Specialized Cells

I. Specialized Cells -all multicellular organisms have specialized cells that work together.

A. Tissue -group of cells that have a common structure and function. *both animals and plants have tissues that perform specific jobs. ex. tissue that covers plant’s leaves protects the leaf.

1. Epithelial Tissue

-sheets of cells that cover surfaces. -they also line certain body cavities and blood vessels. *usually smooth

2. Connective Tissue

-joins other tissue together and also stores fat and makes blood cells. - made of specialized cells and fibers that stick to living cells. *exs. Bone, cartilage, and blood.

3. Muscle Tissue

-animals use this tissue to move. -all muscle tissue create movement in one direction only, either by getting longer or shorter.

4. Nervous Tissue

-send electrical impulses through your body to help muscles contract.

-some send signals, while others protect nerves and provides them with nutrients.

B. Organs -are made up of several tissue types that work together to perform one or more functions. *exs. -heart beating -eating -walking -running

- a plant’s leaves, roots, and flowers are the organs.

C. Organ Systems -group of organs that work together to perform complex tasks. *exs. All plant’s leaves make up an organ system that provides energy for the plant.

- the more complex the organism, the greater the number of organ systems that are needed to carry out life processes. -humans have 11 organ systems. -some organs work for more than one organ system.

1. Circulatory System

a. carries oxygen through the body and removes carbon dioxide and other wastes. b. also helps keep our body temperature constant.

c. this system includes your: *heart * arteries *and veins

- at the kidneys, it connects to the 2. urinary system. * this system helps regulate the amount of water and salt in the blood, as well as removing liquid wastes.

3. Musculoskeletal System

a. supports all parts of your body and allows you to move. b. bones anchor other body parts and provide the structure needed for movement. c. muscles also generate warmth for your body.

4. Nervous System

a. the brain is an indispensable organ, the headquarters. -all your senses feed information into the brain. -the brain processes and responds to this information often, responding by sending signals down the nerves to the muscles.

* the brain also controls the other organ systems.

5. Skin * the internal and external layers of skin cells protect you from injury and retain moisture.

6. Digestive System

- obtains nutrients from food

7. Respiratory System

-the air you breath in travels through ever- narrower passageways. -the passageways ends at alveoli-tiny sacs where oxygen diffuses into blood and carbon dioxide diffuses out.

8. Endocrine System - works like chemical messenger system. -the glands of this system act as the communication centers. *the glands are a specialized group of cells that make and send out hormones. *humans contain 50 different hormones.

* some glands help regulate growth and energy use. (thyroid) * others control blood sugar, minerals, and other chemicals. (adrenal, pancreas) *some cause specific changes in the body. (thymus) -ex. dramatic changes in muscles and bones as you grow up.

- Growth hormones also influence when your growth will stop. -Many plants use hormones too. *the hormones in plants may cause a stem to bend towards the light. *some could direct a plant to grow taller instead of wider.

II. Cells and Disease

A. Causes of Disease 1. invasions by alien organisms or viruses 2. when body systems do not function properly. a. infectious disease-caused by harmful organisms or viruses

-examples: *bacteria and some other types of fungi are common causes of infectious disease. *worms can lodge in the intestines or muscles, causing several serious diseases.

*protozoa carried by mosquitoes cause malaria.

3. Many organisms enter the body through the food people eat. -ex. Salmonella bacteria

*live in chickens and other animals. *cooking destroys the bacteria.

-cholera is transmitted by water that has been contaminated by humans or animal waste products.

4. Contagious disease can be spread easily from one person to another. 5. Viruses are not organisms because they are not made of cells. -common cause of infectious disease -contain genetic instructions that take over a cell’s normal instructions.

6. Many viral diseases are mild. -exs. cold, flu, and chicken pox

7. Other viral diseases are more dangerous, even deadly. -exs. hepatitis and AIDS

b. non-infectious diseases 1. occur when a body system does not function properly. 2. can not spread from person to person. 3. sometimes the diseases are caused by a condition that is inherited. -ex. sickle cell anemia

4. other times a disease appears as a person’s body ages. *healthy life style and habits can help prevent many of these later in life diseases.

5. Type II Diabetes -can often be prevented by diet and exercise.

6. Poor nutrition causes many non-infectious diseases. * orange juice contains vitamin C, which helps prevent scurvy. *people who do not receive the proper vitamins in their food can suffer a variety of illnesses.

B. Fighting Disease

1. Your body has three main lines of defense against invasion by disease agents. a. First line of defense is made up of your body’s physical and chemical barriers. *these barriers include skin, tears, saliva, ear wax, and mucus.

b. second line of defense consists of processes that kick in, should harmful agents enter. -ex. Should you cut your skin and the cut becomes infected, defense mechanisms in the blood are activated.

* the second line of defense can include the production of special cells called phagocytes. -they surround and consume harmful disease agents that invade your body.

- Phagocytes are one type of white blood cells.

C. Immune System

1. a very powerful weapon to fight specific harmful agents 2. third line of defense 3. uses special cells that travel throughout the body and recognize invading pathogens, the agents of disease.

* they can recognize harmful invaders because they have different surface structures of normal body cells. *many cells produced by the immune system are designed to attack the invading disease agents and destroy them.

*certain types of white blood cells produce special proteins called antibodies that also fight invaders.

4. After the immune system destroys the invaders, the body begins to recover from illness. *if the same pathogens invade the body again, these cells can immediately produce the needed antibodies.

-this means that the body is now immune to, or protected from, that particular illness.

D. Disease Prevention and Treatment

1. Vaccine -a way of stopping a disease before it enters the body. -usually contains an inactive version of a pathogen. -when the body is exposed to the vaccine, it slowly makes antibodies against it.

* later if should the real pathogen enters the body, the antibodies are ready right away to stop it.

-vaccines have helped stop diseases such as: a. small pox b. polio c. measles

2. Today scientists continue working on new ways to prevent, treat, and cure diseases.