Protection of the Brain. Overview of the Brain. Visual Anatomy & Physiology First Edition. Martini & Ober. Chapter 13. Lecture 20

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1 Visual Anatomy & Physiology First Edition Martini & Ober Chapter 13 Brain and Cranial Nerves Lecture 20 1 Overview of the Brain Functions Major Parts regulates visceral activities cerebrum (two hemispheres) coordinates muscular diencephalon movements thalamus interprets sensations hypothalamus determines perception stores memory carries out reasoning makes decisions determines personality brain stem midbrain (mesencephalon) pons medulla oblongata cerebellum 2 Protection of the Brain The brain is protected Mechanically by The skull bones The meninges The cerebrospinal (CSF) fluid Biochemically by the blood-brain barrier Capillaries interconnected by tight junctions Astrocytes/ependymal cells control permeability of general capillaries/choroid capillaries May be obstacle to delivery of drugs May become more permeable during stress 3 1

2 Meninges of the Brain - dura mater outer, tough (anchoring dural folds) - Subdural space like interstitial fluid - arachnoid mater web-like - Subarachnoid space CSF - pia mater inner, delicate *Singular of meninges is meninx 4 Dural Folds Figure from: Martini, Fundamentals of Anatomy & Physiology, Benjamin Cummings, Ventricles of the Brain interconnected cavities within cerebral hemispheres and brain stem continuous with central canal of spinal cord filled with cerebrospinal fluid (CSF) lateral ventricles (1, 2) third ventricle (3) fourth ventricle (4) cerebral aqueduct 6 2

3 secreted by choroid plexus of ventricles (~500 ml/day) circulates in ventricles, central canal of spinal cord, and subarachnoid space completely surrounds brain and spinal cord clear liquid (more Na + and Cl -, but less K +, Ca 2+, glucose, and protein than plasma) nutritive and protective helps maintain stable ion concentrations in CNS Cerebrospinal Fluid 7 Structure of Cerebrum corpus callosum connects hemispheres gyri bumps or convolutions sulci grooves longitudinal fissure separates hemispheres transverse fissure separates cerebrum from cerebellum lateral sulcus separates the frontal from the temporal lobes Figures from: Saladin, Anatomy & Physiology, McGraw Hill, Functions of Cerebrum interpretation initiating voluntary movements storing memory retrieving memory reasoning center for intelligence and personality The cerebrum can be divided into several functional areas: - Motor (frontal cortex) - Sensory (parietal, occipital, and temporal cortex) - Association (all lobes) Points to keep in mind: - Each cerebral hemisphere receives information from, and sends information to, the opposite side of the body - Although symmetrical, the cerebral hemispheres are not entirely equal in function 10 3

4 Overview of Cerebral Cortex Figure from: Martini, Anatomy & Physiology, Prentice Hall, Primary Motor Areas Primary Motor Cortex - voluntary control of skeletal muscles 12 Motor Areas of the Cortex Notice the relative amount of cortical tissue devoted to each motor function. What would this be proportional to? The Motor Homunculus? Figures from: Saladin, Anatomy & Physiology, McGraw Hill,

5 Broca s Area (Motor) Broca s Area in one (dominant, usually left) hemisphere controls muscles needed for speech 14 Frontal Eye Field (Motor) Controls voluntary movements of eyes and eyelids 15 Sensory Areas Cutaneous Sensory Area parietal lobe interprets sensations on skin Visual Area occipital lobe interprets vision Auditory Area temporal lobe interprets hearing 16 5

6 Sensory Areas of the Cortex Notice the relative amount of cortical tissue devoted to each sensory function. The Somatosensory Homunculus Figures from: Saladin, Anatomy & Physiology, McGraw Hill, Association Areas regions of cortex that are not primary motor or primary sensory areas widespread throughout the cerebral cortex analyze and interpret sensory experiences; coordinate motor responses memory, reasoning, verbalization, judgment, emotions 18 Hemispheric (Cerebral) Lateralization Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Categorical hemisphere Representational hemisphere 20 6

7 nuclei are masses of gray matter in CNS Basal Nuclei deep within cerebral hemispheres caudate nucleus, putamen, globus pallidus (together called the corpus striatum) subconscious control certain muscular activities, e.g., learned movement patterns Relay motor impulses originating in the cerebral cortex and substantia nigra of the midbrain. 21 Consists of portions of frontal lobe portions of temporal lobe hypothalamus thalamus basal nuclei other deep nuclei associated with sense of smell (less significant) Functions controls emotions produces feelings interprets sensory impulses facilitates memory storage and retrieval (learning!) The motivational system Limbic System Figure from: Saladin, Anatomy & Physiology, McGraw Hill, Memory A Memory is the persistence of knowledge that can be accessed (we hope!) at a later time. Memories are not stored in individual memory cells or neurons; they are stored as pathways called engrams, or memory traces that use strengthened or altered synapses. Immediate memory lasts a few seconds, e.g., remembering the earliest part of a sentence to make sense of it. Short-term memory (STM) lasts a few seconds to a few hours Working memory is a form of this (repeating a phone number over to yourself just long enough to dial it and then forget it!) Limited to a few bits of information (about 7-9). So, chunk up! Long-term memory (LTM) can last a lifetime Can hold much more information that STM Declarative (events and facts) Procedural (motor skills) 23 7

8 Diencephalon between cerebral hemispheres and brainstem surrounds third ventricle thalamus hypothalamus epithalamus optic tracts optic chiasm infundibulum posterior pituitary mammillary bodies pineal gland (Tectum) 24 Diencephalon Thalamus gateway for sensory impulses heading to cerebral cortex receives all sensory impulses (except smell) channels impulses to appropriate part of cerebral cortex and to the basal nuclei for interpretation Hypothalamus maintains homeostasis by regulating visceral activities - Heart rate and blood pressure - Body temperature - Water and electrolyte balance - Hunger and body weight - Movement/secretions of glands and intestines - Stimulation of the pituitary (links nervous and endocrine) - Sleep and wakefulness 25 Brain Stem Three Parts 1. Midbrain 2. Pons 3. Medulla Oblongata (Tectum) 27 8

9 between diencephalon and pons contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain Midbrain Major connecting center between spinal cord and brain and parts of brainstem (Tectum) cerebral aqueduct cerebral peduncles bundles of nerve fibers contains red nucleus (rubro-) and substantia nigra corpora quadrigemina centers for visual and auditory reflexes Figure from: Saladin, Anatomy & Physiology, McGraw Hill, Pons rounded bulge on underside of brainstem between medulla oblongata and midbrain helps regulate rate and depth of breathing relays nerve impulses to and from medulla oblongata and cerebellum (Tectum) Ventral view Dorsal view 29 Medulla Oblongata enlarged continuation of spinal cord conducts ascending (olive) and descending (pyramids) impulses between brain and spinal cord (Tectum) contains cardiac, vasomotor, and respiratory control centers contains various nonvital reflex control centers (coughing, sneezing, vomiting) Ventral view Dorsal view 30 9

10 complex network of nerve fibers scattered throughout the brain stem extends into the diencephalon connects to centers of hypothalamus, basal nuclei, cerebellum, and cerebrum filters incoming sensory information; habituation Reticular Formation modulates pain arouses cerebral cortex into state of wakefulness Ascending portion is called the reticular activating system (prefix = reticulo-) 31 Cerebellum integrates sensory information concerning position of body parts coordinates skeletal muscle activity maintains posture May also be involved in several sensory, linguistic, emotional and non-motor functions Figure from: Saladin, Anatomy & Physiology, McGraw Hill, Peripheral Nervous System You are here CNS PNS 33 10

11 Peripheral Nervous System Cranial nerves arising from the brain Somatic fibers connecting to the skin and skeletal muscles Autonomic fibers connecting to viscera Spinal nerves arising from the spinal cord Somatic fibers connecting to the skin and skeletal muscles Autonomic fibers connecting to viscera 34 Cranial Nerves Paired. Numbered (roughly) in the order of their occurrence from anterior to posterior. Abbreviated using N or CN. 35 The Cranial Nerves Numeral Name Function Sensory, Motor, or Both (Mixed Nerve) I OLFACTORY (OLD) OLFACTION/SMELL SENSORY (SOME) II OPTIC (OPIE) VISION SENSORY (SAY) III OCULOMOTOR (OCCASIONALLY) MOVE EYE MOTOR (MARRY) IV TROCHLEAR (TRIES) MOVE EYE (superior oblique) MOTOR (MONEY) V TRIGEMINAL (TRIGONOMETRY) MAJOR SENSORY NERVE FROM FACE BOTH (BUT) VI ABDUCENS (AND) MOVE EYE (lateral rectus) MOTOR (MY) VII FACIAL (FEELS) MAJOR MOTOR NERVE OF FACE BOTH (BROTHER) VIII VESTIBULOCOCHLEAR (VERY) HEARING AND EQUILIBRIUM SENSORY (SAYS) IX GLOSSOPHARYNGEAL (GLOOMY) MOVE MUSCLES OF TONGUE AND PHARYNX X VAGUS (VAGUE) INNERVATE VISCERAL SMOOTH MUSCLE; MUSCLES OF SPEECH BOTH (BIG) BOTH (BOOBS) XI ACCESSORY (AND) MOVE NECK MUSCLES MOTOR (MATTER) XII HYPOGLOSSAL (HYPOACTIVE) MOVE TONGUE MOTOR (MOST) You should know this table 36 11

12 Cranial Nerves I and II Olfactory (I) sensory fibers transmit impulses associated with smell Optic (II) sensory fibers transmit impulses associated with vision Figures from: Martini, Anatomy & Physiology, Prentice Hall, Cranial Nerves III, IV, and VI Oculomotor (III) primarily motor motor impulses to muscles that raise eyelids move the eyes focus lens adjust light entering eye Abducens (VI) primarily motor motor impulses to the lateral rectus (LR) muscles that move the eyes Trochlear (IV) primarily motor motor impulses to the superior oblique (SO) muscles that move the eyes What s a ganglion? Figure from: Martini, Anatomy & Physiology, Prentice Hall, Cranial Nerve V Trigeminal (V) both sensory and motor opthalmic division sensory from surface of eyes, tear glands, scalp, forehead, and upper eyelids maxillary division i i sensory from upper teeth, upper gum, upper lip, palate, and skin of face mandibular division sensory from scalp, skin of jaw, lower teeth, lower gum, and lower lip motor to muscles of mastication and muscles in floor of mouth Major sensory nerve of face 39 12

13 Cranial Nerve VII Facial (VII) both sensory and motor sensory from taste receptors motor to muscles of facial expression, tear glands, and salivary glands Major MOTOR nerve of face Figures from: Saladin, Anatomy & Physiology, McGraw Hill, Cranial Nerves VIII and IX Vestibulocochlear (VIII) sensory sensory from equilibrium receptors of ear sensory from hearing receptors Glossopharyngeal (IX) both sensory and motor sensory from pharynx, tonsils, tongue, and carotid arteries motor to salivary glands and muscles of pharynx Figures from: Martini, Anatomy & Physiology, Prentice Hall, Cranial Nerve X Vagus (X) both sensory and motor somatic motor to muscles of speech and swallowing autonomic motor (parasympathetic) to viscera of thorax and abdomen sensory from pharynx, larynx, esophagus, and viscera of thorax and abdomen Figure from: Saladin, Anatomy & Physiology, McGraw Hill,

14 Cranial Nerves XI and XII Accessory (XI) primarily motor motor to muscles of soft palate, pharynx, larynx, neck, and back Hypoglossal (XII) primarily motor motor to muscles of the tongue Figure from: Martini, Fundamentals of Anatomy & Physiology, Pearson Education, Review The brain is protected by the Skull bones Meninges CSF Blood-brain barrier The meninges of the brain and spinal cord consist of the Dura mater Arachnoid (membrane) Pia mater 44 Review Important motor areas of cerebral cortex Precentral gyrus (Primary motor area) Broca s area Frontal eye field Important sensory areas of cerebral cortex Postcentral gyrus (Primary cutaneous sensory) Visual area (occipital lobe) Auditory area (temporal lobe) 45 14

15 Review Table from: Hole s Human A&P, 12 th edition, The Cranial Nerves Numeral Name Function Sensory, Motor, or Both (Mixed Nerve) I OLFACTORY (OLD) OLFACTION/SMELL SENSORY (SOME) II OPTIC (OPIE) VISION SENSORY (SAY) III OCULOMOTOR (OCCASIONALLY) MOVE EYE MOTOR (MARRY) IV TROCHLEAR (TRIES) MOVE EYE MOTOR (MONEY) V TRIGEMINAL (TRIGONOMETRY) CHEWING, MASTICATION AND BOTH (BUT) SENSORY FROM FACE VI ABDUCENS (AND) MOVE EYE MOTOR (MY) VII FACIAL (FEELS) FACIAL EXPRESSION BOTH (BROTHER) VIII VESTIBULOCOCHLEAR (VERY) HEARING AND EQUILIBRIUM SENSORY (SAYS) IX GLOSSOPHARYNGEAL (GLOOMY) MOVE MUSCLES OF TONGUE AND PHARYNX X VAGUS (VAGUE) INNERVATE VISCERAL SMOOTH MUSCLE BOTH (BIG) BOTH (BOOBS) XI ACCESSORY (AND) MOVE NECK MUSCLES MOTOR (MATTER) XII HYPOGLOSSAL (HYPOACTIVE) MOVE TONGUE MOTOR (MOST) 47 15