COORDINATION AND RESPONSE
Irritability/sensitivity is a characteristic of all living organisms. It has three main components: sensitivity,
coordination and response. Cells and organs do not work independently. Their activities are coordinated
to carry out their various functions at certain times and certain rates according to the needs of the body.
Coordination in mammals is achieved through two systems each with its particular role.
The two systems are nervous and endocrine system. The nervous system deals with a rapid but short
lasting response whereas the endocrine system deals with slower responses.
THE NERVOUS SYSTEM
Specific objectives
Discuss the principle of detecting change in the environment and responding to it
Discuss the relationship of sensory (receptor) cells, sense organs and the effector organs.
Describe the functions of a sensory neurone, a motor neurone and a relay neurone.
Draw a labelled diagram of a sensory neurone, a motor neurone and a relay neurone.
SENSE ORGAN STIMULI RESPONSE
Eye light sight
Ear sound hearing
Nose Chemical in the smell
air
Skin Pressure, touch
temperature
Tongue Chemical in food taste
The nervous system in human consists of
i. The central nervous system: consists of the brain and the spinal cord, the function of which is to
receive information, integrate and process it.
ii. The peripheral nervous system: consists of the neurons, sense organs and effector organs.
The neurones link the central nervous system with the body’s receptors and effectors.
Sensory organs contain sensory cells called receptors
Receptors are sensory cells that receive stimuli from the internal and external
environment and convert them into nerve impulses. [N.B: Stimulus is any change
detected in the environment]
Effectors are structures that bring about a response .They include muscles and glands.
NEURONES
Neurones are also called nerve cells. Neurons are specialized to conduct electrical impulses.
All neurons have the following structures:
The cell body which contains a nucleus, many mitochondria and ribosomes. The nucleus in the
cell body controls all activities taking place within neurone.
Axon- transmit nerve impulses away from the cell body
dendron /dendrites conducts impulses towards the cell body .
myelin sheath which provides insulation. This increases speed of transmission of impulses
Synaptic knob –produces a chemical called neurotransmitter.
Node of ranvier –speed up transmission of impulses
Types of neurones
1. A sensory neurone - transmit impulses from the sense organs or receptors to the central nervous
system (CNS).
DRAWING
2. Motor neurone -transmit impulses from the central nervous system to effector organs.
DRAWING
3. Relay neurone (Intermediate/Multipolar neurone): are found within the central nervous
system and transmit impulses within the CNS.
DRAWING
ACTIVITY: use a table to compare sensory and motor neurones
