UNIT 1 NATURAL SCIENCE: THE NERVOUS SYSTEM

Which are the three vital functions?

• Nutrition: it is a combination of processes by which living things obtain the nutrients and the energy they need to live. 
• Interaction: all living beings ineract with their enviroment and with other living beings to survive. Interaction enables living beings to receive and respond to a stimulus. 
• Reproduction: it is the biological process by which new individual organisms are produced. 

What is sensivity?

The sensitivity is something essential in the interaction function. Through sesitivity, we respond to changes in the external enviroment. These changes are called stimuli. For example: if someone throws a ball to us, we respond by trying to catch it.

For that, in this process various organs and systems are involved:

• Sense organs: capture information from the enviroment. 
• Nevous system: controls the function of sensitivity. 
• The locomotor system is made up of the muscular system and the skeletal system. Both of them produce the movement. 

Senses organs and senses

Sight --> Eyes. The eyes are the organs of sight. They detect light and colors, and estimate distances. The information captured by receptors in the retina travels to the brain through the optic nerve. The brain receives and interprets this information.




Hearing --> Ears. The ears are the sense organs of hearing. They detect sounds and their properties, and where this sounds come from. The information captured by receptors in the cochlea travels to the brain through the auditory nerve. The brain receives and interprets this information.


Smell --> Nose. The nose is the sense organ of smell. It detects different smells in the air. The information captured by receptors in the olfactory epithelium travels to the brain through the olfactory nerves. The brain receives and interprets this information.



Touch --> Skin. The skin is the sense organ of touch. It detects temperature, pain, pressure… The information captured by receptors in the skin travels to the brain through the nerves. The brain receives and interprets this information.







Taste --> Tongue. The tongue is the sense organ of taste. It detects different flavours. The information captured by receptors in the taste buds travels to the brain through the taste nerves. The brain receives and interprets this information.

The nervous system

The nervous system carries out the function of sensitivity. The nervous system is in charge of three important tasks:

• It receives and interprets information from external and internal environments. 
• It gives the appropriate orders for our body to respond to stimuli. 
• It controls and coordinates all organs and systems in our body. 

The nervous system is made up of two parts:

• Central nervous system. 
• Peripheral nervous system. 

Central nervous system

The central nervous system has two parts:

• The BRAIN. It is protected by cranium and has 3 parts. 
• The CEREBRUM controls voluntary actions, for example running. It also store data and memories. 
• The CEREBELLUM controls movement, coordination and balance.  
• The BRAINSTEM controls internal organ activities that we do not need to think about it, like heart rate.  
• The SPINAL CORD is protected by the spinal column. The spinal cord produce involuntary responses, such as we move our hand away from very hot objects.

The peripheral nervous system

The peripheral nervous system consists of nerves that extend throghou the body. It connect the central nervous system to our sense organs, muscles and internal organs. There are two types of nerves:

• Sensory nerves. These receive messages from receptors in the sense organs and send these messages to the central nervous system.
• Motor nerves. These send orders from the central nervous system to the other organs.

Neurons

Nervous tissue is made up of neurons (nerve cells). These are grouped together to form nerves. Neurons have three parts:

• The body.
• Dendrites, which receive messages from the sense organs or other neurons.
• The axon, which transmits messages to other neurons.

Movements

Our body is capable of two different types of movements: voluntary movements and reflex movements.

• Voluntary movements: we make voluntary movements in response to different stimuli. They are actions that we perform consciously.
• Reflex movements: reflex movements are rapdid, automatic responses to stimuli. We perform these involuntary movements without thinking about them. The response is produced by the spinal cord, not the brain.

VOLUNTARY MOVEMENT

INVOLUNTARY MOVEMENT