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Main Points
The human nervous system consists of the central nervous system (CNS) and peripheral
nervous system (PNS). The former consists of the brain and spinal cord, while the latter
composes the nerves extending to and from the brain and spinal cord. The primary
functions of the nervous system are to monitor, integrate (process) and respond to informa-
tion inside and outside the body. The brain consists of soft, delicate, non-replaceable neural
tissue. It is supported and protected by the surrounding skin, skull, meninges and cerebro-
spinal fluid.
The brain
Ø Human brain weighs about 1.2 to 1.4kg.
Ø It consumes 25% of the body oxygen supply to generate energy;
Ø It is covered by a membrane called the Meninges.
Ø It is enclosed in a bony case called the skull or cranium.
Ø It is made up of 2 types of nervous tissues, (Nerves cells or grey matter and Nerves fibers or white matter.)
Human brain is divided into 3 parts
a. Fore brain (i.e. Large, forward part).
b. Mid brain (i.e. narrow brain).
c. Hind brain (i.e. rare path).
Fore Brain: - it consist mainly cerebrum, thalamus and hypothalamus.
Midbrain: links the forebrain to the hindbrain. It controls auditory and visual reflexes.
Hindbrain: composed of 3 parts
(A) Cerebellum
(B) Pons varolii
(C) Medulla oblongota
SELF-ASSESSMENT EXERCISE 1
i. The autonomic nervous system consists of -- and --------
ii. Mention two portions of the hind brain.
Functions of the parts of the brain
Cerebrum controls all the bodies’ voluntary action and
consciousness.
Frontal lobe – seat of intelligence, Memory, Imagination,
thought, judgment, emotional reaction and movement of
skeletal muscles.
. Parietal lobe – Receives and interprets the sensations of pressure,
temperature and position.
Temporal lobe is concerned with hearing, memory and
understanding of speech.
Integration with other Systems
To function effectively, every cell in the body must communicate with
its neighbors and with cells and tissues in distant portions of the body.
In a few specialized cases, cellular activities are coordinated by the
exchange of ions and molecules from one cell to the next across gap
junctions. This direct communication occurs between cells of the same
type, and the two cells must be in extensive physical contact. The two
cells communicate so closely that they function as single entity. For
example, gap junctions (1) coordinate ciliary movement among
epithelial cells, (2) coordinate the contractions of cardiac muscle cells,
and (3) facilitate the propagation of action potentials from one neuron to
the next at electrical synapses.
Direct communications is highly specialized and relatively rare. Most of
the communications between cells involves the release and receipt of
chemical messages. Each cell continuously “talks” to its neighbors by
releasing chemicals into the extra cellular fluid. These chemicals tell
what their neighbors are doing at any moment; the result is the
coordination of tissue function at the local level. The use of chemical
messengers to transfer information from cell to cell within a single
tissue is called paracrine communications. The chemicals involved are
called paracrine factors, also known as cytokines, or local hormones.
Examples of paracrine factors include the prostaglandins.
SELF-ASSESSMENT EXERCISE B
(I) What is the function of the temporal lobe?
(II) --------------- is an example of paracrine factors.
CONCLUSION
The nervous system includes the neural tissues that make up the
autonomic nervous system and the peripheral nervous system. The
neurons are the basic functional unit. The nervous system and the
endocrine systems are closely linked.
SUMMARY
In this unit we have learnt the two major anatomical divisions of the
nervous system; (1) the central nervous system (II) peripheral nervous
system; their divisions and various functions.
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