NERVOUS SYSTEM
NERVOUS SYSTEM
• NERVOUS SYSTEMS RECEIVE SENSORY INPUT,
INTEPRET IT, AND SENT OUT APPROPRIATE
COMMANDS
– NERVOUS SYSTEMS
• MOST INTRICATELY ORGANIZED DATA PROCESSING
SYSTEM ON EARTH
– NEURON
• FUNCTIONAL UNIT; SPECIALIZED NERVE CELL FOR
CARRYING SIGNALS FROM ONE LOCATION IN THE BODY
TO ANOTHER
NERVOUS SYSTEM
• NERVOUS SYSTEMS RECEIVE SENSORY INPUT,
INTEPRET IT, AND SENT OUT APPROPRIATE
COMMANDS
– NERVOUS
SYSTEM HAS 3
INTERCONNECTED
FUNCTIONS
NERVOUS SYSTEM
• NERVOUS SYSTEMS RECEIVE SENSORY INPUT,
INTEPRET IT, AND SENT OUT APPROPRIATE
COMMANDS
– NERVOUS SYSTEM HAS 3 INTERCONNECTED
FUNCTIONS
• SENSORY INPUT  CONDUCTION OF SIGNALS FROM
SENSORY RECEPTORS TO INTEGRATION CENTERS
• INTEGRATION  INTERPRETATION OF THE SENSORY
SIGNALS AND THE FORMULATION OF RESPONSES
• MOTOR OUTPUT  THE CONDUCCTION OF SIGNALS FROM
THE INTEGRATION CENTERS TO EFFECTORS
– MUSCLES OR GLANDS THAT PERFORM BODY FUNCTIONS
NERVOUS SYSTEM
• NERVOUS SYSTEMS HAVE TWO MAIN DIVISIONS
– CENTRAL NERVOUS SYSTEM (CNS)
• WHERE MOST INTEGRATION OCCURS; CONSISTS OF THE
BRAIN AND SPINAL CORD (IN VERTEBRATES)
– PERIPHERAL NERVOUS SYSTEM (PNS)
• MADE UP OF COMMUNICATION LINES CALLED NERVES THAT
CARRY SIGNALS IN AND OUT OF THE CNS
• NERVE
– A CABLE-LIKE BUNDLE OF NEURON EXTENSIONS TIGHTLY
WRAPPED IN CONNECTIVE TISSUE
• GANGLIA
– CLUSTERS OF NEURON CELL BODIES IN THE NERVES
NERVOUS SYSTEM
• THREE FUNCTIONAL TYPES OF NEURONS
NERVOUS SYSTEM
• THREE FUNCTIONAL TYPES OF NEURONS
– SENSORY NEURONS
– INTERNEURONS
– MOTOR NEURONS
NERVOUS SYSTEM
• NEURONS ARE THE FUNCTIONAL UNITS OF
NERVOUS SYSTEMS
– STRUCTURE OF A NEURON
NERVOUS SYSTEM
• STRUCTURE OF A NEURON
– CELL BODY  HOUSES THE NUCLEUS AND OTHER
ORGANELLES
• DENDRITES  SHORT, MANY BRANCHES; RECEIVE
INCOMING MESSAGES AND DIRECT THEM TOWARD
CELL BODY
• AXON  USUALLY A SINGLE FIBER; CONDUCTS SIGNAL
TOWARDS ANOTHER NEURON OR EFFECTOR
NERVOUS SYSTEM
• STRUCTURE OF A NEURON
– SUPPORTING CELLS  PROTECT, INSULATE, AND
REINFORCE THE NEURONS
• SHCHWANN CELLS
– MYELIN SHEATH
– NODES OF RANVIER
» INCREASE SPEED
AT WHICH SIGNAL TRAVELS
NERVOUS SYSTEM
• STRUCTURE OF A NEURON
– SYNAPTIC KNOB (TERMINAL BRANCH)
• ENDS THE NEURON; RELAYS SIGNALS TO ANOTHER
NEURON OR EFFECTOR
– SYNAPSE
• THE JUNCTION, OR RELAY POINT, BETWEEN TWO
NEURONS OR BETWEEN A NEURON AND AN EFFECTOR
CELL
NERVOUS SYSTEM
• A NEURON MAINTAINS A MEMBRANE
POTENTIAL ACROSS ITS MEMBRANE
– RESTING POTENTIAL
• THE VOLTAGE ACROSS THE PLASMA OF A RESTING
NEURON
– SODIUM-POTASSIUM (NA+ / K+) PUMPS
• ACTIVELY TRANSPORT NA+ OUT OF THE CELL AND K+ IN
NERVOUS SYSTEM
• A NERVE SIGNAL BEGINS AS A CHANGE IN THE
MEMBRANE POTENTIAL
NERVOUS SYSTEM
• A NERVE SIGNAL BEGINS AS A CHANGE IN THE
MEMBRANE POTENTIAL
– STIMULUS
• ANY FACTOR THAT CAUSES A NERVE SIGNAL TO BE
GENERATED
– ACTION POTENTIAL
• THE TECHNICAL NAME FOR THE NERVE
SIGNAL
– THRESHOLD POTENTIAL
• THE MINIMUM CHANGE THAT MUST
OCCUR TO GENERATE AN ACTION
POTENTIAL
– **CYCLIC PROCESS**
NERVOUS SYSTEM
• THE ACTION POTENTIAL PROPAGATES ITSELF
ALONG THE NEURON
– ALL-OR-NONE EVENTS
– DIFFERENT INTENSITIES RESULT FROM
FREQUENCY OF POTENTIALS
NERVOUS SYSTEM
• NEURONS COMMUNICATE AT SYNAPSES
– SYNAPSE
• THE JUNCTION, OR RELAY POINT, BETWEEN TWO NEURONS
OR BETWEEN A NEURON AND AN EFFECTOR CELL
– SYNAPSES CAN BE
EITHER ELECTRICAL
OR CHEMICAL
• ELECTRICAL
SYNAPSES
TRANSFER SIGNALS
FASTER
NERVOUS SYSTEM
• NEURONS COMMUNICATE AT SYNAPSES
– SYNAPSE
• THE JUNCTION, OR RELAY POINT, BETWEEN TWO NEURONS
OR BETWEEN A NEURON AND AN EFFECTOR CELL
– SYNAPSES CAN BE
EITHER ELECTRICAL
OR CHEMICAL
• CHEMICAL
SYNAPSES HAVE
A NARROW GAP
CALLED A
SYNAPTIC CLEFT
NERVOUS SYSTEM
• NEURONS COMMUNICATE AT SYNAPSES
– SYNAPSE
• THE JUNCTION, OR RELAY POINT, BETWEEN TWO NEURONS
OR BETWEEN A NEURON AND AN EFFECTOR CELL
– SYNAPSES CAN BE
EITHER ELECTRICAL
OR CHEMICAL
• SYNAPTIC CLEFT
– SEPARATES
SYNAPTIC KNOBS
FROM RECEIVING
NEURON
NERVOUS SYSTEM
• CHEMICAL SYNAPSES MAKE COMPLEX
INFORMATION PROCESSING POSSIBLE
– MULTIPLE SIGNALS CAN BE SENT TO THE SAME
RECEIVING NEURON
– NEUROTRANSMITTER
• CHEMICAL SIGNAL
• NERVOUS SYSTEM EQUIVALENT TO A HORMONE
NERVOUS SYSTEM
• A VARIETY OF SMALL MOLECULES FUNCTION AS
NEUROTRANSMITTERS
– ACETYLCHOLINE
• IMPORTANT IN THE BRAIN; MAY BE EXCITATORY OR INHIBITORY
– BIOGENIC AMINES
• NITROGEN CONTAINING NEUROTRANSMITTERS DERIVED FROM
AMINO ACIDS
• EXAMPLES INCLUDE EPINEPHRINE, NOREPINEPHRINE, SEROTONIC,
DOPAMINE
– ENDORPHINS ARE PEPTIDES THAT DECREASE PAIN
PERCEPTION
– DISSOLEVD GASES LIKE NO (NITROUS OXIDE) ACT AS
NEUROTRANSMITTERS
NERVOUS SYSTEM
• MANY DRUGS ACT AT CHEMICAL SYNAPSES
– EFFECT US BY ACTING AT SYNAPSES OR
CHANGING THE NEUROTRANSMITTER
NERVOUS SYSTEM
• NERVOUS SYSTEM ORGANIZATION USUALLY
CORRELATES WITH BODY SYMMETRY
NERVOUS SYSTEM
• NERVOUS SYSTEM ORGANIZATION USUALLY
CORRELATES WITH BODY SYMMETRY
– NERVE NET
• WEB-LIKE SYSTEM OF
NEURONS EXTENDING
THROUGHOUT THE
BODY
– CEPHALIZATION
• CONCENTRATION OF
NERVOUS SYSTEM AT
HEAD END
– CENTRALIZATION
• THE PRESENCE OF A CNS
DISTINCT FROM A PNS
NERVOUS SYSTEM
• VERTEBRATE NERVOUS SYSTEMS ARE HIGHLY
CENTRALIZED AND CEPHALIZED
NERVOUS SYSTEM
• VERTEBRATE NERVOUS SYSTEMS ARE HIGHLY
CENTRALIZED AND CEPHALIZED
– CNS IS MADE UP OF THE SPINAL CORD
AND BRAIN
• SPINAL CORD
– LIES INSIDE THE VERTEBRAL COLUMN, OR
SPINE, RECEIVES SENSORY INFORMATION
FROM THE SKIN AND MUSCLES AND
INTEGRATES SIMPLE RESPONSES TO CERTAIN KINDS OF
STIMULI
NERVOUS SYSTEM
• VERTEBRATE NERVOUS SYSTEMS ARE HIGHLY
CENTRALIZED AND CEPHALIZED
– CNS IS MADE UP OF THE SPINAL CORD
AND BRAIN
• BRAIN
– MASTER CONTROL CENTER; INCLUDES
HOMEOSTATIC CENTERS THAT KEEP THE BODY
FUNCTIONING SMOOTHLY; SENSORY CENTERS
THAT INTEGRATE DATA FROM THE SENSE ORGANS; IN
HUMANS, CENTERS OF EMOTIONS AND INTELLIGENCE; ALSO
SEND OUT MOTOR COMMANDS TO MUSCLES
NERVOUS SYSTEM
• VERTEBRATE NERVOUS SYSTEMS ARE HIGHLY
CENTRALIZED AND CEPHALIZED
– CNS IS MADE UP OF THE SPINAL CORD
AND BRAIN
• BLOOD-BRAIN BARRIER
– MAINTAINS A STABLE CHEMICAL
ENVIRONMENT IN THE BRAIN; ONLY ESSENTIAL
NUTRIENTS AND OXYGEN PASS FREELY INTO
THE BRAIN
NERVOUS SYSTEM
• VERTEBRATE NERVOUS SYSTEMS ARE HIGHLY
CENTRALIZED AND CEPHALIZED
– CNS IS MADE UP OF THE SPINAL CORD
AND BRAIN
• VENTRICLES AND CENTRAL CANAL
– FLUID-FILLED SPACES IN BRAIN AND
SPINAL CORD, RESPECTIVELY
– CEREBROSPINAL FLUID
» FLUID THAT CUSHIONS THE CNS AND HELPS SUPPLY IT
WITH NUTRIENTS, HORMONES, AND WHITE BLOOD CELLS
– MENINGES
» LAYERS OF CONNECTIVE TISSUE, ALSO SUPPLY CUSHION
NERVOUS SYSTEM
• VERTEBRATE NERVOUS SYSTEMS ARE HIGHLY
CENTRALIZED AND CEPHALIZED
– CNS HAS 2 DISTINCT AREAS
NERVOUS SYSTEM
• VERTEBRATE NERVOUS SYSTEMS ARE HIGHLY
CENTRALIZED AND CEPHALIZED
– CNS HAS 2 DISTINCT AREAS
• WHITE MATTER
– MAINLY AXONS
– WITH WHITISH MYELIN SHEATH
• GRAY MATTER
– MAINLY NERVE BODIES AND DENDRITES; IN MAMMALS IT IS
THE AREA OF HIGHER BRAIN FUNCTION
NERVOUS SYSTEM
• VERTEBRATE NERVOUS SYSTEMS ARE HIGHLY
CENTRALIZED AND CEPHALIZED
– PNS HAS
• CRANIAL NERVES
– CARRY SIGNALS TO OR FROM THE BRAIN
• SPINAL NERVES
– CARRY SIGNALS TO OR FROM THE SPINAL CORD
NERVOUS SYSTEM
• THE PERIPHERAL NERVOUS SYSTEM OF
VERTEBRATES IS A FUNCTIONAL HIERARCHY
NERVOUS SYSTEM
• OPPOSING ACTIONS OF SYMPATHETIC AND
PARASYMPATHETIC NEURONS REGULATE THE
INTERNAL ENVIRONMENT
– AUTONOMIC NERVOUS SYSTEM HAS 2 DIVISIONS
NERVOUS SYSTEM
• OPPOSING ACTIONS OF SYMPATHETIC AND
PARASYMPATHETIC NEURONS REGULATE THE
INTERNAL ENVIRONMENT
– AUTONOMIC NERVOUS SYSTEM HAS 2 DIVISIONS
• PARASYMPATHETIC DIVISION
– PRIMES THE BODY FOR
DIGESTING FOOD AND RESTING
• SYMPATHETIC DIVISION
– PREPARES THE BODY FOR INTENSE,
ENERGY-CONSUMING ACTIVITIES,
SUCH AS FIGHTING, FLEEING,
OR COMPETING IN A STRENUOUS
GAME
NERVOUS SYSTEM
• THE VERTEBRATE BRAIN DEVELOPS FROM
THREE ANTERIOR BULGES OF THE NEURAL
TUBE
NERVOUS SYSTEM
• THE VERTEBRATE BRAIN DEVELOPS FROM
THREE ANTERIOR BULGES OF THE NEURAL
TUBE
– 3 ANCESTRAL REGIONS
• FOREBRAIN  LEADS TO CEREBUM (DOMINANT PART
OF FOREBRAIN)
• MIDBRAIN
• HINDBRAIN
NERVOUS SYSTEM
• THE STRUCTURE OF A LIVING
SUPERCOMPUTER: THE HUMAN BRAIN
NERVOUS SYSTEM
• THE STRUCTURE OF A LIVING
SUPERCOMPUTER: THE HUMAN BRAIN
– MAJOR STRUCTURES
•
•
•
•
•
CEREBRUM
CEREBELLUM
MEDULLA OBLONGATA
PONS
CORPUS COLLOSUM
NERVOUS SYSTEM
• THE CEREBRAL CORTEX IS A MOSAIC OF
SPECIALIZED, INTERACTIVE REGIONS
– CEREBRAL CORTEX
• ACCOUNTS FOR 80% OF BRAINS TOTAL MASS; INVOLVED IN
REASONING AND
MATHEMATICAL
ABILITIES,
LANGUAGE SKILLS,
IMAGINATION,
ARTISTIC TALENT,
AND PERSONALITY
TRAITS
NERVOUS SYSTEM
• THE CEREBRAL CORTEX IS A MOSAIC OF
SPECIALIZED, INTERACTIVE REGIONS
– LATERALIZATION
• AREAS IN THE TWO HEMISPHERES BECOME
SPECIALIZED FOR
DIFFERENT
FUNCTIONS
NERVOUS SYSTEM
• INJURIES AND BRAIN OPERATIONS HAVE
PROVIDED INSIGHT INTO BRAIN FUNCTION
– “BROKEN BRAINS” HAVE GIVEN INSIGHT INTO
NORMAL BRAIN FUNCTION
– LACK OF NERVES ON THE BRAIN ALLOW
NEUROSURGEONS TO OPERATE AND DISCERN
SPECIFIC ASPECTS OF BRAIN FUNCTION
NERVOUS SYSTEM
• SEVERAL PARTS OF THE BRAIN REGULATE
SLEEP AND AROUSAL
– RETICULAR FORMATION
• SYSTEM OF NEURONS
THAT EXTENDS
THROUGH THE CORE
OF THE BRAINSTEM;
RECEIVES DATA FROM
SENSORY RECEPTORS,
FILTERS AND SENDS
USEFUL DATA TO
CEREBRAL CORTEX
NERVOUS SYSTEM
• SEVERAL PARTS OF THE BRAIN REGULATE
SLEEP AND AROUSAL
– ELECTROENCEPHALOGRAM (EEG)
• MEASURES BRAIN WAVE ACTIVITY
• REM SLEEP
– RAPID EYE MOVEMENT
– UNIQUE BRAIN-WAVE PATTERN DURING DEEP SLEEP; TIME
WHEN DREAMS OCCUR
NERVOUS SYSTEM
• THE LIMBIC SYSTEM IS INVOLVED IN
EMOTIONS, MEMORY, AND LEARNING
– LIMBIC SYSTEM
• INCLUDES PARTS OF THALMAMUS; HYPOTHALAMUS,
PORTIONS OF CEREBRAL CORTEX; AMYGDALA AND
HIPPOCAMPUS PLAY
KEY ROLES IN
MEMORY, LEARNING,
AND EMOTION
NERVOUS SYSTEM
• THE LIMBIC SYSTEM IS INVOLVED IN
EMOTIONS, MEMORY, AND LEARNING
– LIMBIC SYSTEM
• AMYGDALA
– CENTRAL IN RECOGNIZING THE EMOTIONAL CONTENT OF
FACIAL EXPRESSIONS
AND LAYING DOWN
EMOTIONAL MEMORIES
• HIPPOCAMPUS
– INVOLVED IN FORMATION
OF MEMORIES AND
THEIR RECALL
NERVOUS SYSTEM
• WE NEED TO SPRINKLE IN A FEW MORE
PIECES OF INFO ON THE HUMAN BODY
– SENSES
– MUSCLES