Download The Nervous System

The Nervous System
A System for Communication
& Regulation of Life Process
What Does the Nervous
System Do?
It Helps Maintain Homeostasis
How?
It brings messages
from one place to
another.
By Using Special Cells
Neurons
(Nerve cells)
are the basic functional unit of the
nervous system.
Neurons
receive, conduct, and send
impulses.
A Typical Neuron
Terminal Bulbs
Dendrite
Terminal Branches
Cyton
Axon
Cyton
How Do Impulses Start?
They Need a Stimulus
Stimulus
(plural = stimuli)
a change in the external or internal
environment that an organism
responds to.
Examples
External
Light, Sound, Pressure, Cold, Hot, etc..
Examples
Internal
Chemicals Changes, Temperature Changes, etc...
Different Types of Neurons
next slide
Inter-neuron
Sensory Neuron
Motor neuron
???
Parts of the Neuron
Explained
The Dendrite
Dendrites
receive stimuli from sense
organs or from other
neurons in the form of a
neurotransmitter.
Cell Body
Cell Body
conducts impulses from
the dendrites toward
the axon
Axon
Axon
conducts impulses from
the cyton toward the
terminal branches
Myelin Sheath
Myelin Sheath - an
arrangement of cells
around the axon. It helps
protect the axon and
speed up impulses.
Terminal Branches
Terminal Branches
a fork in the axon.
Synaptic Knobs
Synaptic KnobsReleases chemicals
called
Neurotransmitters,
which allow the message
to be received by the
next neuron, or a muscle,
gland, organ etc…
Terminal (Synaptic) Knobs
Neurotransmitters
Impulse Direction
Neurotransmitters
Synapse
How Neurotransmitters Work
neurotransmitters
Neurotransmitters diffuse from the end of one neuron to receptors on the next
neuron. When they land on the specific receptor they allow gates to open that
allow sodium to enter - this ignites the electro-chemical impulse to begin in the
the next neuron.
Impulses
What are impulses?
The cell membrane of a neuron
conducts electrical signals from on
end to another - in one direction.
The inside of a neuron has an
overall negative charge, and the
outside has an overall positive
charge.
Outside Neuron
Inside neuron
Channels
The outside of a neuron has sodium
ions (Na+). The inside has
negatively charged proteins.
Neither of these chemicals can
pass through the cell membrane.
They are attracted to each other
because of their opposite charge.
There are many protein channels
along the membrane where sodium
(Na+) can enter, but only when the
gate is open.
Stimuli cause the gates to open
The flow of charge (negatives or
positives)across the membrane is
electricity. This is why the impulse
of a neuron is said to have an
electrico-chemical nature.
Steps in making an impulse
Steps in making an impulse
A stimulus occurs
Either an external (sound, light,
etc..) source or an internal
source (such as a
neurotransmitter).
Steps in making an impulse
Gates Open
This allows the sodium to enter the
cell.
Steps in making an impulse
Adjacent Gates Open
The opening of one gate cause the
next gate to open - like dominos
Steps in making an impulse
The Impulse Travels to the
End of the Neuron
Steps in making an impulse
Neurotransmitters are released
when the impulse reaches the
Terminal Knobs
The Reflex Arc
A special pathway
The Advantage of a Reflex
The advantage of a reflex is that we can
respond quickly to a stimulus.
A reflex pathway does not involve the
brain which is an advantage because the
reflex is quicker.
Pathway of a Reflex
Sensory
Organ
Stimulus
Sensory
Neuron
Interneuron
Effector
(Muscle or Gland)
Motor Neuron
Diseases
of the Nervous System
Cerebral Palsy
Results from brain damage, usually at
birth. It is a term used to describe a
group of diseases that affect the ability
to control movement.
Multiple Sclerosis (MS)
Results from damage to the Myelin Sheath.
Symptoms vary but may include: shaking,
blurred vision, slurred speech, and weakness.
Parkinson’s Disease
Involves a particular group of brain cells
in the brain.
Symptoms: Tremors, poor balance,
stiffening of the muscles.
* The thinking functions is usually OK.
Alzheimer's Disease
Degenerative disease of the brain. The
person usually loses the ability to
remember, think correctly and speak.
The condition usually gets worse over
time once it starts. It may take years to
notice.
Notes
This slide presentation is a work in progress.
Please feel free to notify the author of any
mistakes or suggestion for improvement.