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By Po-Han Chen. The Nervous System. What good does it make?.

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By po han chen

By Po-Han Chen

The Nervous System

What good does it make
What good does it make?

Creatures on the world can feel the surrounding in order to adapt the environment for survival. Animals relies on Endocrine system and Nervous system to adjust itself. Nervous system controls muscle contraction and coordinate the organs within a short time in order to protect itself.

3% of overall mass, but it is the most complicated system in body

Nervous system
Nervous System

  • The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body


Your Nervous system is mainly made up of

The Nerves

Spinal cord

The Brain

Nerve cells
Nerve Cells

The nervous system is made up of Neurones.

Each neurone consists of a cell body and extending nerve fibre

Neurons can be divided into 3 types sensory motor interneurons

Neurons can be divided into 3 types




Neurons and Synapses

Sensory neurons
Sensory Neurons

INPUT Fromsensory organs to the brain and spinal cord.

I.e., from Nose, eyes to brain

Motor neurons
Motor Neurons

OUTPUTFrom the brain and spinal cord To the muscles and glands.

Interneurons relay neurons
Interneurons (Relay Neurons)

Interneurons carry information between other neurons only found in the brain and spinal cord.

The neuron can be separated into 4 parts the cell body dendrites axon myelin sheath

The Neuron can be separated into 4 parts :

The cell body



Myelin sheath

Structure of Neuron

The cell body
The cell body

Round structure

Contains DNA

Dose Protein manufacturing

Directs metabolism

No role in neural signaling

Contains the Cell’s Nucleus


Information collectors

Receive inputs from neighboring neurons

If enough inputs the cell’s AXON may generate an output

The nervous system

Output structure

One axon per cell, 2 distinct parts

The tube branches at the end and attaches to other cells.

Youtube video
YouTube Video


How neurons communicate
How neurons communicate

  • Neurons communicate by electrical signal called the Action Potential.

  • it is based on movements of ions between cells.

  • When an Action Potential occurs a molecular message is sent to neighboring neurons

The big boss
The Big Boss

Brain is the organ that controls everything in your body, including your thought and reaction.

Nervous system1
Nervous System

The nervous system is divided into two sections:

Central Nervous System


Outer Nervous System

Central nervous system
Central Nervous System

The Central Nervous System is made up of Brain and Spinal cord

Electrical Signals are carried from the Brain to the receptors through Spinal cord

The path
The Path

  • Betweenthe receptors and the effectors, the Central Nervous system coordinates the action potentials passing through the nervous system.

Outer nervous system
Outer Nervous System

The Outer Nervous System is made of the nerves and the sense organs

Sense Organs includes

Skin - Touch

Nose - Smell

Tongue - Taste

Nerve impulse
Nerve Impulse

Electrical signals are carried through nerve impulse which is widely spread in the body

Action potential
Action Potential

An action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a stereotyped trajectory


  • Resting neurons have Potential Difference

    Outer surface-> Positively charged

    Inner surface -> Negatively charged

  • Resting potential (-65mV), therefore said Polarised

How does it work
How does it work?

  • Resting potential is generated by Sodium-potassium pump and a potassium channel

  • The pump moves three sodium ions out by active transport for every two potassium ions brings in.

  • The facilitated diffusion allowed to let potassium ions back out.

  • More positive ions move out than move in.

Depolarise when stimulated
Depolarise when Stimulated

  • Sodium potassium pumps work all the time, but Channel protein can be opened or closed.

  • Depolarisation requires another protein channel, which is Sodium Channel.

    When Stimulated, sodium channel opens and then ions diffuses in. This increases the positive charge inside the cell. Charge is now Reversed. With a potential difference of +40mV, This is Action Potential and membrane is depolarised.

Makes it much easier
Makes it much easier


Practice questions
Practice Questions

  • Q: What do sensory, relay and motor neurons do in the nervous system?

  • Answer:

    Sensory – INPUT Fromsensory organs to the brain and spinal cord.

    Relay – Interneurons carry information between other neurons only found in the brain and spinal cord.

    Motor – OUTPUTFrom the brain and spinal cord To the muscles and glands.

Practice questions1
Practice Questions

  • Q: Give two factors that increases the speed of conduction of action potentials

  • Answer:

    Bigger axon diameters

    Increase in temperature


  • Notes from Richard