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Module 3
The
Neuron
Structure of the Brain
• Genes
– chains of chemicals that are arranged
like rungs on a twisting ladder
– there are about 100,000 genes that
contain chemical instructions that
equal about 1,000,000 pages of
written instructions
– genes program the development of
individual parts into a complex & brain
body
STRUCTURE OF THE BRAIN
•
There are (2) types of cells that make up
your brain.
1. Glial cells have many functions
– guide the growth of developing neurons
– wrap around neurons and form an
insulation to prevent interference from
other electrical signals
– release chemicals that influence a
neuron’s growth and function
– help repair neurons when damaged
– remove the carcasses of dead neurons
STRUCTURE OF THE BRAIN
2. Neurons
– Transmit messages to other neurons
as well as the rest of the body
– Are responsible for all psychological
activities either physical or mental:
1. physical: beating of heart, voluntary
movement, sweating, pain etc.
2. mental: emotions, intelligence,
language, etc.
they have….
STRUCTURE OF THE BRAIN
…… 2 specialized extensions
– one extension is for receiving
chemical signals
– the other extension is for
transmitting chemical signals
Types of Neurons
6 PARTS OF THE NEURON
1.Cell Body
– large egg-shaped structure that provides fuel,
manufactures chemicals, and maintains the entire
neuron in working order
2.Dendrite
– branchlike extensions that arise from the cell body
– receive signals from other neurons, muscles, or
sense organs
– pass these signals onto the cell body
6 PARTS OF THE NEURON
3. Axon
– a single threadlike structure that extends
from and carries signals away from the
cell body to the axon terminals.
4. Myelin Sheath
- segments of fatty material that wrap
around the axon insulating it from the
electricity of other axons
6 PARTS OF THE NEURON
5. End/Terminal Bulbs
- tiny bulbs at the end of the axon where
neurotransmitters are stored and released to
other neurons
6. Synapse
- a “infinitely” small space (20-30 billionths of
a meter) between the end bulb and a muscle,
organ, or other neuron
Neuron Types
Next…..Functions of a Neuron
•Neurons function by creating small
electrical currents.
•This currents make the neuron send
signals in the form of chemicals to
other neurons, organs, muscles.
FUNCTIONS: SENDING INFORMATION
ACTION POTENTIAL SEQUENCE
• Sending information
– action potential is a tiny electrical
current that is generated when the
positive sodium ions rush inside the
axon
– the enormous increase of Na ions
inside the axon causes the inside to
reverse its charge
– the inside becomes positive & the
outside becomes negative
….How?: SENDING INFORMATION
ACTION POTENTIAL SEQUENCE
– axon membrane has chemical gates
that can open to allow electrically
charged particles to enter or can close
to keep out these particles
– ions are chemical particles that have
electrical charges
– opposite charges attract and like
charges repel
FUNCTIONS: SENDING INFORMATION
ACTION POTENTIAL SEQUENCE
• Sending Information
– the neural impulse refers to the series of
separate action potentials that take place
segment by segment as they move down
the length of the axon (Like a Fuse)
• All-or-None law
-if an action potential starts at the beginning
of the axon, the action potential will continue
at the same speed segment to segment to the
very end of the axon
FUNCTIONS: SENDING INFORMATION
ACTION POTENTIAL SEQUENCE
• Resting state
– the axon has a charge
– the charge results from the axon
membrane separating positive ions on
the outside from negative ions on the
inside
To Review:Functions of a
Neuron
• 1. Neurons do not actually touch
each other
• 2. They are separated by the
synapse.
• 3. Neural impulses force the
neuron (terminal buttons) to
release chemicals into this
synapse.
• 4. The chemicals then attach to
the dendrites from another
neuron.
Synapse
The synapse is a small gap separating
neurons.
This space is absolutely microscopic.
Neuron Structure (including Synapse)
NEUROTRANSMITTER
• Neurotransmitters
– dozens of different chemicals that are
made by neurons and then used for
communication between neurons during
the performance of mental or physical
activities
NEUROTRANSMITTER
• Excitatory transmitters
– open receptor locks and turn on neurons
therefore “exciting” organs,
muscles,other neurons
• Inhibitory transmitters
– close locks and turn off neurons
therefore “slowing” down organs,
muscles, other neurons
Neurotransmitters
Chemicals released to other
neurons or body organs.
•Some are excitatory
Ex: they speed up your heart
when you’re angry, prepare
you for “fight or flight”
Neurotransmitters

Some types of transmitters
can be inhibitory:
***That is they relax,
depress, or slow you down.
Ex:Slow your heart while
you sleep, slow down the
feelings of pain to your
brain (alcohol, painkillers)
Types of
Neurotransmitters
Acetylcholine- Movement, memory
-If these neurons are destroyed what can
happen?

Dopamine- dopamine is similar to
adrenaline, affects movement, emotional
response, and ability to experience
pleasure and pain.
*** Schizophrenia
Types Of Neurotransmitters
Norepinephrine- this
chemical can effect your
mood, arousal, memory
etc.
**Cocaine produces more
of this chemical to
drastically affecting your
mood

Types of Neurotransmitters

Serotonin- low levels in the
brain to abnormal behaviors,
such as: depression, suicide,
alcoholism, and explosive
rage. High levels: obsessive
compulsion, fearfulness, lack
of self-confidence, and
shyness.
Overlap of Specific
Neurotransmitters
Lastly: Endorphins

Endorphins- relieve pain,
control your well-being.
Cocaine, Heroin, Alcohol create
these feelings and sometimes
leads to addiction.
Types of Neurotransmitters

GABA- relaxes,
controls your
movement. Alcohol
acts like GABA on
the brain and
reduces tension and
also effects other
transmitters.
WHAT DOES ALCOHOL DO?
• GABA Neurons
– GABA neurons have chemical locks that
can be opened by chemical keys in the
form of the neurotransmitter GABA
• GABA Keys
– alcohol molecules so closely resemble
those of the GABA neurotransmitter that
alcohol can function like GABA keys and
open GABA receptors
– when GABA neurons are excited, they
decrease neural activity
PERIPHERAL & CENTRAL
NERVOUS SYSTEM
• Peripheral Nervous System
– made up of nerves that are located
throughout the body, except in the brain
& spinal cord
• Central Nervous System
– made up of neurons located in the brain
& spinal cord
PERIPHERAL & CENTRAL
NERVOUS SYSTEM
• Nerves (Very different from neurons!)
– string-like bundles of axons and dendrites
that come from the spinal cord and are held
together by connective tissue
– carry information from the senses, skin,
muscles, and the body’s organs to and from
the spinal cord
– nerves in the peripheral nervous system
have the ability to grow or reattach if
severed or damaged
…Did You Know? REFLEX
• Reflex
– unlearned, involuntary reaction to some
stimulus
– neural connections underlying a reflex
are pre-wired by genetic instructions
REFLEX (CONT.)
• Reflex sequence
– sensors
• sensors trigger neurons that
start the withdrawal effect
– afferent neurons
• carry information from the
senses to the spinal cord
REFLEX (CONT.)
– Interneuron
• relatively short neuron whose primary
task is making connections between
other neurons
– Efferent neuron
• carry information away from the
spinal cord to produce responses in
various muscles and organs
throughout the body
(Basically…. the point is, reflexes
are involuntary and sometimes
don’t involve any connections to
your brain!