The Body by Bill Bryson

  Another informative book by Bill Bryson. 

1. How to Build a Human

     Genes provide instructions for building proteins (2 percent). Enzymes speed up chemical changes. Hormones convey chemical messages. Antibodies attack pathogens. Titin controls muscle elasticity.

3. Microbial You

     The only way to spread cold germs is by touch. Coughing, sneezing, and kissing didn't work well. In the US 80 % of antibiotics are fed to farm animals.

4. The Brain

     It uses 20 % of our energy. The limbic system -- hypothalamus, amygdala, hippocampus, etc., regulate memory, appetite, emotions, alertness, etc. Photons have no color, our brain creates our impression. Same for sound. 

5. The Head

     Six universal expressions, fear, anger, pleasure, surprise, disgust and sorrow.  A true smile requires a contraction that we can't control, so we can't fake it. Flashes of emotion betray our true feelings. We have as many as 33 sensory systems, like balance, acceleration, time, appetite, etc. Color-blind lack one of the three types of cones. We have three types of cones compared to four for birds, reptiles, and fish. Being nocturnal we gave up some cones to get rods. If we could hear quieter sounds we would hear the air all the time. We smell the world differently because only half our receptors are in common.

6> The Mouth

     We produce little saliva while we sleep ao microbes can proliferate and give a foul mouth in the morning. We have pain receptors in the tongue which chili peppers aggravate just like a hot spoon. Odors and flavors are created in our head.

8. The Chemistry Department

     As we age the bladder can't expand as much.

9. The Skeleton

     Cutting the wrist is hard to get to the arteries. When you jump from height the legs crumple making death more difficult. The hands and feet have more than half the bones in the body. Tendons connect muscle to bone. Ligaments connect bone to bone. You need 100 muscles to stand up and 12 to move your eyes. Cartilage cannot repair or replenish itself. Slightly overweight people survive diseases better.

and lots more in 23 chapters