1. Human body
By Noel

2. What are Muscles?
Muscle tissue functions mainly as a source of power and motion in the body
Muscles' main responsibility: changing\maintaining posture, locomotion, movement of internal organs
The human body has
about 650 muscles,
they make up appr.
half our body weight

3. What are Voluntary Muscles?
Voluntary muscles are muscles that you have the ability to consciously control, like your arms, legs, face muscles, etc.

4. What are Involuntary Muscles?
Involuntary muscles are muscles that you can't consciously control, they tend to control themselves without any recognition of them doing so: heart muscle, intestine muscles...

5. What are Tendons?
Tendons, or sinews, connect muscle to bone. They consist of a band of fibrous tissue, which is made of
collagen (like muscles),
is tough and can withstand
tension. Muscles and
tendons work together.

6. What Do Contracted and Relaxed Mean?
When a muscle contracts, it becomes shorter and pulls/moves the bone it is attached to.
At the same time, the counterpart muscle relaxes in order to allow the movement, because they cannot contract both at the same time.

7. What Do I Wonder About the Muscular System?
Q: I wonder why muscles only pull, not push?
A: Muscles can only actively contract and therefore move the bones they are connected to.
Q: Why do we have involuntary muscles?
A: Because if we forgot to make the heart beat or to breathe, we would die!
Q: How can you make muscles grow?
A: By exercising (doing sports/bodybuilding), muscles grow. Their density is three times higher than that of fat.

8. What is the Nervous System?
Your nervous system is the control and communication system of the body
Its job is to send and receive messages from and to the brain and spinal cord
Your nervous system controls all your thoughts and movements

9. How is the Nervous System Related to the Brain?
The brain acts as a command and control center for the body's voluntary and automatic actions. It is protected by the skull.
The spinal cord, protected by the spine, is attached to the brain and runs down your back.

10. How is the Nervous System Related to the Brain? (continued)
The brain and spinal cord together make up the central nervous system (C.N.S.).
All of our nerves spread out from the spinal cord into the body and organs.

11. What are Your Sense Organs?
We have five senses/sense organs:
the sense of sight (the eye)
the sense of hearing (the ear)
the sense of touch (the nerves)
the sense of smell (the nose)
the sense of taste (the tongue)

12. What Do Your Sense Organs Do?
The sense organs are important for your everyday life, just imagine how hard it is if one of your senses doesn't work.
The sense that makes us most human is our eyesight. Roughly 80 percent of what our brain processes, come from what we see. We may not always be feeling, smelling, or listening, but unless we’re sleeping, meditating, or praying, we’re constantly processing information visually

13. What is Your Spinal Cord and What Does it Do?
The spinal cord is the pathway for information from your brain
The spinal cord coordinates reflexes
It consists of a long, thin bundle of nervous tissue

14. What are Nerves and how are They Related to the Brain?
Nerves consist of nerve cells, also called neurons, which have a long, cable-like axon to connect with other nerve cells and to send signals around
The brain is connected to the spinal cord, which runs down through the back and contains nerves that branch out to every organ and body part.

15. Wonders About the Nervous System
Q: I wonder why the reflexes are coordinated by the spinal cord and not by the brain?
A: In a reflex action, a very quick response is needed. Thus, the signal is already being processed in the spinal cord.
Q: How long can an axon be?
A: They can be up to 1 meter long.
Q: How do nerve cells (neurons) communicate with each other?
A: They communicate via electrical impulses.