The Nervous and Digestive Systems

The Nervous System• your nervous system

controls all parts of your body– receives and sends

messages

• brain is the control center of your nervous system– neurons: nerve cells

• brain and all other parts of nervous system made of neurons

Click on brain forwebsite

• brain gets a lot of info from sense organs in your head– eyes, ears, tongue, and nose

• brain gets info from other parts of your body

• your body has nerves, that pass along info– nerves: groups of neurons

• sense organs in your head have nerves that connect directly to your brain

• spinal cord connects the nerves in the rest of your body to your brain– spinal cord: a tube of nerves that runs through your

spine• backbone

• info from your body goes up your spinal cord to your brain– brain acts on info and sends a message back

• playing a baseball game - at bat, your eyes watch the ball; eyes send info to the brain about speed and direction of the ball; in less than a second your brain decides whether or not to swing

• if you decide to swing, your brain will send information down your spinal cord to nerves in your arms; the message will tell your arm muscles when and how hard to swing

• if you hit the ball your brain will tell your leg muscles to run

– the more you practice, the better your brain will get at telling your muscles how to hit the ball

The Digestive System

• provides nutrients for the whole body– breaks down, digestes, the food you eat

into nutrients your body’s cells can use

• begins in your mouth– teeth grind up food into smaller pieces– salvia softens food and begins to digest it

• after swallowing, food enters esophagus– esophagus: a tube that connects your

mouth with your stomach– actions of smooth muscles in your

esophagus move the food to your stomach

• stomach is a bag made of smooth muscles– muscles squeeze food and mix it with

digestive juices• juices digest some parts of the food

– food is mixed and squeezed – until it becomes mostly liquid

• the liquid food then passes into the small intestine, a long tube of muscle– different digestive juices are added and other

parts of food are digested• small intestine does more than any other part of

the digestive system

– the nutrients from digested food pass through the walls of the small intestine into capillaries

• blood carries nutrients to body’s cells

• large intestine is the last part of digestive system– most food that reaches the large intestine

can’t be broken down any more– large intestine removes water from this food– what is left travels through the large intestine

until it passes out of the body

Summary

• brain sends messages to and from all parts of the body through the spinal cord and nerves

• controls the way all other body systems work

• the digestive system breaks down food to provide nutrients for all body’s cells

• blood carries nutrients to every cell in body