Topics: Nervous system, Neuron, Axon Pages: 3 (423 words) Published: November 23, 2013
The Nervous System
The nervous system of a mammal consists of:
The central nervous system (CNS) comprising the brain and the spinal cord. The peripheral nervous system (PNS) comprising the cranial nerves, spinal nerves and sense organs. Neurone
A neurone is a nerve cell.
A nerve fibre is a long protoplasmic extensions of the cell body of a neurone. It serves to transmit impulses. A nerve is a collection of nerve fibres.
Types of neurons
1. Sensory neurones:
a receptor neurone,
transmits impulses from the sense organ (receptor) to the CNS. 2. Motor neurone:
an effector neurone.
transmits impulses from the CNS to the effectors.
3. Relay neurone:
connects sensory neurones to motor neurones.
A synapse is a junction between two neurones.
A dendron transmits impulses towards the cell body of a neurone. An axon transmits impulses away from the cell body of a neurone.  
 Parts of mammalian brain
voluntary actions
 regulation of body temperature and blood osmotic pressure
 pituitary gland
 secretes a number of hormones
 optic lobes
 sight and movement of eyeball
 muscular coordination
body balance
 medulla oblongata
 involuntary actions, eg:
respiratory movements

Reflex Actions
Reflex actions involve messages being transmitted from the sensory neurone to the motor neurone without involving the conscious part of the brain. A reflex arc is the shortest pathway by which impulses travel from the receptor to the effector in a reflex action. Ecosystem:

1. Deforestation
soil erosion
loss of habitat
loss of valuable species
climatic changes
upsets oxygen and carbon dioxide balance
2. Air pollution
Caused by
burning of fossil fuel
exhaust fumes from motor vehicles
burning of garbage
3. Water pollution
Caused by
discharge of...
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