Fiiro gaar sii waa muhiimee
Biology Grade 12
CHAPTER ONE
COMMUNICATION AND CO-ORDINATION
1.1. Introduction
Animals need to detect and respond suitably to change in the environment. Lower animals
possess simple structures; whereas higher animals have evolved elaborate structures for
detection and co-ordination of the affecting responses.
Irritability in animals is brought about by the nervous system. In higher animals such as
vertebrates, irritability is brought about by a more elaborate nervous (neuro-sensory)
system and the endocrine (hormonal) system. The nervous (neurosensory) system provides
the quickest means of communication in animals.
Fig. 1.1 (a): The human nervous system.
1.2. The Nervous System
The human nervous system consists of the central
nervous system (CNS) and peripheral nervous
system.
See figure 1.1(a).
1. Central Nervous System is made up of the
brain and spinal cord. It receives and
integrate impulses from the receptors and
then relays them to the effector organs.
It is the centre of co-ordination.
2. Peripheral nervous system These is made
up of sensory nerves and transmit nerve impulses from the receptors in sensory
organs to the CNS and motor nerves that transmit impulses from CNS to effector
organs. Figure 1.2 shows this relationship.
Figure: 1.1 (b) Summary of nervous system
• Figure: 1.2 Relationship of CNS and motor organs
Ka baro badmaceeye iskuul madooyiinka cilmiga.....
•https://.www.badmaceeye.blogspot.com
CHAPTER ONE
COMMUNICATION AND CO-ORDINATION
1.1. Introduction
Animals need to detect and respond suitably to change in the environment. Lower animals
possess simple structures; whereas higher animals have evolved elaborate structures for
detection and co-ordination of the affecting responses.
Irritability in animals is brought about by the nervous system. In higher animals such as
vertebrates, irritability is brought about by a more elaborate nervous (neuro-sensory)
system and the endocrine (hormonal) system. The nervous (neurosensory) system provides
the quickest means of communication in animals.
Fig. 1.1 (a): The human nervous system.
1.2. The Nervous System
The human nervous system consists of the central
nervous system (CNS) and peripheral nervous
system.
See figure 1.1(a).
1. Central Nervous System is made up of the
brain and spinal cord. It receives and
integrate impulses from the receptors and
then relays them to the effector organs.
It is the centre of co-ordination.
2. Peripheral nervous system These is made
up of sensory nerves and transmit nerve impulses from the receptors in sensory
organs to the CNS and motor nerves that transmit impulses from CNS to effector
organs. Figure 1.2 shows this relationship.
Figure: 1.1 (b) Summary of nervous system
• Figure: 1.2 Relationship of CNS and motor organs
Ka baro badmaceeye iskuul madooyiinka cilmiga.....
•https://.www.badmaceeye.blogspot.com
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