Anatomy Physiology Lecture 10 Chapter 14 The Brain

Anatomy & Physiology Lecture 10: Chapter 14 The Brain and Cranial Nerves Pages : 451 - 494 Lecturer: Dr. Barjis Room P 313 /P 307 Phone: (718) 260 -5285 E-Mail: ibarjis@citytech. cuny. edu Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Frederic H. Martini Fundamentals of

Learning 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.

Learning Objectives • Identify the major anatomical subdivisions of the cerebrum. • Locate the motor, sensory and association areas of the cerebral cortex and discuss their functions. • Describe representative examples of cranial reflexes.

An Introduction to the Organization of the Brain 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 Adult Brain

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 • Telecephalon will become cerebrum • Mesencephalon will become midbrain • Rhombencephalon • Forms the metencephalon (cerebellum and pons) and myelencephalon (medulla oblongata)

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

Ventricles of the Brain Animation: Brain Dissections (see tutorial)

Protection and Support of the Brain 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

The Relationship among the Brain, Cranium, and Meninges

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

The Circulation of Cerebrospinal Fluid

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 – relay impulses from proprioceptor (receptors monitoring joint and muscle position) to cerebellum. • Cardiovascular and respiratory rhythmicity centers • Other nuclei in the medulla control reflexes such as vomiting, coughing, sneezing, blood pressure. • Reticular formation begins in the medulla oblongata and extends into more superior portions of the brainstem

The Diencephalon and Brain Stem

The Medulla Oblongata and Pons

The pons contains • Sensory and motor nuclei for four cranial nerves • Nuclei that help control respiration • Connects part of the brain with one another: • Nuclei and tracts linking the cerebellum with the brain stem, cerebrum and spinal cord • Connections are provided by bundles of axons (tracts). • Ascending, descending and transverse tracts

The Medulla Oblongata and Pons

The cerebellum • Adjusts postural muscles and tunes on-going movements • Cerebellar hemispheres • Anterior and posterior lobes – govern subconscious aspects of skeletal muscle. • Vermis – the central area • Flocculonodular lobe – contributes to equilibrium and balance. • Superior, middle and inferior cerebellar peduncles link cerebellum with brain stem, diencephalon, cerebrum, and spinal cord • Interconnects the two cerebellar hemispheres

The Cerebellum

The mesencephalon • The tectum (roof) contains the corpora quadrigemina (four rounded elevations) • Two Superior - they serve as a reflex centers for some visual activities. • Two inferior colliculi – are part of auditory pathway • The mesencephalon contains many nuclei • Red nucleus • Substantia nigra • Cerebral peduncles • RAS (Reticular Activating System) headquarters

The Mesencephalon

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

The Thalamus

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

The Hypothalamus in Sagittal Section

The limbic system or motivational system includes • Amygdaloid body • Cingulated gyrus • Parahippocampal gyrus • Hippocampus • Fornix • Functions of the limbic system: • emotions and behavioral drives • linking conscious intellectual functions of cortex with unconscious and autonomic functions • Facilitate memory storage and retrival

The Limbic System

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

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

The Cerebral Hemispheres PLAY

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

Hemispheric Lateralization PLAY

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

Brain Waves PLAY

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

Origins of the Cranial Nerves PLAY

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

The Olfactory Nerve PLAY

cranial nerves II, 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

Cranial Nerves Controlling the Extra-ocular Muscles PLAY

cranial nerves V, 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

The Trigeminal Nerve PLAY

The Facial Nerve PLAY

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

The Vestibulocochlear Nerve PLAY

The Glossopharyngeal Nerve PLAY

The Vagus Nerve PLAY

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

The Accessory and Hypoglossal Nerve PLAY

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.