Systems of the Human Body 1: Moving and Controlling the Body

Science, Grade 6


Table Of Contents: Systems of the Human Body 1: Moving and Controlling the Body

1. Body Organization

2.1. Levels of Organization - Organ Systems
The human body is a collection of interacting organ systems. Some of those systems are the cardiovascular system, the digestive system and the nervous system. These organ systems work together to sustain life in the human body.
2.2. Levels of Organization - Organs.
Within organ systems, each organ has a different function or set of functions. For example, as food travels through the digestive system, the organs of the digestive tract break down the food into nutrients the body can use and waste products the body doesn’t need. The pancreas helps us process sugar by producing insulin while the liver processes fats and produces cholesterol, among other substances.
2.3. Levels of Organization - Tissues
Each organ is made up of tissues that support the organ function. There are four types of organ tissues: epithelium, connective, muscle and nerve tissue.
2.4. Levels of Organization - Cells
Tissues are collections of cells of different types that interact to support the function of the tissues, organs and overall organ system.
2.5. Homeostasis Principle
Our organ systems work constantly to keep every aspect of the system stable and functioning well. The organ systems are challenged by changes from inside and outside the body and must help the body adjust to those changes and keep the organs functioning effectively. This ongoing effort by the body to maintain a stable internal environment in the face of change is known as the principle of homeostasis.
2.6. Homeostasis Example - Temperature Regulation
Human body temperature is regulated very tightly to keep it to 98.6 degrees Fahrenheit by an internal thermostat found at the base of the brain. If your body gets too cold, you shiver to generate heat and regain your normal body temperature. If your body gets too warm, the blood vessels dilate and you also sweat to regain normal temperature. These methods of adjusting to body temperature help your body systems maintain homeostasis despite changing external conditions.

2. Body Organization:Pause and Interact

3.1. Review
Use the whiteboard text tool to fill in the table with examples for each level of body organization. One example is provided.
3.2. Body Organization
Follow the instructions provided.

3. Skeletal System

4.1. Functions of the Skeletal System
Your body has a total of 206 bones, which are attached to your muscles with tendons. The bones of your body have several important functions. They provide support for your body position and movement so you can walk upright. Bones protect vital organs such as your brain and your heart. Bones also help manage and store minerals and even create new blood cells.
4.2. The Axial Skeleton
The axial skeleton includes the skull, spine, ribs and sternum, which total 80 bones. These bones anchor the body and have limited flexibility. For example, the only bone of your skull which can move freely is your jawbone.
4.3. The Appendicular Skeleton
The highly movable, flexible regions of your body are called your appendicular skeleton. This includes your shoulders and your hips and the limbs attached to them. The 126 bones in this part of your skeleton help you turn and twist in many directions and support a wide range of movement for your arms and legs.
4.4. Bone Structure
Your bones may feel hard, but they are constantly changing. Bone is a very dynamic tissue with two key properties that combine to provide strength and support to your body. The outer, smooth part of bone is made up of compact bone. It looks hard to the naked eye and is densely packed tissue. The inner structure of bone is called spongy bone. This bone tissue provides great strength, especially at the ends of bones, because of its honeycomb type structure.
4.5. Bone Formation
Most bones in the body begin as softer cartilage molds that grow and are slowly replaced by bone tissue rich in calcium that makes the tissue stronger and more rigid. Our bony skeleton and overall body size grows under the control of growth hormone, released by our pituitary gland, most rapidly during adolescence and late teen years. Growth and shaping of bone structure, however, continues throughout our entire life under the effects of gravity and other physical forces.
4.6. Common Bone Fractures
Some of the most commonly fractured bones include the radius (at your wrist) and clavicle (your collarbone). Fractures can be simple, where the bone has not separated, or they can be compound, where the broken bone piece or pieces pierce the skin and require both resetting of the bone and repair of the skin. If a broken bone is held motionless for some time, as in a plaster cast for weeks, it can be repaired by natural remodeling processes within the bone tissue.
4.7. Types of Joints Between Bones
The places where your bones meet are called joints. There are three types of joints in the human body. Fixed joints don’t move, such as the places where skull bones meet. Some joints are slightly movable, such as the joints between the bones in your spine. Other joints are freely movable (synovial), such as the knee and elbow and other joints in your arms and legs.
4.8. Freely Moving Joints - Synovial Joints
There are several types of synovial, or freely moving, joints in the human body. Along the spine and in the arms and legs, synovial joints allow a wide range of motions to support how we move around our environment. Ball and socket joints are the most movable and are found in the shoulder and the hip. Condyloid joints, seen in the wrist and ankles, have more limitations in how they move and are not quite as flexible as ball and socket joints. Hinge joints, which only allow limited movement of flexion and extension, are located in the knee, the elbow and between bones of the fingers and toes.
4.9. Sprains and Strains
Sprains and strains sound alike and many people don’t understand the difference. But your musculoskeletal system does. Sprains occur at joints and strains happen to muscles. A sprain occurs when one or more of the bones at a joint are pushed too far in a direction they are not positioned to go. For example, when you sprain your ankle, you put weight on your ankle at an unstable angle or position and the bones are sprained. A strain occurs when a muscle is pulled or stretched more than it can support or bear. Both are painful indicators that the human body has limits in motion.
4.10. Taking Care of Your Bones
Since bones are so important to our everyday lives, it is important to take care of them. Making sure the substance of bones remains intact will go a long way toward keeping bones healthy. That means you must consume enough calcium and protein in your diet to keep bones strong. Routine exercise prevents bone tissue from breaking down with lack of use.

4. Pause and Interact

5.1. Review
Use the whiteboard tools to label several bones and joints of the skeletal system.
5.2. The Skeletal System
Click on the Terms button. Then click and drag each term to the correct box. Use the reset button to clear the terms and start over. Use the gear button to customize the draggable terms.
5.3. Types of Joints
Follow the instructions provided.

5. Muscular System

6.1. Muscle Action
In the muscular system, there are voluntary and involuntary muscles. We can control movements of the skeleton using voluntary muscles, as in bending an arm. We have much less control over our involuntary muscles, including movements within internal organs of the body such as the heart.
6.2. Types of Muscles
Muscles of the human body help to create movement and fall into three different categories. Skeletal muscle moves the body skeleton in the external environment. Smooth muscle controls movement within the body such as moving nutrients and waste through the intestines. Cardiac muscle is the muscle of the heart.
6.3. Structure of Muscle
Muscles are made of fibers that are actually long cells in varying shapes that can stretch the length of the muscle. When a nerve impulse reaches a muscle fiber, the fiber shortens, creating a muscle contraction, which then causes movement in the body.
6.4. Principles of Muscle Contraction
Muscle cells within a given muscle (such as the biceps muscle) work together to provide different degrees of contraction strength. There is almost always an antagonist (in this case, the triceps muscle): a muscle that works to oppose the other to make for a more smooth action or to return the bone to the original position.
6.5. Special Features of Heart Muscle
Cardiac muscle cells are highly specialized in their function and their makeup. They contract over and over without fatigue in a systematic way so that blood will move through the heart chambers in a regulated manner.

6. Pause and Interact

7.1. Review
Use the whiteboard tools to create a concept map for the different types of muscle.
7.2. Types of Muscles
Click on the Terms button. Then click and drag each term to the correct box. Use the reset button to clear the terms and start over. Use the gear button to customize the draggable terms.

7. Nervous System

8.1. Functions of Nervous System
The nervous system provides electrical circuit pathways that can connect neurons throughout the body. When the body’s electrical stimulus connects neurons, this neural connection allows us the capacity to sense changes within and outside of the body, to interpret and understand those changes, to make very complex decisions and judgments, and to control our body functions and reactions.
8.2. Organs of the Nervous System
The main component of the nervous system is the nerve cell, or neuron. Neurons are special cells with attributes that support the functions of the nervous system. The central nervous system’s organs, the brain and the spinal cord, are complex, organized collections of neurons. These organs connect to all parts of the body through neurons of the peripheral nervous system.
8.3. Structure of Neurons
Neurons have a large cell body that includes two key parts. Dendrites are little extensions at the end of the neuron which receive electrical impulses. The impulse travels to the axon in the neuron, which then conducts the impulse toward a target.
8.4. Types of Neurons
Within the human body, there are three different types of neurons. Sensory neurons carry impulses toward the brain and spinal cord. Motor neurons carry impulses away from the brain and spinal cord, and interneurons carry impulses within the brain and spinal cord.
8.5. The Nerve Impulse
The electrical impulses that neurons receive and send travel extremely fast, in milliseconds. Impulses travel down the insulated axon. At the end of the axon, a chemical called a neurotransmitter is released into a space called the synapse. These neurotransmitters cause a change at the target site, such as a muscle contraction.
8.6. Central Nervous System
The central nervous system is composed of the brain and spinal cord. The spinal cord serves as a neuron highway of neurological information. It enables communication of information up to the brain and from the brain down to body organ systems.
8.7. Structure of the Brain
The brain is the center of higher function in the human body. The large cerebrum is the part of the brain that connects to the spinal cord via the brain stem. The neuron activity of the cerebrum determines our personality, decision-making, behavior, and emotions. It also controls how we initiate body movement and speech as well as how we interpret everything in the world around us that we see, hear, taste, smell and feel. The cerebellum, a mini-brain attached to our brainstem, controls body movement and coordination.
8.8. Peripheral Nervous System
The brain and spinal cord communicate with all other parts of the body through the nerves that make up the peripheral nervous system. A reflex is a motor response to a sensory stimulus and is either involuntary (automatic) or a learned response that serves as a controlled reaction to a challenging situation or stimulus. Reflex systems are found connected with muscles, tendons, ligaments and skin (somatic) and are also found within internal organs, such as in the control of urination and blood pressure.
8.9. Senses: Vision, Hearing and Balance, Smell, Taste
Humans possess specialized neuron receptors in various regions of the head which respond to different stimuli and provide valuable, diverse information about the surrounding environment. These specialized neurons allow complex interpretations of data from sounds, sights, tastes, smells and the overall position of the body. The eyes, for example, interpret visual information, and the ears include neurons that capture sounds.
8.10. How We See
The neurons in our retinas translate light signals into impulses the body can comprehend. Light travels to the back of the eye to the retina where light stimuli are converted to neuron impulses. The neurons transmit these impulses to the back of the brain where the brain enables us to interpret what we see. Think how quickly this all happens!
8.11. How We Hear
Sound waves enter the ear and cause movements of the eardrum and the smallest bones in the body, the ossicles, within the middle ear compartment. Those movements ultimately cause nerve impulses to be generated that travel up to the brain so we can make sense of what we hear.
8.12. How We Taste and Smell
There are specialized neurons in our nose and tongue that respond to molecules in the air we breathe and the food and fluids we eat and drink. Impulses travel from these regions back to our brain so we can understand differences in taste and smell.
8.13. Drug and Alcohol Abuse
Neurons communicate with each other through the release of chemical neurotransmitters. Drugs and alcohol can alter the release and uptake of neurotransmitters, thus changing our reactions and perceptions. For example, alcohol inhibits neuron function of the brain and poisons other organ systems, such as the liver. Cocaine changes the release of “feel-good” neurotransmitters. This results in dependency and elevated feelings of pleasure that can lead to addiction.

8. Pause and Interact

9.1. Review
Identify and use the whiteboard tools to label the parts of the nervous system and a neuron.
9.2. Nervous System
Click on the Terms button. Then click and drag each term to the correct box. Use the reset button to clear the terms and start over. Use the gear button to customize the draggable terms.

9. Endocrine System

10.1. The Role of the Endocrine System
The human endocrine system, like the nervous system, acts to control and influence the activity of cells and tissues of the body. While the nervous system works quickly, in milliseconds, the endocrine system functions more slowly, taking seconds or even days to make an impact through the release of chemicals into the bloodstream.
10.2. How the Endocrine System Functions
The endocrine system consists of a variety of glands that release hormones. These hormones travel through the blood to cause an effect at some distant site. For example, when a person is frightened, the adrenal glands release adrenaline that travels to the heart and increases the heart rate.
10.3. Endocrine Glands
Endocrine glands are spread out over the body. These glands, the pituitary, thyroid and parathyroid, adrenal, ovaries, testes, pancreas and pineal glands, all produce hormones. A complex system regulates the secretion of the hormones through a feedback mechanism.
10.4. Function and Control of Endocrine Glands
Endocrine glands are controlled by feedback systems that work to turn on or shut down gland function. The “master gland” of this system is the pituitary gland. It is also the smallest of the endocrine glands but it releases many different hormones that control body and bone growth and water balance, and that help regulate many of the other endocrine glands.
10.5. Hormones
Hormones are chemicals that can regulate functions and chemical reactions in the human body. For example, the growth hormone released by the pituitary gland increases bone growth. Insulin released by the pancreas helps control blood glucose levels. The thyroid releases thyroid hormone that helps regulate a wide range of chemical reactions in the body.
10.6. Negative Feedback Mechanism
Most endocrine gland functions are controlled by a negative feedback mechanism that acts to turn off hormone release as a means of controlling hormone effects. For example, after a meal, when blood glucose levels go up, the pancreas releases insulin to bind to glucose to deliver it to vital body tissues. As cells of the pancreas sense a decrease in blood glucose, release of insulin is shut off.

10. Pause and Interact

11.1. Review
Use the whiteboard tools to fill in the table by listing four endocrine glands and describing their location and function.
11.2. The Endocrine System
Click on the Terms button. Then click and drag each term to the correct box. Use the reset button to clear the terms and start over. Use the gear button to customize the draggable terms.

11. Vocabulary Review

12.1. Vocabulary Matching Review
The human endocrine system, like the nervous system, acts to control and influence the activity of cells and tissues of the body. While the nervous system works quickly, in milliseconds, the endocrine system functions more slowly, taking seconds or even days to make an impact through the release of chemicals into the bloodstream.

12. Virtual Investigation

13.1. Nerve Conduction
In this lab you will learn about how a reflex controlled by sensory and motor neurons is affected by different conditions. You will explore the effects of coffee, an energy drink, alcohol, local anesthesia and sleep deprivation on the neurons controlling the pin prick reflex. Using simulated timers, you will record the time (in milliseconds) it takes for the nerve impulse to travel along the sensory and motor neurons during a pin prick test. Repeating the pin prick stimulus will allow you to conduct multiple trials for each condition. Once data is collected, you can describe the effects of each condition on nerve conduction time.

13. Assessment

14.1. Human Body 1