ORGANIZATION OF THE NERVOUS SYSTEM

D. C. MikuleckyProfessor of Physiology

COMPUTERS VS BRAINS

FEATURE COMPUTERS BRAINARCHITECTURE von NEUMAN UNKNOWN, BUT

COMPLEXOPERATION SEQUENTIALLY PARALLEL &

SEQUENTIALTIME SCALE MICRO TO NANO

SECSEC TO MSEC

PROCESSORS 1 TO HUNDREDS 10-100 BILLION

INPUT/OUTPUT A FEW PORTS 5-10 MILLION

STATES WELL DEFINED ILL DEFINED(NOISENEEDED)

HABITUATION NONE FUNDAMENTALFEATURE

ORGANIZATION OF THE NERVOUS SYSTEM

BRAINSPINAL CORD

CENTRALNERVOUSSYSTEM (CNS)

PERIPHERALNERVOUS SYSTEM

AFFERENT

NERVES

EFFERENT

NERVES

EXTERO-RECEPTORS

INTERO-RECEPTORS

SOMATIC AUTONOMIC

EFFECTORORGANS

SKELETALMUSCLES

SMOOTH AND CARDIAC MUSCLES AND GLANDS

THE CENTRAL NERVOUS SYSTEM CONSISTS OF THE BRAIN AND SPINAL

CORDBRAINSTEM:MIDBRAINPONSMEDULLA

FOREBRAIN:CORTEXTHALAMUS AND HYPOTHALAMUSBASIL GANGLIA

SPINALCORD

MAJOR DIVISIONS OF THE CEREBRAL CORTEX

FRONTAL LOBEPARIETAL LOBE

OCCIPITAL LOBE

TEMPORAL LOBE

BRAIN VESSICLES

• FIRST AND SECOND (LATERAL):PRIMARY MOTOR AND SENSORY CORTEX,LIMBIC SYSTEM, BASAL GANGLIA

• THIRD:THALMUS AND HYPOTHALMUS

• FOURTH:CAUDAL BRAIN STEM AND CEREBELLUM

BRAIN VESSICLESFRONT SIDE

III

LV

III

IV

LV

IV

MAINTENANCE AND PROTECTION OF THE CNS

• Glial Cells: physical and metabolic support• Skull and Spinal Column• Cerebrospinal fluid• Blood-brain barrier

GLIAL CELLS OR NEUROGLIA:

• PHYSICAL AND METABOLIC SUPPORT

• 90% OF CELLS IN BRAIN• FOUR TYPES: ASTROCYTES,

OLIGODENDROCYTES, EPENDYMAL CELLS, AND MICROGLIA

Skull and Spinal Column

• PROVIDE MECHANICAL SUPPORT

• PROTECTS THE NEURAL AND SUPPORTING TISSUE

CEREBROSPINAL FLUID

• DENSITY IS THE SAME AS BRAIN

• SHOCK ABSORBER

Blood-brain barrier

• LIMITS ACCESS OF BLOOD MATERIALS TO BRAIN TISSUE

• PROTECTS BRAIN FROM FLUCTUATIONS IN BLOOD LEVELS

WHITE AND GRAY

• GRAY MATTER - MAINLY CELL BODIES

• WHITE MATTER - MYELINATED AXONS

BASAL GANGLIA

• PLAY A COMPLEX ROLE IN THE CONTROL OF MOVEMENT

• INHIBIT MUSCLE TONE THROUGHOUT BODY

• SUPPRESS USELESS OR UNWANTED PATTERNS OF MOVEMENT

THALAMUS

• RELAY STATION• HELP US DIRECT OUR ATTENTION• FILTERS OUT INSIGNIFICANT

SIGNALS

HYPOTHALAMUS

• REGULATES HOMEOSTATIC FUNCTIONS

• THIRST AND URINE OUTPUT• FOOD INTAKE• HORMONE SECRETION• BODY TEMPERATURE• AUTONOMIC NERVOUS SYSTEM’S

COORDINATING CENTER

LIMBIC SYSTEM

• AMYGDALA• HIPPOCAMPUS• CORPUS CALLOSUM• FORNIX• CINGULATE GYRUS

LIMBIC SYSTEM

• COMPLEX NETWORK OF FOREBRAIN STRUCTURES

• EMOTIONS• BASIC SURVIVAL• SOCIOSEXUAL BEHAVIOR• MOTIVATION• LEARNING

THE SPINAL CORD IN SOMATIC SENSORY FUNCTION

• WHITE AND GREY MATTER• SEGMENTAL ORGANIZATION

SPINAL CORDDORSAL HORN GRAY

MATTER

DORSAL

VENTRALSPINAL NERVE

DORSALROOTGANGLION

VENTRALHORN

WHITEMATTER

LATERAL

TOUCH AND PRESSUREDORSALCOLUMNPATHWAY

INCOMONG SENSORY NERVE TRAVELS UPWARD IN THE DORSAL COLUMN AND SYNAPSES IN THE DORSAL COLUMN NUCLEUS

PAIN AND TEMPERATURE

ANTEROLATERALPATHWAY

SEGMENTAL STRUCTURE OF SPINAL NERVES

DERMATOMES

THE THALAMUS IN SOMATIC SENSATION

• MAJOR SITE FOR RECEIVING SENSORY INFORMATION

• VENTRAL POSTERIOR LATERAL NUCLEUS (VPL)

• SENDS SENSORY INFORMATION TO THE CORTEX

THE THALAMUS IN SOMATIC SENSATION

DORSAL COLUMN

MEDULLA

MEDIALLEMNISCUS

SENSORYNEOCORTEX

DORSAL COLUMNNUCLEI

SOMATOTOPIC ORGANIZATION OF THE SENSORY CORTEX

THE SOMATOSENSORY CORTEX

CORTICAL AREAS INVOVED IN MOTOR CONTROL

SOMATOTOPIC ORGANIZATION OF THE MOTOR CORTEX

MOTIVATIONAL SYSTEMS

• HUNGER

• THIRST

• SEXUAL BEHAVIOR

HUNGER

LACK OF

FOOD

REDUCEDAVAILABILITYOF GLUCOSE

CONTRACTIONS OF EMPTYSTOMACH

LOWTRIGLYCERIDELEVELSIN FAT CELLS

GLUCOSE RECEPTORSIN HYPOTHALAMUS

MECHANO-RECEPTORSIN STOMACH

PANCREAS

HUNGER

THIRST

WATERDEFICIENCY

OSMORECEPTORSIN SUPRAOPTICAND SUPRA-VENTRICULARNUCLEI OFHYPOTHALAMUS

THIRST

ADHSERETIONBY PITUITARY

WATERRETENTION BY KIDNEY

SEXUAL BEHAVIOR

• ANTERIOR HYPOTHALAMUS ORGANIZES RESPONSES TO PHERMONES

• OLIFACTORY CUES SENT TO PYRIFORM CORTEX AND AMYGDALA AND INDIRECTLY TO HYPOTHALAMUS

• ANDROGENS DETERMINE RELEASE OF LEUTINIZING HORMONE- CONSTANT OR CYCLIC