The document summarizes key topics in a 6th level natural science unit on how humans respond to stimuli. It discusses the life processes of nutrition, interaction, and reproduction. It then describes the main parts of the nervous system including the central nervous system and nerves. It lists the five senses of touch, taste, smell, sight, and hearing. It concludes with an overview of the musculoskeletal system and its roles in movement and support.

1. NATURAL SCIENCE 6th LEVEL
UNIT 1- HOW DO WE RESPOND TO STIMULI?
LIFE PROCESSES OF THE HUMAN BODY
• NUTRITON:
Humans ingest food and break it into smaller particles so that it can
reach all the cells. The digestive system, the circulatory system,
the respiratory system and the excretory system all participate in
the life process of nutrition.
• INTERACTION:
Human percive and respond to internal or external stimuli using a
combination of their sensory organs, nervous system and
musculoskeletal system.
• REPRODUCTION:
This is the creation of new organisms with characteristics similar
to their parents.
Male sex cells (sperm) are formed in the male reproductive system,
and female sex cells (ovules) are formed in the female
reproduction system. They unite and create a new organism.
THE PARTS OF THE NERVOUS SYSTEM
The nervous system consists of the organs and other structures that
control and coordinate all the actions involved in the process of
interaction.
The system perceives external and internal stimuli. The nervous
system's reactions of these stimuli are called responses.
The nervous system respond to stimuli throught voluntary or involuntary
actions.
PARTS OF THE NERVOUS SYSTEM:
• The CENTRAL NERVOUS SYSTEM consists in four organs:
- BRAIN
- CEREBELLUM
- BRAINSTEM
- SPINAL CORD
• The NERVES are distributed throughout the body.

2. THE SENSES
• TOUCH: The skin is the sensory organ that covers and protects
our body. It has receptors that respond to stimuli such as pressure,
temperature and pain.
• TASTE: The sense of taste is located in the tongue, which has
taste receptors that detect the flavours: bitter, sour, sweet,
salty and umami.
• SMELL: The nose is the organ of smell. The olfatory receptors
perceive smells.
• SIGHT: Sight consists of the perception of images through our
eyes.The eyes are the sensory organs of sight.
• HEARING: Hearing occurs when our ears detect and process
sound. The sensory organs we use for hearing are our ears.
THE MUSCULOSKELETAL SYSTEM
The musculoskeleton system allows us to move.
It has two elements:
• The skeleton supports our bodies and gives them shape.
It consists of bones and joins.
• The muscular system, which consists of muscles and tendons.