NERVOUS
SYSTEM
Table 9
P R E P A R E D
B Y : P A D I L L O - O R E A - C A M P O S A N O B O R R O M E O
NERVOUS SYSTEM
Nervous system is a complex
collection of nerves and
specialized cells known as
neurons that transmit signals
between different parts of the
body.
TYPES OF
NEURON
NEURONS
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.
Sensory Neurons
Activated by sensory input and carry messages
from the outside environment. Carry impulses from
the sensory receptors, to the spinal cord and
brain.
Motor Neurons
These neurons take impulses from the spinal
chord to an effector.
There are in fact two types of motor neurons:
those that travel from spinal cord to muscle are
called lower motor neurons, whereas those that
travel between the brain and spinal cord are
called upper motor neurons.
Relay Neurons
Relay neurons are found in the brain and spinal
cord and allow sensory and motor neurons to
communicate. It carry impulses through the spinal
chord and up to the brain and from the brain back
along the spinal chord.
REFLEX ARC
The neural pathway that controls the
reflexes occurs through the reflex arc.
It acts on an impulse even before it
reaches the brain. There are some
stimuli that require an automatic,
instantaneous response without the
need of conscious thought.
It is an immediate response to a
stimulus by the nervous system.
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HOW IT WORKS:
The receptor here is the sense organ that senses danger. The
sensory neurons pick up signals from the sensory organ and send
them through other neurons which are interconnected. It is then
received by the relay neuron which is present in the spinal cord.
Immediately, the spinal cord sends back signals to the muscle
through the motor neuron. The muscles attached to the sense
organ move the organ away from danger. In reflex actions, the
signals do not travel up to the brain.
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BLOCK DIAGRAM OF
REFLEX ARC
SYNAPSES
Synapses is the connection between two neurons and it is
where neurons communicate with one another.
A small gap at the end of a neuron that allows a signal to
pass from one neuron to the next.
SYNAPSES
Synapses are found where nerve cells connect with other
nerve cells.
Synapses are key to the brain's function, especially when
it comes to memory.
SYNAPSES
WHAT SYNAPSES DO?
1. When a nerve signal reaches the end of the neuron, it cannot simply continue
to the next cell. Instead, it must trigger the release of neurotransmitters which can
then carry the impulse across the synapse to the next neuron.
2. Once a nerve impulse has triggered the release of neurotransmitters, these
chemical messengers cross the tiny synaptic gap and are taken up by receptors
on the surface of the next cell.
3. These receptors act much like a lock, while the neurotransmitters function much
like keys.
4. Neurotransmitters may excite the neuron they bind to or inhibit it.
Think of the nerve signal like the electrical current, and the neurons like
wires. Synapses would be the outlets or junction boxes that connect the
current to a lamp (or other electrical appliance of your choosing), allowing the
lamp to light.
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