OUT OF CLASS LESSON
BIOLOGY SSIII
Week one:
Topic: central nervous system.
This is the part of the nervous system where impulses are received, interpreted and
coordinated in order to bring about the right responses to stimuli in animals.
It consists of the brain and the spinal cord.
The brain:
This is located within the skull. It consists of an inner white portion called the white matter
surrounded by a grey portion called the grey matter. It is enclosed by a membrane called the
meninges. The outer part of the grey mater is called the cortex.
Olfactory lobe
Right cerebral hemisphere
left cerebral hemisphere
fore brain
Pineal body
Midbrain
Right cerebella hemisphere
left cerebella hemisphere
Medulla oblongata
Spinal cord
Dorsal view of the brain of a rabbit
hind brain
Above is the diagram of a typical mammalian brain. It can be divided into three major parts:
The forebrain;
The midbrain;
And the hind brain as shown in the diagram above
Parts of the brain and their functions:
Parts of the mammalian brain
Olfactory lobe
Cerebrum(consisting of two cerebral
hemispheres)
Functions
Interprets stimuli of smell
- Receives, interprets and coordinates
sensory impulses from various parts of
the body.
- Generates and sends motor impulses
to muscles and glands for appropriate
responses to stimuli.
- It is the center of learning, reasoning,
memory, imagination and creativity.
Thalamus: oval shaped structures attached to
- Receives and coordinate sensory
lower surface of forebrain.
impulses from various parts of the
body.
- Sends impulses to appropriate parts of
the cerebral cortex for responses to
different stimuli
- Receives motor impulses from the
cortex and relay them to appropriate
muscles and glands for right responses
to stimuli
Hypothalamus: part of the forebrain below the
- Controls homeostasis example thirst
thalamus.
and body temperature
Cerebellum (consisting of two hemispheres as
- Controls body posture and balance
in diagram above)
Medulla oblongata
- Coordinate body reflexes like, heart
beat, breathing, salivation and
peristalsis
Spinal cord:
Long cylindrical organ located within the neural canal of the vertebral column, and extending
from the base of the brain to the waist region of the body. In cross section, it consists of small
narrow canal(spinal canal) surrounded by two layers of nerve tissues; an inner grey matter and
an outer white matter enclosed in an envelope of membranous material called meninges.
Below is a diagram of the cross section of a spinal cord.
Dorsal root
white matter
grey matter
Spinal canal
Ventral root
meninges
Cross section of the spinal cord
Parts of the spinal cord and their functions:
Parts
Spinal canal
Functions
Contains a fluid called cerebrospinal fluid
which supplies the brain and spinal cord with
oxygen and nutrients and drains it of waste
like CO2.
Path through which the sensory nerves enters
the spinal cord
Path through which motor nerves leaves the
spinal cord
Dorsal root
Ventral root
Functions of the spinal cord
-
Center of coordination of simple reflex actions like blinking of the eyes, knee jerk, etc
-
Connects the brain with the peripheral nervous system
Assignment:
1. A) name two parts each of the
i)
Mammalian forebrain.
ii)
Mammalian hindbrain.
b) State at least one function of each of the parts listed in 1a) above.
c) Describe the function of the mammalian mid brain (use your text/browse)
2. Tabulate three differences and state two similarities between the brain and the spinal
cord.