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Nervous System | What Is Nervous System | Central Nervous System | Brain and Nervous System

  • Nervous system is a complex communication network and a powerful computer (Brain).
  • This powerful computer thinks, calculates, feels and controls the human body.

Structure Of Nervous System

  • Nervous system is a complex communication network and a powerful computer (Brain).
  • This powerful computer thinks, calculates, feels and controls the human body.

There are two main types of nervous system.

The Central Nervous System:

The central nervous system consists of the brain and the spinal cord.

Peripheral Nervous system:

Peripheral Nervous system consists of the nervous that branch from the brain and the spinal cord to other parts of the body.

  • Some nerves carry messages from the body to the brain to keep it informed.
  • Other nerves carry messages from the brain to the body parts to regulate the body parts and the person’s behavior.
  • Without nervous system there would be no psychological life.

Nervous Units of the System:

  • All the messages in the body are passed through specialized cells called neurons.
  • Neurons range from less than a millimeter to more than a meter in length about 1 trillion in number.

Parts Of a Neuron:

  1. Cell body
  2. Dendrites
  3. Axon
  4. Myelin sheath
  5. Terminal buttons
  6. Synapse

central part of neuron cell

Cell Body:

  • Central part of the nerve cell.
  • Contains nucleus (hereditary material).


  • Small branches that extend out of cell body.
  • Specialized to receive information.
  • Tree like spread out structure.


  • Small branches carrying messages away from the cell body (to the next neuron).
  • Length depends on the function that they are performing and the location that they are present in.

Myelin Sheath:

  • Axons are covered with fatty fiber called myelin sheath.
  • Insulates the axon and greatly increases the speed of neural transmission.
  • Axons carrying important messages are thickly sheathed of myelin for prompt action e.g. refer action.
  • Lots of muscle control is a disease called multiple sclerosis is due to degeneration of myelin sheaths.

Terminal Buttons:

  • Axons end in small bulges called TB. The terminal buttons secrete ‘Neuro transmitters’.
  • Neuro-transmitters send messages across neurons.


  • The gap between continues neurons is S-gap.
  • Messages are transmitted chemically through it.
  • The junction between one neuron and another is called the synapse.

Neural Transmission:

  • Neurons are filled with chemical fluid as well as bathed in chemical fluid (of different nature).
  • Both fluids contains charged particles called ions.
  • Negative charges on the inside positive NA + charges on the outside of semi-permeable membrane.
  • Resting state polarized neutrons.
  • When membrane is stimulated by an adjacent neutron semi-permeability of the neutron is charged.
  • Na + (positive) charges comes in depolarization.
  • All or none principle either there is or there is not.
  • Magnitude of the neural transmission is always the same.
  • Action potential created membrane regains its semi-permeability and NA+ ions are pushed out.
  • Tiny electrical storm of Na+ ions going in and out of the cell in 1/1000th of a second disturbs adjacent cells to cause the active potential to flow forward and carry the message.
  • The speed at which the active potential travels along an atom depends upon size and thickness of myelin sheath.
  • ------> Longer and thicker axons carry messages with high speed.
  • -------> Thicker myelin sheath carries messages with high speed.
  • Local anesthetics e.g. Novocain used by dentists stops pain by chemically interrupting the floe of active potential in the axon that carry pain messages.

Neuro Transmitters:

  • The neural message is carried across th synaptic gap by chemical substances called neurotransmitters.
  • Important link between the nervous system and behavior.
  • Excess or deficiency of neurotransmitters can produce severe behavior disorders. e.g. dopamine.
  • Most neurotransmitters are stored in “synaptic vesicles” located in the ends of axon called “synaptic knobs”.
  • There are different neuro transmitters in different areas of the body, thus the process of synaptic transmission in a certain part of a body, through the use of drugs that chemically changes the function of the neurotransmitters of that specific part.
  • Drugs can increase or decrease the effectiveness of N7.
  • Most drugs that have psychological effect influence neural transmission at the synapse e.g. alcohol or valium.

How Neurotransmitters Alter the Psychology and Behavior.

  • To reduce the symptoms of depression an anti depressant drag is introduced called selective “serotonin reuptake inhibitions”.
  • It permits certain neurotransmitters to remain active for larger and avoid being reabsorbed by terminal button.
  • Alcohol and valium ( tranquilizer are effective because they permit GABA to operate more efficiently).
  • Involved in variety of behavior ranging from eating to aggression.
  • Glutamate plays a role in memory.
  • Dopamine is involved in moment, attention and learning.
  • Effective treatment like physical and mental including Parkinson disease.
  • Overproduction schizophrenia due to cocaine drug abuse.
  • Acetyl choline plays a role in dreaming memory and wakefulness.
  • Serotonin helps in regulating sleep cycles dreaming appetite, anxiety, depression and inhibition.
  • Can be used to treat alcholists suicidal people, depressed aggressive etc.
  • Endorphin is released in people who believe drugs (meds) will make them better and they take placebos Leading to a reducing of pain.

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