Neurons (also called neurones or nerve cells) are the fundamental units of the brain and nervous system, the cells responsible for receiving sensory input from the external world, for sending motor commands to our muscles, and for transforming and relaying the electrical signals at every step in between.and A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell.

1. Neurons and
Neurotransmitters
Presented by:
Mr.Vijay salvekar
Associate Professor
GRY Institute of Pharmacy,Borawan

2. Nervous System
– Central nervous system (CNS):
• Brain
• Spinal cord
– Peripheral nervous system (PNS):
• Sensory neurons
• Motor neurons (somatic and
autonomic)

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Central Nervous System (CNS)
Brain Spinal Cord
Peripheral Nervous System (PNS)
Sensory Neurons
Motor Neurons
Somatic Nervous System
• voluntary movements via
skeletal muscles
Autonomic Nervous System
• organs, smooth muscles
Sympathetic
- “Fight-or-Flight” responses
Parasympathetic
- maintenance
The Nervous System
The Nervous System

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Divisions of the autonomic nervous system

5. The Nervous System
• A physical organ system like any other
• 2 main kinds of cells
– Neurons
– Glia

6.  Basic units of the nervous system
 Receive, integrate, and transmit
information
 Operate through electrical impulses
 Communicate with other neurons
through chemical signals
 More about neurons and neuronal
anatomy later
Neurons

7. Glial cells
• 100 billion neurons
• 10x more glial cells
• Glial cells
– Support neurons ( provide physical support,
as well as nutrients)
– Cover neurons with myelin
– Clean up debris
– “Housewives”

8. • Regulate
external
environment
(ions, etc.)
• Most abundant
glial cell
• May contribute
to blood-brain
barrier
and to synapses
Astrocytes

9. Three main types of neurons
• Sensory Neurons
• Interneurons
• Motor Neurons

10. Sensory (Afferent) vs. Motor (Efferent)
e.g., skin
e.g., muscle
Gray’s Anatomy 38 1999
sensory (afferent) nerve
motor (efferent) nerve
Neurons that send signals from the senses,
skin, muscles, and internal organs to the CNS
Neurons that transmit commands from the
CNS to the muscles, glands, and organs

11. The Withdrawal Reflex

12. Neuron Anatomy and Neural
Communication

13. Neurons
Axon of another
neuron
Cell Body
Dendrites
Axon
Myelin
Sheath
Dendrites of
another neuron

14. Neural Anatomy
 Dendrite
 the bushy, branching extensions of a
neuron that receive messages and
conduct impulses toward the cell body
 Axon
 the extension of a neuron, ending in
branching terminal fibers, through which
messages are sent to other neurons or to
muscles or glands

15. Neural Anatomy and
communication
 Synapse
 junction between the axon tip of the sending
neuron and the dendrite or cell body of the
receiving neuron
 tiny gap at this junction is called the synaptic
gap or cleft
 Synapse movie

16. Specific Parts: The Neuron
Structure

17. Specific Parts: The Neuron
Function
Neurons = 3 functions: Reception, Conduction, Transmission
1.
3.
2.

18. Action Potential
When dendrites stimulated, the delicate
balance is altered
Membrane breaks down
Positively charged ions rush in
(depolarization)
Charge = less negative
Causes release of chemicals from
terminal buttons

20. Relay Race
• Action Potential starts at dendrite
– Through cell body
– Down Axon
– Axon Terminals
• How does it get to the next cell’s dendrites?
• Neurons don’t touch
– Synapse = millionth inch gap
– In synapse = vesicles w/ neurotransmitters
» Chemical messengers that transmit info

21. Communication
• Impulse releases
neurotransmitter from
vesicles
• Neurotransmitter
enters synaptic gap
• Neurotransmitter
binds to receptors on
the receiving neuron

22. Myelin Sheath
–Fatty material made by glial cells
–Insulates the axon
–Allows for rapid movement of
electrical impulses along axon
–Nodes of Ranvier: gaps in myelin sheath
where action potentials are transmitted
–Multiple sclerosis is a breakdown of
myelin sheath
–Speed of neural impulse Ranges from 2 –
200+ mph

23. Myelinization clip
Myelin conduction clip

24. • Different types of cells secrete different
neurotransmitters.
• Each brain chemical works in widely
spread but fairly specific brain locations
and may have a different effect according to
where it is activated.
• All of the major neurotransmitters are
made from amino acids except
acetylcholine. Some 60 neurotransmitters
have been identified.

25. • Neurotransmitters are the chemicals
which allow the transmission of signals
from one neuron to the next across
synapses.
• They are also found at the axon
endings of motor neurons, where they
stimulate the muscle fibers.
• They and their close relatives are
produced by some glands such as the
pituitary and the adrenal glands.

26. Neurotransmitters
 chemical messengers that traverse the
synaptic gaps between neurons
 when released by the sending neuron,
neurotransmitters travel across the
synapse and bind to receptor sites on
the receiving neuron, thereby
influencing whether it will generate a
neural impulse

27. Neurotransmitters (>60)
• Acetylcholine (ACh)
– 1st substance identified as NT
– Links motor neurons and muscles (contract or relax)
• e.g. curare vs black widow spider
– Also involved in memory, learning, sleep, dreaming
(acetylcholine movie)
• Endorphins (the brain’s own morphine)
– 1973 injected rats with morphine
– Bound like NTs
– Brain had receptors for exogenous substance?
• Brain must produce its own morphine
• Released during pain and discomfort

28. More neurotransmitters
Receptor binding movie