The Nervous System. The nervous system is made of: . Interconnected neurones , specialised for rapid transmission of impulses These carry impulses from receptor cells Neurones also carry impulses to effector cells which carryout appropriate responses.
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Simplest nervous system is made up of a receptor, neurone and nerve endings associated with an effector
(brain and spinal cord in us)
Neurones are individual cells each one having a nerve fibre that carries impulses
(axons ordendronsthe name relates to direction of impulse)
(from the Latin saltare – to jump)
The molecules diffuse across the synaptic cleft and bond with receptors on the post-synaptic membrane
Once the transmitter has had its effect, it is broken down by enzymes in the cleft so it can react with new impulses.
Neurones interact in a variety of complex ways…
Sometimes, if one knob isnt enough to stimulate a response, but a second impulse from the same one arrives soon after, it may trigger an AP
Secondary receptors are made up of one or more completely specialised cells (NOT neurones)
eg slows down the rate of dopamine reabsorption in synapses
MDMA blocks serotonin reuptake so the synapses are flooded with serotonin
Day length determines bud development, flowering, fruit ripening and leaf fall. Chlorophyll formation needs light. Without light plants die.
If the whole plant is kept in the dark but one leaf is given usual levels of light and dark – flowering occurs as normal.
If a number of plants are grafted together, but only one is exposed to correct lighting regime, all flower!
They all require chemical signals.
The side of a plant exposed to light has less auxin in than the darker side