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The
Nervous System (part I)
Adrian
Whyte and Joanna Johnson, Contributor
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| Papine's
goalkeeper Jerome Burrell (right)
bends to kick away the ball while
making a save off a shot from
Wolmer's Boys Ovane Dixon (left),
while Burrell's teammates Oraine
Reed (second left) and Kimani
Airey react during the Jamaica
Hockey Federation (JHF)/Inter-Secondary
Schools Sports Association (ISSA)
Under-19 competition at the Mona
hockey field in January. The game
ended 1-1. - Ricardo Makyn Photo |
The
nervous system performs three main functions:
-
To receive sensory input from internal
and external environments
-
To integrate the input
- To
respond to stimuli
The
nervous system is made up of two main
parts:
- Central
nervous system (CNS)
- Peripheral
nervous system (PNS)
THE
CENTRAL NERVOUS SYSTEM
The
central nervous system (CNS) consists
of the brain and the spinal cord.
All of the CNS is protected by bone;
the brain in the skull and the spinal
cord within the vertebrae.
The
brain is composed of three parts:
the medulla oblongata, the cerebellum
and the cerebrum.
MEDULLA
OBLONGATA
The
medulla oblongata is closest to the
spinal cord and is involved with the
regulation of heartbeat, breathing,
vasoconstriction (blood pressure),
and reflex centres for vomiting, coughing,
sneezing, swallowing, and hiccupping.
The
hypothalamus, also found in the medulla
oblongata, regulates homeostasis.
It has regulatory areas for thirst,
hunger, body temperature, water balance
and blood pressure, and links the
nervous system to the endocrine system.
THE
CEREBELLUM
The
cerebellum is the second largest part
of the brain. It is responsible for
muscle coordination and maintaining
of normal muscle tone and posture.
It coordinates balance.
THE
CEREBRUM
The
cerebrum controls the body voluntary
behaviour. It governs intelligence
and reasoning, learning and memory.
THE
SPINAL CORD
This
is a long, fragile tube-like structure
that begins at the end of the brain
stem and continues down almost to
the bottom of the spine (spinal column).
It carries messages from the body
to the brain, where they are analysed
and interpreted.
Response
messages are then passed from the
brain through the spinal cord and
to the rest of the body. It is also
the centre for reflex action such
as the knee jerk reflex.
Just
as the skull protects the brain, the
vertebrae protect the spinal cord.
These are separated by disks made
of cartilage which act as cushions,
reducing the forces generated by movements
such as walking and jumping.
Protruding
from the spinal cord between the vertebrae
are 31 pairs of spinal nerves.
The
spinal cord consists of grey and white
matter. The butterfly-shaped centre
of the cord consists of grey matter.
The front 'wings' (called horns) contain
motor nerves which transmit information
from the brain or spinal cord to muscles,
stimulating movement.
The
back horns contain sensory nerves
which transmit sensory information
from other parts of the body through
the spinal cord to the brain. The
white matter contains nerve fibres
that carry sensory information to
the brain from the rest of the body
and columns that carry impulses from
the brain to the muscles.
*
Adrian Whyte and Joanna Johnson
teach Biology at Ardenne High School
masterbio@gmail.com.
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