Body Systems and Senses — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
Sense organs send signals straight to the muscles, skipping the brain.
Corrected: Sense organs send signals through nerves to the brain, which then tells muscles to respond.
In Grade 4 science, the brain processes signals from sense organs before muscles act on them.
2. Fix the sentence:
Nerves are bones that carry messages around the body.
Corrected: Nerves are thin fibers that carry messages around the body.
Grade 4 students learn that nerves are like thin wires that carry electrical signals, not hard bones.
3. Fix the sentence:
The brain is part of the digestive system.
Corrected: The brain is part of the nervous system.
In Grade 4 science, the brain is the control center of the nervous system, not the digestive system.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. Information from sense organs travels along nerves to reach the brain.
Grade 4 science teaches that nerves act like wires, carrying signals from sense organs to the brain.
2. The brain processes signals and decides how the body should respond.
In Grade 4, students learn that the brain is the control center that processes information from the senses.
3. After the brain decides what to do, it sends a message to the muscles to move the body.
Grade 4 science shows that the brain signals muscles to contract, producing a response such as moving a hand.
4. When a sense organ detects something, it creates a signal that travels to the brain.
In Grade 4 science, sense organs change information from the world into signals that nerves carry to the brain.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Describe the path information takes from a sense organ to a body response in Grade 4 terms.
Sample answer: First, a sense organ like the eye detects information. The signal travels through nerves to the brain. The brain processes the signal and decides what to do, then sends a message back through nerves to the muscles, which move the body.
Grade 4 students should understand the full information path: detect, send, process, respond.
2. Why is the brain called the control center of the body?
Sample answer: The brain is the control center because it receives signals from all sense organs, processes them, and decides how the body should respond. Without the brain, the body would not know what the senses detect.
Grade 4 science highlights the brain as the part that makes sense of information and directs the body.