There are two
ways in which responses are controlled in the body: the first is by using
nerves. The diagram below shows a motor nerve cell. The cell body would
be embed into the spine and the Synaptic knob at the opposing end would
be embedded into the effecter (usually a muscle). Electrical/nerve impulses
travel down the axon from the cell body; in mammals the axon is surrounded by a
second kind of cell called the Schwann cell and these form what is
called a Myelin sheath to increase the speed of nerve conduction.
The second
way of linking a receptor to an effector is known as the Endocrine system.
This involves an endocrine gland which produces Hormones (Proteins
or Steroids). The Hormone then enters the blood stream and travels through the
blood to the target tissue/organ where it will have an effect. Because
of this it is possible for hormones to have multiple targets and effects.
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