Download The Nervous System - Science with Mr. Enns

The Nervous System
Part 1: Neurons
3 Major Functions
The nervous system is made up of
your brain, spinal cord and neurons.
Your nervous system has 3 main jobs:
To SENSE
To INTERPRET
To REACT
Monitors
changes
(stimuli) inside
or outside
the body using
receptors
Analyzes
information
from the
receptors and
decides what
to do
Activates
muscles or
glands to
produce a
suitable
response
Stimulus
Stimulus
A stimulus is any change
or signal in the
environment that makes
an organism react.
Stimulus
Response
After your nervous
system detects a
stimulus, it causes
a response.
The Senses
The nervous system monitors the
environment using the 5 senses.
Sight
Touch
Taste
Smell
Hearing
Neurons
Neurons are special cells that carry
messages around the body.
These messages are called impulses.
There are over 100 billion
neurons in the human body.
Each neuron connects with
roughly 100,000 others!
Neurons
Cell body
Dendrites
Axon
Synapse
Types of Neurons
There are 3 main types of neurons.
Sensory
Neuron
Motor
Neuron
Interneuron
Detects a
stimulus and
sends an
impulse to
other
neurons.
Carries an
impulse to a
muscle or
gland to
create a
response.
Connects
neurons
together.
Found in
brain and
spinal cord.
Types of Neurons
Response
Motor
Interneuron
Stimulus
Sensory
Neuron
Stimulus
Sensory Neuron
1. Stimulus
Detected by a
sensory neuron…
Cell
Body
1. Stimulus
Detected by a
sensory neuron…
2. Dendrite
Impulse starts
at the dendrite
and moves to
the cell body…
Axon
1. Stimulus
Detected by a
sensory neuron…
2. Dendrite
Impulse starts
at the dendrite
and moves to
the cell body…
3. Axon
Nerve impulse
then moves down
the axon …
Synapse
1. Stimulus
Detected by a
sensory neuron…
2. Dendrite
Nerve impulse
begins in the
dendrite and moves
to the cell body…
4. Synapse
3. Axon
The axon ends at
Nerve impulse
a synapse: a
then moves down
junction between
the axon …
two neurons…
Synapse
There is a gap where 2 neurons meet.
This gap is called a synapse.
The synapse is where the impulse
jumps from one neuron to the next
But electricity cannot “jump”!
So chemicals called
neurotransmitters
do the jumping!
Step 1
Impulse in the first
neuron causes
neurotransmitter
molecules to move
to the synapse…
Step 2
1
Neurotransmitter
molecules jump
across the synapse
to the other neuron
Step 3
Neurotransmitters
reach the other side
and start the
impulse in the
second neuron
Any Questions?
The Nervous System
Part 2: The CNS and PNS
The Nervous System
The nervous system is made up of 2 divisions.
Central Nervous
System (CNS)
Peripheral Nervous
System (PNS)
Made up of the
brain and spinal
cord.
A network of nerves
connecting the rest
of the body.
Acts as the control
center of the body.
Carry impulses to
and from the CNS
CNS vs. PNS
CNS
brain
spinal cord
PNS
all other
neurons
CNS – The Brain
The brain makes up the main
part of the central nervous system.
It controls most functions in the body.
Some actions require thinking:
conscious actions
Other actions are automatic:
subconscious actions
Cool Brain Facts
An adult human brain weighs 3 pounds.
It is the most complex thing in the universe.
It contains roughly 100 billion neurons.
Each neuron connects with 100,000 others.
The brain uses 1/3 of the food we eat each day.
The fastest supercomputer in the world is nothing
compared to the average brain.
Parts of the Brain
The brain has 4 major parts:
Cerebrum
Cerebellum
Brain Stem
Cortex
Each part controls different things…
Parts of the Brain
Cerebrum
Interprets input from the
senses, controls movement,
and carries out complex
thought and memory
Cerebellum
Coordinates your muscles
during movement,
helps maintain balance
Parts of the Brain
Brain Stem
Controls involuntary actions,
like heartbeat, breathing
and digestion
Cortex
Connects the two brain
hemispheres together,
coordinates brain activity
Brain Hemispheres
Left Hemisphere
Right Hemisphere
“Logical”
“Creative”
Words & Symbols
Pictures & Graphs
Read & remember
Do & remember
Orderly
Chaotic
Likes predictability
Likes spontaneity
CNS - The Spinal Cord
The spinal cord is the main information pathway.
It connects the brain to the
peripheral nervous system.
The spinal cord is a small tube
packed with interneurons
It is well-protected inside the
vertebral column – your spine.
The PNS
The peripheral nervous system is a huge
network of nerves throughout the body.
It carries impulses to and from the CNS.
There are a total of
43 nerves, in 23 pairs.
It is involved in voluntary
and involuntary actions.
The PNS
The PNS is split into 2 divisions:
Somatic
Nervous System
Autonomic
Nervous System
Nerves that control
voluntary actions.
Nerves that control
involuntary actions.
Walking, learning,
talking, eating, etc.
Breathing, digestion,
reflexes, etc.
Reflexes
A reflex is a rapid, automatic response
that happens without conscious control.
Reflexes protect the body from harm.
Reflexes are complex
actions that bypass the brain
They involve the spinal cord
and other nerves ONLY
Reflex Arc
Effector
Motor
Interneuron
Stimulus
Sensory
Neuron
Reflex Arc
A reflex arc follows several steps:
1. A sensory receptor detects a stimulus.
2. An impulse is sent down a sensory neuron.
3. Interneurons in spinal cord interpret it.
4. An impulse is sent down a motor neuron.
5. A muscle or gland carries out a response.
Any Questions?