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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.