Download Co-ordination - BIFS IGCSE SCIENCE

Co-ordination
Overview
Analogy
NERVOUS SYSTEM is analogous to how a
telephone system may work i.e. fast but
short lasting in effect
ENDOCRINE SYSTEM is similar to sending
a letter through the post i.e. takes longer
to arrive but longer lasting
THE NERVOUS SYSTEM
This provides constant input (stimuli) from
our environment. It is designed to detect
changes that will increase an organisms
chances of survival.
We have 5 senses or sensations we can
detect. Cells or organs that detect these are
called SENSORY ORGANS, RECEPTORS
or AFFECTORS
CNS and PNS
The central nervous system consists of the
BRAIN and the SPINAL CORD it acts as
an exchange and data processing system.
The spinal cord is involved in REFLEX or
AUTOMATIC RESPONSES where no
thinking is involved.
The Peripheral nervous system are the
other nerves
NERVES AND NERVE CELLS
A nerve is a group of nerve cells rather like
an electric cable may be considered a
group of wires
Nerve cells are called NEURONS or
neurones. A neuron can only carry a nerve
impulse in ONE DIRECTION ONLY
Types of nerve/organ
 SENSORY
 RECEPTOR
 AFFERENT
 Run to CNS
 MOTOR
 EFFECTOR ORGAN
 EFFERENT NERVE
 Run from CNS
The synapse
This is a gap between one neuron and
another. The more synapses there are the
greater the delay in getting a reaction.
Reflex actions involve only one or two
synapses and the nerve impulse travels in
a REFLEX ARC
The “All or Nothing” law
A neuron either “fires” an impulse or it
does not. It can not send half a message
just in the same way as a rifle either fires a
bullet or it doesn’t.
Endocrine system
This produces a number of HORMONES
which are made in ductless glands around
the body. They reach their target organs
via the blood system and have an effect.
Try to learn the names of at least 3
hormones and know where they are made,
what the target organs are and what effect
they have.