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Biology revision – Nervous Coordination and Muscles (Unit 15)
Neurones and nervous coordination
- Specialisation of cells means that they have lost other functions and thus rely on other
cells to carry out the function that they no longer specialise in
- These different functional systems must be coordinated if they are to efficiently work
- No body system works in isolation – all must be integrated in coordinated fashion
Principles of coordination
- Two main forms of coordination in animals as a whole – nerves and hormones
Nervous system:
- Uses nerve cells to pass electrical impulses along length
- Stimulate target cells by secreting chemicals (neurotransmitters) directly onto them
o Leads to rapid communication between specific parts of an organism
- Responses produced are often short-lived and restricted to a localised region of the
body – example is a reflex action
Hormonal system:
- Produces chemicals that are transported in the blood plasma to their target cells
- Target cells have specific receptors on cell surface membranes and the change in the
conc of hormones stimulates them
- Results in slower, less specific form of communication between organism parts
- Results normally long lasting and widespread – example is control of blood glucose
Hormonal system Nervous system
Communication is by chemicals called hormones Communication is by nerve impulses
Transmission by blood Transmission by neurones
Transmission is slow Transmission rapid
Hormones travel to all parts of the body, but only the target Nerve impulses travel to specific parts
cells respond
Response is widespread Response is localised
Response is slow Response is rapid
Response is long-lasting Response is short-lived
Effect may be permanent and irreversible Effect is temporary and reversible
Neurones
- Specialised cells adapted to rapidly carrying electrochemical changes called nerve
impulses from one part of the body to another
Mammalian motor neurone is made up of:
- Cell body – contains all the usual cell organelles, including a nucleus and large
amount of RER
o This is associated with the production of proteins and neurotransmitters
- Dendrons – extensions of the cell body which divide into smaller branched fibres
called dendrites that carry nerve impulses to the cell body
- Axon – single long fibre that carries nerve impulses from the cell body
- Schwann cells – surround axon, protecting it and providing electrical insulation
o Also carry out phagocytosis and play a part in nerve regeneration
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