These slides contain the basic information and principle of nervous transduction, It also includes the information about the type of the neurons, structure of the neuron, resting and active membrane potential, synapes and events occurring in it, and introduction to the neurotransmitters.

1. NERVOUS TRANSDUCTION
 Haris Talha

2. SIGNAL TRANSDUCTION
 Transduction in the nervous system typically refers to stimulus alerting events
wherein a physical stimulus is converted into an action potential, which is
transmitted along axons towards the central nervous system where it is
integrated.
Electrical impulses jump from neuron to neuron in the brain through their
branching nerve fibers. This movement of electrical potentials is called signal
transduction.

3. MULTI DENDRITE NERVE

4. HOW IT IS GENERATED?
 Depolarization:
A decrease in the difference in voltage between the inside and outside of the neuron.
 Action Potential:
A short term change in the electrical potential that travels along a cell.
 Hyperpolarize:
To increase the polarity of something, especially the polarity across a biological membrane.
 Node of Ranvier:
A small constriction in the myelin sheath of axons.
 Salutatory Conduction:
The process of regenerating the action potential at each node of Ranvier.

5. NEURON
 NEURON or NERVE CELLS is defined as structural
and functional unit of the nervous system.
 Neuron can be differentiated from other cells on the 2
basis.
1. Neurons has branches or processors called axons
or dendrites
2. Neurons does not have centrosome

6. CLASSIFICATION
 Neurons are classified by 3 different methods:
A. Depending upon the number of poles
B. Depending upon function
C. Depending upon the length of axon

7. DEPENDING UPON THE NUMBER OF
POLES
 Base on the number of poles from which the nerve
fiber arise , neurons are divided into three types
• Unipolar neurons
• Bipolar neurons
• Multipolar neurons

8. DEPENDING UPON THE FUNCTION
 On the basis of function , nerve cells are classified
into two types
• Motor or Efferent neurons
• Sensory or Afferent neurons

9. Depending Upon The Length Of Axon
 Under this classification the two types are
present. Which are as follow:
• Golgi type 1 neuron
• Golgi type 2 neuron

10. STRUCTURE
 Neuron is made up of three parts
1. Nerve cell body
2. Dendrite
3. Axon
 Dendrites and axons forms the processes of neuron. Dendrites are
short processes and the axon are long processes. Dendrites and axons
are usually called nerve fibers.

11. NEURON THE FUNCTIONAL UNIT OF
CNS

12. NERVE CELL BODY
Nerve cell body is also known as soma or perikaryon. it is irregular in shape.
Like any other cell , it is constituted by a mass of cytoplasm called neuroplasm ,
which is covered by a cell membrane. The cytoplasm contains a large nucles ,
Nissl bodies , neurofibrils , mitochondria and golgi apparatus. Nissl bodies and
neurofibrils are found only in nerve cells and not in other cells.
 Following are the organalles present in the cytoplasm:
• NUCLEUS
• NISSL BODIES
• NEUROFIBRILS
• MITOCHONDRIA
• GOLGI APPARATUS

13. DENDRITE
Dendrites are the branched process of neurons and it is
branched repeatedly. Dendrites may be present or absent, if
present it may be one or many in number. Dendrites has
Nissl granules and neurofibrils.
Dendrites transmits impulses towards the nerve cell body.
Usually the dendrite is shorter than the axon

14. AXON
 Axon is the longer process of the nerve cell. Each neuron
has only one axon. Axon arises from axon hilock of the nerve
cell body and it is devoid of nissl granules. Axon extend for a
long distance away from the nerve cell body. length of longest
axon is about 1 meter.
 Axon transmits nerve impulses away from the body.

15. ORGANIZATION & COVERING OF NERVE
 Each nerve is formed by b bundles or groups of nerve
fibers. Each bundle of nerve fiber is called a fasciculus.
 The whole nerve is covered by tubular sheath. which is
formed by areolar membrane. This sheath is called
epimeurium. Each fasciculus is covered by perineurium.
And each nerve fiber is covered by endoneurium.

16. NERVE IMPULSE
•Nerve impulse is wave of electrochemical
changes , which travel along the length of
the neuron involving chemical reactions and
movement of ions across the cell membrane.

17. MEMBRANE POTENTIAL
In neurons there are positive and negative
ions, and a charge separating barrier is a
plasma membrane. The electrical potential
that exists across a cell membrane is known
as membrane potential.

18. RESTING MEMBRANE POTENTIAL
 When a neuron is at rest it is much more positive electrically
outside then inside the cell membrane. The net difference in charge
between inner side and outer side of a non-conducting neuron is
called resting membrane potential. The major factors which are
involved in resting membrane potential are as follows:

19. FACTORS
1.Sodium and potassium ions.
2. Negative organic ions.
3. Leakage of potassium ions from neurons.
4. No conduction of nerve impulse.

20. SODIUM AND POTASSIUM IONS
 Sodium ions are tenfold higher in concentration outside then inside the
membrane surface.
 Potassium ions are twenty times more concentrated inside then outside.
 All the neurons have very active sodium and potassium pumps located in their
cell membranes.
 By the splitting of ATP these pumps transport sodium and potassium out and
potassium inside the cell, both against their concentration gradients.
 For every two potassium that are actively transported inward, three sodium
are pumped out. So inside become more negative then the outside of the cell
membrane or neurons.

21. NEGATIVE ORGANIC IONS
 The large numbers or organic ions such as
(proteins, organic acids etc) are much more inside
then outside of the membrane, where they are only
in negligible concentration. This makes inside of the
neuron much more negative

22. LEAKAGE OF POTASSIUM IONS
FROM NEURONS
 The cell membrane is virtually impermeable to all ions
except potassium. As the membrane is slightly permeable
to potassium, some of it leaks out of the cell . the loss of
this positive ion from the neuron by diffusion account for
more negative charges inside then out side the cell
membrane of neuron.

23. NO CONDUCTION OF NERVE
IMPULSE
 In unstimulated state the neuron has a membrane potential of approximately
-70mV.

24. INITIATION OF NERVE IMPULSE
A nerve impulse is initiated by an appropriate stimulus applied at
one end of tha neuron and it results in remarkable localized change in
the resting membrane potential . It disappears for a brief instant and
is replaced by a new potential called Action or Active membrane
potential which is in the form of impulse.
During this state, the inner membrane surface become more
positive than outside. This change is so brief that only a portion os the
neuron is in the active membrane potential state.

25. FACTORS
1.Sodium and potassium ions movement.
2.Charges are reversed.
3. Passage of Nerve Impulse.
4. Membrane potential.

26. SODIUM & POTASSIUM IONS
MOVEMENT
 The passage of nerve impulse is associated with increase
in permeability of Sodium ions moving inwards upsetting the
potential momentarily, making the inside more positive than
outside .Neurophysiologists believe that the increased
permeability is due to opening of specific pores in the
membrane ,termed “sodium gates” .when these gates open,
sodium ions rush into neuron by diffusion . Some K+ moves
out.

27. CHARGES ARE REVERSED
 The inner side of the cell membrane has excess of positive
ions as its internal surface, and the outer surface become
more negative.

28. PROPAGATION OF NERVE IMPULSE
 During active membrane potential, the neuron conducts the
impulse in the form of nerve impulse.

29. MEMBRANE POTENTIAL
Active membrane potential of +0.05 volts (+50mv) exists.
These changes occur along the length of the neuron till the impulse
reaches synapse. Soon after passage of the impulse, the resting
membrane potential is restored by the movement of a small number
of ions especially potassium moving out. This neuron now is ready to
conduct another impulse.

30. SALTATORY IMPULSE
 It may be added that in myelinated neurons the impulse jumps from node to
node. This is called Saltatory Impulse.

31. SYNAPSE

32. INTRODUCTION
 Synapses are bridges
 Function of the synapse is to transfer electric
activity (information) from one cell to another
 The transfer can be neuro-neuro or neuro-myo

33. PARTS OF SYNAPSE
Synapses consist of 3 parts:
 Pre synaptic end
 Synaptic cleft
 Post synaptic end

34. PRE-SYNAPTIC END
Efferent end of the synapse
Axon
Presynaptic end knob
Presynaptic membrane

36. SYNAPTIC CLEFT
Intermediate zone between the two
synaptic knobs Comprises of:
 Synaptic gap
 Neurotransmitters

37. POST-SYNAPTIC END
Post synaptic membrane
Postsynaptic receptors
Either muscle or postsynaptic knob

38. EVENTS OF TRANSMISSION
Calcium channels open
Neurotransmitter released
Receptors at post synaptic membrane
activated
sodium channels open
Nerve impulse arrives
Nerve impulse is regenerated

40. DIFFERENCE BETWEEN SYNAPSE
AND NEUROMUSCULAR JUNCTION
 Structural difference
Neurotransmitters
Inhibition and excitatory

41. NEUROTRANSMITTERS
 DEFINATION:
Neurotransmitter is a chemical substance that acts as a mediator for
the transmission of nerve impulse from one neuron to another neuron through a
synapse.
 FUNCTION:
The neurotransmitters are stored in tiny sac-like structures called
vesicles at the end of axons. When an impulse, or nerve signal, reaches the end of
the axon, the vesicles release a neurotransmitter into the small space between
the adjoining cells (synaptic gap). Neurotransmitters diffuse across the synapse
and bind to receptors in the receiving cell that are specific for the
neurotransmitter.

42. IMPORTANT NEUROTRANSMITTERS
Acetylcholine.
 Serotonin.
 Dopamine.
 Norepinephrine.
 Tryptophan.

43. ACETYLCHOLINE
 Location:
1. Neuromuscular Junctions
2. CNS
 Function:
1. Muscle Control 3. Sensory Response
2. Memory Formation 4. Excitatory
 Receptors:
1. Nicotinic 2. Muscurinic

44. SEROTONIN
LOCATATION:
1. Gut
2. CNS
FUNCTION:
1. Intestinal movement control
2. Mood regulation
3. Apitite
4. Sleep
5. Muscle control
RECEPTORS:
5-HT

45. DOPAMINE
 LOCATION:
Hypothalamus
 FUNCTION:
1. Voluntary motion
2. cognition
3. reward pathways
 RECEPTORS:
D1 , D2 , D3 , D4 , D5

46. NOREPINEPHRINE
 LOCATION:
Adrenal Medulla
 FUNCTION:
Fight or flight responce (increased heart beat ,
increased glucose level , increase oxygen to brain and muscles)
 RECEPTORS:
Adrenergic

47. TRYPTOPHAN
 LOCATION:
Blood
 FUNCTION:
Precursor to serotonin
 RECEPTORS:
N/A

48. THE END
 Thank You 