2.6 Organ Systems and Homeostasis

2.6 Organ Systems and Homeostasis

Introduction:

We are now moving on from cells and will be learning about tissues, organs, and organ systems.  We will learn about plant and animal structures, but we will focus most on human tissues, organs, and organ systems. It is first important to understand that we have a lot in common with other organisms. It is easy to see that a cat has skin like us, called an epidermis, but did you know that plants have an epidermis too?  A plant epidermis is very different than human skin, but as with humans,  it helps plants to prevent water loss and protect against pathogens. We learned that humans have reproductive cells and organs, but did you know that flowering plants have stamen and ovaries and do sexual reproduction?  Pollen is part of plant reproduction.  We are similar, and different from organisms around us. 

TISSUES

A tissue is an interacting group of cells and intercellular substances that do a specialized task.    

We have studied cell differentiation, which is cells taking on the shapes and tasks for specialized work in the body.  A fertilized egg is called a Zygote, and very soon after fertilization, cells begin to differentiate into tissues that serve four functions.

The Four Functions of Animal Tissues and Organs:

Every animal is structurally adapted to perform these tasks.

1. maintain internal operating conditions- homeostasis

2. Locate and take in nutrients and dispose of wastes

3. Protect itself from attack, macro or micro, from the big to the small.

4. Reproduce and protect new individuals

The Language of Anatomy.

When Doctors and Scientists discuss the Anatomy, they use vocabulary that tells them directional information.  The anatomical position of a human body is defined as a body standing upright with the head facing forward, arms down at the sides with the palms turned forward, and feet parallel facing forward. A human body, Dorsal refers to the back portion of the body, whereas Ventral refers to the front part of the body.  Lateral means to the side or away from the midline. Medial means toward the midline.  Superior means above another portion of the body, and Inferior means below another portion of the body.  Distal means toward the back or behind, or further from,  and Mesial or Proximal means toward the front, closer to.  

The terms dorsal and ventral are also often used to describe the relative location of a body part. For example, the stomach is ventral to the spinal cord, which means that the stomach is located in front of the spinal cord.

Body Cavities:

We can also describe where an organ is, by describing which body cavity it is in.

Below are the major Body Cavities: 

Types of Tissues

All complex animals have four types of tissues:

Epithelial tissue- one side faces a body fluid and the other the outside environment. Its our skin!  It protects us.  It has tight junctions between cells that keeps bad stuff out. 

Connective tissue-cartilage, bone, adipose tissue, blood.  Most of these cells secrete fibers. They support our organs, skin, bones, and support our weight.

Muscle- cells contract (shorten) and  lengthen when stimulated.  They move and support the body. There are 3 types Skeletal, Smooth, Cardiac

Nerve- communications lines that extend throughout the body. 

These tissues combine to make organs.  There are 11 major organ systems that we will learn about. 

The major organ systems are

ORGANS and Organ Systems

Remember the different levels of organization of life.

The major levels of organization in the body, from the simplest to the most complex are: organelles, cells, tissues, organs, organ systems, organism, population, community, ecosystem, biosphere. 

An Organ is different tissues organized in specific patterns to do a specialized task.  An Organ System is two or more organs that interact physically, chemically, or both in a common task.  

 Organs are made of one or more types of tissues. Human organs include the brain, stomach, kidney, and liver. Plant organs include roots, stems, and leaves.

Organs work together to perform a specific function forming an organ system. Organ systems also work together to perform tasks. Examples of organ systems in a human include the skeletal, nervous, and reproductive systems. Organ systems in a plant include the root and reproductive systems.

The previous figure shows how multiple organs work together to transport blood around the body. The heart and blood vessels are two of the organs that work together and form the circulatory system.

There are 11 Major Organ Systems- some organs are in more than one system

1. Integumentary System- skin, hair , nails, exocrine glands

2. Muscular System- skeletal muscle, smooth muscle, cardiac muscle

3. Skeletal System- bones, cartilage, ligaments, tendons, connective tissue 

4. Nervous System-Brain, Spinal Cord, Peripheral nerves, Sensory Organs, ( Eyes, Ears, Taste Buds, Olfactory nerves)

5. Endocrine System-Hypothalamus, Pineal, Pituitary, thyroid/parathyroid, thymus, adrenal, pancreas, ovaries, testis

6. Circulatory System- Heart and Blood Vessels ( the blood itself is connective tissues and part of skeletal)

7. Lymphatic System- Lymph nodes, lymph vessels, spleen and bone marrow

8. Respiratory System- Nose, Mouth, Lungs, Pharynx, Windpipe, Larynx, bronchi, alveoli

9. Digestive System- Teeth, mouth, Pharynx, esophagus, stomach, liver, pancreas, gallbladder, small intestine, large intestine, rectum, anus

10. Urinary System-Kidneys, renal pelvis, ureters, bladder, urethra

11. Reproductive System: 

     Male-Penis, scrotum, testes, epididymis, vas deferens, prostate, seminal vesicles

     Female-Ovaries, fallopian tubes, uterus, cervix, vagina

HOMEOSTASIS

Organ systems work to create an environment for the body which is within a normal range of tolerance. ... WNL.   The circulatory system brings oxygen to cells, clean away waste, and gets rid of the CO_2, so it doesn't build up in the interstitial fluid- that is fluid that surrounds cells.  The endocrine system sends hormone messengers throughout the body, signaling cells to do different functions, like release insulin for digestion, or adrenaline for the fight or flight instinct, reproductive hormones' that mature our gametes.   The nervous system and the endocrine system are a team that control all the other organ systems.  The Endocrine system sends chemical messengers out to the body, and the nervous system sends electrical/ chemical signals that control the other organs.  An electrical impulse runs through the neuron cell itself, and then a chemical signal leaps to the next neuron, across a gap called a synapse.  

Each organ system plays its part in meeting  one of the four functions  of organs we learned in the first part of this assignment. We will not have a chance to learn about every organ system in detail.  If you would like to understand Anatomy better, sign up for Anatomy and Physiology class.  We will however learn about a few of these organ system. 

EXAMPLES OF ORGAN SYSTEMS MAINTAINING HOMEOSTASIS

One example of an organ working to maintain homeostasis is the way your pancreas works to keep the sugar in your blood relatively stable. When blood sugar is high, the pancreas releases the hormone insulin. The insulin signals cells to take in more sugar, lowering the amount of sugar in the blood. When blood sugar is low, the pancreas releases a different hormone, called glucagon. The glucagon signals cells and the liver to release sugar into the bloodstream.

The nervous, endocrine, and immune systems work together to help your body maintain homeostasis. For example, your nervous system can sense when you are in a dangerous situation. Your nervous system detects danger through sight, smell, or sound, and will send a signal to your endocrine system. Your endocrine system will respond to the signal by releasing adrenaline. The adrenaline travels to different cells in your body. The release of adrenaline causes your heart to beat faster, the release of glucose into your bloodstream, and the relaxing of muscle tissue in your lungs to allow for increased breathing. These changes are referred to as the fight or flight response, because they prepare your body to either fight or run away from danger.

You can learn more about the fight or flight response and how your nervous and endocrine systems work together by watching this video:

https://learn.genetics.utah.edu/content/cells/cellcom/ .

FEEDBACK SYSTEMS

There is fluid between all the cells, called interstitial fluid.  There is fluid in the blood called plasma.  This fluid must be maintained at levels that are compatible with cell survival.  A fluid can not become too acidic, or basic, it must be full of the right minerals and nutrients, it can't be too dehydrated, and their cant be too much of it either.  For the cells to live the body and its organs must respond to the changing conditions within the body and in the outside environment. 

Homeostasis is the stable operating conditions in the internal environment.  Three components interact to maintain that state.  

1. Receptor-cells or cell parts that detect stimulus.  Stimulus- a specific change in the environment

2. Integrator- a control point where different pieces of info are pulled together to select a response- your brain

3. Effectors- Carry out the response- muscles and organs

The sensory receptors tell the brain "HOW THINGS ARE" .  The brain compares that information to "SET POINTS".  When how things are deviates too far from the set points, the brain responds by reversing the condition.  For instance, human beings have a typical temperature set point from about 97.5 to 98.6 ${}^{\circ }$F. If you begin too get cold (somewhere around 96 degrees), your brain tells your muscles to contract "shiver" in order to create heat.   This reverses the trend toward the body cooling.

A NEGATIVE FEEDBACK MECHANISM- is a response triggered by alteration of the internal environment, that reverses the altered condition.

A POSITIVE FEEDBACK MECHANISM- is a less common response by the body, that intensifies a changed condition.  The body intensifies its reaction to the stimulus, until an acceptable conclusion happens.  Examples of this are Childbirth, Blood Clotting, Lactation, Ovulation.