Science across the curriculum 2 Exercise 2, page 40.0:01
The nervous system the nervous system is the control center of the body.0:13
It consists of the brain, the spinal cord, which runs from the brain and down through the backbone, and a gigantic network of nerves.0:30
The brain is like the central computer for the nervous system.0:41
It receives messages from different parts of the body and then tells the body how to react.0:45
If you touch a hot pan by accident, for example, the nerves in your skin form a message of pain.0:52
The message gets passed on through the nerves in the spinal cord to the nerves in the brain.0:59
The brain takes this message, translates it, then sends a message back, telling the muscles to pull your hand away from the heat.1:06
This all happens in less than a second.1:15
The brain is a very complex organ with many different parts.1:20
The biggest part is the cerebrum, responsible for intelligence, memory, personality, emotion, speech, and the ability to feel and move.1:24
Next is the smaller cerebellum, controlling balance, movement and coordination, and the brainstem.1:36
This is responsible for taking in, sending out and coordinating all of the brain's messages.1:45
Just like a secretary, it also controls many automatic body functions such as breathing, heart rate and digestion.1:52
The thalamus carries messages from the sensory organs like the eyes, ears, nose and fingers.2:02
And the hypothalamus controls other automatic processes such as body temperature and appetite.2:11
Lastly, there is the tiny pituitary gland, which produces and releases hormones to control growth, metabolism, our response to stress, and many other things.2:19
Nerve cells or neurons are like long thin threads with fingers called dendrites at each end.2:33
The dendrites of one neuron almost touch the dendrites of the next neuron.2:42
When a neuron is stimulated by heat, touch or sound, for example, or by some other message, it actually generates a tiny electrical signal.2:48
This releases chemicals and that enable the signal to be passed on from the dendrites of one neuron to the next until the message reaches the brain.3:00
The brain alone contains around 100 billion neurons.3:10
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