Medical Terminology for Cancer

© Copyright 1996-2013

13: The Nervous System (Brain and nerves)

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Functions of the Nervous System
About Neurons
Nerves, Neuroglia, and Ganglia
The Spinal Cord
The Brian
The Sensory Systems
The Autonomic Nervous system (ANS)
Roots, suffixes, and prefixes
Cancer Focus
Related Abbreviations and Acronyms
Further Resources

Functions of the Nervous System

The complex activities of the body are controlled jointly by the Endocrine and the Nervous systems. As opposed to the Endocrine system the Nervous system has a more or less instant effect on the body via a complex network of nerves and control centres. The Central Nervous System (CNS) includes the brain and spinal cord, while Peripheral Nervous System (PNS) includes nerves connected to the spinal cord. The nervous system can be further divided into sub-systems, all of which are composed of neurons and connective tissue:

Nervous system

About Neurons

Neurons are specialised cells of the nervous system, they vary greatly in appearance and length, but contain a similar structure:

The three categories of neurons:

Properties and characteristics of Neurons:

Nerves, Neuroglia, and Ganglia

A nerve is a bundle of fibres (axons and/or dendrites) outside the CNS.

Neuroglia are cells of the nervous system that help protect and support it.

Ganglia are groups of nerve cell bodies lying outside the CNS.

The Spinal Cord

A spinal tract is a bundle of fibres in the CNS that travel long distances up or down the spinal cord. Ascending tracts carry impulses up the cord to the brain, while descending tracts carry impulses down the cord from the brain. Tracts run along the spinal canal inside the protective spinal column, conveying sensory and motor (movement ) information to and from the brain. Spinal meninges are tough tubes of tissue which protect the cord.

The Brian

The brain is highly complex, it contains about 1000 billion neurons, and weighs about 3 lbs in adults.

There are four main areas of the brain:

  1. The brain stem is at the base of the brain where it joins the spinal chord (contains the medulla, pons, and mid brain)
  2. The diencephalon is above the brain stem (contains the thalamus and hypothalamus)
  3. The cerebrum is above the diencephalon and forms the majority of the brain
  4. The cerebellum is the lower back of the brain

The brain has two hemispheres , there are functional differences, for example the left had side of the brain controls the right hand side of the body and visa versa (lateralisation).

Neurotransmitters are substances which excite or inhibit the neurons of the brain, facilitating communication between brain cells. These include endorphins, neuropeptides.

Cerebrospinal fluid circulates around the brain and spinal tracts to provide protection in addition to that provided by the meninges and protective bones of the spine and skull. A lumbar puncture (spinal tap) is where a needle is placed between the vertebra in the lower back. A sample of cerebrospinal fluid might be taken to see if cancerous cells have entered the CNS, or chemotherapy might be administrated to prevent or combat CNS involvement.

The Sensory Systems

A receptor or sense organ picks up stimulus and converts it into a nerve impulse. This impulse is then conducted along a neural pathway to the brain, where the signal is converted into a sensation. There are various receptors:

The Autonomic Nervous system (ANS)

The nerves of the ANS activate the involuntary smooth muscles, cardiac muscles, and some glands.

Roots, suffixes, and prefixes

Most medical terms are comprised of a root word plus a suffix (word ending) and/or a prefix (beginning of the word). Here are some examples related to the Nervous System. For more details see Chapter 4: Understanding the Components of Medical Terminology

ASTRO-star astrocyte = star shaped brain cell
CRANI-skull cranial radiation = radiation to the head
CEPHAL-head encephal = the brain, en(in) cephal (the head)
MENING-membrane meningitis = inflammation of the membranes of the spinal chord
NEUR-nerve neuroblast = an immature nerve cell
VENTRICULO-cavity ventricles are small cavities in the brain & spinal cord. Ventriculscopy = examination of ventricles
-MALACIAsoftening neuromalacia = morbid softening of the nerves
-GRAMrecord electroencephalogram (EEG) = brain scan

Cancer Focus

Overview of CNS Tumours
Childhood CNS Tumours
Childhood Brain tumours are the second most common type of childhood cancer. They are however a diverse group of different types of tumours. Classification of brain tumours is based on both histopathology and location in the brain. For example, undifferentiated neuroectodermal tumours of the cerebellum are referred to as medulloblastomas, while tumours with similar histology in the pineal region would be diagnosed as pineoblastomas. Patients may present with headaches, drowsiness, weakness, or vomiting caused by the pressure inside the skull caused by the growing tumour.

Medulloblastoma is nearly always found in children or young adults, 80% are found in children aged under 15. It can spread from the medulla (part of the brain stem) to the spine or to other parts of the body. Prognosis will depend on the child's age, how much of the tumour remains following surgery, and whether the cancer has metastasised.

Cerebellar astrocytoma arise in brain cells called astrocytes. Cerebellar astrocytoma is usually low grade (slow growing and non metastatic cells), while Cerebral astrocytoma can be malignant.

Brainstem gliomas are tumours arising in the mid brain, pons or medulla. They may grow rapidly or slowly, depending on the grade of the tumour, but overall have a less favourable prognosis compared to other tumours such as Cerebellar astrocytoma.

Other brain tumours include: Primitive neuroectodermal tumour (PNET), craniopharyngioma, intracranial germ cell tumour, pineal parenchymal tumour, and optic tract glioma.

Internet Resources for Childhood Brain Tumours
Adult CNS Tumours
Internet Resources for Brain Tumours
Cancers of the Eye
Retinoblastoma is a rare tumour of the eye which develops in the cells of the retina, most patients are under 5 years old. Sometimes only one eye is affected (unilateral-retinoblastoma ), but in about two fifths of patients both eyes have the disease (bilateral-retinoblastoma ). Some cases are known to be hereditary.

Internet Resources for Retinoblastoma
Intraocular Melanoma
Intraocular melanoma is a rare cancer, in which malignant cells are found in the uvea (this is the part of the eye which contains the iris and other tissues). The uvea contains melanocytes which are cells that contain colour, intraocular melanoma occurs when these cells become cancerous.

Internet Resources for IntraOcular Melanoma
Neuroblastoma occurs most often in babies, very young children. It is a disease in which cancer cells are found in certain nerve cells in the body, it originates in the adrenal medulla or other sites of sympathetic nervous system tissue. The most common site is the abdomen, either in the adrenal glands or around the spinal cord. The majority of patients present with metastatic disease. Age and stage are the main prognostic factors. Patients aged under one year at diagnosis have a more favourable prognosis. Stage 4S are a special group of patients aged under one year whose neuroblastoma may undergo spontaneous regression (tumour disappears without treatment). Also patients aged under one a higher proportion of low stage patients compared to older patients. There is an excess of males compared to females, there are a higher proportion of males in patients with less favourable sites and stage.

Internet Resources for Neuroblastoma

Related Abbreviations and Acronyms

ABTAAmerican Brain Tumour Association
BAERBrainstem Auditory Evoked Responce
CNSCentral nervous system - the brain and spine
CSFCerebro spinal fluid
EANOEuropean Association for NeuroOncology
EEGElectroencephalogram - brain scan
INFAInternational Neurofibromatosis Association
INSSInternational Neuroblastoma Staging System
LPLumbar puncture
NNFFNational Neurofibromatosis Foundation (USA)
NSENeuron-Specific Enolase - a neural marker
PNETPrimitive neuroectodermal tumour Context: CNS tumours
PNSPeripheral nervous system - nervous system outside the brain and spine.

Further Resources (3 links)

Main Contents of this Guide Alphabetical Index Next Chapter: Reproductive System

This guide by Simon Cotterill

First created 4th March 1996
Last modified: 1st February 2014

Medical Terminology for Cancer

What is Cancer?
Basic Terms
Components of Terminology

Body Systems

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