Page 38 - Biology_Form_3

Biology for Secondary Schools

close to the spinal cord to form two branches; dorsal and ventral roots. Sensory fibres
enter through dorsal root while motor fibres leave the spinal cord through ventral root.

White matter Grey matter Interneurone

Dorsal root Dorsal root
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Sensory
neurone
Ventral root Ventral root
Spinal canal Motor neurone

Figure 2.9: Cross-section of spinal cord
Function of spinal cord 3. What are the structural and functional
The spinal cord acts as a coordinating centre. differences between white matter and
It serves as a nerve impulse conduction grey matter of the spinal cord?
pathway between the brain and the rest of
the body. Nerve impulses transmitted by 4. Draw a well labelled diagram showing
the spinal nerve are relayed to the brain. the structure of the human brain and
Nerve impulses from the brain are sent to describe the function of each part.
the spinal cord. From the spinal cord nerve
impulses are transmitted to the effector Peripheral nervous system
organs. Furthermore, it controls involuntary
actions. Involuntary actions are the actions Task 2.6
which are fast and automatic and cannot be Search from the library and internet
controlled by will-power and need not to sources on the information about the
be learnt. Such responses are called reflex peripheral nervous system. Write short
actions. Examples of reflex actions include; notes about the searched information.
coughing, sneezing, blinking and removing
a hand or leg when it accidentally touches All nerves that link the body to the brain and
a hot or sharp object. spinal cord make up the peripheral nervous

system. The peripheral nervous system can
Exercise 2.2 be divided into voluntary (somatic) and
involuntary (autonomic) nervous system as
1. Explain the functions of the shown in Figure 2.9. The voluntary nervous
hypothalamus. system is composed of sensory and motor

2. Discuss the components that make neurones that link the central nervous
up the spinal cord. system and skeletal muscles. It is concerned
with activities under the direct control of

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