Transcript Sensory neurons

Neuron’s and The Nervous System
Created by Stella Thalluri 2013
www.beaconmedia.com.au
Neuron’s and The Nervous System
Humans are created in the image of God before birth. God is the Life behind
and beyond the simple flickering of biological cells, systems and processes.
“For you formed my inward parts; you knitted me together in my mother's
womb. I praise you, for I am fearfully and wonderfully made. Wonderful are
your works; my soul knows it very well. My frame was not hidden from you,
when I was being made in secret, intricately woven in the depths of the earth.
Your eyes saw my unformed substance; in your book were written, every one of
them, the days that were formed for me, when as yet there was none of them”.
Psalms 139:13-16
“Before I formed you in the womb I knew you, and before you were born I
consecrated you”. Jeremiah 1:5
Contents:
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The Stimulus Response Model
CNS AND PNS
ANS: Sympathetic and Parasympathetic
Signal Transduction
Myelin Sheath
Motor Neurons
Sensory Neurons
Interneurons
How does a electric signal move from neuron to neuron.
Toxins and Neuron Transmission
Motor Neurons
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A Motor Neuron is a specialised nerve cell that has the main purpose to carry a message from the CNS
to a muscle cell.
Motor Neurons send short pulses which produce a twitch in the body, if these twitches become so
fast, they produce smooth movement of the body which is known as Tetanus.
Motor Neurons are part of the PNS and are very important in movement, homeostasis and practically
every other system in the body from digestions, to making the heart beat at a constant and steady
rate.
Sensory Neurons
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Sensory Neurons are a part of the bodies nervous system that are responsible for
detecting external signals.
These neurons are rather important and special as they do not receive signals from
the body, but from external sources like sound, light and temperature.
In complex organisms like Humans, most signals travel through the CNS to the
brain but some reaction signals do not need to be processed by the brain and can
be sent directly to the appropriate motor neuron.
Interneurons
• Interneurons are a specific type of neuron that is
generally small and only connects to other neurons.
They are neither sensory or motor and have the
primary goal to send a message. They are primarily
found in the CNS (Brain and spinal cord)
Myelin Sheath
• Some important nerve cells have an axon that is covered in Myelin.
• Myelin is a fatty substance that acts as an insulator and allows an
nerve impulse to travel very quickly.
• Multiple Sclerosis is a disease where the Myelin Sheath is damaged
causing some signals to ‘short-circuit’.
How does a electric signal pass from
neuron to neuron
• When an electrical signal travels down an axon it must cross over a
gap between cells called the ‘synapse’. This occurs with a special
kind of signaling molecule called a ‘neurotransmitter’.
• Neurotransmitters are sent across the synapse and bind onto the
surfaces of special protein receptors. Once they reach the next cell
they are able to either inhibit or provoke the cell
The Stimulus Response Model
• The stimulus response model is a visual way to
communicate how the nervous system causes a
response to a specific stimulus. If the response directly
affects the stimulus, it is known as feed back.
Signal Transduction
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Signal transduction occurs when a cell converts one type of signal, into a different type that the cell
can understand.
In the nervous system, this involves the conversion of an electric signal to a chemical signal that can
move across the synapse between neurons to be converted back into an electric signal.
This process is split into three different sections which are known as Reception, Transduction and
Induction.
Reception: When a signaling molecule binds to its specific receptor
on a cell.
Transduction: Through a reaction with the receptor and its signaling
molecule, a ‘second messenger’ is created which enters the cytosol
of a cell.
Induction: The second messenger reaches its specific target and the
activation of specific cellular processes occurs.
Through signal transduction, a relatively small signal can eventually
cause a large response through the replication of the ‘second
messengers’.
CNS and the PNS
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The nervous system can be split into two
distinct sections. The CNS (Central Nervous
System) and the PNS (Peripheral Nervous
System).
The CNS includes the Brain and Spinal cord and
generally processes nearly all sensory inputs
and outputs in our body.
The PNS is generally responsibly for acting out
messages from the brain including regulating
systems and moving the body.
Some reactions from the body do not need to
be processed via the brain and can be directly
sent through the peripheral nervous system to
the correct neuron.
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The ANS: Sympathetic and
Parasympathetic
The sympathetic and parasympathetic
systems form the Autonomous Nervous
System (ANS) which is responsible for
controlling and regulating the body below
a conscious level. While it was originally
considered the sympathetic was ‘excitory’
and the parasympathetic ‘inhibitory’, this
has since been over-turned as there are
far too many exceptions for this. Both of
these systems have many different roles
but they both go together to form the
ANS.
This is a simpler way to think of it… (but
there are some exceptions)
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Parasympathetic: “Rest and Digest”
Sympathetic: “Fight or Flight”
Toxins and Neuron Transmission
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Many animals and bacteria contain toxins in their venom
or body and when these interact with the human body,
they can potentially cause devastating effects. This is
especially true for toxins that target the nervous system.
Some toxins are small enough to enter the axon and
interfere with the electrical pathway, causing paralysis
which can quickly result in death if the victim cannot
breathe.
Larger toxins often affect neurotransmitters crossing the
synapse causing a loss of nervous control.
One animal that can cause severe paralysis is the Blue
Ringed Octopus. This octopus can quickly inhibit a victims
breathing and death can occur within minutes. There is no
anti-toxin and artificial breathing must be used until the
toxin has been excreted from the body.
References
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http://txtwriter.com/Backgrounders/Drugaddiction/synapse.jpg
http://upclose.unimelb.edu.au/sites/upclose.unimelb.edu.au/files/images/myelin
_sheath.jpg
http://upclose.unimelb.edu.au/sites/upclose.unimelb.edu.au/files/
http://upclose.unimelb.edu.au/sites/upclose.unimelb.edu.au/files/
http://txtwriter.com/Backgrounders/Drugaddiction/synaps
http://upclose.unimelb.edu.au/sites/upclose.unimelb.edu.au/files/
http://encyclopediascience.files.wordpress.com/2011/05/sensory_neuron.gif
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/autonomic.gif
http://visual.merriam-webster.com/images/animalkingdom/reptiles/snake/morphology-venomous-snake-head.jpg
http://marinebio.org/upload/_cephs/Hapalochlaena-maculosa/3.jpg
Nature of Biology Book 1 4E by Judith Kinnear and Marjory Martin