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Overview

1. The Nervous System Group 2

2. Contents The Nervous System
The Neuron
Basic Parts of a Neuron
Classification of Neurons
How Neurons Communicate
Neurotransmitters

3. The Nervous System The nervous system is the body’s most complex and organized system. It gathers
information from the senses, transmits it through the spinal cord, and processes it in the
brain to control movements, internal functions, and reactions. By sending rapid electrical
and chemical signals, it not only manages the body’s functions but also serves as the basis
of behavior, since it allows a person to detect and respond to stimuli.

4. Basic Functions Performed by the
Nervous System:
Receive sensory input from internal and external
environments
Integrate the input
Respond to stimuli

5. Basic Functions Performed by the
Nervous System:
The brain’s sensory centers and the spinal cord act like processing hubs for the
information our body receives. When signals from the senses flood in, these areas
organize and interpret them, then decide on the most suitable reaction. This
reaction, called a motor output, is the signal sent out to parts of the body—like
muscles, glands, or organs—that can turn it into action. Depending on the situation,
that action could be moving a muscle, adjusting the heartbeat, or releasing
hormones to regulate body functions.

6. Nervous Tissue
Composed of two main cell types: Neurons and Glial Cells
Neurons (Nerve Cells):
Transmit electrical signals
Control communication in the nervous system
Glial Cells:
Support, protect, and nourish neurons
Maintain balance and improve signal efficiency

7. The Neuron
The human body is made up of trillions of cells. Cells of the
nervous system, called nerve cells or neurons, are specialized to
carry "messages" through an electrochemical process. The
human brain has approximately 100 billion neurons.
Neurons come in many different shapes and sizes. Some of the
smallest neurons have cell bodies that are only 4 microns wide.
Some of the biggest neurons have cell bodies that are 100
microns wide.

8. The Neuron
Differences and Similarities of Neurons to Other Cells in the Body

9. BASIC PARTS OF A NEURON

10. Cell Body (Soma)
Nucleus – contains the cell’s genetic material and directs metabolic
functions.
Found in high density in the gray matter of the brain and spinal cord,
where processing occurs.
BASIC PARTS OF A NEURON

11. Axon
Carries signals away from the cell body to other neurons, muscles, or
glands.
Ends in branches tipped with terminal buttons that send messages.
The white matter of the brain and spinal cord is mainly bundles of
myelinated axons.
A nerve is simply a bundle of axons
BASIC PARTS OF A NEURON

12. Presynaptic Terminal / Membrane
Releases chemical messages (neurotransmitters) to communicate with
the next cell.
Dendrites
Carry signals toward the cell body from other neurons.
The postsynaptic membrane receives incoming messages.
Found in high density in gray matter, allowing extensive
communication between neurons.
BASIC PARTS OF A NEURON

13. Axons Vs Dendrites
BASIC PARTS OF A NEURON

14. Myelin Sheath
A fatty covering that wraps around the axon.
Functions as insulation, allowing signals to travel faster and more
efficiently.
Formed by specialized glial cells (Schwann cells in the PNS,
oligodendrocytes in the CNS).
BASIC PARTS OF A NEURON

15. Node of Ranvier
Small gaps between segments of the myelin sheath.
Enable saltatory conduction, where electrical signals “jump” from node
to node.
This greatly speeds up nerve impulse transmission.

BASIC PARTS OF A NEURON

16. Neurons can be classified by their structure and
function. Structurally, they differ in the number of
extensions from the cell body, while functionally, they
vary in the direction they transmit signals. These
classifications show how neurons are specialized to
detect, relay, and respond to information in the nervous
system
Classificication of Neurons

17. Bipolar Neurons
Have two processes extending from the cell body:
one axon and one dendrite.
Specialized for sensory pathways.
Examples: retinal cells (vision) and olfactory
epithelium cells (smell).
Classification of Neurons (by number of extensions
from the cell body)

18. Pseudounipolar Neurons
Appear to have a single process but actually have
two axons instead of an axon and dendrites.
One axon extends centrally toward the spinal cord,
while the other extends peripherally toward the
skin or muscle.
Example: dorsal root ganglion cells, which transmit
sensory information from the body to the spinal
cord.
Classification of Neurons (by number of extensions
from the cell body)

19. Multipolar Neurons
Has many processes extending from the cell body,
but only one axon.
Most common type of neuron in the nervous system.
Examples: spinal motor neurons (movement
control), pyramidal neurons (cerebral cortex), and
Purkinje cells (cerebellum).
Classification of Neurons (by number of extensions
from the cell body)

20. Sensory (Afferent) Neurons
Carry information from sensory receptors (skin, eyes, ears, nose,
tongue) toward the central nervous system (CNS).
Allow the body to detect changes in the environment (e.g., touch,
sound, light, smell, taste).
Classification of Neurons (by direction of information
flow)

21. Motor (Efferent) Neurons
Carry information away from the CNS to muscles or glands.
Responsible for actions like muscle contraction and gland
secretion.
Classification of Neurons (by direction of information
flow)

22. Interneurons
Connect sensory and motor neurons, serving as communication
links.
Found mostly in the CNS (brain and spinal cord).
Play a key role in reflexes, thought processes, and complex
signaling.
Classification of Neurons (by direction of information
flow)

23. Within a Neuron
Neurons send messages using an electrical signal called an action
potential. This is a rapid electrical charge that travels down the axon.
The action potential is generated by the movement of ions (charged
particles) across the neuron's membrane, creating the electrical flow
necessary to carry the signal.
Signal → Action Potential → Travels down axon (via ion movement)
How Neurons Communicate

24. From One Neuron to Another
Communication between neurons happens at a junction called a synapse. When an
action potential reaches the end of an axon, tiny sacs known as synaptic vesicles
release chemical messengers called neurotransmitters. These neurotransmitters
cross the small gap between neurons, known as the synaptic cleft, and bind to
receptor sites on the next neuron’s dendrites. This process stimulates the receiving
neuron, allowing the signal to continue through the nervous system.
Action Potential → Synaptic Vesicles release neurotransmitters →
Neurotransmitters cross the Synaptic Gap → Bind to Receptors on Dendrites
→ Next Neuron is Stimulated
How Neurons Communicate

25. Neurotransmitters are chemical messengers in the brain that transmit
signals between neurons and other parts of the body. They play a vital
role in regulating mood, movement, memory, and behavior. Imbalances
in these chemicals are associated with conditions such as anxiety,
depression, memory disorders, seizures, and paralysis.
Neurotransmitters

26. Acetylcholine (ACh) – The first neurotransmitter discovered; essential
for nerve-to-muscle communication.
Function: Enables muscle action (excitatory), learning, and memory.
Malfunctions:
Deterioration → Alzheimer’s disease;
Curare poison blocks ACh → paralysis;
Black widow spider venom floods ACh → violent muscle
contractions.
Examples of Neurotransmitters

27. Glutamate – The brain’s main excitatory neurotransmitter, often
described as its “on switch.”
Function:
Triggers body activity, supports learning and memory.
Malfunctions:
Excess glutamate may overstimulate the brain, leading to
seizures or cell damage.
Examples of Neurotransmitters

28. GABA (Gamma-aminobutyric acid) – The primary inhibitory
neurotransmitter, acting as the brain’s “off switch.”
Function:
Reduces brain activity and promotes relaxation.
Malfunctions:
Low GABA levels are linked to anxiety, seizures, and insomnia.
Examples of Neurotransmitters

29. Dopamine – Known as the “pleasure chemical,” linked to motivation
and reward.
Function:
Reinforces pleasurable behavior, regulates movement,
attention, and learning.
Malfunctions:
Low dopamine → Parkinson’s disease
Excess dopamine → schizophrenia, addiction
Examples of Neurotransmitters

30. Norepinephrine – A neurotransmitter involved in stress and alertness.
Function:
Increases attention, alertness, and supports REM sleep.
Malfunctions:
Low levels are associated with depression and low energy.
Examples of Neurotransmitters

31. Serotonin – Often called the “mood stabilizer.”
Function:
Regulates mood, appetite, sleep, arousal, and pain perception.
Malfunctions:
Deficiency may lead to depression, anxiety, and sleep
problems.
Examples of Neurotransmitters

32. Anandamide – Known as the “bliss molecule,” it produces effects
similar to cannabinoids (chemicals that affect mood, pain, and memory).
Function:
Relieves pain, reduces nausea, stimulates appetite, and
produces feelings of pleasure.
Malfunctions:
Excess can interfere with short-term memory and focus.
Examples of Neurotransmitters

33. Endorphins – Natural painkillers produced by the body.
Function:
Reduce pain, enhance pleasure, and reinforce positive
behavior.
Malfunctions:
Low levels increase pain sensitivity and risk of depression.
Examples of Neurotransmitters

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