how does the neurons are comminicate b/w them they understood their neurotransmitter whether it's excitatory or inhibitarory

1. 10-11-2019

2. Receptors

3. • Receptors are sensory (afferent) nerve endings that
terminate in periphery as bare unmyelinated
endings or in the form of specialized capsulated
structures.
• receptors are often defined as the biological
transducers, which convert (transducer)
various forms of energy (stimuli) in the environment
into action potentials in nerve fiber.
• Generally, receptors are classified into two types:
A. Exteroceptors.
B. Interoceptors.

4. 1- EXTEROCEPTORS:
• Exteroceptors are the receptors, which give
response to stimuli arising from outside the
body.
• Exteroceptors are divided into three groups:
1. Cutaneous Receptors OR
Mechanoreceptors.
2. Chemoreceptors.
3. Telereceptors.

5. Cutaneous Receptors

6. 2- INTEROCEPTORS:
• Interoceptors are the receptors, which give
response to stimuli arising from within the
body.
• Interoceptors are of two types which are as
follows:
1. Visceroceptors.
2. Proprioceptors.

8. PROPERTIES OF RECEPTORS:
1. SPECIFICITY OF RESPONSE – MÜLLER LAW:
The response given by a particular type of receptor to
a specific sensation. For example, pain receptors
give response only to pain sensation.
2. ADAPTATION – SENSORY ADAPTATION:
Decline in discharge of sensory impulses when a
receptor is stimulated continuously with constant
strength.
a) Phasic receptors= Touch and pressure receptors
(adapted rapidly).
b) Tonic receptors= Muscle spindle, pain receptors
and cold receptors (adapted slowly).

9. 3. RESPONSE TO INCREASE IN STRENGTH OF
STIMULUS – WEBERFECHNER LAW:
During the stimulation of a receptor, if the response
given by the receptor is to be doubled, the strength
of stimulus must be increased 100 times.
4. SENSORY TRANSDUCTION:
is a process by which the energy (stimulus) in the
environment is converted into electrical impulses
(action potentials) in nerve fiber.
e.g. if pressure stimuli is applied to the nerve under
the skin, causes transmission of this stimuli as an
action potential inside the nerve fiber not as a
pressure.

10. 5. RECEPTOR POTENTIAL or generator potential:
a nonpropagated transmembrane potential
difference that develops when a receptor is
stimulated.
6. LAW OF PROJECTION:
When a sensory pathway
from receptor to cerebral
cortex is stimulated on any
particular site along its
course, the sensation
caused by stimulus is always
felt (referred) at the
location of receptor,
irrespective of site
stimulated.

12. • Synapse is the junction between two neurons.
• Synapse is classifed by two methods:
A. Anatomical classifcation
B. Functional classifcation.
• ANATOMICAL CLASSIFICATION:
o Axoaxonic synapse.
o Axodendritic synapse.
o Axosomatic synapse.

13. • FUNCTIONAL CLASSIFICATION:
o Electrical Synapse.
o Chemical Synapse.

14. • Neuron from which the axon arises is called the
presynaptic neuron and the neuron on which the
axon ends is called postsynaptic neuron.
• Axon of the presynaptic neuron divides into many
small branches before forming the synapse.
• These branches are known as presynaptic axon
terminals.
• Types of Axon Terminals:
1. Terminal knobs (excitatory function).
2. Terminal coils or free endings
(inhibitory function ).

16. Structures in pre and post-synaptic:
• Presynaptic axon:
Mitochondria.
Synaptic vesicles.
Presynaptic membtane.
• Synaptic cleft:
cholinesterase,
which destroys acetylcholine.
• Postsynaptic neuron:
Postsynaptic membrane.
Receptor protein.

17. FUNCTIONS OF SYNAPSE:
• Main function of the synapse is to transmit the
impulses, i.e. action potential from one neuron to
another.
On the basis of functions, synapses are divided into
two types:
1. Excitatory synapses, which transmit the impulses
(excitatory function).
2. Inhibitory synapses, which inhibit the transmission
of impulses (inhibitory function).
EXCITATORY FUNCTION:
Excitatory Postsynaptic Potential
• Is the non-propagated electrical potential that develops
during the process of synaptic transmission.

18. Steps of EPSP:
Common excitatory
neurotransmitter in a synapse is
acetylcholine.

20. INHIBITORY FUNCTION:
Inhibitory Postsynaptic Potential
• Inhibitory postsynaptic potential (IPSP) is the
electrical potential in the form of
hyperpolarization that develops during
postsynaptic inhibition.
• Types:
1. Postsynaptic or direct inhibition
2. Presynaptic or indirect inhibition
3. Negative feedback or Renshaw cell inhibition
4. Feedforward inhibition
5. Reciprocal inhibition.

21. 1. Postsynaptic or Direct Inhibition :
• Release of an inhibitory neurotransmitter from
presynaptic terminal instead of an excitatory
neurotransmitter substance.
• It is also called direct inhibition.
• Inhibitory neurotransmitters are
gammaaminobutyric acid (GABA), dopamine and
glycine.

22. Steps of IPSP:

23. 2. Presynaptic or Indirect Inhibition:
• Failure of presynaptic axon terminal to release
sufficient quantity of excitatory neurotransmitter
substance.
• Axoaxonal synapses.
• Prominent in spinal cord.

24. 3. Renshaw Cell or Negative Feedback
Inhibition:
• Renshaw cells are small motor neurons
present in anterior gray horn of spinal cord.

25. 4. Feedforward Inhibition :
• occurs in
cerebellum and
it controls the
neuronal
activity in
cerebellum.

26. 5. Reciprocal Inhibition:
• Inhibition of antagonistic muscles when a group
of muscles are activated.

27. PROPERTIES OF SYNAPSE:
A. ONE WAY CONDUCTION – BELL-MAGENDIE LAW.
B. SYNAPTIC DELAY (short delay, in which
neurotransmitter is released and cellular response
is done).
C. FATIGUE (depletion of neurotransmitter substance
either by destruction or not synthesized).
D. SUMMATION:
I- Spatial Summation.
II- Temporal Summation.
E. ELECTRICAL PROPERTY (EPSP and IPSP).

29. CONVERGENCE AND DIVERGENCE:
• Convergence is the process by which many
presynaptic neurons terminate on a single
postsynaptic neuron.
• Divergence is the process by which one presynaptic
neuron terminates on many postsynaptic neurons.

30. Neurotransmitters

31. • 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.
Properties of the neurotransmitters:
• Neurotransmitters must be present, produced, or
released by the neuron.
• Neurotransmitters must be act on target ells and
produced the response.
• Neurotransmitters must be inactivated after the
response.
• (amino acids, amines, others {nitric oxide,
Acetylcholine}).
• Excitatory or inhibitory neurotransmitters.

32. 1- ACETYLCHOLINE:
• Acetylcholine is a cholinergic neurotransmitter
• It possesses “excitatory function”.
• (acetyl CoA + choline).
• It is hydrolyzed into acetate and choline by the
enzyme acetylcholinesterase
• Muscarinic receptors and Nicotinic receptors.
• Nicotinic receptors are also present in the
neuromuscular junction on membrane of skeletal
muscle.

34. 2- NORADRENALINE:
• Noradrenaline is the neurotransmitter in
adrenergic nerve fibers.
• Excitatory chemical mediator.
• Inhibition in few places.
• Involved in dreams,
arousal and elevation
of moods.

35. 3- DOPAMINE:
• Dopamine possesses inhibitory action.
• Prolactin inhibitory hormone secreted by
hypothalamus is considered to be dopamine.

36. 4- SEROTONIN:
• Serotonin is otherwise known as 5-
hydroxytryptamine (5-HT) .
• Large amount of serotonin (90%) is found in
enterochromatin cells of GI tract.
• Small amount is found in platelets and nervous
system.
• It is an inhibitory substance. It inhibits impulses of
pain sensation in posterior gray horn of spinal cord.
• It is supposed to cause depression of mood and
sleep.

38. 5- HISTAMINE :
• is an excitatory neurotransmitter.
• Play an important role in arousal mechanism.

39. 6- GAMMAAMINOBUTYRIC ACID:
• Is an inhibitory neuro transmitter in synapses
particularly in CNS.
• Causes synaptic inhibition by opening potassium
channels and chloride channels.

40. 7- SUBSTANCE P:
• Substance P is secreted by the nerve endings
(first order neurons) of pain pathway in spinal cord.
• It mediates pain sensation.
• It is responsible for regulation of anxiety, stress,
mood disorders, neurotoxicity, nausea and vomiting.

41. 8- NITRIC OXIDE:
• Nitric oxide (NO) is a neurotransmitter in the
CNS.
• Dilator effect.
• Endothelial cells of blood vessels.

42. •NEUROMODULATORS

43. • Neuromodulator is the chemical messenger, which
modifies and regulates activities that take place
during the synaptic transmission.
• Not propagate nerve impulses like neurotransmitters.
• Action of neuromodulators:
Regulation of synthesis, breakdown or reuptake of
neurotransmitter.
Excitation or inhibition of membrane receptors by
acting independently or together with
neurotransmitter.
Control of gene expression.
Regulation of local blood flow.
a) NONOPIOID PEPTIDES.
b) OPIOID PEPTIDES.

44. poppy
(Papaver
somniferum)

45. Nonopioid
neuromodulators
Opioid
neuromodulators:

46. COTRANSMISSION:
• Release of many neurotransmitters from a single
nerve terminal.
Examples of cotransmitters:
1. Calcitonin
2. Dopamine
3. Dynorphin
4. GABA
5. Gene-related peptide
6. Glutamate
7. Glycine
8. Neuropeptide Y
9. Substance P
10. Vasoactive intestinal
polypeptide (VIP).