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The Human Body

Investigation 1

The Human Body: Investigation 1

The human body is composed of different physiological systems which work together as a whole. In this CELL, students will study six of these systems: the nervous system, the skeletal system, the muscular system, the respiratory system, the circulatory system, and the digestive system. Students will explore the workings of these systems through models and experimentation, and discover that each system depends on the other systems in the body in order to function properly. Investigation One introduces students to the nervous system.

The nervous system serves as the body’s command center. The center of the nervous system is the brain. The brain is a large organ located inside the skull. It acts as a central processing unit for all the information received from the body and controls the body’s functions. It communicates with the other tissues and organs by sending and receiving electrical signals through a system of special cells called nerves. These signals are called nerve impulses. Within the brain, nerves send signals to each other to organize information for storage as memory, and to process all the information which enters from other parts of the body. The brain also uses nerve impulses for thought processes such as problem-solving and thinking.

The brain sends and receives many impulses to other tissues through a specialized bundle of nerves called the spinal cord. The spinal cord is located inside the vertebrae, which are the bones that make up the spine. Nerve endings from the spinal cord exit from between the vertebrae. These nerve endings send and collect signals to the nerves serving the other tissues and organs of the body.

Not all nerves communicate with the brain through the spinal cord. Some nerves communicate directly with the brain. These nerves are known collectively as the cranial nerves. The cranial nerves are responsible for communicating with the eyes, ears, face, mouth, and scalp. The optic nerve is a special cranial nerve responsible for transmitting visual signals from the eyes to the brain, where they are translated into visual images. Some cranial nerves are responsible for collecting information from the ears, tongue, and skin. Still other cranial nerves control muscle movement in the face to cause the eyes to blink or expressions to form.

The brain and spinal cord together are referred to as the central nervous system for two reasons. One reason is that these two parts of the nervous system work together to control the rest of the body. The other reason is that they are located centrally within the body, and all other nerves radiate outward from the central nervous system. The remainder of the nerves in the body are referred to as the peripheral nervous system. The peripheral nervous system serves the muscles, skin, and other physiological systems in the body.

Scientists use central and peripheral to refer to sections of the nervous system based on their location within the body. Scientists also divide the nervous system based on function. The autonomic nervous system is responsible for controlling the life-sustaining and other automatic functions within the body. The autonomic nervous system controls a special type of muscle called smooth muscle. Smooth muscle cells are scattered throughout tissues such as the skin, digestive tract, blood vessels, and diaphragm. The autonomic nerves tell these muscles when to contract and relax. Contraction of smooth muscle cells in the skin can result in the formation of “goosebumps” in response to a chill, or to raise the tiny hairs covering most of the body. Contraction and relaxation of smooth muscle cells in the digestive tract move food during the digestive process. Contraction and relaxation of smooth muscle tissue in the blood vessels regulate blood pressure and helps blood move through the cardiovascular system. Autonomic nervous system activity does not require conscious thought. Therefore, the autonomic nervous system governs involuntary activities. Another example of involuntary muscle response controls pupil size in response to the amount t of light reaching our eyes. This is known as the pupillary response and cannot be conscientiously controlled.

 

The sensory-motor nervous system does as its name suggests: it is involved in transmitting signals from tissues involved in the five senses. For example, when a person touches something hot, the person instinctively draws his or her hand away from the hot surface. This is a result of the sensory nerves detecting the heat and sending a signal through the sensory pathway to the brain indicating pain. The brain processes this signal and quickly sends a signal back to the person’s hand through the motor nerves telling the muscles to contract and move the hand away from the heat. This process is called stimulation and reaction. The sensory-motor system is often referred to as the voluntary nervous system because the activity is based on conscious thought. However, some sensory-motor responses are less voluntary and are called reflexes. Students may have experienced the common knee-jerk reflex during a visit to the doctor.

In Investigation One, students will conduct experiments to explore the process of stimulation and reaction by catching a dropped ruler as quickly as possible. Students will count eye blinks as a way of studying the autonomic nervous system. Students will test the brain’s memory and thought processes by using the sound made when objects are dropped to identify the objects. Students will explore memory skills by trying to correctly remember a sequence of shapes shown to them earlier in the investigation.

The Human Body: Investigation 1 - Mathematics Concepts

Prelab

  • classifying groups
  • parts/whole
  • sequential order

Lab

  • geometry
  • patterns
  • parts/whole
  • counting whole numbers
  • sequential order
  • length in cm
  • data table
  • time in seconds/minutes
  • estimate/verify predictions/measurements

Postlab

  • counting whole numbers
  • sequential order
  • parts/whole
  • problem-solving
  • geometry