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Understanding the basic anatomy and physiology of the human body

The nervous system

The nervous system is responsible for coordinating all of the body's activities. It controls not only the maintenance of normal functions but also the body's ability to cope with emergency situations.

Function

The nervous system has three general functions: a sensory function, an interpretative function and a motor function.

  1. Sensory nerves gather information from inside the body and the outside environment. The nerves then carry the information to central nervous system (CNS).
  2. Sensory information brought to the CNS is processed and interpreted.
  3. Motor nerves convey information from the CNS to the muscles and the glands of the body.

Structure

The nervous system is divided into two parts:

  1. the central nervous system consisting of the brain and spinal cord. These structures are protected by bone and cushioned from injury by the cerebrospinal fluid (CSF)
  2. the peripheral system which connects the central nervous system to the rest of the body.
Drawing of a human showing the location of the brain and the spinal cord

The central nervous system

Central nervous system

These structures are protected by bone and cushioned from injury by the cerebrospinal fluid (CSF).

Brain

The brain is a mass of soft nerve tissue, which is encapsulated within the skull. It is made up of grey matter, mainly nerve cell bodies, and white matter which are the cell processes. The grey matter is found at the periphery of the brain and in the centre of the spinal cord. White matter is found deep within the brain, at the periphery of the spinal cord and as the peripheral nerves.

The brain is divided into:

Click here and roll the cursor over the different sections of the brain to see its name and function.

Activity 12

In this activity you will check your understanding of the structures of the brain. Click here.

Lobes of the brain

It is important to have an understanding of how the brain functions and which parts control our functioning and behaviour. For example, when a casualty suffers from a stroke, the part of the brain that is affected controls function. If it is the frontal lobe, speech, thought and movement may be affected.

Click here and roll the cursor over the different quadrants of the brain to see their names and functions.

Activity 13

In this activity you will test your understanding of the function of the lobes of the brain. Click here

The spinal cord

The spinal cord is about 45 cms long, extending from the medulla down to the second lumbar vertebrae. It acts as a message pathway between the brain and the rest of the body. Nerves conveying impulses from the brain, otherwise known as efferent or motor nerves, travel through the spinal cord down to the various organs of the body. When the impulses reach the appropriate level they leave the cord to travel to the' target organ.

Sensory or afferent nerve impulses also use the spinal cord to travel from various parts of the body up to the brain.

Click here and roll over the diagram to see parts of the spinal chord.

Peripheral system

The peripheral system connects the central nervous system to the rest of the body. The main divisions of the Peripheral Nervous System are:

As messages travel from one neuron to the next they move across a synapse. At each synapse there is a chemical called a neurotransmitter. At various parts of the body specific neurotransmitters facilitate communication, for example dopamine (motor function), serotonin (mood) and endorphins (painkillers). Sensory neurons carry messages from a receptor to the brain. The brain then interprets the message. Motor neurons then send the message to an affector in muscles and glands.

Receptor (sensory organ) sends a signal to the sensory neuron which sends a signal to the brain/spinal chord which sends a signal to the motor neuron which sends a signal to the affector (muscle/gland).

The neurone

The basic unit of the nervous system, is a specialised cell called the neurone. These nerve cells make up a massive network of specialised cells that transmit messages, very rapidly, from one part of the body to another. Information is transmitted via electrical impulses.

The neurone is comprised of a nerve cell and its adjoining processes called an axon and dendrites. Every nerve cell has one or more processes attached to it. Electrical impulses enter the neurone via the dendrites and leave via the axon. The space between the axon of one cell and the dendrites of another is called a synapse. Specialised chemicals called neurotransmitters help conduct impulses through the synapse onto the next cell.

Activity 14

In this activity you will learn how to locate and identify the structures of the neurone. Click here to begin.

For further information, go to the Virtual Body at http://www.medtropolis.com/Vbody.asp