CNS) Brain and Spinal Cord Peripheral Nervous System (PNS) Cranial and spinal nerves, ganglia, sensory receptors

Division of the Peripheral Nervous System Sensory or afferent Somatic Visceral Motor or efferent Somatic - voluntary Visceral or Autonomic Nervous System (ANS) - involuntary Sympathetic Parasympathetic

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

The Cerebrum

The cerebral hemispheres Surface contains gyri, sulci, fissures Fissures Longitudinal fissure separates two cerebral hemispheres Transverse fissure separates cerebellum from cerebrum

The Cerebrum

The cerebral hemispheres Sulci Parieto-occipital sulcus separates parietal from occipital lobe Lateral sulcus separates temporal from parietal lobe Central sulcus separates frontal and parietal lobe

The cerebral hemispheres Gyri Precentral gyrus Poscentral gyrus

The cerebral lobes Frontal Precentral gyrus Primary motor area – conscious control of voluntary movements. Premotor cortex – memory bank for skilled motor activities or of patterned and repetitious nature. Broca’s area Located on the left hemisphere. Controls speech.

The cerebral lobes Prefrontal cortex – responsible for personality, cognition, intellect. Lesion cause mental and personality disorder Parietal Primary Somatosensory Area – touch, pressure, temperature, vibration, and pain from body wall Somatosensory association area – interprets stimulus sent by the above area. Ex: recognizes objects by touch.

The cerebral lobes Temporal Primary Auditory area – temporal lobe. Primary association auditory area – interprets the sound heard by above area Wernicke’s area – only on left hemisphere, between parietal and temporal lobes. Area responsible for understanding spoken language Olfactory area –uncus. Smell area.

The cerebral lobes Occipital Primary visual area – perception of light Visual association area – interprets the images seen on the area above Insula Gustatory cortex

Cerebral hemispheres - internal structures Gray matter Cell bodies of the neurons Dendrites Small unmyelinated axons Neuroglias

Cerebral hemispheres - internal structures White matter Tracts Association – connects 2 areas of the same hemisphere Projection – connects upper and lower brain. Ex: internal capsule Commissure – connects the 2 hemispheres.

Tracts

Sagittal Section

Cerebral hemispheres - internal structures Corpus callosum Connects the 2 hemispheres Fornix Connects limbic system areas Septum pellucidum Separates the 2 lateral ventricles

Cerebral hemispheres - internal structures Basal Nuclei – regulation of voluntary motor activities. Allows smooth movements. Caudate Nucleus Putamen Globus pallidus

The Diencephalon

Diencephalon: external view Olfactory tract Olfactory bulb Optic nerve Chiasma optic Pituitary gland or hypophysis Mammilary bodies – relay for olfaction

The diencephalon is composed of Epithalamus Hypothalamus Thalamus

Sagittal Section Figure 14.12b

The Epithalamus Roof of the third ventricle Contains choroid plexus Contains pineal gland Regulates sleep-awake cycle

The thalamus Relay area for impulses Two large lobes of gray matter Interthalamic adhesion or intermediate mass

The hypothalamus Autonomic center for regulation of body temperature, water balance, etc Secretes hormones Mammilary bodies – relay station for olfaction Pituitary glands – secretes hormones Optic chiasm

The Brain Stem Midbrain Cerebral Aqueduct – connects third and forth ventricles Cerebral peduncles – connects pons to cerebrum Corpora quadrigemina Superior colliculi – visual reflex center Inferior colliculi – auditory reflex center

The Brain Stem Pons Consists of tracts and nuclei Connects brain to lower CNS Medulla Oblongata Tracts Decussation of the pyramids Autonomic reflex centers – heart rate, blood pressure, vomiting, swallowing, respiratory rhythm Olives

PART 2

Cerebellum Two hemispheres connected by the vermis Arbor vitae – white matter Cortex of gray matter

The Cerebellum

The Cerebellum

The cranial meninges Dura mater Falx cerebri-formed by dura mater that dips into the longitudinal fissure and separates the 2 hemispheres Falx cerebelli – separate the two cerebellar hemispheres

The cranial meninges – dura mater Superior sagittal Sinus – collects blood from the brain Tentorium cerebelli – separates the cerebrum from the cerebellum

The cranial meninges Arachnoid Subarachnoid space Filled with CSF Arachnoid villi – projections of the mater that protrude through the dura For the CSF to drain back to the venous circulation

The cranial meninges Pia mater Highly vascular Covers the entire brain Meningites

The Relationship among the Brain, Cranium, and Meninges

Ventricles of the brain Filled with cerebrospinal fluid (CSF) Lateral ventricles Septum pellucidum Interventricular foramina or foramen of Monro

Ventricles of the brain Third ventricle Cerebral aqueduct Forth ventricle 3 Apertures

Ventricles of the Brain

Cerebrospinal fluid (CSF) CSF cushions delicate neural structures Supports the brain Pathway of CSF Produced at the Choroid plexus Travels through the apertures on the 4th ventricle to the subarachnoid space Diffuses across the arachnoid villus (granulation) into the superior sagittal sinus

The Circulation of CSF

Cranial Nerves 12 pairs of cranial nerves To help to remember “Old Opie Occasionally Tries Trigonometry And Fells Very Gloomy Vague And Hypoactive”

The Cranial Nerves PLAY

Cranial Nerves Number Name Major Functions I Olfactory (sens) Smell II Optic (sens) Vision III Oculomotor (mot) Eye movement IV Trochlear (mot) V Trigeminal (mix) Chewing muscles, head and face sensation

Cranial nerves VI Abducens (mot) Eye movement VII Facial (mix) Face expression, taste VIII Vestibulocochlear (sen) Vestibular: posture and balance Cochlear: hearing

Cranial Nerves IX Glossopharyngeal (mix) Swallowing, taste, general sensation for pharynx X Vagus (mix) Visceral muscle movement and taste sensation XI Accessory (mot) Swallowing, and head movement XII Hypoglossal (mot) Movement of tongue for speaking, swallowing and mixing food

Brain Dissection Whole Brain Pia-Arachnoid Gyrus Sulcus Fissure Transverse Longitudinal Cerebrum

Brain Dissection Pons Medulla Oblongata Cerebellum Cranial nerves: I (bulb, tract) II (nerve, chiasma) III

Brain Dissection Colliculi Superior Inferior Pineal Gland

Brain Dissection Sagittal Cut Diencephalon Epithalamus Thalamus Hypothalamus Ventricles Lateral, third, forth

Brain Dissection Septum pellucidum Corpus callosum Fornix Arbor vitae (cerebellum)