THE NERVOUS SYSTEM
Humans have a complex nervous system with a brain, which
is large in proportion to our body size. The nervous system
performs three basic functions:
1.
2.
3.
It receives, stores and analyses information from sense organs such as the
eyes and ears, making us aware of our environment.
It controls the physiological activities of the body systems and maintains
constant conditions (homeostasis) within the body.
It controls our muscles, enabling us to move and speak.
The structure of the nervous system
The nervous system can be classified into two major divisions – CNS and PNS, and
one minor division – ANS.
1.
Central Nervous System (CNS) – consists of the brain and spinal cord
2.
Peripheral Nervous System (PNS) – is composed of 12 pairs of cranial
nerves and 31 pairs of spinal nerves which connect the CNS with sense
organs, muscles and glands. Functions of these nerves are mainly voluntary.
Peripheral nerves carry impulses to the brain and spinal cord from receptors in
the skin, eye, ear and nose and are called afferent (sensory) nerves (af- is a
prefix that means towards, ferent means carry). Those that carry impulses
from the CNS to organs that produce responses such as, muscles and glands
are called efferent (motor) nerves, (ef- means away, ferent means carry).
3.
Autonomic Nervous System (ANS) – this describes certain peripheral nerves
that send impulses to internal organs and glands. It consists of involuntary or
automatic nerves.
Neur is the word root for the nervous system and a nerve, neuro is the combining
form. It is the most complex of all the body systems.
Word root
Neur
Combing form
Meaning
Neur/o
nerve
Neurons are the basic structural units of the nervous system. They are specialised
cells, for the transmission of nerve impulses. There are three basic types of neuron sensory, motor and connector
Activity 1 Write the meaning of:
1.
neurology
__________________________________________________
2.
neuropathy
__________________________________________________
3.
neurohistology __________________________________________________
4.
polyneuritis
__________________________________________________
5.
neurospasm
__________________________________________________
THE NERVOUS SYSTEM
Page 1 of 6
Plex
Combining
form
Plex/o
Cephal
Cephal/o
Head
Encephal
Encephal/o
Brain
Cerebr
Cerebr/o
The cerebral hemispheres or cerebrum of the brain
Word root
Meaning
Network of nerves
Activity 2 Write the meaning of;
1.
Cephalalgia
__________________________________________________
2.
Cephalocele
__________________________________________________
3.
Hydrocephalus __________________________________________________
4.
Anencephalic
5.
Electroencephalograph ____________________________________________
__________________________________________________
Build words which mean;
1.
X-ray picture of the head ___________________________________________
2.
Pertaining to a very small head ______________________________________
3.
Tumour of a nerve ________________________________________________
4.
Hardening of a nerve ______________________________________________
5.
A specialist who studies nerves and their disorders ______________________
Disorders within blood vessels of the cerebrum can result in a stroke or apoplexy.
Reduction of blood flow (ischaemia) within the cerebrum causes cells to die due to
lack of oxygen and nutrients. As cells in this area control movements of many parts
of the body, paralysis of limbs and loss of speech are common symptoms of a CVA.
The severity of symptoms depends of the area of brain tissue damaged. Sometimes
there is recovery and the patient is left with slight paralysis.
The cerebral cortex
The outer layer of the cerebrum is known as the cerebral cortex. It is extensively
folded into fissures, giving it a large surface area. This part of the brain contains
motor and sensory areas and is the site of consciousness and intelligence.
Word root
Combining form
Meaning
Ventricul
Ventricul/o
Ventricle
Crani
Crani/o
Bones of the skull (cranium)
Gangli
Gangli/o, ganglion
Swelling – knot of nerve body
THE NERVOUS SYSTEM
Page 2 of 6
Mening
Mening/o, mening/i
Membrane
Radicul
Radicul/o
Spinal nerve roots
Myel
Myel/o
Marrow
Pleg
-plegia
Paralysis
Aesthesi
Aesthesi/o
Narc
Narc/o
Alges
Algesi/o, -algesia
Perception of sensation
Stupor – abnormally deep sleep induced by
a drug
Sense of pain
Rachi
Rachi/o
Spine
Activity 3 Write the meaning of;
1.
Postganglionic ___________________________________________________
2.
Meningioma _____________________________________________________
3.
Epidural
4.
Subdural haematoma ______________________________________________
______________________________________________________
Build words which mean;
1.
Incision into the skull ______________________________________________
2.
Condition of softening of the skull ____________________________________
3.
Inflammation of the meninges _______________________________________
SPINAL CORD
The spinal cord (myel is the word root, myel/o the combining form) extends from the
medulla oblongata to the second lumbar vertebra (the bony portion of the spine). It
carries all of the nerves that affect the limbs and the lower parts of the body; it is the
pathway for impulses going to and from the brain. The spinal cord is composed of
an inner section of grey matter (poli/o is the combining form meaning grey matter of
the brain or spinal cord) and an outer section of white matter.
MENINGES
The meninges are three layers of tissue that surround the brain and spinal cord;
1.
The dura mater is the outermost membrane, it is tough and thick and it contains
channels for blood to enter the brain tissue. The subdural space is below the
dura membrane, it contains many blood vessels.
2.
The arachnoid membrane is the second layer around the brain and spinal cord.
The space is called the subarachnoid space which contains cerebrospinal fluid
(CSF).
THE NERVOUS SYSTEM
Page 3 of 6
3.
The third layer which is closest to the brain and spinal cord is the pia mater. It
has a rich supply of blood vessels.
Rachiocentesis is performed to obtain a sample of cerebrospinal fluid (CSF) from the
subarachnoid space in the lumbar region of the spinal cord. This procedure is
commonly known as a lumbar puncture or spinal tap. Damage to the brain or spinal
cord can result in loss of movement in varying degrees, and to different parts of the
body. There can be paralysis of limbs, paralysis of right or left side of the body, or
paralysis of various activities such as speech. The term paraesthesia is used to
mean any abnormal sensations, such as ‘pins and needles’.
Activity 4 Write the meaning of:
1.
Quadriplegia _____________________________________________________
2.
Hemiplegia ______________________________________________________
3.
Paraplegia ______________________________________________________
4.
Anaesthesia _____________________________________________________
5.
Anaesthetic _____________________________________________________
6.
Anaesthesiology __________________________________________________
7.
Anaesthesiologist _________________________________________________
8.
Analgesia ______________________________________________________
9.
Analgesic ______________________________________________________
10. Narcosis
______________________________________________________
BRAIN
‘Encephal’ is the word root for the brain, (en- is a prefix that means in / within,
cephal is the root for head- within the head is the brain)
Parts
Combining
form
Cerebrum
cerebr/o
Cerebellum
cerebell/o
Thalamus
thalam/o
Hypothalamus (hypomeans below) is situated
below the thalamus
Brain stem consists of the
pons, and medulla
oblongata
THE NERVOUS SYSTEM
Function/Description
The cerebrum is the largest part of the brain
and has many functions:all thought;
judgement; memory; association;
discrimination; sensation
The cerebellum coordinates voluntary
movement
The thalamus is a large grey mass that acts
as a relay centre for body sensations, pain
The hypothalamus contains neurons that
control body temperature, sleep, appetite
and emotions such as fear and pleasure
The brain stem is the connection of nerve
fibre tracts. The medulla oblongata is where
nerve fibres cross over and contains
centres to regulate heat, blood vessels and
the respiratory system
Page 4 of 6
COMMON CONDITIONS OF THE BRAIN
Condition
Alzheimer’s disease
Palsy
Bell’s palsy
Cerebral palsy
Parkinson’s disease
Multiple sclerosis
(ms)
Epilepsy
Meaning
Brain disorder marked by deterioration of mental capacity
(dementia), resulting in degeneration of neurons and
neurofibrillary tangles in the cerebral cortex
unilateral (uni- is a prefix which means one) facial paralysis,
due to disorder of the facial nerve, aetiology unknown, but
recovery is usually complete
partial paralysis and lack of muscular coordination due to
damage to the cerebrum during birth
Degeneration of the nerves in the brain, leads to tremors,
weakness of muscles and slowness of movement
One of the leading causes of neurological disability, and a
chronic disease. The conduction of nerve impulses through
the axon is prevented leading to paraesthesia, muscle
weakness, unsteady gait and paralysis
Chronic disorder characterised by recurrent seizures and/or
fitting activity. Seizures and/or fitting are often symptoms of
brain disease conditions, such as tumours, meningitis,
vascular disease or tissue scarring from a head injury.
Terms and Word Parts:
cephal/o
encephal/o
cerebell/o
cerebr/o
chord/o
hemilamin/o
-lexia
lumbar
mening/o
meninges
myel/o
narc/o
neur/o
occipit/o
-paresis
-plegia
plexus
synapse
head
brain
cerebellum (reflex centre for the control of skeletal muscles (largest part of
the hindbrain)
cerebrum (largest and uppermost part of the brain - controls higher brain
functions)
a cord
half
lamino /thin plate / part of vertebral arch
condition of speech / words
pertaining to the lower back or loin
meninges
three membranes that surround the brain and spinal cord. outer –dura
mater, then arachnoid mater then pia mater
spinal cord or bone marrow
numbness, stupor
nerves
occiput, posterior region of the skull
weakness, slight paralysis
paralysis
a network of vessels or nerves
membrane-to-membrane contact of the nerve cell with another nerve cell
THE NERVOUS SYSTEM
Page 5 of 6
Abbreviations:
CAT or
CT Scan
CNS
EEG
MRI (Magnetic
Resonance
Imaging)
Computerised Axial Tomography - for the examination of the soft
tissues of the body. Ionising x-rays are beamed through the patient at
multiple angles, and a computer synthesises the information.
Central Nervous System
Electroencephalogram. (brainwave recording)
X-rays or a contrast medium are not used. Uses movement of hydrogen
nuclei (present in water and living tissue) to a larger magnetic field.
Conditions and Terms:
anaesthesia
loss of sensation resulting from medication
analgesia
loss or reduction of pain sensation
cerebrospinal
pertaining to the brain and spinal cord
encephalitis
inflammation of the brain
hemiparesis
weakness on one side (half) of the body
hemiplegia
paralysis on one side (half) of the body
hydrocephalus
excessive amount of cerebrospinal fluid within the skull
lumbar
pertaining to the lower back or loin
puncture of the lumbar area of the spinal canal for removal of
cerebrospinal fluid especially for diagnostic purposes or the
introduction of medication
complete or partial loss of controlled movement
pain that radiates along the sciatic nerve, usually affects buttocks,
thigh, and foot
sensation that one or one's surroundings are spinning
lumbar puncture
paralysis
sciatica
vertigo
TRAUMATIC DISORDERS
Cerebral Contusion
bruising of the brain
Subdural Haematoma
Sub
prefix meaning below
dur
word root for dura
-al
suffix meaning pertaining to
Haemat
word root for blood
-oma
suffix meaning
tumour/swelling
Epidural Haematoma
Epi
prefix meaning above/upon
dur
word root for dura
-al
suffix meaning pertaining to
Haemat
word root for blood
-oma
suffix meaning
tumour/swelling
THE NERVOUS SYSTEM
Page 6 of 6