Nervous System 2 Unit 4 Lecture 10 PDF

NERVOUS SYSTEM 2 UNIT 4. LECTURE 10 DR. M. BLAIR-THOMAS NOVEMBER 2024  OVERVIEW: THIS LECTURE BASIC PATTERN OF CNS (RECALL EMBRYOLOGY FROM LAST LECTURE) BRAIN SPINAL CORD DERMATOME MAP CERVICAL PLEXUS BRACHIAL P...

NERVOUS SYSTEM 2 UNIT 4. LECTURE 10 DR. M. BLAIR-THOMAS NOVEMBER 2024  OVERVIEW: THIS LECTURE BASIC PATTERN OF CNS (RECALL EMBRYOLOGY FROM LAST LECTURE) BRAIN SPINAL CORD DERMATOME MAP CERVICAL PLEXUS BRACHIAL PLEXUS INJURIES TO CERVICAL CORD LUMBOSACRAL PLEXUS AUTONOMIC NERVOUS SYSTEM CRANIAL NERVES BASIC PATTERN OF THE CENTRAL NERVOUS SYSTEM Figure 12.5  CENTRAL NERVOUS SYSTEM MAIN ORGANS OF CNS - BRAIN AND THE SPINAL CORD BRAIN – 4 MAIN REGIONS: CEREBRUM, DIENCEPHALON (FOREBRAIN); BRAIN STEM, CEREBELLUM CONSCIOUS EXPERIENCES & REGULATION OF HOMEOSTASIS SPINAL CORD - SINGLE STRUCTURE COORDINATION OF REFLEXES (INTEGRATION OF SENSORY AND MOTOR PATHWAYS)  BRAIN FOREBRAIN – CEREBRUM – DIENCEPHALON BRAINSTEM – MIDBRAIN – PONS – MEDULLA OBLONGATA CEREBELLUM  FOREBRAIN TWO REGIONS CEREBRUM DIENCEPHALON CEREBRUM – DEVELOPS FROM ANT PORTION OF FOREBRAIN MAKES UP MOST OF MASS OF BRAIN MOST OBVIOUS ASPECT IS FOLDED/WRINKLED OUTER SURFACE/GRAY MATTER CALLED CEREBRAL CORTEX (2-5MM THICK, & CONTAINS ~75% OF NEURAL CELL BODIES IN NS) BENEATH CORTEX IS WHITE MATTER (BULK OF CEREBRUM; CONTAINS BUNDLES OF MYELINATED NERVE FIBERS LONGITUDINAL FISSURE – SEPARATES CEREBRUM INTO HALVES (RIGHT AND LEFT CEREBRAL HEMISPHERES) CORPUS CALLOSUM - WHITE MATTER OF CEREBRUM THAT PROVIDES MAJOR PATHWAY FOR COMMUNICATION BETWEEN THE TWO HEMISPHERES OF CEREBRAL CORTEX.  CEREBRAL CORTEX: GYRI, SULCI, FISSURES & LOBES GYRUS (PL= GYRI) IS RIDGE/CONVOLUTIONS SULCUS (PL = SULCI) IS SHALLOW-DEEP GROOVE BETWEEN TWO GYRI FISSURE – VERY DEEP GROOVE LOBES FRONTAL LOBE (ANT PORTION BORDERED POSTERIORLY BY CENTRAL SULCUS (FISSURE OF ROLANDO), LATERALLY BY LATERAL SULCUS (SYLVIAN FISSURE) PARIETAL LOBE- POSTERIOR TO SEPARATED FR FRONTAL BY CENTRAL SULCUS TEMPORAL LOBE: INFERIOR TO AND SEPARATED FR FRONTAL AND PARIETAL BY LATERAL SULCUS OCCIPITAL LOBE: SEPARATED FR CEREBELLUM BY TENTORIUM CEREBELLI INSULA (ISLAND OF REIL) LOCATED DEEP TO LATERAL FISSURE  CEREBRAL FUNCTIONS - HIGHER NEUROLOGICAL FUNCTIONS, SUCH AS MEMORY, EMOTION, AND CONSCIOUSNESS CEREBRUM COMPRISES: OUTER GRAY MATTER – CORTEX DEEP NUCLEI – 3 IMP FUNCTIONAL GROUPS: BASAL NUCLEI - RESPONSIBLE FOR COGNITIVE PROCESSING, THE MOST IMPORTANT FUNCTION BEING THAT ASSOCIATED WITH PLANNING MOVEMENTS. BASAL FOREBRAIN CONTAINS NUCLEI THAT ARE IMPORTANT IN LEARNING AND MEMORY. LIMBIC CORTEX IS PART OF THE LIMBIC SYSTEM, A COLLECTION OF STRUCTURES INVOLVED IN EMOTION, MEMORY, AND BEHAVIOUR.  CEREBRAL CORTEX: FUNCTIONS LOCALIZATION FUNCTION BRODMANN’S AREAS - DESCRIPTION OF ANATOMICAL DISTINCTIONS WITHIN THE CORTEX EXAMPLES FRONTAL LOBE - VOLUNTARY MOVEMENT, EXPRESSIVE LANGUAGE AND FOR MANAGING HIGHER LEVEL EXECUTIVE FUNCTIONS AREAS 17 &18 IN OCCIPITAL LOBE: PRIMARY VISUAL PERCEPTION/PROCESSING AREAS 41&42 TEMPORAL LOBE: PRIMARY AUDITORY SENSATION; TEMPORAL LOBE PART OF LIMBIC SYSTEM (MEMORY IS IMP FUNCTION) PARIETAL LOBE IS SOMATOSENSORY SENSATION/SENSORY PERCEPTION AND INTEGRATION, INCLUDING THE MANAGEMENT OF TASTE, HEARING, SIGHT, TOUCH, SMELL, PRESSURE, PAIN, TEMPERATURE, VIBRATION, AND POSITION.  FUNCTIONS OF CEREBRUM MOTOR, SENSORY, ASSOCIATION MOTOR AREAS PRIMARY MOTOR AREAS – FRONTAL LOBE CONTAINS MANY PYRAMIDAL CELLS IMPULSE FR CELLS ---THRU BRAIN STEM…..TO SPINAL CORD ON CORTICOSPINAL TRACTS: CROSS OVER FR ONE SIDE OF BRAIN TO OTHER SIDE AND DESCEND AS LATERAL CORTIOSPINAL TRACTS. WITHIN SPINAL CORD CORTICOSPINAL FIBERS SYNAPSE WITH MOTOR NEURONS IN GRAY MATTER OF ANTERIOR HORNS AXONS OF MOTOR NEURONS LEAD THRU PERIPHERAL NERVES TO VOLUNTARY MUSCLES RETICULOSPINAL AND RUBROSPINAL TRACTS CONTROL MOTOR FUNCTIONS THAT MAINTAIN BALANCE AND POSTURE BROCA’S AREA IN LEFT CEREBRAL HEMISPHERE COORDINATES MUSCULAR ACTIONS OF MOUTH, TONGUE & LARYNX AND MAKES SPEECH POSSIBLE FRONTAL EYE FIELD (ABOVE BROCA’S AREA) CONTROLS MOVEMENTS OF EYES AND EYELIDS NEARBY (FRONTAL EYE FIELD) – MOVEMENTS OF HEAD THAT DIRECT EYES WERNICKE'S AREA IS THE LANGUAGE AREA (RESPONSIBLE FOR COMPREHENDING SPOKEN WORD & FORMULATING WRITTEN AND SPOKEN LANGUAGE. A PERSON WITH DAMAGE TO THIS AREA COULD DEVELOP SPEECH THAT IS INCOMPREHENSIBLE.  SENSORY AREAS INTERPRET IMPULSES FROM SENSORY RECEPTORS, PRODUCING FEELINGS OR SENSATIONS SENSATION OF TEMPERATURE, TOUCH, PRESSURE & PAIN IN SKIN – ANTERIOR PORTION OF PARIETAL LOBE VISION – POSTERIOR PART OF OCCIPITAL LOBES HEARING – SUPERIOR POSTERIOR PORTIONS OF TEMPORAL LOBE TASTE – NEAR BASES OF CENTRAL SULCI ALONG LATERAL SULCI SMELL – ARISE FROM CENTERS DEEP WITHIN CEREBRUM **SENSORY FIBERS CROSS OVER IN SPINAL CORD OR BRAIN STEM, THEREFORE CENTERS IN RT HEMISPHERE INTERPRET IMPULSES FR LEFT SIDE OF BODY ETC BUT SENSORY AREAS FOR VISION RECEIVE IMPULSES FR BOTH EYES & AREAS CONCERNED WITH HEARING RECEIVE IMPULSES FR BOTH EARS  ASSOCIATION AREAS NOT PRIMARILY SENSORY OR MOTOR & INTERCONNECT WITH EACH OTHER & OTHER BRAIN STRUCTURES OCCUPY ANTERIOR PORTION OF FRONTAL LOBES AND LATERAL PORTIONS OF PARIETAL, TEMPORAL AND OCCIPITAL LOBES THEY ANALYZE AND INTERPRET SENSORY EXPERIENCES AND HELP PROVIDE MEMORY, REASONING, VERBALIZING, JUDGEMENT AND EMOTIONS  CEREBRAL CORTEX – FUNCTIONAL AREAS SENSORIMOTOR CORTEX = ALL OF THE PARTS OF THE CEREBRAL CORTEX THAT ACT TOGETHER IN THE CONTROL OF MUSCLE MOVEMENT PRIMARY MOTOR CORTEX PREMOTOR AREA SUPPLEMENTARY MOTOR CORTEX PARIETAL-LOBE ASSOCIATION CORTEX SOMATOSENSORY CORTEX FUNCTIONAL AREAS: LEFT CEREBRAL CORTEX Figure 12.8a PRIMARY MOTOR CORTEX Figure 12.9.1  SENSORIMOTOR CORTEX PREMOTOR CORTEX – THE PART OF THE BRAIN RESPONSIBLE FOR PLANNING, SELECTION AND EXECUTION OF ACTIONS SUPPLEMENTARY MOTOR CORTEX – RESPONSIBLE FOR PLANNING AND COORDINATION OF COMPLEX MOVEMENTS PARIETAL-LOBE ASSOCIATION CORTEX – RESPONSIBLE FOR TRANSFORMING VISUAL INFORMATION TO MOTOR COMMANDS  SOMATOSENSORY CORTEX Somatosensory - “Relating to or denoting a sensation (such as pressure, pain, or warmth) which can occur anywhere in the body, in contrast to one localized at a sense organ (such as sight, balance, or taste)” Somatosensory function is the ability to interpret bodily sensation. Sensation takes a number of forms, including touch, pressure, vibration, temperature, itch, tickle, and pain. Somatosensory cortex (located on the postcentral gyrus of the parietal lobe) (See Lect Notes): Receives tactile information from the body, incld sensations above... The sensory homunculus is a map along the cerebral cortex where each part of the body is processed The primary motor cortex (located in the precentral gyrus), handles signals coming from the premotor area of the frontal lobes. The motor homunculus represents a map of brain areas dedicated to motor processing for different anatomical divisions of the body. Watch (Cortical Homunculus): https://youtu.be/tYf4_E7fCRw SOMATOSENSORY CORTEX  HEMISPHERE DOMINANCE & MEMORY BOTH CEREBRAL HEMISPHERES PARTICIPATE IN BASIC FUNCTIONS, BUT IN MOST PERSONS ONE SIDE ACTS AS A DOMINANT HEMISPHERE FOR CERTAIN FUNCTIONS IN 90% OF PEOPLE: LEFT HEMISPHERE DOMINANT FOR LANGUAGE-RELATED ACTIVITIES OF SPEECH, WRITING AND READING AS WELL AS INTELLECTUAL FXNS REQUIRING VERBAL, ANALYTICAL & COMPUTATIONAL SKILLS IN SOME, THE RT HEMISPHERE IS DOMINANT WHILE IN OTHERS, THE HEMISPHERES ARE EQUALLY DOMINANT NON-DOMINANT HEMISPHERE – SPECIALIZES IN NONVERBAL FUNCTIONS S.A. MOTOR TASKS FOR ORIENTATION OF THE BODY IN SPACE, UNDERSTANDING MUSICAL PATTERNS ETC/EMOTIONAL AND INTUITIVE THOUGHT PROCESSES MEMORY LEARNING IS THE ACQUISITION OF NEW KNOWLEDGE MEMORY IS THE PERSISTENCE OF LEARNING SHORT TERM VS LONG TERM MEMORY SHORT TERM IS ELECTRICAL IN NATURE LONG TERM MEMORY CHANGES THE STRUCTURE OR FXN OF NEURONS TO ENHANCE SYNAPTIC TRANSMISSION, BY ESTABLISHING PATTERNS OF SYNAPTIC TRANSMISSIONS ONE THEORY: LONG TERM SYNAPTIC POTENTIATION OCCURS PRIMARILY IN AREA OF CEREBRAL CORTEX CALLED HIPPOCAMPUS  DIENCEPHALON THREE MAJOR PARTS THALAMUS HYPOTHALAMUS EPITHALAMUS  LIMBIC SYSTEM STRUCTURES LOCATED ON THE MEDIAL ASPECTS OF CEREBRAL HEMISPHERES AND DIENCEPHALON INCLUDES THE RHINENCEPHALON, AMYGDALA, HYPOTHALAMUS, HIPPOCAMPUS, CINGULATE GYRUS, AND ANTERIOR NUCLEUS OF THE THALAMUS HYPOCAMPAL STRUCTURES PARTS ESPECIALLY IMPORTANT IN EMOTIONS: AMYGDALA CINGULATE GYRUS BRAIN STEM Figure 12.15  MIDBRAIN LOCATED BETWEEN THE DIENCEPHALON AND THE PONS MIDBRAIN STRUCTURES INCLUDE: CEREBRAL PEDUNCLES CEREBRAL AQUEDUCT VARIOUS NUCLEI  MIDBRAIN NUCLEI NUCLEI THAT CONTROL CRANIAL NERVES III (OCULOMOTOR) AND IV (TROCHLEAR) CORPORA QUADRIGEMINA SUPERIOR COLLICULI INFERIOR COLLICULI SUBSTANTIA NIGRA RED NUCLEUS – LARGEST NUCLEUS OF THE RETICULAR FORMATION  PONS BULGING BRAINSTEM REGION BETWEEN THE MIDBRAIN AND THE MEDULLA OBLONGATA FORMS PART OF THE ANTERIOR WALL OF THE FOURTH VENTRICLE FIBERS OF THE PONS: CONNECT HIGHER BRAIN CENTERS AND THE SPINAL CORD RELAY IMPULSES BETWEEN THE MOTOR CORTEX AND THE CEREBELLUM ORIGIN OF CRANIAL NERVES V (TRIGEMINAL), VI (ABDUCENS), AND VII (FACIAL) CONTAINS NUCLEI OF THE RETICULAR FORMATION  RETICULAR FORMATION RAS – reticular activating system Sends impulses to the cerebral cortex to keep it conscious and alert Filters out repetitive and weak stimuli - Motor function - Helps control coarse motor movements - Autonomic centers regulate visceral motor functions Figure 12.19  MEDULLA OBLONGATA MOST INFERIOR PART OF THE BRAIN STEM CONTAINS A CHOROID PLEXUS ON THE VENTRAL WALL OF THE FOURTH VENTRICLE PYRAMIDS – TWO LONGITUDINAL RIDGES FORMED BY CORTICOSPINAL TRACTS  MEDULLA NUCLEI INFERIOR OLIVARY NUCLEI – GRAY MATTER THAT RELAYS SENSORY INFORMATION CRANIAL NERVES X, XI, AND XII ARE ASSOCIATED WITH THE MEDULLA VESTIBULAR NUCLEAR COMPLEX CARDIOVASCULAR CONTROL CENTER – ADJUSTS FORCE AND RATE OF HEART CONTRACTION RESPIRATORY CENTERS – CONTROL RATE AND DEPTH OF BREATHING  CEREBELLUM PROPRIOCEPTORS AND VISUAL SIGNALS “INFORM” THE CEREBELLUM OF THE BODY’S CONDITION CEREBELLUM IS PRIMARILY RESPONSIBLE FOR MUSCLE CONTROL, INCLUDING BALANCE AND MOVEMENT. CEREBELLAR CORTEX CALCULATES THE BEST WAY TO PERFORM A MOVEMENT PLAYS A ROLE IN LANGUAGE AND PROBLEM SOLVING RECOGNIZES AND PREDICTS SEQUENCES OF EVENTS  VENTRICLES OF THE BRAIN - Network of fluid-filled cavities located in the brain's core & responsible for circulating and absorbing cerebrospinal fluid (CSF) - 4 ventricles - 2 lateral ventricles (in each cerebral hemisphere) - 3rd ventricle (in diencephalon) - 4th ventricle (in pons and medulla) The choroid plexus, which is located in the ventricles, produces CSF CSF flows from the ventricles into the subarachnoid space Figure 12.6  CHOROID PLEXUSES A PLEXUS OF CELLS/SECRETORY TISSUE RESPONSIBLE FOR PRODUCING CEREBROSPINAL FLUID (CSF) IN BRAIN A NETWORK OF CAPILLARIES AND SPECIALIZED EPENDYMAL CELLS THAT FORM TISSUE FLUID FILTERS HANG FROM THE ROOF OF EACH VENTRICLE HAVE ION PUMPS THAT ALLOW THEM TO ALTER ION CONCENTRATIONS OF THE CSF HELP CLEANSE CSF BY REMOVING WASTES  CEREBROSPINAL FLUID (CSF) CSF FORMED BY THE CHOROID PLEXUS IN THE LATERAL, 3RD & 4TH VENTRICLES CSF FLOWS FROM THE LATERAL TO THE THIRD VENTRICLE VIA THE INTERVENTRICULAR FORAMINA (ALSO KNOWN AS THE FORAMEN OF MONRO), AND THEN THROUGH THE CEREBRAL AQUEDUCT TO THE FOURTH VENTRICLE AIDED BY CIRCULATORY, RESPIRATORY AND POSTURAL CHANGES BARRIER BETWEEN THE BLOOD IN THE CAPILLARIES OF THE CHOROIDS PLEXUS WATERY SOLUTION SIMILAR IN COMPOSITION TO BLOOD PLASMA CONTAINS LESS PROTEIN AND DIFFERENT ION CONCENTRATIONS THAN PLASMA FORMS A LIQUID CUSHION THAT GIVES BUOYANCY TO THE CNS ORGANS  HYDROCEPHALUS A CONDITION IN WHICH EXCESS CEREBROSPINAL FLUID (CSF) BUILDS UP WITHIN THE FLUID- CONTAINING CAVITIES OR VENTRICLES OF THE BRAIN. THE EXCESS FLUID INCREASES THE SIZE OF THE VENTRICLES AND PUTS PRESSURE ON THE BRAIN. * Inflammation in the ventricles can occur due to infection, head trauma, or bleeding in the brain. This inflammation can block CSF flow, causing the ventricles to swell and putting pressure on the brain.  PROTECTION OF THE BRAIN THE BRAIN IS PROTECTED BY BONE, MENINGES, AND CEREBROSPINAL FLUID HARMFUL SUBSTANCES ARE SHIELDED FROM THE BRAIN BY THE BLOOD- BRAIN BARRIER  MENINGES 3 CONNECTIVE TISSUE MEMBRANES THAT LIE EXTERNAL TO THE CNS – DURA MATER, ARACHNOID MATER, AND PIA MATER FUNCTIONS OF THE MENINGES INCLUDE: COVER PROTECT CONTAIN FORM  DURA MATER LEATHERY, STRONG MENINX COMPOSED OF TWO FIBROUS CONNECTIVE TISSUE LAYERS THE TWO LAYERS SEPARATE IN CERTAIN AREAS AND FORM DURAL SINUSES THREE DURAL SEPTA EXTEND INWARD AND LIMIT EXCESSIVE MOVEMENT OF THE BRAIN FALX CEREBRI FALX CEREBELLI TENTORIUM CEREBELLI  THE FALX CEREBRI IS A STRONG CRESCENT-SHAPED SHEET THAT REPRESENTS AN INVAGINATION OF THE MENINGEAL LAYER OF THE DURA MATER INTO THE LONGITUDINAL FISSURE, FOUND BETWEEN THE MEDIAL SURFACES OF THE CEREBRAL HEMISPHERES THE FALX CEREBELLI IS A SMALL SICKLE SHAPED FOLD OF DURA MATER, PROJECTING FORWARDS INTO THE POSTERIOR CEREBELLAR NOTCH AS WELL AS PROJECTING INTO THE VALLECULA OF THE CEREBELLUM BETWEEN THE TWO CEREBELLAR HEMISPHERES.. THE TENTORIUM CEREBELLI (LATIN FOR "TENT OF THE CEREBELLUM") IS AN INVAGINATION OF THE MENINGEAL LAYER OF THE DURA MATER THAT SEPARATES THE OCCIPITAL AND TEMPORAL LOBES OF THE CEREBRAL HEMISPHERES FROM THE CEREBELLUM AND BRAINSTEM.  ARACHNOID MATER THE MIDDLE MENINX, WHICH FORMS A LOOSE BRAIN COVERING IT IS SEPARATED FROM THE DURA MATER BY THE SUBDURAL SPACE  PIA MATER DEEP MENINX COMPOSED OF DELICATE CONNECTIVE TISSUE THAT CLINGS TIGHTLY TO THE BRAIN  LUMBAR PUNCTURE A LUMBAR PUNCTURE (LP) OR SPINAL TAP MAY BE DONE TO DIAGNOSE OR TREAT CONDITIONS INCLUDING MENINGITIS, SUBARACHNOID HEMORRHAGE, AND NEUROLOGICAL DISORDERS. IT CAN ALSO BE USED TO MEASURE INTRACRANIAL PRESSURE OR ADMINISTER MEDICATIONS A HOLLOW NEEDLE INTO THE SPACE SURROUNDING THE SPINAL COLUMN (SUBARACHNOID SPACE) IN THE LOWER BACK TO WITHDRAW SOME CEREBROSPINAL FLUID (CSF) OR INJECT MEDICINE. USED TO DIAGNOSE OR TREAT A NUMBER OF CONDITIONS, INCLUDING MENINGITIS, SUBARACHNOID HEMORRHAGE, AND NEUROLOGICAL DISORDERS. IT CAN ALSO BE USED TO MEASURE INTRACRANIAL PRESSURE OR ADMINISTER MEDICATIONS  BLOOD SUPPLY ADULT BRAIN MAKES UP ONLY 2% OF THE BODY WEIGHT, IT RECEIVES 12 – 15% OF THE TOTAL BLOOD SUPPLY GLUCOSE IS THE ONLY ENERGY SOURCE THAT THE BRAIN USES FOR ENERGY PRODUCTION (UNDER NORMAL CIRCUMSTANCES) BRAIN’S GLYCOGEN STORES ARE MINIMAL SO DEPENDENT ON A CONTINUOUS BLOOD SUPPLY FOR OXYGEN AND SUGAR DEPRIVATION OF EITHER OXYGEN OR GLUCOSE CAN LEAD TO BRAIN DEATH  BLOOD-BRAIN BARRIER PROTECTIVE MECHANISM THAT HELPS MAINTAIN A STABLE ENVIRONMENT FOR THE BRAIN BLOOD-BORNE SUBSTANCES ARE SEPARATED FROM NEURONS BY: CONTINUOUS ENDOTHELIUM OF CAPILLARY WALLS RELATIVELY THICK BASAL LAMINA BULBOUS FEET OF ASTROCYTES  BLOOD-BRAIN BARRIER: FUNCTIONS THE BLOOD–BRAIN BARRIER IS A HIGHLY SELECTIVE SEMIPERMEABLE BORDER OF ENDOTHELIAL CELLS THAT PREVENTS SOLUTES IN THE CIRCULATING BLOOD FROM NON-SELECTIVELY CROSSING INTO THE EXTRACELLULAR FLUID OF THE CENTRAL NERVOUS SYSTEM WHERE NEURONS RESIDE PROTECTS AGAINST CIRCULATING TOXINS OR PATHOGENS THAT COULD CAUSE BRAIN INFECTIONS, WHILE AT THE SAME TIME ALLOWING VITAL NUTRIENTS TO REACH THE BRAIN ALL AREAS DO NOT HAVE A BBB E.G. PITUITARY & PINEAL GLAND RESPONDS TO STRESS REDUCE THE IMMUNE SYSTEMS ACCESS TO THE BRAIN SUBSTANCES WITH HIGH LIPID SOLUBILITY MAY MOVE ACROSS THE BBB BY SIMPLE DIFFUSION WATER. WATER READILY ENTERS THE BRAIN. GASES. GASES SUCH AS CO2, O2 AND VOLATILE ANESTHETICS DIFFUSE RAPIDLY INTO THE BRAIN. CARRIER-MEDIATED TRANSPORT ENABLES MOLECULES WITH LOW LIPID SOLUBILITY TO TRAVERSE THE BLOOD-BRAIN BARRIER E.G. GLUCOSE & AMINO ACIDS PHYSIOLOGICAL TRANSPORT SYSTEMS - ACCOUNTS FOR SOME DRUG ACTIONS MORPHINE VS. HEROIN MANY SUBSTANCES ARE NOT LIPID SOLUBLE GLUCOSE AND OTHER IMPORTANT BRAIN SUBSTRATES  SPINAL CORD SPINAL CORD AND SPINAL NERVES SERVE 2 IMP FUNCTIONS: A PATHWAY Dorsal horn FOR SENSORY AND MOTOR receives sensory IMPULSES AND RESPONSIBLE FOR IMPULSES input from peripheral neurons FUNCTIONAL AREAS DORSAL ROOT The ventral horn VENTRAL ROOT largely contains motor neurons that SPINAL TRACTS exit the spinal cord ASCENDING TRACTS to innervate DORSAL skeletal muscle. COLUMN TRACT ANTEROLATERAL SYSTEM DESCENDING TRACTS CORTICOSPINAL TRACT  SPINAL NERVES 31 PAIRS OF SPINAL NERVES ORIGINATING FR SPINAL CORD; MIXED NERVES AND PROVIDE COMMUN. BET SP CORD & UPPER & LOWER LIMBS, NECK &TRUNK GROUP ACCORDING TO THE LEVEL FR WHICH THEY ARISE AND NUMBERED IN SEQUENCE 8 CERVICAL (C1-C8) 12 THORACIC (T1-T12) 5 LUMBAR (L1-L5) 5 SACRAL (S1-S5) 1 COCCYGEAL (C0) CAUDA EQUINA – ROOTS OF LUMBAR AND SACRAL SPINAL NERVES FORMING A BUNDLE WITHIN LOWEST PT OF SPINAL COLUMN Figure 13.5 Spinal cord ends at L1–L2 vertebrae. Conus medullaris - tapered end of the spinal cord (Regulates bladder function and lower extremity movement and sensation etc.) Cauda equina – bundle of nerves extending beyond spinal cord(carries motor and sensory nerve impulses to and from the legs). Filum terminale - a fibrous band that extends from the spinal cord to the coccyx (stabilizes and protects the distal spinal cord from normal and abnormal forces )  SPINAL NERVES EACH SPINAL NERVE CONNECTS TO THE SPINAL CORD BY A DORSAL ROOT AND VENTRAL ROOT SPINAL NERVES ARE SHORT BECAUSE AFTER EMERGING IT DIVIDES IN THREE PARTS DORSAL RAMUS VENTRAL RAMUS MENINGEAL BRANCH – REENTERS THE SPINAL CORD TO INNERVATE THE MENINGES AND THE BLOOD VESSELS IN THE CNS  INNERVATION OF SPECIFIC BODY REGIONS THE SPINAL NERVE RAMI AND THEIR MAIN BRANCHES SUPPLY THE ENTIRE SOMATIC REGION OF THE BODY FROM THE NECK DOWN DORSAL RAMI SUPPLY THE POSTERIOR BODY TRUNK VENTRAL RAMI SUPPLY THE REST OF THE TRUNK AND LIMBS  CERVICAL PLEXUS LIE DEEP IN THE NECK ON EITHER SIDE FORMED BY THE VENTRAL RAMI OF THE FIRST FOUR CERVICAL NERVES FIBERS FR CERVICAL PLEXUS SUPPLY THE MUSCLES AND SKIN IN THE NECK MOST BRANCHES ARE CUTANEOUS NERVES FIBERS FR THE 3RD, 4TH AND 5TH CERVICAL NERVES PASS INTO RT AND LEFT PHRENIC NERVES WHICH CONDUCT MOTOR IMPULSES TO DIAPHRAGM Figure 13.7  CERVICAL PLEXUS BRANCHES ALSO INNERVATE THE MUSCLES OF THE ANTERIOR NECK PHRENIC NERVE – DIAPHRAGM - HICCUPS Figure 13.7  BRACHIAL PLEXUS GIVES RISE TO ALMOST ALL THE NERVES THAT INNERVATE THE UPPER LIMB PLEXUS FORMED FROM INTERMIXING OF VENTRAL RAMI FROM C5-C8 (LOWER 4 CERVICAL NERVES) AND MOST OF THE T1 RAMUS THE NETWORK IS LOCATED DEEP WITHIN THE SHOULDERS BETWEEN THE NECK AND THE AXILLAE INJURIES ARE COMMON WHEN THE UPPER LIMB IS PULLED HARD OR RECEIVES A BLOW TO THE TOP OF THE SHOULDER  BRACHIAL PLEXUS THE MAJOR BRANCHES EMERGING FROM THE BRACHIAL PLEXUS INCLUDE: MUSCULOTANEOUS NERVES – TRAVELS INFERIORLY IN THE ANTERIOR ARM AND SUPPLY MUSCLES ON THE ANTERIOR SIDES AND THE SKIN OF THE FOREARM AXILLARY NERVES – RUNS POSTERIOR TO THE SURGICAL NECK OF THE HUMERUS; SUPPLY MUSCLES AND SKIN OF THE SUPERIOR, LATERAL AND POSTERIOR REGIONS OF THE ARM MEDIAN NERVES – SUPPLY MUSCLES OF THE FOREARMS AND MUSCLES AND SKIN OF HANDS ULNAR NERVES – SUPPLY MUSCLES OF THE FOREARMS AND HANDS AND SKIN OF HANDS RADIAL NERVES- SUPPLY MUSCLES OF ARMS ON THE POSTERIOR SIDES AND SKIN OF FOREARMS AND HANDS BRACHIAL PLEXUS: DISTRIBUTION OF NERVES Median nerves – supply muscles of the forearms and muscles and skin of hands Ulnar nerves – supply muscles of the forearms and hands and skin of hands Figure 13.8c  BRACHIAL PLEXUS: DISTRIBUTION OF NERVES Other nerves associated with the brachial plexus include: Lateral and medial pectoral nerves Dorsal scapular nerves Lower subscapular nerves Thoracodorsal nerves Subscapular nerve Figure 13.8c  LUMBAR PLEXUS ARISES FROM L1-L4 AND INNERVATES THE THIGH, ABDOMINAL WALL, AND PSOAS MUSCLE THE MAJOR NERVES ARE THE FEMORAL AND THE OBTURATOR NERVE FEMORAL NERVE – DIVIDES INTO MANY BRANCHES; SUPPLY MUSCLES OF THIGH AND LEG OBTURATOR NERVE – SUPPLY ADDUCTOR MUSCLES OF THIGH Figure 13.9 LUMBAR PLEXUS Figure 13.9  SACRAL PLEXUS ARISES FROM SPINAL NERVES L4-S4 HAS NERVES THAT SERVE THE BUTTOCK AND LOWER LIMB SCIATIC NERVE LARGEST AND LONGEST NERVES IN THE BODY PASS DOWNWARD INTO BUTTOCKS AND DESCEND TO THIGH, WHERE DIVIDE INTO TIBIAL AND COMMON PERONEAL NERVES SCIATICA SACRAL PLEXUS Figure 13.10  SKIN INNERVATION - DERMATOMES DERMATOMES A DERMATOME IS AN AREA OF SKIN SUPPLIED BY SENSORY NERVE FIBERS OF A PARTICULAR SPINAL NERVE EVERY SPINAL NERVE EXCEPT C1 INNERVATES DERMATOMES SOME OVERLAP BETWEEN INNERVATION REGIONS DERMATOMES ARE HIGHLY ORGANIZED BUT VARY IN SIZE AND SHAPE A MAP OF DERMATOMES IS USEFUL IN LOCALIZING THE SITES OF INJURIES TO DORSAL ROOTS OF THE SPINAL CORD THE SHAPE AND LOCATION OF KEY SENSORY DERMATOMES ARE AS FOLLOWS: C1 – NO SENSORY DERMATOME C2 – SKULL CAP C3- A HIGH COLLAR (TURTLE-NECK SWEATER) C4 - CAPE AROUND SHOULDER C5-T1 – UPPER EXTREMETIES T5- NIPPLE T10-BELLY BUTTON L1-INGUINAL LIGAMENT L4-KNEE; BIG TOE L5-3 MIDDLE FINGERS S1-ANKLE JERK REFEX S1-S2 REAR OF LOWER EXTREMITY S2-S5: GENITAL TO ANAL AREAS Figure 13.11  REFLEXES A REFLEX IS A RAPID, PREDICTABLE MOTOR RESPONSE TO A STIMULUS REFLEXES MAY: – BE INBORN OR LEARNED (ACQUIRED) – INVOLVE ONLY PERIPHERAL NERVES AND THE SPINAL CORD – INVOLVE HIGHER BRAIN CENTERS AS WELL  REFLEX ARC NEURAL PATHWAY OF THE REFLEX THERE ARE 5 COMPONENTS OF A REFLEX ARC RECEPTOR SENSORY NEURON (TO DORSAL HORN) INTEGRATION CENTER MOTOR NEURON (IN VENTRAL HORN) EFFECTOR  REFLEX CLASSIFICATION CLASSIFIED FUNCTIONALLY SOMATIC REFLEXES (INVOLUNTARY RESPONSE TO A STIMULUS, E.G.PULLING ONE’S HAND AWAY AFTER TOUCHING A HOT SURFACE) AUTONOMIC REFLEXES (UNCONSCIOUS MOTOR REFLEXES FROM ORGANS AND GLANDS)  REFLEXES IN ADULT HUMANS MAMMALIAN DIVING REFLEX ACCOMMODATION REFLEX PATELLAR REFLEX (KNEE-JERK REFLEX) ACHILLES REFLEX PHOTIC SNEEZE REFLEX BICEPS STRETCH REFLEX PLANTAR REFLEX (BABINSKI REFLEX) BRACHIORADIALIS REFLEX PUPILLARY REFLEX CORNEAL REFLEX (ALSO KNOWN AS THE BLINK REFLEX) QUADRICEPS REFLEX GAG REFLEX SALIVATION SCRATCH REFLEX SNEEZE TENDON REFLEX TRICEPS STRETCH REFLEX VESTIBULO-OCULAR REFLEX WITHDRAWAL REFLEX YAWN  MAMMALIAN DIVING REFLEX SUBMERGING THE FACE INTO WATER CAUSES THE MAMMALIAN DIVING REFLEX INCLUDES THREE FACTORS: BRADYCARDIA (SLOW HEART RATE) PERIPHERAL VASOCONSTRICTION BLOOD SHIFT WHEN THE FACE IS SUBMERGED, RECEPTORS THAT ARE SENSITIVE TO WATER WITHIN THE NASAL CAVITY AND OTHER AREAS OF THE FACE SUPPLIED BY CRANIAL NERVE V (TRIGEMINAL) RELAYS THE INFORMATION TO THE BRAIN AND THEN INNERVATES CRANIAL NERVE X (VAGUS).  PHOTIC SNEEZE REFLEX A MEDICAL CONDITION BY WHICH PEOPLE EXPOSED TO BRIGHT LIGHT SNEEZE. OCCURS IN 17% TO 25% OF HUMANS THE PROBABLE CAUSE IS A CONGENITAL MALFUNCTION IN NERVE SIGNALS IN THE TRIGEMINAL NERVE NUCLEUS. OVERSTIMULATION OF THE OPTIC NERVE TRIGGERS THE TRIGEMINAL NERVE, AND THIS CAUSES THE PHOTIC SNEEZE REFLEX.  YAWN A REFLEX OF DEEP INHALATION AND EXHALATION ASSOCIATED WITH BEING TIRED, WITH A NEED TO SLEEP, OR FROM LACK OF STIMULATION. PANDICULATION (THE ACT OF STRETCHING AND YAWNING, ESPECIALLY WHEN WAKING UP OR FEELING DROWSY) IT IS CLAIMED TO HELP INCREASE THE STATE OF ALERTNESS OF A PERSON. IT COULD POSSIBLY BE FROM LACK OF OXYGEN. THE EXACT CAUSES OF YAWNING ARE STILL UNKNOWN. CNS DIORDERS & DISEASES  CEREBROVASCULAR ACCIDENTS (STROKES) CAUSED WHEN BLOOD CIRCULATION TO THE BRAIN IS BLOCKED AND BRAIN TISSUE DIES TRANSIENT ISCHEMIC ATTACKS (TIAS) – TEMPORARY EPISODES OF REVERSIBLE CEREBRAL ISCHEMIA (BLOOD FLOW HENCE OXYGEN IS RESTRICTED)  ALZHEIMERS DISEASE NEUROGENERATIVE DISEASE PROGRESSIVE LOSS OF HIGHER FUNCTION CAUSED BY NEURONAL LOSS AND ATROPHY  HUNTINGTONS DISEASE GENETIC DISORDER – HD GENE LOCATED ON CHROMOSOME 4 – EXTRA CAG REPEAT ON THE END OF THE GENE CAUSED BY DEGENERATION OF NEURONAL CELLS – FRONTAL LOBES – BASAL GANGLIA – CAUDATE NUCLEUS SYMPTOMS – JERKY. UNCOORDINATED MOVEMENTS WHICH BECOME PROGRESSIVELY WORSE – EXECUTIVE FUNCTION, ABSTRACT THINKING, SPEECH AND PERCEPTUAL AND SPATIAL FUNCTION ARE ALL AFFECTED  SPINAL CORD TRAUMA PARALYSIS – LOSS OF MOTOR FUNCTION FLACCID PARALYSIS – SEVERE DAMAGE TO THE VENTRAL ROOT OR ANTERIOR HORN CELLS SPASTIC PARALYSIS – ONLY UPPER MOTOR NEURONS OF THE PRIMARY MOTOR CORTEX ARE DAMAGED  SPINAL CORD TRAUMA: TRANSECTION CROSS SECTIONING OF THE SPINAL CORD AT ANY LEVEL RESULTS IN TOTAL MOTOR AND SENSORY LOSS IN REGIONS INFERIOR TO THE CUT PARAPLEGIA (LEGS AND LOWER BODY PARALYSIS) – TRANSECTION BETWEEN T1 AND L1 QUADRIPLEGIA(PARALYSIS AFFECTING LIMBS AND BODY FROM NECK DOWN) – TRANSECTION IN THE CERVICAL REGION  POLIOMYELITIS DESTRUCTION OF THE ANTERIOR HORN MOTOR NEURONS BY THE POLIOVIRUS EARLY SYMPTOMS – FEVER, HEADACHE, MUSCLE PAIN AND WEAKNESS, AND LOSS OF SOMATIC REFLEXES  AMYOTROPHIC LATERAL SCLEROSIS (ALS) LOU GEHRIG’S DISEASE SYMPTOMS – LOSS OF THE ABILITY TO SPEAK, SWALLOW, AND BREATHE