The nervous system has several key functions including sensation, perception, proprioception, motor control, integration of sensory information, sleep, learning, memory, and plasticity. Sensory receptors detect changes and stimuli which are transmitted as nerve impulses to the central nervous system. The motor system then coordinates muscle movements through upper and lower motor neurons. Integration involves processing sensory information to make decisions and engage in complex behaviors and states like arousal, learning, memory and sleep.

1. NERVOUS SYSTEM
CLASS 6
FUNCTIONS OF THE NERVOUS
SYSTEM

2. • SENSORY FUNCTION
– SENSATION IS THE AWARENESS OF CHANGES IN
THE EXTERNAL AND INTERNAL ENVIRONMENT
WHEN SENSORY IMPULSES REACH THE CORTEX,
WE BECOME AWARE OF THEM. WHAT REACHES
THE SPINAL CORD IS USEFUL FOR REFLEXES
FUNCTIONS OF NERVOUS SYSTEM

3. • PERCEPTION
– IS THE CONSIOUS AWARENESS AND
INTERPRETATION OF SENSATION. IT IS A CORTICAL
FUNCTION. EACH UNIQUE TYPE OF SENSATION IS
CALLED A SENSORY MODALITY. A PARTICULAR
SENSORY NEURON CARRIES ONLY ONE
PARTICULAR SENSATION.
FUNCTIONS OF NERVOUS SYSTEM

4. • PROPRIOCEPTION:
– SENSATION WHICH ALLOWS PERCEPTION OF
STATIC POSITION, BODY MOVEMENTS OF LIMBS
AND HEAD.
• SENSATION BEGINS AT THE SENSORY
RECEPTOR AND THEY ARE SELECTIVE
FUNCTIONS OF NERVOUS SYSTEM

5. • SENSATION
– STIMULATION OF THE RECEPTOR
– TRANSDUCTION OF THE STIMULUS ( RECEPTOR
TRANSMITS ENERGY INTO GRADED POTENTIAL)
– WHEN THE POTENTIAL REACHES THE THRESHOLD,
IT TRIGGERS IMPULSE WHICH IS PROPOGATED TO
CNS
– PARTICULAR REGION OF THE CNS RECEIVES THE
IMPULSE, INTEGRATES AND PERCEPTION OCCURS
FUNCTIONS OF NERVOUS SYSTEM

6. • SENSORY RECEPTORS
– FREE NERVE ENDINGS e.g. PAIN, TEMPERATURE
– ENCAPSULATED NERVE ENDINGS e.g. VISCERAL PAIN,
PRESSURE
– SPECIALISED CELLS e.g. VISION, TASTE etc.
• ANOTHER CLASSIFICATION – EXTEROCEPTOR,
ENTEROCEPTOR AND PROPRIOCEPTOR
• SENSORY RECEPTORS SHOW ADAPTABILITY
– IF THE STIMULUS IS MAINTAINED THE IMPULSE IS
REDUCED GRADUALLY ; RAPID OR SLOW
FUNCTIONS OF NERVOUS SYSTEM

7. • SOMATIC SENSATION
– RECEPTORS IN THE SKIN OR SUBCUTANEOUS
TISSUE ARE NOT EVENLY DITRIBUTED.
– 4 TYPES OF SOMATIC SENSATION
• TOUCH – TACTILE RECEPTORS DIFFERENTIATE BETWEEN
FINE AND CRUDE TOUCH, PRESSURE AND VIBRATION,
ITCH AND TICKLE.
• THERMAL - COLD AND WARMTH, EPIDERMIS 10 TO
400, DERMIS 40 – 480, LESS THAN 100 AND MORE THAN
480 PAIN
FUNCTIONS OF NERVOUS SYSTEM

8. • 4 TYPES OF SOMATIC SENSATION
• PAIN – RECEPTORS ARE FREE NERVE ENDINGS. PRESENT
IN ALL TISSUES EXCEPT BRAIN. TISSUE IRRITATION
RELEASES CHEMICALS WHICH STIMULATE
NOCICEPTORS.
– TWO TYPES OF PAIN RECEPTORS – FAST AND SLOW.
SUPERFICIAL SOMATIC PAIN AND DEEP SOMATIC PAIN. FAST
PAIN IS LOCALISED TO SITE OF INJURY. DEEP PAIN IS DIFFUSE.
VISCERAL PAIN IS REFERRED TO THE SURFACE
• PROPRIOCEPTION = PERCEPTION OF BODY
MOVEMENTS. IMPORTANT FOR MAINTAINING
POSTURE AND BALANCE.
– MUSCLE SPINDLE IS THE RECEPTOR
FUNCTIONS OF NERVOUS SYSTEM

9. • SENSORY PATHWAYS
– RELAY INFORMATION FROM RECEPTORS TO THE
PRIMARY SOMATO SENSORY AREA IN THE CORTEX
– 1ST ORDER NEURONS
– FROM SENSE ORGAN TO BRAIN STEM OR SPINAL
CORD– 2ND ORDER NEURONS FROM THERE TO
THALAMUS THEY DECCUSATE.
– 3RD ORDER NEURON IS FROM THALAMUS TO
CORTEX.
FUNCTIONS OF NERVOUS SYSTEM

10. • SENSORY PATHWAYS
– SPINAL CORD HAS TWO COLUMNS – POSTERIOR
COLUMN
• FIRST ORDER NEURONS SYNAPSE IN THE MEDULLA
• 2ND ORDER NEURONS DECCUSATE AND REACH MEDIAL
LEMNISCUS ( MEDULLA TO THALAMUS TRACT)
• 3RD ORDER NEURONS REACH CORTEX.
– FINE TOUCH, STEREOGNOSIS ( ABILITY TO
RECOGNISE OBJECT BY FEELING IT)
FUNCTIONS OF NERVOUS SYSTEM

11. • ANTEROLATERAL PATHWAYS
• SPINOTHALAMIC -3 ORDERS OF NEURONS
– 1ST ORDER- CELL BODIES ARE IN THE POSTERIOR ROOT
GANGLIA
– 2ND ORDER – IN THE GREY HORN. DECCUSATION AT
MEDULLA AND ASCENT
– 3RD ORDER – FROM THALAMUS TO CORTEX
• LATERAL SPINOTHALAMIC TRACT CARRY PAIN &
TEMPERATURE
• ANTERIOR CARRY CRUDE TOUCH & PRESSURE
FUNCTIONS OF NERVOUS SYSTEM

12. • SOMATO SENSORY PATHWAY TO CEREBELLUM
• POSTERIOR & ANTERIOR SPINO CEREBELLAR
TRACTS
• IMPORTANT IN MAINTAINING POSTURE,
BALANCE, CO-ORDINATION AND SKILLED
MOVEMENTS.
FUNCTIONS OF NERVOUS SYSTEM

13. • MOTOR PATHWAYS
– ALL THE SIGNALS THAT CONTROL THE MOVEMENT
EXTEND OUT OF BRAIN STEM AND SPINAL CORD TO
INNERVATE SKELETAL MUSCLES IN THE HEAD AND
BODY.
– THESE ARE LOWER MOTOR NEURONS.
– INPUT FROM UPPER MOTOR NEURONS
– OR INTER NEURONS CALLED LOCAL CIRCUIT NEURONS
– THEY ARE IN THE BRAIN STEM OR SPINAL CORD.
– RECIEVE INPUT FROM LOCAL SENSORY NEURONS FOR
REFLEX OR FROM HIGHER CENTRES.
– THEY CO-ORDINATE RHYTHMIC ACTIVITY
FUNCTIONS OF NERVOUS SYSTEM

14. • UPPER MOTOR NEURONS
– FROM CORTEX – ESSENTIAL FOR PLANNING AND
DIRECTING VOLUNTARY MOVEMENTS.
– FROM RED NUCLEUS, SUPERIOR COLLICULUS,
RETICULAR FORMATION, BASAL GANGLIA FOR
INITIATION AND TERMINATION OF MOVEMENTS &
MAINTENANCE OF MUSCLE TONE
– FROM CEREBELLAR NEURON FROM CEREBELLUM –
MONITORS THE DIFFERENCE BETWEEN INTENDED
MOVEMENTS AND PERFORMED MOVEMENTS,
POSTURE & BALANCE
FUNCTIONS OF NERVOUS SYSTEM

15. • ORGANISATION OF UPPER MOTOR NEURONS
DIRECT PATHWAY – CORTEX TO LMN
– PYRAMIDAL PATHWAY – 90% DECUSSATE AT
MEDULLA AND BECOME CONTRA LATERAL; 10%
IPSILATERAL- DECUSSATE AT SPINAL CORD
– LATERAL CORTICO SPINAL TRACTS FOR HANDS,
FEET AND FINE MOVEMENTS.
– ANTERIOR CORTICO SPINAL TRACTS FOR NECK &
TRUNK – DO NOT DECUSSATE
– CORTICO BULBAR – EYES, TONGUE AND NECK
FUNCTIONS OF NERVOUS SYSTEM

16. • ORGANISATION OF UPPER MOTOR NEURONS
INDIRECT PATHWAY
– EXTRAPYRAMIDAL PATHWAY – COMPLEX
POLYSYNAPTIC WITH CIRCUITS WHICH INVOLVE
THE CORTEX, BASAL GANGLIA, THALAMUS,
CEREBELLUM. RETICULAR FORMATION & RED
NUCLEUS
– FORM 5 MAJOR TRACTS: RUBEROSPINAL,
TECTOSPINAL, VESTIBULOSPINAL, LATERAL &
MEDIAL RETICULOSPINAL
FUNCTIONS OF NERVOUS SYSTEM

17. • ORGANISATION OF UPPER MOTOR NEURONS
INDIRECT PATHWAY
– BASAL GANGLIA – SENSORY ASSOICATION AND
MOTOR OUTPUT
– MODULATE MOTOR MOVEMENTS AND
SUPPRESSES UNWANTED MOVEMENTS
– CEREBELLUM MAINTAINS POSTURE, BALANCE,
LEARNING & PERFORMING MOVEMENTS.
FUNCTIONS OF NERVOUS SYSTEM

18. • INTEGRATIVE FUNCTION
• IS THE PROCESSING OF SENSORY
INFORMATION BY ANALYSING, STORING &
MAKING DECISIONS
• SLEEP, AWAKE LEARNING, MEMORY,
EMOTIONAL RESPONSE
• AROUSAL – RAS IS STIMULATED BY PAINFUL
STIMULII
FUNCTIONS OF NERVOUS SYSTEM

19. • SLEEP
• IS A STATE OF ALTERED CONSCIOUSNESS FROM WHICH
ONE CAN BE AROUSED.
• 2 PHASES - NREM & REM
• NREM 4 STAGES:
– STAGE 1 – TRANSITION – 1 – 7 MINUTES; IF WOKEN UP –
“NOT SLEEPING”
– STAGE II – LIGHT SLEEP WITH DREAMS
– STAGE III – MODERATE DEEP SLEEP; BP, TEMP FALLS –
DIFFICULT TO WAKE THE PERSON
– STAGE IV – DEEP SLEEP -BRAIN METABOLISM IS
DECREASED, SLEEPWALKNG OCCURS IN THIS STAGE.
– STAGE IV REACHED IN ONE HOUR FROM THE BEGINNING
FUNCTIONS OF NERVOUS SYSTEM

20. SLEEP
• IN 7-8 HOURS THERE ARE 3-5 EPISODES OF REM
SLEEP.
• EYES MOVE BACK & FORTH AND EACH EPISODE
LASTS FOR 10 TO 12 MINUTES.
• INFANTS HAVE MORE REM SLEEP
• IMPORTANT FOR BRAIN METABOLISM.
• BRAIN BLOOD FLOW AND METABOLISM
INCREASE WHILE DREAMING.
• CAFFIENE INHIBITS SLEEP
• PARASYMPATHETIC ACTIVITY INCREASES SLEEP
FUNCTIONS OF NERVOUS SYSTEM

21. LEARNING & MEMORY:
• LEARNING- THE ABILITY TO ACQUIRE NEW
INFORMATION OR SKILL THROUGH
INSTRUCTIONS OR EXPERIENCE.
• MEMORY – THE PROCESS BY WHICH THE
INFORMATION ACQUIRED THROUGH LEARNING
IS STORED AND RETRIEVED WHEN REQUIRED,
• FOR AN EXPERIENCE TO BECOME MEMORY, IT
MUST PRODUCE PERSISTENT STRUCTURAL AND
FUNCTIONAL CHANGES IN THE NEURON.
FUNCTIONS OF NERVOUS SYSTEM

22. PLASTICITY
• IS THE CAPACITY FOR CHANGE ASSOCIATED
WITH LEARNING
• OUR ABILITY TO CHANGE OUR BEHAVIOUR IN
RESPONSE TO STIMULLI FROM INTERNAL
ENVIRONMENT CAUSING :
– CHANGE IN INDIVIDUAL NEURONS
– SYSNTHESIS OF NEW PROTIEN
– SPROUTING NEW DENDRITES
FUNCTIONS OF NERVOUS SYSTEM

23. MEMORY
• PART OF BRAIN ASSOCIATED WITH MEMORY ARE THE
ASSOCIATION AREAS
• IF A PARTICULAR ACTIVITY IS PRACTISED MORE OFTEN,
THAT AREA DEVELOPS
• IMMEDIATE MEMORY – ABILITY TO RECALL INFORMATION
FOR SECONDS
• SHORT TERM MEMORY – FEW MINUTES
• (PROBABLY THERE ARE CHEMICAL CHANGES RATHER THAN
STRUCTURAL
• LONG TERM MEMORY – DAYS TO YEARS. CAN BE RECALLED
ANY TIME.
• FREQUENT RECALLING MAKES IT EASILY ACCESIBLE.
• STORED IN CORTEX. ONLY 1% OF OUR EXPERIENCE IS
STORED AS LONG TERM MEMORY
FUNCTIONS OF NERVOUS SYSTEM