6. • NERVE—BUNDLE OF AXONS COVERED WITH
CONNECTIVE TISSUE & BLOOD VESSELS
• OUTSIDE BRAIN & SPINAL CORD
• GANGLIA—SMALL MASSES OF NERVOUS
TISSUE-MAINLY CELL BODIES OUTSIDE BRAIN
& SPINAL CORD
NERVOUS SYSTEM
7. – SENSORY FUNCTION
• RECEPTORS SENSE INTERNAL CHANGES LIKE SLOOD
SUGAR, Ph & EXTERNAL STIMULI LIKE TOUCH,PAIN etc
VIA SENSORY NERVES
– INTEGRATIVE FUNCTION
• PROCESSING OF INFORMATION TO MAKE
APPROPRIATE RESPONSE---PERCEPTION—
INTERNEURONS
– MOTOR FUNCTION
• ONCE THE SENSORY INFORMATION IS INTEGRATED
MOTOR RESPONSE IS ELICITED—MUSCLE
CONTRACTION /GLAND SECRETION VIA MOTOR
NEURONS
NERVOUS SYSTEM--FUNCTIONS
8. NEURONS
• BASIC FUNCTIONAL UNIT OF NS
• PARTS OF A NEURON
– BODY
– DENDRITES
– AXON
• SYNAPSE-JUNCTION BETWEEN TWO NEURONS
/ AXONS / NEURON & EFFECTOR CELL
– CONTAINS NEUROTRANSMITTERS
9.
10. NEURON--STRUCTURE
• CELLBODY
• CONTAINS NUCLEUS SURROUNDED BY
CYTOPLASM WITH ORGANELLE LIKE
MITOCHONDRIA, GOLGI APPARATUS,
RIBOSOMES --SITE OF PROTEIN SYNTHESIS
16. FUNCTIONS OF NEURONS
• ELECTRICAL EXCITABILITY &CONDUCTIVITY
– ABILITY TO RESPOND TO STIMULUS & GENERATE
ACTION POTENTIAL
• STIMULUS IS A CHANGE IN THE
ENVIRONMENT THAT IS ABLE TO GENERATE
ACTION POTENTIAL
• NERVE IMPULSE IS AN ELECTRICAL SIGNAL
THAT TRAVELS ALONG THE NEURON DUE TO
MOVEMENT OF IONS SPEED 1-1.5m/S
17. • NERVE IMPULSE -WHEN AN ACTION
POTENTIAL OCCURS IN A NERVE
• AP IS TRANSMITTED BY THE MOVEMENT OF
IONS ACROSS THE CELLMEMBRANE
• PLASMA MEMBRANE OF EXCITABLE CELLS
EXHIBIT MEMBRANE POTENTIAL—ELECTRICAL
VOLTAGE DIFFERENCE ACROSS THE
MEMBRANE CALLED RESTING MEMBRANE
POTENTIAL
FUNCTIONS OF NEURONS
18.
19. • WHEN A NERVE IS STIMULATED THE
PERMEABILITY OF Na+, K+ INCREASE Na+ FLOODS
IN TO THE NEURON AND DEPOLARISATION
STARTS
• THE INITIALLY –ve CHARGE WILL BECOME
NEUTRAL AND THEN +ve
• THIS CREATES AN IMPULSE THAT IS
TRANSMITTED AWAY TO THE END OF THE AXON
FAST
• THEN REPOLARISATION OCCURS –CHANNELS
OPEN AND K+ RUSHES OUT
NERVE IMPULSE
20. NERVE IMPULSE
• THE PLASMA MEMBRANE CONTAINS DIFFERENT
KINDS OF ION CHANNELS THAT OPEN & CLOSE IN
RESPONSE TO STIMULI
• AT REST THE CHARGE ON THE OUTSIDE IS
POSITIVE –Na+ AND INSIDE IS NEGATIVE
• THERE IS A TENDANCY FOR THE IONS TO MOVE
ACROSS THE MEMBRANE THAT CHANGES THE
MEMBRANE POTENTIAL
• TOGETHER THE MEMBRANE IS ELECTRICALY
NEUTRAL
21.
22. • AP IS ACCORDING TO ALL OR NONE
PHENOMENON
• IF THRESHOLD POTENTIAL IS CROSSED THEN
DEPOLARISATION OCCURS AND ACTION
POTENTIAL IS GENERATD & TRANSMITTED
• REFRACTORY PERIOD—THE PERIOD OF TIME
AFTER AN AP BEGINS DURING WHICH TIME
AN EXCITABLE CELL CANNOY GENERATE
ANOTHER AP
NERVE IMPULSE
23.
24.
25.
26.
27.
28. • AFTER REPOLARISATION Na+ IS PUSHED OUT OF
THE CELL BY PUMP
• IN MYELINATED NEURONS THE MOVEMENT OF
IONS OCCUR ONLY AT NODES OF RANVIER
CALLED SALTATORY CONDUCTION
• CONDUCTION IS CONTINUOUS IN MUSCLES &
NONMYELINATED NERVE FIBRES
• SPEED OF CONDUCTION DEPENDS ON THE
DIAMETER OF THE AXON
• LARGER ONES CONDUCT FASTER
NERVE IMPULSE
29. NERVE FIBRES
• TYPE A—MYELINATED LARGE FIBRES FASTEST
• MOTOR NERVES TO SKELETAL MUSCLES
• TYPE B---MYELINATED MEDIUM SIZED
• SENSORY & VISION
• TYPE C—NONMYELINATED SMALL
• AUTONOMIC FIBRES & SENSORY FROM SKIN
30. SYNAPSE
• JUNCTION BETWEEN NEURONS OR NEURONS
& END ORGANS
– AXO-AXONIC
– AXO-SOMATIC
– AXO-DENDRITIC
• ONE WAY CHANNELS
• PRESYNAPTIC NEURON-SENDS
• POST SYNAPTIC NEURON -RECEIVES
31. SYNAPSE
• ELECTRICAL
– THEY HAVE SMALL TUBULAR CONNECTION BETWEEN
THEM THROUGH WHICH AP TRAVELS
– FASTER & SYNCHRONISED
• CHEMICAL
– GAP JUNCTION
– THERE IS SYNAPTIC CLEFT SPACE FILLED WITH
INTERSTITIAL FLUID
– INVOLVES NEUROYRANSMITTERS
– THERE IS SYNAPTIC DELAY
34. NEUROTRANSMITTERS
• SMALL MOLECULE NEUROTRANSMITTERS
– ACETYL CHOLINE
• SECRETED BY NEURONES BOTH IN PNS & CNS
• CAN BE INHIBITORY OR EXCITATORY
• ACETYL CHOLINE ESTERASE INACTIVATES IT
– BIOGENIC AMINES
• AA ARE DECARBOXYLATED TO PRODUCE Eg DOPAMINE,
EPINEPHRINE,NOREPINEPHRINE
• CALLED CATECHOLAMINES HAVE AMINO GROUP &
CATECHOL RING
– AMINOACIDS-GLUTAMIC ACID, ASPARTIC ACID
EXCITATORY
• GABA,GLYCINE INHIBITORY
– NITRIC OXIDE—USED AS ANESTHETIC AGENT
35. • NEUROPEPTIDES
– SECRETED BY VESICLES BOTH PNS & CNS
– 3-40 AA LINKED TOGETHER BY PEPTIDE BONDS
– EXCITATORY & INHIBITORY
– ENCEPHALINS & ENDORPHINS
– FORMED FROM CELL BODY
NEUROTRANSMITTERS
36. REGENERATION OF NEURONS
• NEURONS EXHIBIT PLASTICITY
• THEY CAN CHANGE ACCORDING TO
ENVIRONMENT
• POWER FOR REGENERATION IS VERY LIMITED
• WHEN NEURONS ARE INJURED GLIAL CELLS
PROLIFERATE FORMING A BARRIER FOR
REGENERATION
37.
38. NEUROGLIA
• HALF OF THE VOLUME OF CNS IS NEUROGLIA
• HOLD THE NERVE CELLS TOGETHER LIKE GLUE
• IN INJURY GLIA PROLIFERATE TO FILL THE GAP
• 4 TYPES DEPENDING ON THE SIZE &
CYTOPLASMIC PROCESSES
39.
40. • ASTROCYTES
– STAR SHAPED—MANY PROCESSES
– LARGEST & MOST NUMEROUS
– CONTAIN MICROFILAMENTS, SUPPORTS NEURONS
– FOOT PROCESSES FORM PART OF THE BLOOD BRAIN
BARRIER
– IN THE EMBRYO THEY SECRETE REGULATORY SUBSTANCES
FOR THE NEURAL GROWTH
– THEY REGULATE THE CHEMICAL ENVIRONMENT,LIKE
CONCENTRATION OF K+,NUTRIENTS
– FORMATION OF NEURAL SYNAPSES WHICH AFFECT
LEARNING & MEMORY
NEUROGLIA --CNS
41. • OLIGODENDROCYTES
– SMALL CELLS WITH FEWER PROCESSES
– FORM & MAINTAIN THE MYELIN SHEATH
– CONTROL THE SPEED OF TRANSMISSION
– ONE CELL CAN MYELINATE MANY AXONS
• MICROGLIA
– SMALL CELLS WITH SLENDER PROCESSES
– PHAGOCYTOSIS—THEY REMOVE CELLULAR DEBRIS
DURING DEVELOPMENT
NEUROGLIA
42. • EPENDYMAL CELLS
– CUBOID/COLUMNAR CELLS ARRANGED IN SINGLE
LAYER
– THEY HAVE CILIA & MICROVILLI
– THEY LINE THE VENTRICLE
– THEY PRODUCE & MONITOR CIRCULATION OF CSF
NEUROGLIA
43. ORGANIZATION
• GREY MATTER
– NEURONALCELL BODIES, DENDRITES,UNMYELINATED
AXONS, AXON TERMINALS & NEUROGLIA
• WHITE MATTER
– MYELINATED AXONS
– WHITE COLOUR IS DUE TO MYELIN
• NUCLEUS –CLUSTER OF NEURONAL CELL BODIES
IN CNS
• GANGLION--CLUSTER OF NEURONAL CELL BODIES
IN PNS
44.
45. • SCHWANN CELLS
– THEY ENCIRCLE THE AXON & MYELINATE 1 AXON
– HELP IN AXON REGENERATION
• SATELLITE CELLS
– FLAT CELLS AROUND GANGLIA
– THEY SUPPORT & REGULATE EXCHANGE OF
MATERIALS BETWEEN NEURONS & INTERSTITIAL
FLUID
NEUROGLIA --PNS
