Homeostasis and Human Body Systems

Homeostasis and Human Body Systems

Imagine you are playing softball on a warm summer day. Write down two ways that your body would adjust to keep you cool and to keep your muscles working.

Key Ideas • How does a change in the external environment affect an organism? • How does an organism respond to changes, and what happens if the organism fails to respond to changes? • What organ systems do humans need in order to survive? • How is the human body organized? • What is Homeostasis?

Human Body Systems • Which body systems are the basketball players using? • Recall levels of organization in an organism • Cells • Tissues • Organs • Organ system

What is Homeostasis? • The process by which organisms maintain a relatively stable internal environment • How does the human body maintain homeostasis? • The eleven organ systems of the human body work together to maintain homeostasis. • Homeostasis is the process by which organisms keep internal conditions relatively constantdespite changes in external environments.

To help understand homeostasis lets think about how a thermostat works Decrease room temperature Increase room temperature Increase room temperature

A Changing Environment • The external environment around an organism is constantly changing. • These changes threaten the stability of an organism’s internal environment. • The maintenance of a relatively stable internal environment is called homeostasis.

Change in seasons, light level, water availability, or other changes to the external environment can change an organism’s internal environment. • Different organisms deal with these changes in different ways. • In a colder environment, for example, organisms may eat more food, puff out fur or feathers, fly to warmer areas, or hibernate.

Responses to Change • Organisms must carry out many chemical reactions to grow, obtain energy, and reproduce. • Many organisms also move, breathe, produce heat, and do other tasks. • All of these activities require the organism to maintain a relatively stable internal environment.

Responses to Change • Organisms detect and respond to both internal and external environments in a variety of ways. • Detection and response can take place at both the cellular and organismal level. • Failure to respond to change can result in an organism’s death.

Now let’s take a look at how plants maintain homeostasis: • Leaves of plants are covered on the top and bottom by epidermis made of a layer of tough, irregularly shaped cells. • The epidermis of many leaves is also covered by the cuticle. • Together, the cuticle and epidermal cells form a waterproof barrier that protects tissues and limits the loss of water through evaporation.

Stomata (singular: stoma), are pore-like openings in the underside of the leaf that allow carbondioxide and oxygen to diffuse into and out of the leaf. Each stoma consist of: two guardcells, the specialized cells in the epidermis that control the opening and closing of stomata by responding to changes in water pressure.

Responses to Change • The pores on a plant’s leaf help the plant to regulate water loss and gas exchange. • During the day, tissues perform photosynthesis. • Guard cells near these active tissues swell with water. This opens pores, letting in the carbon dioxide that is needed for photosynthesis

Responses to Change • Open pores also allow water to exit the leaf. • At night, when photosynthesis slows, water exits the guard cells. • The cells shrink and close the pores, preventing excess water loss at night.

Control of Stomatal Opening

Responses to Change • If an organism is not able to respond to changes in its environment, disease or death can result. • Consider what would happen if a plant could not slow water loss. • When the amount of water in a plant’s tissues got too low, the plant would wilt, collapse, and die.

Responses to Change • Humans must also control internal water levels. • About 2/3 of the human body is made of water. • If a person loses too much water, by sweating or urination, dehydration will occur. • Dehydration causes blood pressure to drop significantly until death occurs.

Responses to Change • Some deep-water fish must be adapted to deal with high water pressure. • The coelacanth is a fish that lives in the deep waters off the coast of Africa. • At the depth where the fish lives, water pressure is several hundred times greater than the water pressure at the ocean’s surface.

Responses to Change • If a person tried to swim at this pressure, the person’s body would be crushed. • The coelacanth will actually die in the low-pressure environment at the water’s surface. • The coelacanth’s body is adapted to require high pressure, in order to keep gases from bubbling out of the fish’s bloodstream and blocking flow to the fish’s heart.

Humans and Homeostasis • Humans are constantly subjected to environmental stresses that threaten to upset the delicate balance that exists within our cells and tissues. • Humans require multiple systems for digestion, respiration, reproduction, circulation, movement, coordination, and immunity. • These systems interact to maintain homeostasis.

Summary of Human Body Systems

Humans and Homeostasis • The organs and systems of the human body help to provide all of the cells with their basic needs. • Each cell needs a constant supply of nutrients and oxygen, removal of waste materials, and protection from disease. • With the exception of the reproductive system, each of the human body systems performs a task that helps stabilize the body’s internal environment.

Humans and Homeostasis • In the human body, the main components of homeostasis are the following: • the concentration of salts • The pH of the internal environment • The concentration of nutrients and waste products • The concentration of oxygen and carbon dioxide • The volumeand pressure of extracellular fluid

Humans and Homeostasis • When these five components are adequately controlled, homeostasis is maintained and the body is most likely healthy. • No organ system can maintain homeostasis by itself. • Organ systems must work together in a synchronized manner.

Humans and Homeostasis • For example, the concentration of oxygen and carbon dioxide is controlled by four different body systems. • First, the respiratory system brings oxygen into and carbon dioxide out of the body. • The circulatory system distributes the oxygen to the body’s tissues and picks up carbon dioxide.

Humans and Homeostasis • If the level of carbon dioxide gets too high, the nervous system instructs the muscular system to make the muscles around the rib cage work harder. • This action allows the lungs of the respiratory system to breathe faster, to get rid of excess carbon dioxide.

Key Ideas • How does a change in the external environment affect an organism? • The external environment around an organism is constantly changing. These changes threaten the stability of an organism’s internal environment. • How does an organism respond to changes, and what happens if the organism fails to respond to changes? • Organisms detect and respond to change in a variety of ways: both at the cellular level and at the organismal level. Failure to respond to change can result in an organism’s death.

Key Ideas • What organ systems do humans need in order to survive? • Humans require multiple systems for digestion, respiration, reproduction, circulation, movement, coordination, and immunity. The systems interact to maintain homeostasis.

Human Body Systems

Alternately bend and straighten your arms or legs while feeling the muscles in the front and the back. Write down what you feel when the limb is straightened and what you feel when the limb is bent.

Key Ideas • How do the skeletal and muscular systems help the body maintain homeostasis? • How does the integumentary system help the body maintain homeostasis? • How do the nervous and endocrine systems help the body maintain homeostasis?

Key Ideas • How do the digestive and excretory systems help the body maintain homeostasis? • How do the circulatory and respiratory systems help the body maintain homeostasis?

Skeletal and Muscular Systems • The skeletal and muscular systems enable movement and provide support for tissues and organs. • Bones and muscles work together to make movement possible. • The ability to move increases the chance of survival by allowing a person to gather food, seek shelter, and escape from danger.

Skeletal and Muscular Systems • The skeleton provides an anchor for the muscles that move the body. • There are 206 bones in a human adult

Axial skeleton – supports the central axis of the body; skull, vertebral column, and rib cageAppendicular skeleton – bones of arms and legsWhat do you think is a better model of a bone, a stick of chalk or a sponge?The chalk may look more like a bone but the sponge shows what the structure actually looks like inside.

What passes through the tubes and spaces inside bone? Blood vessels and nerves PERIOSTEUM Bone is surrounded by a tough layer of connective tissue Haversian canals Network of tubes that contain blood vessels and nerves.

Bone marrowCavities that contain a soft tissue • There are two types of bone marrow: • yellow and red • Yellow marrow is made up primarily of fat cells. • Red marrow produces red blood cells, some kinds of white blood cells, and cell fragments called platelets.

Cartilage-Cells are scattered in a network of protein fibers—tough collagen and flexible elastin. • Cartilage does not contain blood vessels. • Cartilage cells must rely on nutrients from the tiny blood vessels in surrounding tissues. • Cartilage is dense and fibrous, it can support weight, despite its extreme flexibility

Ossification-Cartilage is replaced by bone during the process of bone formation • Osteoblasts create bone. • Osteocytes maintain the cellular activities of bone. • Osteoclasts break down boneForce must be placed on bone for ossification to occur, because it is force that stimulates the osteoblasts to secrete the minerals that replace cartilage

What effect do you think an exercise such as walking would have on the bones of the legs? • It would stimulate ossification, so the bones would contain more minerals and be stronger. What do you think might happen to the bones that are not exposed to force, such as the bones of astronauts in zero gravity? • The bones would lose minerals because of lack of force exerted on them, so they become weaker

Bone formation occurs in babies and children • Seven months before birth cartilage is gradually replaced by bone • When a person grows, the growth plates are lengthening in the long bones • When you stop growing, those growth plates are then filled in with bone • Adults do retain some cartilage • Tip of nose, ears, where ribs attach to the sternum

Bone formation also occurs when a bone is broken • Osteoclasts remove damaged bone tissue • Osteoblasts produce new bone tissue • The repair of a broken bone can take months because the process is slow and gradual

Depending on its type of movement, a joint is classified as immovable, slightly movable, or freely movable Immovable Joints • Where the bones in the skull meet Slightly Movable Joints • The joints between the two bones of the lower leg and the joints between adjacent vertebrae are examples of slightly movable joints. Freely Movable Joints • Ball-and-socket joints permit circular movement—the widest range of movement • Hinge joints permit back-and-forth motion, like the opening and closing of a door • Pivot joints allow one bone to rotate around another • Saddle joints permit one bone to slide in two directions

Structure of joints • Ends of bones are covered with a smooth layer of cartilage • Joints are surrounded by a fibrous joint capsule that helps hold bones together

Tendons attach muscles to bones. • When muscles contract, tendons pull on bones to cause movement. • LIGAMENTS – strip of tough connective tissue that hold bones together • Synovial fluid – lubricates the ends so bones can slide past each other smoothly

Opposing Muscles in the Arms

Skeletal and Muscular Systems What are the three types of muscle? • Skeletal • Smooth • Cardiac

Skeletal Muscle • Skeletal muscles are usually attached to bones • Skeletal muscles are responsible for such voluntary movements as typing on a computer keyboard, dancing, or winking an eye • When viewed under a microscope at high magnification, skeletal muscle appears to have alternating light and dark bands or stripes called striations. For this reason, skeletal muscle is sometimes called striated muscle • Most skeletal muscles are controlled by the central nervous system.

Smooth Muscles • Smooth muscles are usually not under voluntary control • A smooth muscle cell is spindle-shaped, has one nucleus, and is not striated • Smooth muscles are found in hollow structures such as the stomach, blood vessels, and the small and large intestines • Smooth muscles move food through your digestive tract, control the way blood flows through your circulatory system, and decrease the size of the pupils of your eyes in bright light.

Cardiac Muscle • Cardiac muscle is found in just one place in the body—the heart • The prefix cardio- comes from a Greek word meaning “heart.” • Cardiac muscle is striated like skeletal muscle, although its cells are smaller. • Cardiac muscle cells usually have one nucleus, but they may have two. • Cardiac muscle is similar to smooth muscle because it is usually not under the direct control of the central nervous system

Homeostasis and Human Body Systems