2. Nervous system
• Touching a hot object is an urgent and dangerous
situation for us. We need to detect it, and
respond to it. How do we detect that we are
touching a hot object? All information from our
environment is detected by the specialised tips of
some nerve cells. These receptors are usually
located in our sense organs, such as the inner ear,
the nose, the tongue, and so on. So gustatory
receptors will detect taste while olfactory
receptors will detect smell.
5. SPINAL REFLEX ACTION
• The reflexes of this type which involve only the
spinal cord are called spinal reflexes.
• Please note that when we lift a hot plate, then
along with heat, the pain produced by heat also
acts as a 'stimulus'.
• Most of the reflex actions involve only the spinal
cord. They are called spinal reflexes.
6. BRAIN REFLEX ACTION
• Reflex actions which involve brain are called
cerebral reflexes.
• Cerebral reflexes occur in the organs present in the
head because these organs are directly connected
to the brain.
• Example. Our eyes are present in the head. In dim
light, the pupil (a hole in the front of eye) is large so
that more light can enter into the eye and make us
see properly even in dim light.
10. Cerebrum -The largest division of the brain. It is
divided into two hemispheres, each of which is
divided into four lobes.
Cerebrum
Cerebrum
Cerebellum
13. Brain has 3 regions
• Fore- Brain - cerebrum, thalamus, and
hypothalamus (part of the limbic system).
• Mid-brain - The midbrain consists of the tectum
and tegmentum.
• Hind-brain - cerebellum, pons and medulla. Often
the midbrain, pons, and medulla are referred to
together as the brainstem.
14. Fore- brain
• The forebrain is divided into 2 halves – the right and
left cerebral hemispheres.
• The cerebral hemispheres control your movement,
thinking, memory, emotions, senses and speech.
• As the nerve fibres leave the brain, they cross over
from one side to the other.
• This means that the nerves that come from the
right side of your brain control the left side of your
body.
• Each hemisphere is divided into 4 areas called the
16. How brain tissues are protected?
• The brain is protected by a series of bone, membrane,
and fluid.
• The outermost protection is the cranium, or skull,
which protects the brain from blows that could easily
damage it.
• Then there are three membranes called meninges.
• Then brain is protected by a clear liquid called
cerebrospinal fluid. This forms a cushion between the
soft brain tissue and the hard cranial bones. This same
fluid also fills spaces inside the brain.
• Tissues inside the spaces produce cerebrospinal fluid,
which flow through the spaces between the
membranes.
